OU - Dissertations

Permanent URI for this collection

https://hdl.handle.net/11244/10476

Browse

Now showing 1 - 20 of 67

Open Access
A SYSTEMATIC APPROACH FOR THE CLASSIFICATION OF AGE-RELATED MUSCLE LOSS AND ELDERLY OBESITY USING FIELD-BASED TESTING METHODS AND ISOPERFORMANCE CURVES
(2012) Fukuda, David H.; Stout, Jeffrey R
The process of aging causes a wide variety of physiological changes that can manifest in the form of differing body composition phenotypes. A systematic approach to body composition classification and the subsequent selection of appropriate interventions is needed for community-based health care and fitness specialists. The primary purpose of this investigation was to determine body composition classification using field-based testing measurements in healthy elderly men and women. The use of isoperformance curves is presented as a method for this determination. Baseline values from 107 healthy Caucasian men and women over the age of 65 years old who participated in a separate longitudinal study were used for this investigation. Age, height, weight, body mass index (BMI), and handgrip strength were recorded on an individual basis. Relative skeletal muscle index (RSMI) and body fat percentage (FAT%) were determined by dual-energy X-ray absorptiometry (DXA) for each participant. Sarcopenia cut-off values for RSMI of 7.26 kg·m-2 for men and 5.45 kg·m-2 for women and elderly obesity cut-off values for FAT% of 27% for men and 38% for women were used. Individuals above the RSMI cut-off and below the FAT% cut-off were classified in the normal phenotype category, while individuals below the RSMI cut-off and above the FAT% cut-off were classified in the sarcopenic-obese phenotype category. The relationship between age and BMI, handgrip strength, RSMI, and FAT% was characterized using linear regression. Prevalence values for body composition phenotypes from actual DXA-based criteria and predicted RSMI and FAT% were evaluated. Using the DXA criterion values for RSMI and FAT%, 34 individuals (32% of the sample) were classified as normal, 50 individuals (47% of the sample) were classified as obese, 10 individuals (9% of the sample) were classified as sarcopenic, and 13 individuals were classified as sarcopenic obese. Prediction equations for RSMI and FAT% from BMI and handgrip strength values were developed using multiple regression analysis. The prediction equations were validated using double cross-validation. The final regression equation developed to predict FAT% from BMI and handgrip strength resulted in a strong relationship (adjusted R2=0.741) to DXA values with a low standard error of the estimate (SEE=3.9937%). The final regression equation developed to predict RSMI from the field-based testing measures also resulted in a strong relationship (adjusted R2=0.841) to DXA values with a low standard error of the estimate (SEE=0.5437 kg·m-2). Using the prediction values for FAT% and RSMI, 30 individuals (28% of the sample) were classified as normal, 58 individuals (54% of the sample) were classified as obese, 17 individuals (16% of the sample) were classified as sarcopenic, and 2 individuals (2% of the sample) were classified as sarcopenic obese. Subsequently, isoperformance curves were used to aid in the classification and evaluation of sarcopenia, obesity, and sarcopenic obesity in elderly individuals by graphically representing the relationship between BMI and handgrip strength with the aforementioned clinical phenotype classification criteria. The final goal of this investigation was to produce easily understood charts that can be used by personal trainers, nutrition specialists, and/or health professionals. The charts could be used in the classification of individuals into these phenotype categories in an inexpensive and non-invasive manner. Future research should be undertaken that enhances the current findings by increasing the sample size and developing tailored interventions for each body composition category.
Open Access
Active Living and Local Government
(2017-05-12) Dunnington, Jamie; Taylor, Laurette; Cheney, Marshall; Wieters, Meghan; Branscum, Paul; Widener, Jeff
Purpose: This qualitative study explored a local government’s perceptions of and support for active living and factors that influenced active living decisions and collaboration in one metropolitan city in the southern region of the United States. Methods: City leaders and municipal employees (n=46) were interviewed. Participants had a role in creating and implementing policies and infrastructure changes that impact physical activity behaviors of city residents. They included the mayor, seven city council members, the city manager, the assistant city manager, fifteen director- and management-level city employees, six public health practitioners, six city planners, three parks and recreation employees, three pubic works employees, and three commissioners. The study took place in a car-dependent and car-prioritized city where physical inactivity is high, inadequate active living supportive policies have been adopted, and few walkable and bikeable areas exist. Interview transcripts were coded using NVivo and then analyzed for themes. Results: Regarding city leaders and active living decisions, five themes were identified: (1) identification of the most influential decision-makers, (2) barriers to making active living supportive design decisions, (3) city assets that facilitate making active living supportive design decisions, (4) younger generation preference, and (5) acknowledgement of particular co-benefits of activity-friendly environments. Regarding municipal employees and perceptions of active living, seven themes were identified: (1) perception of high level of support, (2) identification of the co-benefits of creating activity-friendly environments (3) comparison to other cities in the country, (4) ‘not there yet’ status, (5) acknowledgment of these changes being a long-term process, (6) importance of the mayor’s support, and (7) need for greater citizen involvement and demand. Regarding inter-governmental active living collaboration, eight themes were identified: (1) minimal active living/public health collaboration, (2) strained relationships with city planners, (3) radically different perceptions of planners, (4) the person matters, (5) facilitators to collaboration (history of working together, personal relationships, and regular meetings), (6) barriers to collaboration (silo-ed work environments and turf issues), (7) key decision-makers (the city manager, council, and mayor), and (8) inclusion of citizens in collaboration. Conclusions: These three studies add to the literature that explores the connection between local government and the promotion of physical activity. Findings increase understanding of multiple viewpoints of local government officials and the challenges and opportunities associated with creating activity-friendly policies and environments. Qualitative research can provide guidance to enhance collaboration and facilitate the creation of stronger partnerships and long-lasting policy and environmental changes.
Open Access
Acute and chronic effects of passive stretching on voluntary and evoked muscle force, the length-tension relationship, ankle joint range of motion, and musculotendinous stiffness in the plantar flexors
(2009) Ryan, Eric Dobert; Cramer, Joel T
The purposes of the present study were: (a) to examine the effects of prolonged passive stretching on the length-tension relationship under voluntary (maximal voluntary contraction (MVC) force) and evoked (single and tetanic twitch force) conditions, (b) to determine if four weeks of regular chronic stretching affects the magnitude of the stretching-induced deficit on MVC, single and tetanic twitch force, percent voluntary activation (% VA), electromyographic (EMG) amplitude of the soleus (SOL) and medial gastrocnemius (MG), range of motion (ROM), musculotendinous stiffness (MTS), and corrected calf girth, and (c) to examine the effects of acute versus chronic stretching on changes in ROM and MTS. Twenty-six healthy men volunteered for this investigation and were randomly assigned to either a stretch training (STR) group (mean±SD age = 22 ± 2 yrs; stature = 175 ± 8 cm; mass = 74 ± 12) or control (CON) group (21 ± 2 yrs; stature = 176 ± 7 cm; mass = 76 ± 11) for four weeks. At baseline (week 1) and post-testing (week 5) all subjects completed a flexibility and strength (voluntary and evoked) assessment prior to and following 20 min of passive stretching of the plantar flexor muscles on a custom-built load cell apparatus attached to a calibrated isokinetic dynamometer. To determine ROM and MTS, the dynamometer passively dorsiflexed the foot at 5˚۰s-1 from -20º of dorsiflexion to the maximum tolerable ROM (as acknowledged by the subjects). For the strength assessments, subjects performed a MVC and underwent a single and tetanic stimulus at each randomly-ordered joint angle (-19º, -9º, 1º, and 12º of dorsiflexion, where 0º = neutral ankle joint angle). The stretch training included four 135-s constant-torque passive stretches 3 times per week for 4 weeks. At weeks 1 and 5, from pre- to post-stretching voluntary and evoked force decreased across all joint angles, ROM increased, and MTS decreased, however there were no changes in EMG amplitude or % VA. Following 4 weeks of stretch training, the STR group showed increases in voluntary (MVC) and evoked (single and tetanic twitch) force production at all joint angles, increases in ROM, decreases in MTS, and increases in MG EMG amplitude, but no changes in % VA, SOL EMG amplitude, and corrected calf girth. For the CON group, there were no changes in MVC force, ROM, MTS, %VA, SOL EMG amplitude, and corrected calf girth, but increases in single and tetanic twitch force and EMG MG amplitude. For the length-tension relationship, voluntary and evoked force increased from shorter to longer muscle lengths (19° to 1°) and decreased at the longest muscle length (12°), whereas % VA and EMG MG amplitude decreased from the shortest to the longest muscle lengths. There were no acute or chronic stretching induced changes in the length-tension relationship. The results of the present study suggest due to the lack of changes in %VA and EMG amplitude and decreases in MTS from pre- to post-stretching, the stretching-induced force deficit may be more mechanical in origin. Chronic stretch training also does not appear to influence the stretching-induced force deficit or length-tension relationship. However, chronic stretch training appears to increase maximal force production at all joint angles, increase ROM, and decrease MTS in the plantar flexors with no changes in corrected calf girth. Therefore, it is possible chronic stretch training results in longitudinal hypertrophy (i.e. increased amount of sarcomeres in series), however future studies are needed to determine if there are in fact fascicle length changes following stretch training.
Open Access
Acute hormonal responses after two different exercise protocols in college aged males
(2013) Kim, Eonho; Bemben, Michael
PURPOSE: The purpose of the current study was to compare the acute hormonal responses of two resistance training exercise protocols (Traditional and SuperSlow) that had similar exercise volumes but differed in intensity and contraction speeds in college-aged males.
Open Access
Acute hormonal responses after two different exercise protocols in college aged males
(2013) Kim, Eonho; Bemben, Michael
PURPOSE: The purpose of the current study was to compare the acute hormonal responses of two resistance training exercise protocols (Traditional and SuperSlow) that had similar exercise volumes but differed in intensity and contraction speeds in college-aged males.
Open Access
Acute Neuromuscular and Endocrine Responses Following High and Low External Training Loads in Collegiate Basketball Players
(2020-05-08) Heishman, Aaron; Bemben, Michael; Bemben, Debra; Black, Christopher; Crowson, Michael; Periera, Hugo
INTRODUCTION: Elite athletes undergo aggressive training regimens containing strategically induced fatigue in an attempt to maximize adaptation and performance improvements to meet the individual demands of the various sport. Athlete monitoring strategies are often used to track training loads and subsequent changes in performance. Inertial measurement units are often utilized to quantify the external training loads (eTL), also known as the biomechanical or locomotive stress, during indoor team sport activities, while the countermovement jump (CMJ) is employed to evaluate acute neuromuscular fatigue and performance. Little data exist examining the dose response of eTL and subsequent change in neuromuscular fatigue and performance, especially in basketball players. Additionally, although the CMJ is a commonly used field measure, exploring specific alterations in the CMJ force-time characteristics rather than gross output measures has been proposed to provide more insight with regards to changes in neuromuscular fatigue and performance compared to only considering gross output parameters, however this is yet to be explored among basketball players. PURPOSE: Therefore, the purpose of this dissertation was to examine the acute neuromuscular function and endocrine responses to High versus Low eTL basketball practices in a cohort of collegiate basketball players. A secondary aim sought to examine if neuromuscular alteration were primary central or peripheral in origin in response to a sport-specific basketball training session. METHODS: This dissertation was divided into two parts. Part I included 16 NCAA Division I basketball players (Male = 12; Female = 4) that performed a High and Low eTL practice, in a cross-over study design, where practice intensity measured using IMUs and intensity was characterized by PlayerLoad/minute (PL/min). Prior to each practice, participants provided a salivary sample used to assess testosterone, cortisol, and Testosterone:Cortisol ratio, as well as performed 3 CMJs on a dual cell force platform. At the conclusion of each practice, participants provided another salivary sample and perform 3 more CMJs. Participants returned 24-hours following practice to provide another salivary sample and perform 3 more CMJs. Perceived fatigue and muscle soreness were assessed using subject recovery questionnaires prior to practice and 24-Hours following practice. Part II include 15 NCAA Division I basketball players (Male = 9; Female = 6) underwent neuromuscular performance assessments before, immediately-after, and 24-hours following a team practice. The eTL of each practice was captured using an IMU. Maximal voluntary contraction (MVC) and twitch responses to electrical neuromuscular stimulation were assessed during the isometric knee extensor contraction and at rest to measure central (voluntary activation) and peripheral (twitch torque) fatigue, as well as responses in twitch torque at rest were used examine the prevalence of low frequency fatigue. In addition, participants performed 3 CMJs at each time point to characterize neuromuscular fatigue and performance. STATISTICAL ANALYSIS: Data normality was confirmed using descriptive and graphical information supplemented by the Shapiro-Wilk test statistic. In Part I, a 2-way (Sex [male, female]) × Condition [high load, low load)] repeated measures (RM) analysis of variance (ANOVA), evaluate differences in eTL. Data from the recovery questionnaire exhibited a non-normal distribution, therefore the equivalent nonparametric test was utilized. Friedman's non-parametric test was used to test for significant differences in the median rank scores across the different conditions and time points. A 3-way (Sex [male, female] x Condition [high load, low load) x Time [pre-, immediately post, 24 hours-]) RM ANOVA was used to assess sex, condition, and time main effects, as well as the interaction between Sex, Condition, and Time for each CMJ variable. Additionally, a 2-way (Condition × Time) RM ANOVA was also used to evaluate Sex × Condition, Sex × Time, and Condition × Time interactions, with significant interactions examined using a post-hoc pairwise comparison with a Bonferroni correction to isolate simple effects. In Part II, an independent T-Test was used to evaluate differences in Training Loads during practice between sexes. A 2-way (Sex [male, female] × Time [Pre, 24 hours-post exercise]) was utilized to evaluate difference in Recovery questionnaire parameters, with post-hoc pairwise comparison using Bonferroni corrections used when a significant difference was detected. A 2-way (Sex [male, female] × Time [Pre, immediately post, 24 hours-post exercise]) RM ANOVA was used to examine Sex and Time main effects and the interaction between sex and time for each variable: CMJ variables, MVC, voluntary activation, twitch characteristics and Low frequency fatigue. If a significant Sex × Time interaction was verified, the statistical model was decomposed by examining the simple effects with separate one-way repeated measures ANOVAs with Bonferroni correction factors for each group and time point. For both Part I and Part II, statistical significance was set at p  0.05. When comparing three or more groups, partial eta-squared (ηp2) effect sizes were calculated and interpreted as small (0.0099), medium (0.0588) and large (0.1379). When comparing between two groups, Cohen’s d (d) effect sizes were utilized and interpreted as trivial (0–0.19), small (0.20–0.49), medium (0.50–0.79), and large (≥0.80). RESULTS: In Part I, there were significant differences in eTL during the High compared to the Low condition, including PlayerLoad per Minute and PlayerLoad (p < 0.05), while there were no practical differences in duration. The high condition also exhibited significantly greater iTL response (p < 0.05). However, there were no differences in perceived responses between condition or across time (p < 0.05). No significant differences emerged for any CMJ variable between condition or across time (p < 0.05), however, 6 of 7 CMJ Tradition Variables, 4 of 6 CMJ Concentric Alternative Variables, 3 of 5 CMJ Eccentric Alternative Variables, and 3 of 7 CMJ Phase Duration Alternative Variables did display a small effect (d = 0.20-0.49) during the High condition from Pre to Post-practice, which was none of these effects were observed during the Low condition. Additionally, the majority of these variables that showed an effect following practice during the High condition, revealed trivial to no effect at the 24-hour assessment following practice, signifying a resolved back to baseline. There were significant sex differences in endocrine responses to eTL (p < 0.05). There were no differences in endocrine responses between the high or low eTL conditions (p > 0.0.5) 4) In men, there were significant increases in testosterone from Pre to Post-Practice that returned to baseline at 24-hour following practice (p < 0.05) and cortisol appeared to increase from pre to post practice, but also return to baseline 24-hours following practice. In addition, testosterone:cortisol ratio appeared unaffected by condition and across time (p < 0.05). In testosterone, cortisol and T:C ratio appeared unaffected between conditions and unchanged across time (p < 0.05). In Part II, eTL appeared longer in duration and higher in volume (PlayerLoad), but lower in intensity (Pl/min) compared to those experienced in Part I. There were no significant differences in CMJ variables across time (p < 0.05), with changes exhibiting trivial to no effect. Men experienced a significant decrease in Rate of Torque Development from Pre to Post-practice (p < 0.05), which returned to baseline at 24-hours following practice, while women experienced no changes across time. Low frequency fatigue appeared to emerge immediately following practice but resolved back to baseline at 24H-post practice. There were significant Sex differences in CMJ variables, MVC, Interpolated Twitch Torque, EMG, and twitch characteristics (p > 0.05), but no differences in percent voluntary activation. CONCLUSIONS: These findings suggest High eTL practice evoke a small acute effect on CMJ variables immediately following practice, which resolve to baseline by 24-hours, whereas Low eTL seems to induce no alteration in CMJ performance. In men, practices stimulated acute increase in testosterone and cortisol, while no changes occurred in T:C ratio. Varying eTL did not influence these acute responses in testosterone and cortisol. In women, testosterone, cortisol, and T:C ratio remained unchanged by both High and Low eTLs. Sport-specific practice appears to increase MVC and central components of neuromuscular function (voluntary activation), especially 24-hours following the exposure. Only small signs of mild peripheral fatigue occur following practice, which included low frequency fatigue appear immediately after practice, but resolved by 24-hours following the practice exposure.
Open Access
Acute physiological and perceptual responses to resistance exercise with blood flow restriction in individuals with multiple sclerosis
(2021-05-14) Freitas, Eduardo; Bemben, Michael; Debra, Bemben; Pereira, Hugo; Larson, Rebecca; Song, Hairong
OBJECTIVE: This study aimed to compare the acute physiological and perceptual effects of low-load blood flow restriction (BFR) resistance exercise (LLBFR+RE) and high-load resistance exercise without blood flow restriction (HL-RE) in people living with multiple sclerosis (MS). Fifteen individuals (4 males and 11 females) with a physician-confirmed diagnosis of relapsing remitting MS and a disability score ≤ 6.5 volunteered to participate. METHODS: Participants completed a total of five visits to the laboratory. Visit 1 consisted of consenting and filling out standardized forms and questionnaires. During visit 2, participants completed measurements of several cardiovascular parameters, total arterial occlusion pressure for each leg, and completed the one-repetition maximum (1-RM) test for the leg press and knee extension exercises. Visit 3 included measurements of total body and regional body composition and bone mineral density using dual energy X-ray absorptiometry, then the 1-RM test for the same exercises was repeated. Visits 4 and 5 consisted of randomly completing the following experimental conditions: LLBFR+RE, consisting of 30+15+15+15 repetitions of leg press and knee extension at 20% of 1-RM, combined with 50% of BFR; and HL-RE, which included 4 sets of 10 repetitions of the same leg press and knee extension exercises at 75% of 1-RM, without BFR. Venous blood samples were collected and used to measure the plasma concentrations of whole-blood lactate, cortisol, interleukin-6 (IL-6), myostatin, and the mammalian target of rapamycin (mTOR), at baseline, 5 minutes post- , and 60 minutes post-exercise. The same blood samples were also used to measure hematocrit concentration and plasma volume changes at the same time points. Additionally, muscle swelling was estimated through muscle thickness and thigh circumference measures, taken at baseline and at 30 minutes and 60 minutes post- exercise. Myoelectric activity of the vastus medialis and vastus lateralis muscles of the right and left leg was measured using surface electromyography (sEMG) during each experimental exercise condition. The perceptual responses consisted of ratings of perceived exertion (RPE), measured immediately after completion of each set of exercise; ratings of pain, measure immediately before and immediately after each set; and levels of soreness, measured before exercise and 5 minutes, 30 minutes, 60 minutes, and 24 hours post-exercise. All perceptual variables were measured using validated visual numeric scales. All physiological data were analyzed using parametric statistics; thus, two-way (condition × time) repeated measures analyses of variance were used to test all main effects and interactions. In the case of significant interactions, pairwise t tests were used to test the simple effects. Familywise error rate was controlled using the Bonferroni procedure. The perceptual data were analyzed using non-parametric statistics; therefore, the Wilcoxon test was used to compare the two experimental conditions within specific time points. The Friedman’s nonparametric test was used to test for significant differences in the median rank scores across the time points. If a significant difference was detected, pairwise Wilcoxon nonparametric tests with Bonferroni procedure were used to locate the differences. RESULTS: Whole-blood lactate levels significantly (p < 0.05) increased 5 min post-exercise compared to pre-exercise values, with HL-RE displaying significantly (p < 0.05) greater increases than LLBFR+RE. No significant (p > 0.05) condition or time effects were observed for plasma concentrations of myostatin, IL-6, and mTOR. Although a significant (p < 0.05) condition effect was also not detected for cortisol, a significant (p < 0.05) decrease from baseline was observed for both conditions 1 hour post-exercise. There were also no significant (p > 0.05) time or condition effects for changes in hematocrit concentration and plasma volume. Muscle thickness and thigh circumference significantly (p < 0.05) increased from baseline immediately post-exercise following both experimental trials, with no significant (p > 0.05) differences between conditions. The HL-RE condition elicited significantly (p < 0.05) greater myoelectric activity than the LLBFR+RE trial for the vastus medialis and vastus lateralis muscles and during the leg press and knee extension exercises. Regarding the perceptual responses, HL-RE resulted in significantly (p < 0.05) greater RPE than LLBFR+RE during leg press and knee extension. Similar (p > 0.05) ratings of pain were observed during both experimental exercise conditions immediately after each set, however, for the ratings of pain measured immediately before each set, LLBFR+RE induced significantly (p < 0.05) greater pain than HL-RE. Finally, no significant (p > 0.05) increases in muscle soreness were observed up to 24 hours post-exercise following both trials. CONCLUSIONS: This study demonstrated that people living with MS are capable of tolerating and performing LLBFR+RE without any major adverse effects. This study also demonstrated that LLBFR+RE is capable of acutely increasing many of the physiological parameters related to the hypertrophic response commonly observed following traditional resistance exercise without BFR, indicating that it may potentially serve as a training alternative to HL-RE for MS patients unable or unwilling to lift heavy loads. The perceptual data also demonstrated that LLBFR+RE requires less muscular exertion compared to HL-RE, and does not cause exaggerated pain during exercise or elevated delayed-onset muscle soreness up to 24 h post-exercise.
Open Access
THE ACUTE SKELETAL MUSCLE RESPONSE TO LOWER BODY RESISTANCE TRAINING WITH AND WITHOUT BLOOD FLOW RESTRICTION IN PHYSICALLY ACTIVE MALES BETWEEN THE AGES OF 18-35
(2014) Loenneke, Jeremy; Bemben, Michael; Beck, Travis; Larson, Rebecca; Bemben, Debra; Knapp, Rosemary
Blood flow restriction (BFR) in combination with exercise has been shown to result in favorable effects on skeletal muscle mass and function. However, most protocols have used an arbitrary pressure or they have based the restrictive pressure off of brachial systolic blood pressure, which is not a valid predictor of arterial occlusion in the lower body. This study sought to determine the most effective low load protocol with and without different degrees of BFR (determined based on limb circumference) and determine how it compares to higher load (HL) resistance exercise. PURPOSE: The purpose of this study was to compare acute skeletal muscle changes following differing resistance exercise protocols. In addition, the perceptual response to each of those protocols was investigated. METHODS: Participants completed five separate visits. On the first visit, participants: 1) completed paperwork; 2) were screened further for eligibility (Blood Pressure; BMI); 3) completed one repetition maximum testing on the knee extension; and 4) were familiarized with the BFR stimulus. Following the first visit, participants were randomly assigned to either group A, group B, or group C. Within each group, the participants were further randomized into which condition they completed first, second, third, and fourth. The conditions included three exercise conditions and one control condition. During each visit, participants had their muscle thickness and circumferences measured on their non-dominant leg. Following this, their dominant leg was prepped for electromyography (EMG). Participants completed a maximal voluntary contraction (MVC) with their dominant leg, rested for five minutes, and then completed the protocol designated for that day. The protocols within Group A included HL exercise at 70% 1RM, exercise at 20% 1RM with 40% estimated arterial occlusion (20%/40 BFR), exercise at 30% 1RM with 40% estimated arterial occlusion (30%/40 BFR), and a non-exercise control (CON). The protocols within Group B included exercise to failure at 30% 1RM, exercise at 20% 1RM with 50% estimated arterial occlusion (20%/50 BFR), exercise at 30% 1RM with 50% estimated arterial occlusion (30%/50 BFR), and a non-exercise CON. The protocols within Group C included exercise to failure at 20% 1RM, exercise at 20% 1RM with 60% estimated arterial occlusion (20%/60 BFR), exercise at 30% 1RM with 60% estimated arterial occlusion (30%/60 BFR), and a non-exercise CON. The 70% 1RM protocol was completed with one minute rest between sets. All other protocols were separated by 30s rest. In addition, after every set of exercise, RPE and discomfort were quantified. During the CON conditions, participants sat in the knee extension device for ~5.5 minutes to mimic the estimated time to complete a normal exercise bout. A comparison across groups was plotted and visually examined to descriptively compare conditions when effect sizes were unable to be calculated (i.e. EMG, perceptual responses). RESULTS: Forty-five physically active males passed initial screening and gave informed consent to participate in the study. Of those initial 45 participants, only 40 completed all of the testing sessions. Within the BFR conditions, increasing the load from 20% to 30% 1RM significantly increased the exercise volume, regardless of the pressure applied. Although not examined statistically, plotting the exercise volumes together (i.e. across groups) suggests that the 20% to failure condition results in the greatest volume lifted, followed by 30% to failure and HL conditions, which had similar volumes. The decrease in torque was statistically similar between the exercise conditions within each group, except for the 20%/40 BFR condition whose decrease did not exceed the error of the measurement. When examining the magnitude of the change across groups for each load, the effect sizes were slightly higher in the 30% 1RM BFR conditions compared to the 20% 1RM BFR conditions. In addition, increasing the applied pressure from 40% BFR to 50% BFR increased the magnitude of the effect; however, increasing the pressure up to 60% BFR reduced the effect size in the 30% 1RM BFR conditions. For non-BFR conditions, the effect sizes were similar, but with 20% to failure having the largest effect. With respect to muscle cell swelling, the acute changes in muscle size appeared fairly similar across all exercise conditions within each group regardless of load and pressure. The increase in lactate was similar between the exercise conditions within each group, except for the 20% 1RM BFR conditions, whose increases were always significantly less than those of the other exercise conditions. When examining the magnitude of the change across groups for each load, the effect sizes were higher in the 30% 1RM BFR conditions compared to the 20% 1RM BFR conditions. Increasing the applied pressure from 40% BFR to 50% BFR increased the magnitude of the effect; however, increasing the applied pressure up to 60% BFR reduced the effect size. For the non-BFR conditions, the effect sizes were highest in the HL and 30% to failure conditions, with 20% to failure having the smallest effect. The increase in concentric EMG amplitude was augmented when the load was increased from 20%1RM to 30% 1RM within each group. In addition, the 30%/50 BFR conditions concentric EMG amplitude was statistically similar to the 30% to failure condition. Increasing the applied pressure from 40% BFR to 50% BFR increased concentric EMG amplitude independent of load; however, increasing the applied pressure up to 60% BFR did not appear to augment the response. The HL condition had the highest concentric amplitudes throughout. The increase in eccentric EMG amplitude was augmented when the load was increased from 20%1RM to 30% 1RM within each group except for Group C. In Group C, there was no difference between 20%/60 BFR and 30%/60 BFR for eccentric EMG amplitude of the last three repetitions. In addition, the 30%/50 BFR conditions eccentric EMG amplitude was statistically similar to the 30% to failure condition. Increasing the applied pressure from 40% BFR to 50% BFR increased concentric EMG amplitude independent of load; however, increasing the applied pressure up to 60% BFR did not appear to augment the response. The HL condition had the highest eccentric amplitudes throughout. Concentric EMG mean power frequency increased from set 1 to set 3 within Group A for the last three repetitions, but no differences were observed at any time point within Group B or Group C. Increasing the pressure or the load did not appear to change concentric mean power frequency. Eccentric EMG mean power frequency of the first three repetitions decreased from set 1 to set 2, set 3, and set 4 for each condition within each group. For the last three repetitions, there were differential responses within each group. Increasing the pressure or the load did not appear to change eccentric mean power frequency. The ratings of perceived exertion (RPE) increased within each group. In Group A, 20%/40 BFR had the lowest overall RPE while 30%/40 BFR and HL training had ratings similar to each other. In Group B, 20%/50 BFR had the lowest overall RPE while 30%/50 BFR and 30% to failure were similar to each other. In Group C, there were minor differences in set 1, otherwise the ratings were similar throughout. When examining the change in RPE across groups for each load, the ratings were similar in the 20% 1RM BFR conditions compared to the 30% 1RM BFR conditions. In addition, increasing the applied pressure from 40% BFR to 50% BFR increased RPE at 20% 1RM; however, increasing the applied pressure up to 60% BFR did not lead to a higher RPE. With 30% 1RM, RPE did not appear different across pressures. For the non-BFR conditions, the HL condition had the lowest RPE, while the ratings were similar between 20% and 30% 1RM to failure. The ratings of discomfort increased within each group. In Group A, the 20%/40 BFR had the lowest overall ratings of discomfort while the 30%/40 BFR condition had the highest. Neither group differed from the HL condition, except for set 3 where the 30%/40 BFR condition had higher ratings. In Groups B C, ratings of discomfort were similar throughout except for set 1 in Group B. When examining the change in discomfort across groups for each load, the ratings were lower in the 20% 1RM BFR conditions compared to the 30% 1RM BFR conditions. In addition, increasing the applied pressure from 40% BFR to 50% BFR increased ratings of discomfort at 20% 1RM, and there was a further increase in the rating when the applied pressure was increased to 60% BFR. For 30% 1RM, the ratings of discomfort descriptively differed across each set. In set 1, the ratings of discomfort were highest for 40% BFR and lowest with 60% BFR. In set 2, the ratings of discomfort were similar across conditions. For sets 3 and 4, the ratings of discomfort were higher with 40 and 60% BFR and lower with 50% BFR. For the non-BFR conditions, the HL condition had the lowest ratings of discomfort, while the ratings were highest with the 20% 1RM to failure condition. CONCLUSIONS: This study found that knee extension exercise at 30% 1RM in combination with BFR at an estimated arterial occlusion pressure of 50% resulted in changes similar to those seen with HL exercise. In addition, 30% 1RM to failure also produced changes similar to HL exercise, albeit at a higher exercise volume. However, it is noted that the EMG amplitude of the lower loads never reached that observed with HL exercise. Since similar changes have been observed previously in chronic training studies, these findings suggest that other mechanisms may be playing a more prominent role with lower loads.
Open Access
AGE AND GENDER DIFFERENCES IN TIBIA STRENGTH AND MORPHOLOGY AND RELATIONSHIPS OF TIBIA MORPHOLOGY TO BONE HEALTH
(2011) Sherk, Vanessa; Bemben, Debra A
Variability in peripheral Quantitative Computed Tomography (pQCT) measurement sites limits direct comparisons of results between studies. Further, it is unclear what estimates or surrogates of bone strength are most indicative of changes in fracture resistance due to aging, disease, or interventions. The purpose of this study was to examine the effects of age and gender on tibia morphology, and to relate indicators of tibia mass and shape to hip and spine areal bone mineral densities (aBMD) and bone mineral content (BMC) as assessed by Dual Energy X-ray Absorptiometry (DXA). Additional purposes of this study were to determine which tibia site or sites are most sensitive for detecting age, gender, or menopause-related morphology changes. Methods: Self-identifying Caucasian men (n=55) and women (n=59) ages 20-59 years had their total body, lumbar spine, and dual proximal femur aBMD and BMC measured with DXA (GE Lunar Prodigy). Body composition (total and leg bone free lean body mass (BFLBM) and fat mass (FM)) were assessed from the total body scan. Their non-dominant tibias were measured with pQCT (Stratec XCT 3000) at every 10% of the limb length from 5%-95% from distal to proximal. Volumetric BMD, BMC, and area of the total, cortical and trabecular bone were determined. Also, periosteal (PeriC) and endosteal (EndoC) circumferences, cortical thickness (CTh), bone strength index (BSI), strength strain index (SSI), moments of inertia (Imax, Imin) mass ratios, and strength to mass ratios were quantified. General health information, menstrual history, dietary intake averaged over the previous year, and lifetime bone specific physical activity (BPAQ) were assessed by questionnaires for regression analysis. Participants were grouped by decade and by gender. Results: Bone morphology and strength characteristics varied along the tibia in a nonlinear fashion. There were significant (p<0.01) site effects for all BMC, vBMD, area, strength (SSI, Imin, Imax, SSI:Tot.BMC ratio), PeriC and EndoC. Total vBMD peaked at the 35%, while cortical BMC peaked at 55% with minimums at 5% and 85%. Total BMC, SSI, SSI:Tot.BMC ratio, and Imax all peaked at the 85% site. Large gender differences (21-28%) in Tot.BMC were paralleled by differences in Tot.Area (14-25%), due to differences in Cort.BMC and area (21-25%) (p<0.01). Gender differences (p<0.01) in Imax, SSI, and SSI:Tot.BMC ratio were smallest at the 15% sites and increased through the diaphysis. Women had significantly (p<0.05) greater Cort.vBMD than men. Men had significantly (p<0.01) greater Tot.BMC ratios at 5%:35% 5%:65%, and 5%:85%. Site*gender interaction effects were significant (p<0.05) for area, BMC, circumference, and strength variables. CTh and total vBMD were lowest (p<0.05) in 50-59 yr group, and several trends (p<0.10) existed for BMC variables. EndoC was highest in the 50-59 yr group, and Imax was highest in the 40-49 yr group. Site*age interactions existed for Cort.vBMD, Tot.BMC, SSI, Imax, EndoC, and SSI:Tot.BMC. There were significant age effects for total vBMD and area, trabecular area, cortical area, SSI, Imax, and SSI:Tot.BMC. BMC ratios for 5:35% and 5:65% were highest (p<0.05) the in 20-29 yr group. Tibia total BMC and vBMD were moderately-to-strongly correlated with hip BMC and aBMD values (r = 0.31-0.76). Conclusion: Gender differences were mostly found in bone size variables, whereas age differences were mostly found in density and cortical thickness values. The magnitude of age and gender differences also varied by measurement site. Standardization of measurement sites is recommended for future reference database development and comparison.
Open Access
Age related changes in skeletal muscle activation following short-term resistance training.
(2007) Hartman, Michael J., Iii.; Bemben, Michael G.,
Current research suggests that older adults do not possess the same ability to fully activate skeletal muscle of the lower limb as do young adults. However, it is not known at what age these changes may negatively affect the improvement in neuromuscular activation associated with resistance training. Purpose. To determine the effects of short-term resistance training on measures of muscular strength and skeletal muscle activation of the triceps surae in adult males ranging from 20-79 years of age. Methods. Forty-six normal healthy males volunteered to participate in this research study. Subjects were designated into one of five groups, classified as individuals aged between 20-29 years (n=10), 30-39 years (n=10), 40-49 years (n=7), 50-59 years (n=9), and 60-79 years (n=10). Subjects participated in three supervised resistance training sessions over the course of seven days, performing four lower body exercises during each training session. Subjects were assessed for muscle cross-sectional area, muscular strength, and muscle activation via twitch interpolation and surface electromyography (SEMG) before and after the experimental training. Three-way and two-way repeated measures ANOVA, as well as a one-way ANOVA, was used to determine group differences and changes with training. Results. Analysis of baseline muscular strength data revealed only a significant difference (p=0.02) in muscle strength between Group 2, 30-39 years (132.4 +/- 5.4) and Group 5, 60-79 years (99.8 +/- 7.5) for plantarflexion maximal strength. No significant differences (p>0.05) were observed for muscle cross-sectional area, dorsiflexion muscular strength, muscle activation assessed via twitch interpolation, or antagonist co-activation between age groups. Statistical analysis revealed no significant differences (p>0.05) in SEMG RMS amplitude or median frequency between age groups. However, comparison of muscle groups revealed a significant difference (p=0.003) in RMS amplitude between the soleus (SOL; 145.8 +/- 10.2 muV) and medial gastrocnemius (MG; 254.2 +/- 17.7 muV) muscles. Following training, there was no significant change (p>0.05) in muscle cross-sectional area, muscular strength, muscle activation assessed via twitch interpolation, or antagonist co-activation for any age group. Examination of SEMG data determined significant main effects for muscle group (p=0.001) and time (p=0.013) between SOL and MG for RMS amplitude. A significant decrease for the time main effect (p=0.001) in SEMG median frequency was also observed post-training. Conclusions. A similar pattern of response in all groups was observed in most variables assessed during the present study. The results from the present study indicated that there were no significant pre-test to post-test changes in muscle size, muscular strength, muscle activation, or antagonist co-activation following the experimental training period. These findings were unlike those from previous investigations of the leg extensors t hat have reported increases in performance after only two or three training sessions. This information may be useful for those involved in rehabilitative programs. Specifically, the muscles of the lower limb (i.e. calf) could require more than three training sessions to elicit the strength improvements and neuromuscular adaptations that typically occur during the early stages of a resistance training program.
Restricted
Age-Related Changes in Muscular Strength, Power, Endurance, and Quality in Recreationally Active Women Aged 20 to 89 Years
(2020-05-08) Miller, Ryan; Bemben, Michael; Bemben, Debra; Pereira, Hugo; Kellawan, J. Mikhail; Terry, Robert
The purpose of this study was to investigate the influence of chronological age on muscular strength, power, endurance, and quality in recreationally active women 20 to 89 years of age. One hundred and fifty-two female volunteers completed the study requirements and were divided into five-year age intervals (20 to 24, 25 to 29, 30 to 34, etc.) to 75 to 79 years, with an additional group of 80 to 89 years. Apart from the two oldest groups, each five-year interval contained at least 10 female volunteers. The participants completed physical function assessments (grip strength and vertical jump) as well as comprehensive muscle function testing of the elbow extensors and flexors, the knee extensors and flexors, and the plantar and dorsiflexors. Muscle function testing consisted of measures of maximal isometric strength and isometric rate of torque development; maximal dynamic strength and the time to achieve peak output at 60 and 240 deg/s; components of maximal muscular power such as peak power, peak velocity, and time to peak power, and time to peak velocity during isotonic contractions at 1 Nm and 20, 40, and 60% of maximal isometric strength; dynamic muscular endurance testing at a slow and fast contraction velocity (60 and 240 deg/s); and muscle quality and specific power indices were determined among the isometric, isokinetic, and isotonic assessments made relative to body composition measures. Body composition was assessed using dual energy x-ray absorptiometry (DXA), in addition to site specific measures of muscle cross-sectional area and muscle density of the upper and lower leg via peripheral computed tomography (pQCT). Age-related changes in serum levels of myostatin and interleukin 6 (IL-6) and their relationships with the included muscle characteristics were assessed. Significant age group differences were observed among many of the parameters, with some of these observations being removed when accounting for muscle mass (muscle quality/specific power). Across the force output parameters, critical ages for the onset of rate of decline occurred in the following order: dynamic strength and muscular power, muscular endurance during 240 deg/s, isometric strength/muscle quality/specific power, and latest during the muscular endurance task at 60 deg/s. Further, critical ages were detected within younger age groups for the lower body parameters when compared to the upper body parameters. Muscle groups representing different fiber type composition did not appear to influence the onset of critical changes. Location of the muscle group tended to influence the magnitude of decline since groups located distally and groups located anteriorly displayed greater decreases with increasing age. Contraction velocity also influenced age-related changes with larger declines being observed during the faster contraction conditions. Myostatin and IL-6 were positively associated with age (both p<0.05), however their relationships with muscle mass and performance were diminished when controlling for age. In summary, the influence of age on muscle function is a question that must be further qualified as many factors, namely the muscle group, contraction type, and contraction velocity/intensity each play a role. Although serum myostatin and IL-6 displayed significant relationships with age, their limited relationships with muscle characteristics hinders their ability to serve as age- and muscle-related biomarkers.
Open Access
Age-related influences on markers of inflammation and fibrinolysis.
(2007) Acree, Luke S.; Gardner, Andrew W.,; Taylor, E. Laurette,
Purpose. The primary purpose of this investigation was to determine if age is associated with blood markers of inflammation (C-reactive protein [CRP]) and fibrinolysis (fibrinogen, tissue plasminogen activator [t-PA], and plasminogen activator inhibitor - 1 [PAI-1]), independent of body fat and physical activity levels.
Open Access
ALTERATIONS OF C-MIRNA EXPRESSION FROM WHOLE-BODY VIBRATION AND RESISTANCE EXERCISE IN POSTMENOPAUSAL WOMEN
(2019-08-01) Buchanan, Samuel; Bemben, Debra; Bemben, Michael; Black, Christopher; Kellawan, Mikhail; Berkowitz, Ari
INTRODUCTION: Previous research has examined the effects of exercise on circulating miRNA (c-miRNA) expression. C-miRNAs have been associated with exercise-induced adaptations for skeletal muscle hypertrophy and aerobic capacity in humans, and angiogenesis in rats. Most studies evaluating miRNA expression post-exercise have utilized either running, cycling, or resistance training, but no studies were found where whole-body vibration was used in humans. Furthermore, evaluation of miRNAs in the context of exercise and aging is also sparse in evidence in human populations, especially postmenopausal women. Evaluating alterations in the expression of c-miRNA may provide deeper insight into the positive effects of exercise in the attenuation of the negative effects of aging. PURPOSE: The primary purpose of this study was to characterize the effects of acute bouts of resistance exercise and whole-body vibration on expression of selected c-miRNAs in postmenopausal women aged 65-85 years. The secondary purpose of this study was to determine if correlations exist between baseline c-miRNAs and muscle strength and bone characteristics. METHODS: Ten community-dwelling, postmenopausal women aged 65-85 were recruited for the study. This within-subjects randomized crossover study design compared the relative expression changes of c-miRNA from a bout of resistance exercise and a bout of whole-body vibration. Dual x-ray absorptiometry (DXA) was used to measure body composition and areal bone mineral density (BMD) of the total body, AP lumbar spine, and dual proximal femur. Peripheral quantitative computed tomography (pQCT) was used to measure volumetric values of BMD at the 4%, 38%, and 66% sites. Participants performed resistance exercises in the following order: leg press, shoulder press, lat pulldown, leg extension, and hip adduction. There were three sets of 10 repetitions per exercise at 70% of 1RM with 2-3 min of rest between sets and exercises. Participants performed vibration training on the Vibraflex Vibration Platform. Each of 5 bouts were performed for one min at a 20 Hz frequency with a 3.38 mm peak-to-peak displacement and 1 min of rest between bouts. A blood sample of 7.5 ml was collected via venipuncture by a registered phlebotomist. Baseline samples were collected between 8:00 and 9:00 a.m. after an 8h overnight fast and again immediately-post, 60 min, 24 hrs, and 48 hrs after exercise to measure c-miRNA. After each draw, two hematocrit tubes were filled from the serum separator tubes (SST) for measurement of hematocrit (HCT) and plasma volume shifts. Samples were aliquoted and frozen at -84 °C until shipped for analysis. MicroRNA quantification was performed by TAmiRNA Vienna, Austria for miR-21a-5p, -23a-3p, -133a-3p, -148a-3p. ANALYSIS: Statistical analyses were performed using IBM SPSS Statistics (SPSS Inc., Chicago, IL), version 24. Normality of dependent variables was assessed via Shapiro-Wilk tests. Non-normal distributions were assessed with the Kruskal-Wallis test and Mann-Whitney U tests. A two-way mixed-model repeated measures ANOVA [modality × time] was used to assess changes across time between the two exercise modalities. For significant modality × time interactions, one-way ANOVAs across time for each modality with Bonferroni corrections was used for post-hoc pairwise comparisons. Pearson’s r and Spearman’s rho rank correlation coefficient were utilized to determine associations between microRNAs and muscle strength and bone variables for normal and non-normal data, respectively. The alpha was set at p≤0.05. RESULTS: Nine of 10 participants were highly active based on their IPAQ scores, none presented with osteoporosis at any site, and two were considered sarcopenic based on one EWGSOP definition. There was a significant interaction for miR-21 (p=0.019) where the miRNA decreased in expression from 60p to 24h after WBV that did not occur after RE. There were also multiple negative correlations between miRNAs and bone status variables from DXA and pQCT that were logical based on miRNAs predicted targets, but those correlations did not occur on both testing days. TRAP5b concentrations significantly decreased 24h after exercise (p<0.01) even after correcting for plasma volume shifts (p<0.01). CONCLUSIONS: Both resistance exercise and WBV conditions suppressed TRAP5b concentrations by 24h. The miRNAs chosen for this study were expressed well in all participants and across testing timepoints. There was wide variability in expression and responses to exercise that may have been influenced by uncontrollable environmental factors. Though pre-exercise miRNA expression was inconsistent, the significant correlations between miRNAs that negatively affect bone and bone status that were found had the expected negative associations. TRAP5b absolute changes were not related to miRNA expression changes. Future studies investigating multiple exercise modalities should take care to control for as many environmental factors as possible.
Open Access
An evaluation of the inflammatory time course response following traditional and blood flow restriction resistance exercise measured by peripheral quantitative computed tomography
(2012) Poole, Christopher Norman Ross; Bemben, Michael
Acute muscle swelling following resistance exercise can increase mCSA when assessed by pQCT. This swelling does not reflect muscle hypertrophy, but rather a fluid shift in and around the exercised musculature that may stimulate protein synthesis. This creates a need for determining the inflammatory time course response following a bout of resistance exercise to pinpoint the earliest a pQCT scan can be performed to predict mCSA with minimal error. Furthermore, the degree of muscle swelling following traditional resistance exercise and blood flow restriction resistance exercise has yet to be compared. PURPOSE: The purpose of this investigation was to determine the time course of increased intramuscular fluid following a traditional high-intensity resistance exercise bout and a low-intensity combined with blood flow restriction resistance exercise bout. METHODS: Ten men, aged 18-30 years, completed three experimental conditions in random order separated by at least one week: traditional resistance exercise [TRE], blood flow restriction resistance exercise [BFR], and a non-exercise control [CON]. For TRE subjects completed three sets of 8-10 repetitions on leg press, leg extension, and leg curl machines at an intensity of 75%-80% 1RM with two minutes of rest allowed between sets and exercises. For BFR, subjects wore five cm wide electronically controlled elastic pressure cuffs around their upper thighs during the exercise bout at a restrictive pressure of 160 mmHg. The same three exercises were completed during BFR but at an intensity of 20% 1RM. Subjects completed 30 repetitions for their first set, followed by three sets of 15 thereafter. Rest intervals were set at 30 seconds. For TRE, subjects remained in resting state, seated for approximately 20 minutes. Prior to exercise and 15 minutes, 75 minutes, 24h, 48h, 72h, and 96h after exercise in TRE and BFR protocols, subjects underwent a pQCT scan and thigh circumference measurement. Additionally, blood samples were collected via finger prick prior to, immediately after, and 1h after exercise to assess plasma volume. Muscle thickness of the quadriceps and hamstring were determined prior to exercise and immediately, 30 min, and 1h after exercise via ultrasound. RESULTS: MTQ for BFR was significantly greater immediately post-exercise (p < 0.001) and 30 minutes post-exercise (p = 0.001) when compared to pre-exercise. MTQ for TRE was significantly greater immediately post-exercise (p = 0.010), 30 minutes post-exercise (p = 0.007), and 60 minutes post-exercise (p = 0.019) when compared to pre-exercise. MTQ for BFR was significantly greater than TRE immediately post-exercise (p = 0.016). MTH for BFR was significantly greater immediately post-exercise (p = 0.036) when compared to pre-exercise. PV%Ä significantly decreased from pre- to immediately post-exercise in both BFR (p < 0.001) and TRE (p < 0.001) conditions. In BFR, mCSA was significantly greater at 15 minutes post-exercise (p < 0.001) and 75 minutes post-exercise when compared to pre-exercise mCSA. In TRE, mCSA was significantly greater at 15 minutes post-exercise compared to pre-exercise mCSA. Thigh circumference was significantly greater at 15 minutes post-exercise in BFR (p < 0.001), TRE (p = 0.002), and CON (p = 0.016) compared to their respective pre-exercise thigh circumference values. Additionally, thigh circumference was significantly greater at 75 minutes post-exercise in BFR (p = 0.032) and TRE (p = 0.007) compared to their respective pre-exercise thigh circumference values. CONCLUSION: Muscle swelling returns to pre-exercise levels within 24 hours after completing a moderate to high volume heavy-resistance exercise bout and a low-intensity coupled with blood flow restriction resistance exercise bout.
Open Access
An examination of agonist and antagonist motor unit firing properties
(2013) DeFreitas, Jason M.; Beck, Travis W
The interactions between opposing muscle (i.e. agonist and antagonist) groups can be extremely complex, task-dependent, and are still poorly understood. To identify possible origins of the coordination between antagonistic muscle groups, the common or shared sources of neural input need to be understood. The assessment and manipulation of motor unit firing properties, such as synchronization, can provide information regarding the common inputs to opposing muscles. PURPOSE: The purpose of this study was to introduce various interventions to systematically manipulate both agonist and antagonist motor unit firing properties, and obtain a better understanding of the interactions between the two. METHODS: Muscle activity was detected from the biceps brachii ("agonist") and the triceps brachii ("antagonist") during isometric forearm flexions. The signals from these muscles were decomposed into individual motor unit action potential trains. Subsequently, various firing properties such as mean firing rate, recruitment threshold, and synchronization were calculated. On two separate visits, either the agonist or antagonist muscle was fatigued. During another two visits, either the agonist or antagonist muscle underwent 18 minutes of prolonged stretching, which has been shown to significantly desensitize proprioceptors. RESULTS: During co-activation, the antagonist demonstrated significant motor unit synchronization, but to a lesser extent when compared to the agonist. The antagonist also exhibited a substantially smaller recruitment threshold range and higher average firing rates. Fatigue of the agonist did not show any changes to antagonist motor unit firing properties, despite a significant increase in co-activation. Fatigue of the antagonists produced effects on the motor unit behavior of the agonist, such as decreased motor unit synchronization. It was suggested that group III and IV muscle afferents originating from the antagonist were responsible for the change to the agonist. The stretching interventions provided some mixed results, often providing non-uniform changes across motor unit types. For example, agonist low-threshold motor unit pairs demonstrated an increase in short-term synchronization after agonist stretching, but the high-threshold motor unit pairs exhibited a decrease in synchronization. Future studies to help answer follow-up questions were suggested.
Open Access
APPLICATION OF INTEGRATIVE BEHAVIOR MODEL TO PREDICT INITIATION OR MAINTENANCE OF STOPPING BINGE DRINKING AMONG COLLEGE STUDENTS: A PROSPECTIVE STUDY
(2017-08) Bhochhibhoya, Amir; Branscum, Paul; Crowson, Michael; Taylor, E. Laurette; Maness, Sarah; Larson, Daniel
With the heightened risk for serious social and physiological consequences, binge drinking is arguably the single most important preventable cause of morbidity and mortality among college students. The negative consequences of drinking alcohol such as violence, unprotected and unplanned sexual intercourse, injury and death from accidents significantly increases when one indulges in binge drinking. Yet, the number of drinks (9.3 drinks on each occasion) and prevalence (40%) of binge drinking, both are highest among the college-aged population. To address this health concern, there have been significant public health efforts over the past two decades, but the status of college student binge drinking has not improved. Thus, identifying additional predictive variables is warranted to enhance the effectiveness of the interventions. The purpose of this study to explore various constructs of the Integrative Behavior Model (IBM) and identify major constructs that best predicts binge drinking behavior among college students with different drinking pattern i.e. binge drinker, social drinkers, and abstainers and assist in customizing future interventions for each of these groups. This study utilized a prospective study design with two points at the interval of 30 days. The study sample included undergraduate students from a Southwestern University. A new survey was developed and utilized to understand theory-based determinants of the drinking behaviors. A pilot survey was conducted among 46 participants to evaluate the feasibility of recruitment, retention, assessment procedures, and implementation of the study. After refining the survey, the study was implemented to collect responses from 870 participants in time 1, however after eliminating incomplete data and matching responses at time 2, only 388 responses were considered for final analysis which included 161 binge drinkers, 72 social drinkers, and 155 abstainers. Results indicated certain demographic groups drank at disproportionately higher rates which suggested at-risk groups such as African Americans compared to other ethnic groups, atheist compared to participants with religious beliefs, and age group 18-20 compared to other age groups. The IBM model significantly predicted behavioral intentions towards stopping binge drinking for binge drinkers (48.1%) as well as continuing not to binge drinking for non-binge drinkers (28.2%). Further, when non-binge drinkers were categorized as social drinkers and abstainers, IBM model predicted 60.7% 6% of the intention towards continuing not to binge drinking for social drinkers and abstainers respectively. IBM model also significantly predicted 16.6% of the drinking behavior for binge drinkers and 14.8% for non-binge drinkers. In conclusion, the current study shows promising application of IBM in predicting and explaining binge drinking behavior among college students and furnish with the predictive factors to design effective interventions. Further, this study highlighted the need for customizing interventions based on students drinking behavior i.e. binge drinkers, social drinkers, and abstainers. This study also suggested the need to redefining few aspects of the IBM in the future studies as two components model resulted more effective than one component model for measuring attitudes, perceived norms, and perceived behavioral control. Future research needs to be conducted to determine the efficacy of the IBM for other populations, settings and health behaviors.
Open Access
Associations between Young Adult and Parent Religiosity and Young Adult Mental Health
(2017-08-01) Gwin, Shannon; Taylor, Laurette; Cheney, Marshall; Branscum, Paul; Frey, Melissa; Zhang, Ying; Maness, Sarah
Purpose: The purpose of this study was to examine the relationship between religiosity in young adults and mental health outcomes that include depressive symptoms and suicide ideation, and to examine associations between religious concordance/discordance in young adult/parent pairs and mental health outcomes including depressive symptoms and suicide ideation in a young adult sample. Young adult assets (i.e., relationship with mom, relationship with dad) were also examined to establish influential aspects with the relationship between religiosity and mental health outcomes. Methods: Self-reported data was collected from young adults aged 18 – 24 years and a parent counterpart during Spring 2017. A 15-minute computer-based survey was administered to young adult and parent pairs in a southwestern state. Recruitment was conducted on college and university campuses. Flyers, newsletters, word-of-mouth marketing, web listings (i.e., Facebook, organizational web pages), mass emails, and in-class recruitment was used. Participants were given the link to survey via email, text, phone calls or face-to-face in the classroom per permission of instructor/professor and approval of college/university IRB approval. The PI requested the young adult to forward the parent survey link to one of their parents via email, text, phone call or face-to-face so that the parent can complete the survey. English version was the only translation provided for the survey. All stored data was anonymous. Results: This dissertation encompasses three studies involving relationships between religiosity factors and mental health outcomes in emerging adults. Study 1: The first study examines associations between individual religious beliefs and depressive symptoms and suicide ideation in young adults. Findings suggest significant inverse associations (alpha=0.05) between religious variables and reported depressive symptoms during the last week in young adults. Additionally, higher scores of religiosity subscales were significantly associated with fewer reports of suicide ideation in the last 12 months. Study 2: The second study examines associations between religious concordance/discordance between young adults and their parent counterparts and depressive symptoms. Findings suggest significant inverse associations between Concordance/Discordance for non-organizational religiosity (e.g. private prayer time, Bible study, or meditation) and depressive symptoms in young adults (p=0.0015). Other variables that displayed significant relationships include gender (p=0.0027) and the relationships with mom (p=0.0075) and dad (p=0.0013). Study 3: The third study investigates associations between religious concordance/discordance (C/D) between young adults and their parent counterparts and suicide ideation. There were no significant associations were found between C/D religious variables and suicide ideation. Global Conclusions and Recommendations: With the exception of study 3, overall religiosity beliefs and practices appear to be associated with fewer depressive symptoms and suicide ideation. Inclusion of religious programs may be important to incorporate in emerging adult mental health programming. Future recommendations are discussed. Key words: Emerging adults, religiosity, mental health, depression, suicide
Open Access
Bilateral Fatigue of the Anterior Tibialis in Individuals with Multiple Sclerosis
(2017-08) Lantis, David; Larson, Rebecca; Bemben, Debra; Black, Christopher; Larson, Daniel; Williams, T.H. Lee
Multiple sclerosis (MS) is one of the most common progressive neurological diseases in young adults and is characterized by neurologic disruption within the central nervous system. Fatigue has been reported as one of the most debilitating symptoms in MS patients. Due to limited ankle mobility in MS patients during walking, investigating potential relationships between dorsiflexion strength asymmetry (SA) and walking ability is necessary to better understand the impact on quality of life in MS patients. PURPOSE: To investigate bilateral differences in strength and fatigability during isometric/isokinetic dorsiflexion in MS patients, and determine the relationship between SA and functional performance. Methods: 13 MS patients (MS Group: 8 females, 5 males) and 13 individuals without MS (NON-MS: 8 females, 5 males) participated in the current study. Maximal isometric and isokinetic contractions were conducted to determine peak torque (PT) and other muscle performance variables (voluntary contraction time (VCT), time-rate of muscle tension development (TRTD), and muscle tension-maintaining capacity (MTMC)). Subjects also performed fatiguing isometric and isokinetic exercise on separate days, and fatigability recovery was measured to investigate the effect of fatigue on PT and the muscle performance variables. Functional performance tests were conducted determine the relationship between isometric/isokinetic SA and walking ability. RESULTS: The MS group exhibited significant limb-limb PT differences during isometric (p = 0.01) and all isokinetic contraction speeds (p < 0.02) maximal contractions. The MS group also exhibited significantly greater SA than the NON-MS group (p = 0.03). There were no significant limb-limb differences or between group differences during the fatiguing tests. There were significant limb differences in PT before the isometric and isokinetic fatigue tests (p = 0.03, < 0.001 respectively) and after two minutes of recovery (p = 0.04, 0.002 respectively) in the MS group. The MS group exhibited lower performance in the functional performance tests, and there was a strong relationship between isometric/isokinetic SA and walking ability. CONCLUSION: There are no bilateral differences in fatigability in MS patients; however there are bilateral strength differences in dorsiflexion PT in MS patients. Dorsiflexion SA in MS patients is greater than in individuals without MS, and the dorsiflexion SA in MS patients has a strong relationship with walking performance.
Open Access
Bone and Muscle Specific Circulating MicroRNAs in Postmenopausal Women based on Osteoporosis and Sarcopenia Status
(2017-05-12) Chen, Zhaojing; Bemben, Debra; Bemben, Michael; Larson, Rebecca; Knehans, Allen; Knapp, Rosemary
MicroRNAs (miRNAs) are short, non-coding RNA molecules that fine tune posttranscriptional protein expression. Aging is accompanied by progressive declines in muscle mass and strength, and in bone mineral density (BMD). Although miRNAs in pathology have been extensively studied, the role of circulating miRNAs (c-miRNAs) in osteoporosis and sarcopenia has to date not been well studied. Purposes: 1) To identify specific c-miRNAs that are associated with bone and muscle status in postmenopausal women and to evaluate the use of these c-miRNAs as biomarkers of osteoporosis and sarcopenia; and 2) to determine the associations between specific c-miRNAs and muscle and bone variables. Methods: Seventy-five postmenopausal women aged 60 to 85 years old participated in this study. Body composition and areal BMD (aBMD) were measured by DXA. Volumetric BMD (vBMD) and bone strength were measured by pQCT. Muscle performance tests, including grip strength, gait speed, and countermovement jumps, were assessed. Bone status was classified based on aBMD T-scores: Osteopenia (-2.5 ≤ aBMD T-score ≤ -1) and osteoporosis (aBMD T-score ≤ -2.5). Two sets of criteria were used to classify sarcopenia status: 1) skeletal muscle mass index (SMI) < 5.5 kg/m2; and 2) SMI < 5.5 kg/m2 and low muscle strength (grip strength < 20 kg) or low gait speed (<0.8 m/s). Levels of c-miRNAs (miR-1, -21, -23a, -24, -100, -125b, -133a, -206) were analyzed using real-time PCR, and bone turnover markers were analyzed by enzyme-linked immunosorbent assay (ELISA). Results: There was no significant association between sarcopenia and osteopenia status in postmenopausal women. The sarco-osteopenia group had significantly lower body weight, jump power, and muscle CSA at 66% of the tibia than the normal and osteopenia groups (p < 0.05). Statistically, there were no significant differences in specific c-miRNAs based on sarcopenia and osteoporosis status. However, fold changes of miR-21 (FC=2.59) and -23a (FC=2.09) indicated upregulation and miR-125b (FC=0.46) indicated downregulation. The relative expression level of miR-125b was significantly negatively correlated with age (p < 0.05). The relative expression level of miR-21 was significantly negatively correlated with trochanter BMC and cortical vBMD at tibia 38% site (p < 0.05). Furthermore, the relative expression level of miR-23a was significantly positively correlated with TRAP5b levels (p < 0.05). Conclusion: There were no statistical differences in target circulating miRNAs (miR-1, -21, -23a, -24, -100, -125b, -133a, -206) based on bone and muscle status in postmenopausal women. However, fold changes of circulating miR-21, -23a, -125b indicated biological differential expression. Other circulating miRNAs need to be studied in the future.
Open Access
Cardiovascular and Muscular Responses to Eight Weeks of Resistance Exercise Training in Young and Older Women
(2013) Rossow, Linda Marie; Bemben, Michael
PURPOSE: Resistance training is recommended for all adults of both sexes. The time-course of muscle hypertrophy in young and older women and the arterial stiffness and limb blood flow responses to resistance exercise in young and older women remain to be elucidated. The purpose of this study was to examine the time-course of muscle hypertrophy in young and older women following high-intensity resistance exercise training as well as to examine arterial stiffness and blood flow responses in young and older women to high-intensity resistance exercise training. METHODS: Young (aged 18-25) and older (aged 50-64) women performed full-body high-intensity resistance exercise three times per week for eight weeks. This exercise was performed on six different exercise machines: leg press, chest press, leg extension, shoulder press, leg curl, and lat pull-down. Exercises were alternated so that two lower body exercises or two upper body exercises were never performed together. As the exercise program was meant to be of a high-intensity, subjects began lifting at 80% of their one repetition maximum and training progressed by having subjects perform three sets with ten repetitions performed in the first two sets and the last set being performed to "failure" which was defined as the inability to complete another repetition with good form. All exercise was supervised and performed in the laboratory. At two time points approximately three weeks apart, prior to training, measurements were performed as a control period and no exercise was performed between these measurements. A single post-testing measurement was performed following training. At these three measurement time-points, the following measurements were performed: ultrasound muscle and fat thicknesses at eight body sites (50% and 70% thigh and hamstring, subscapular, chest, deltoid, and -fat only- visceral), thigh circumference, four 50% thigh skin-folds (anterior, posterior, lateral, and medial), whole body dual energy x-ray absorptiometry, carotid to femoral and femoral to tibialis posterior pulse wave velocity, blood pressure, heart rate, resting forearm blood flow, forearm reactive hyperemia, and two functional assessments (an upper and a lower body questionnaire) were performed. Additionally, once every week, the aforementioned ultrasound assessments of muscle and fat at seven and eight sites (respectively), thigh circumference assessment, and four thigh skinfolds were performed. Also, once every two weeks, strength was assessed on each machine by one repetition maximum. Upper body strength was assessed on the second training day of the week and lower body strength was assessed on the third training day of the week. Data was analyzed with ANOVAs and post-hoc t-tests. Alpha was set at p<0.05. Pre values were averaged and the average was used for subsequent analysis if no difference between these values was found. RESULTS: Muscle thickness for all muscles, except at the subscapular site, was found to increase significantly (p<0.05) over time. The first increase in muscle thickness was seen at the 50% quadriceps, 50% hamstrings, 70% hamstrings, and deltoid sites followed by the 70% quadriceps and chest sites. Group differences (p<0.05) were found for the 70% hamstring site only. Carotid-femoral pulse wave velocity showed a significant (p<0.05) group effect only with older subjects having a higher carotid-femoral pulse wave velocity than younger subjects. No significant (p<0.05) effects were found for femoral-tibialis posterior pulse wave velocity or for resting forearm blood flow. A significant (p<0.05) interaction was found for peak forearm blood flow. Total hyperemia increased significantly (p<0.05). Total body mass (kg), total % fat, leg % fat, bone-free lean mass of the arms (kg), bone-free lean mass of the legs (kg), functional scores, and strength all increased significantly (p<0.05) over time. Fat thickness decreased significantly (p<0.05) over time at all sites except the chest and subscapular sites. CONCLUSION: In conclusion, an increase in muscle thickness occurred early in training and followed a similar progression in both groups of women. Thus, young and older women had similar muscular responses to the training. Also, eight weeks of high-intensity resistance training improved microvascular forearm function while not changing carotid-femoral or femoral-tibialis posterior arterial stiffness. These vascular responses to training were the same for young and older women with the exception of the greater peak forearm blood flow (non nitric-oxide dependent) response in the older compared to the young women.