Central and peripheral fatigue indices following resistance exercise with and without blood flow restriction among people with multiple sclerosis

Muscle fatigue is a prevalent and challenging symptom in people with multiple sclerosis (PwMS), typically involving pronounced central (e.g., reduced corticospinal excitability) and relatively lower peripheral contributions (e.g., metabolic stress) compared with healthy controls. Blood flow restriction (BFR) applied during resistance exercise is an innovative approach to facilitate exercise benefits among PwMS. Therefore, the purpose of this investigation was to examine how distinct resistance exercise approaches including low-load (LL), LL with blood flow restriction (LLBFR), and high-load (HL) affect central and peripheral fatigue when applied in a clinically relevant, real-world context. Twelve females (42 ± 12 yr) and three males (41 ± 10 yr) with MS performed unilateral leg extensions with a HL [3 × 12 at 70% of one repetition maximum (1RM)], LL (1 × 30, 3 × 15 at 30% 1RM), and LLBFR (LL with 60% limb occlusion pressure). Prior to and immediately after each exercise bout, maximal voluntary isometric contraction (MVIC) torque and indices of central [surface electromyographic (sEMG) amplitude, superimposed twitch torque (STT), V_WAVE/M_WAVE] and peripheral [potentiated twitch torque (PTT)] fatigue were assessed. There were similar acute decreases in MVIC torque (-21.0% relative to baseline; <i>P</i> < 0.001, <i>g</i> = 1.486), but exercise-specific decreases in PTT between LLBFR (-37.1%; <i>P</i> < 0.001, <i>g</i> = 1.135) and HL (-14.2%; <i>P</i> = 0.093, <i>g</i> = 0.440). STT increased (+24.5%, <i>P</i> = 0.018, <i>g</i> = 0.650), whereas there were decreases in sEMG amplitude (-9.7%; <i>P</i> = 0.004, <i>g</i> = 0.852) and V_WAVE/M_WAVE (-7.9%; <i>P</i> < 0.001, <i>g</i> = 1.037) that were not different among conditions. LLBFR may represent a more effective resistance exercise strategy for PwMS due to its ability to induce greater peripheral fatigue, a proxy for metabolic stress.<b>NEW & NOTEWORTHY</b> Low-load resistance exercise with blood flow restriction (LLBFR) uniquely elevates peripheral fatigue in people with multiple sclerosis (PwMS), a population which typically experiences increased central fatigue mechanisms. Although high- and low-load protocols evoked mixed central and peripheral fatigue, LLBFR was distinctly associated with peripheral fatigue potentially reflecting the metabolite trapping provoked by the occlusive stimulus. These findings suggest that low-load resistance exercise, particularly LLBFR, may provide innovative strategies to enhance exercise efficacy in PwMS.