| dc.description.abstract | 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. | en_US |
