Resistance exercise can attenuate muscular impairments associated with multiple sclerosis (MS), and blood flow restriction (BFR) may provide a viable alternative to prescribing heavy training loads. The purpose of this investigation was to examine the progression of upper and lower body low-load (30

BFR) applied during sprint interval training (SIT) on performance and neuromuscular function. METHODS:Fifteen men completed a randomized bout of SIT with CBFR, IBFR, and without BFR (No-BFR), consisting of 2, 30-s maximal sprints on a cycle ergometer with a resistance of 7.5% of body mass. Concentric peak torque (CPT), maximal voluntary isometric contraction (MVIC) torque, and muscle thickness (MT) were measured before and after SIT, including surface electromyography (sEMG) recorded during the strength assessments. Peak and mean revolutions per minute (RPM) were measured during SIT and power output was examined relative to physical working capacity at the fatigue threshold (PWCFT). RESULTS:CPT and MVIC torque decreased from pre-SIT (220.3±47.6 Nm and 355.1±72.5 Nm, respectively) to post-SIT (147.9±27.7 Nm and 252.2±45.5 Nm, respectively, all P<0.05), while MT increased (1.77±0.31 cm to 1.96±0.30 cm). sEMG mean power frequency decreased during CPT (-12.8±10.5%) and MVIC (-8.7±10.2%) muscle actions. %PWCFT was greater during No-BFR (414.2±121.9%) than CBFR (375.9±121.9%). CONCLUSION:SIT with or without BFR induced comparable alterations in neuromuscular fatigue and sprint performance across all conditions, without affecting neuromuscular function.

To investigate the effects of blood flow restriction (BFR) on electromyographic amplitude (EMGRMS)–force relationships of the biceps brachii (BB) during a single high-load muscle action. Twelve recreationally active males and eleven recreationally active females performed maximal voluntary contractions (MVCs), followed by an isometric trapezoidal muscle action of the elbow flexors at 70

Lubiak, SM, Lawson, JE, Gonzalez Rojas, DH, Proppe, CE, Rivera, PM, Hammer, SM, Trevino, MA, Dinyer-McNeely, TK, Montgomery, TR, Olmos, AA, Sears, KN, Bergstrom, HC, Succi, PJ, Keller, JL, and Hill, EC. A moderate blood flow restriction pressure does not affect maximal strength or neuromuscular responses. J Strength Cond Res 38(12): e727-e734, 2024-The purpose of this study was to examine the acute effects of blood flow restriction (BFR) applied at 60% of total arterial occlusion pressure (AOP) on maximal strength. Eleven college-aged female subjects completed two testing sessions of maximal unilateral concentric, isometric, and eccentric leg extension muscle actions performed with and without BFR. Separate 3 (mode [isometric, concentric, eccentric]) x 2 (condition [BFR, no BFR]) x 2 (visit [2, 3]) repeated-measures analysis of variances were used to examine mean differences in maximal strength, neuromuscular function, rating of perceived exertion (RPE), and pain. For maximal strength (collapsed across condition and visit), isometric (128.5 +/- 22.7 Nm) and eccentric (114.5 +/- 35.4 Nm) strength were greater than concentric maximal strength (89.3 +/- 22.3 Nm) (p < 0.001-0.041). Muscle excitation relative (%) to isometric non-BFR was greater during the concentric (108.6 +/- 31.5%) than during the eccentric (86.7 +/- 29.2%) (p = 0.045) assessments but not different than isometric (93.4 +/- 17.9%) (p = 0.109) assessments, collapsed across condition and visit. For RPE, there was an interaction such that RPE was greater during non-BFR (4.3 +/- 1.7) than during BFR (3.7 +/- 1.7) (p = 0.031) during the maximal concentric strength assessments. Furthermore, during maximal strength assessments performed with BFR, isometric RPE (5.8 +/- 1.9) was greater than concentric (3.7 +/- 1.7) (p = 0.005) and eccentric (4.6 +/- 1.9) (p = 0.009) RPE. Finally, pain was greater during the isometric (2.8 +/- 2.1 au) than during the concentric (1.8 +/- 1.5 au) (p = 0.016), but not eccentric, maximal strength assessments (2.1 +/- 1.6 au) (p = 0.126), collapsed across condition and visit. The application of BFR at 60% AOP did not affect concentric, isometric, or eccentric maximal strength or neuromuscular function. Trainers, clinicians, and researchers can prescribe exercise interventions relative to a restricted (when using a moderate AOP) or nonrestricted assessment of maximal strength.

Objective. Surface mechanomyography (sMMG) can measure oscillations of the activated muscle fibers in three axes (i.e.X,Y, andZ-axes) and has been used to describe motor unit activation patterns (X-axis). The application of blood flow restriction (BFR) is common in exercise studies, but the cuff may restrict muscle fiber oscillations. Therefore, the purpose of this investigation was to examine the acute effects of submaximal, fatiguing exercise with and without BFR on sMMG amplitude in theX,Y, andZ-axes among female participants.Approach. Sixteen females (21 ± 1 years) performed two separate exercise bouts to volitional exhaustion that consisted of unilateral, submaximal (50% maximal voluntary isometric contraction [MVIC]) intermittent, isometric, leg extensions with and without BFR. sMMG was recorded and examined across percent time to exhaustion (%TTE) in 20% increments. Separate 2-way repeated measures ANOVA models were constructed: (condition [BFR, non-BFR]) × (time [20, 40, 60, 80, and 100% TTE]) to examine absolute (m·s-2) and normalized (% of pretest MVIC) sMMG amplitude in theX-(sMMG-X),Y-(sMMG-Y), andZ-(sMMG-Z) axes.Main results. The absolute sMMG-X amplitude responses were attenuated with the application of BFR (mean ± SD = 0.236 ± 0.138 m·s-2) relative to non-BFR (0.366 ± 0.199 m·s-2, collapsed across time) and for sMMG-Y amplitude at 60%-100% of TTE (BFR range = 0.213-0.232 m·s-2versus non-BFR = 0.313-0.445 m·s-2). Normalizing sMMG to pretest MVIC removed most, but not all the attenuation which was still evident for sMMG-Y amplitude at 100% of TTE between BFR (72.9 ± 47.2%) and non-BFR (98.9 ± 53.1%). Interestingly, sMMG-Z amplitude was not affected by the application of BFR and progressively decreased across %TTE (0.332 ± 0.167 m·s-2to 0.219 ± 0.104 m·s-2, collapsed across condition.)Significance. The application of BFR attenuated sMMG-X and sMMG-Y amplitude, although normalizing sMMG removed most of this attenuation. Unlike theXandY-axes, sMMG-Z amplitude was not affected by BFR and progressively decreased across each exercise bout potentially tracking the development of muscle fatigue.

PURPOSE: Resistance exercise with blood flow restriction (BFR) has been shown to elicit positive muscular adaptation but less is known regarding the neuromuscular recruitment patterns following exercise. Therefore, the purpose of this investigation was to assess fatigue and neuromuscular recruitment patterns with and without BFR exercise. METHODS: Twelve women (21 ± 1 years, 66.4 ± 10.1 kg, 166.3 ± 7.5 cm) completed intermittent (duty cycle 5:3 s) isometric leg extensions to failure at 50% of maximal voluntary isometric contractions (MVIC) with and without BFR (60% of total arterial occlusion pressure). Pre- and post-exercise MVICs and trapezoidal contractions at 60% and 80% of MVIC were completed while surface electromyography (EMG) was recorded. The EMG signals were decomposed and a linear regression model was fitted to the mean firing rate vs. recruitment threshold relationships to determine the slopes and y-intercepts. Repetitions to failure were analyzed using a paired samples t-test. MVIC peak torque as well as slopes and y-intercepts during the 60% and 80% trapezoidals were analyzed separately using 2 (Condition [BFR, non-BFR]) x 2 (Time [pre-exercise, post-exercise]) repeated measures ANOVAs. RESULTS: Repetitions to failure were similar (p = 0.070) between BFR (20.3 ± 8.3) and non-BFR (25.7 ± 15.4). MVIC peak torque decreased from pre- (203.1 ± 60.0 Nm) to post-exercise (143.6 ± 36.9 Nm) with no significant (p = 0.323) main effect for Group or interaction (p = 0.068). There were also no significant interactions (p = 0.062 - 0.992) or main effects for Group (p = 0.266-0.903) or Time (p = 0.205 - 0.944) for slopes or y-intercepts during the 60% or 80% trapezoidals. CONCLUSION: The intermittent, isometric protocol elicited comparable muscle fatigue with and without BFR when performed at moderate load. Additionally, isometric muscle fatigue with and without BFR did not affect the motor unit characteristics.

Exercise-induced hypoalgesia (EIH) is the acute pain reduction post-exercise. Typically, high-intensity and/or long-duration exercise is required to elicit EIH. Alternatively, low-load resistance exercise with blood flow restriction (LL+BFR) may elicit EIH. However, there is conflicting evidence regarding the necessary repetitions and volume load. This study evaluated EIH after 75-repetitions (1×30, 3×15) (BFR-75) and four sets to volitional failure (BFR-F) protocols. Twenty-six participants completed unilateral knee extensions at 30% of maximal strength using a BFR-75 and BFR-F protocol. Pain pressure threshold (PPT) of the rectus femoris was assessed before and after exercise. Repetitions completed, volume load, occlusion time, and PPT were analyzed. Participants completed more repetitions (91.4±30.5), volume load (5,204.9±2,367.0 Nm), and had a longer occlusion time (345.8±76.2 seconds) during BFR-F compared to BFR-75 (73.2±3.7 repetitions, 4,451.1±1,498.1 Nm, 300.5±52.2 seconds, respectively). Collapsed across sex, PPT increased from pre- (3.24±1.91 kgf) to post-exercise (3.76±2.27 kgf) for BFR-F but not BFR-75 (3.51±1.67 to 3.68±2.04 kgf). The results indicated that BFR-F, but not BFR-75, elicited EIH, as assessed by an increase in PPT. Lower loads used during LL+BFR may be a clinically relevant alternative to high-intensity and/or long-duration exercise in populations that may not tolerate high-intensity or prolonged exercise to induce EIH.

PURPOSE: The purpose of this study was to assess the chronic effects of low-load blood flow restriction (LLBFR) and traditional (TRAD) resistance training on exercise load (Load) and ratings of perceived exertion (RPE) among women living with relapsing remitting multiple sclerosis (RRMS). METHODS: Six women (36.8 ± 14.5 yrs) with RRMS volunteered to participate in this study and were randomly assigned to LLBFR (n = 3) or TRAD (n = 3). Training involved three upper (chest press [CP], shoulder press, seated row) and lower body (leg press, leg extension [LE], leg curl) exercises performed 2x/wk for 12 wks. LLBFR performed 72 ± 3 reps at 30% estimated one-repetition maximum (1RM) with BFR pressure at 60% of total arterial occlusion pressure and TRAD performed 36 ± 3 reps at 65% of 1RM. Load was increased progressively and RPE was acquired after every set. Each training day Load and RPE were averaged across 4 sets and across each 2-wk training period (4 days) for LE and CP (other exercises excluded in this abstract for simplicity). Thus, for CP and LE, 6 separate data points across the 12 wk intervention were derived for Load, RPE, and Load/RPE (Load per unit of RPE) and examined using separate 2(Group [LLBFR, TRAD]) × 6 (Time [6, 2-wk periods]) mixed factorial repeated measures ANOVAs. RESULTS: For CP, there were no significant interactions or main effects for Group (p = 0.441-0.892). There were, however, significant main effects for Time for Load (p < 0.001 - 0.034) that increased progressively from baseline (32.0 ± 16.8 lbs) to Wk 4 (38.3 ± 15.1 lbs), Wk 6 (41.7 ± 15.3 lbs), Wk 8 (43.2 ± 18.5 lbs), Wk 10 (48.5 ± 17.4 lbs), and Wk 12 (50.7 ± 20.0 lbs), and for RPE (p = 0.022 - 0.046) that increased progressively from baseline (5.2 ± 1.3) to Wk 4 (6.4 ± 1.6), Wk 6 (6.8 ± 1.4), Wk 8 (7.0 ± 1.0), and Wk 10 (7.6 ± 1.1). For LE, there were no significant interactions or main effects for Time (p = 0.086-0.725). There was, however, a significant (p < 0.001) main effect for Group for Load/RPE (LLBFR [9.4 ± 0.7] < TRAD [15.8 ± 1.0]), but not for Load (p = 0.216) or RPE (p = 0.409). CONCLUSIONS: Resistance training increased Load for CP, but not LE. Furthermore, there was no difference in RPE between LLBFR and TRAD, but greater Load was achieved per unit of RPE during LE for TRAD versus LLBFR. Thus, LLBFR and TRAD may induce different perceptions of effort between upper and lower body exercise.

OBJECTIVES:The purpose of this investigation was to examine the acute effects of low-load blood flow restriction (LLBFR) and low-load (LL) resistance exercise on muscle excitation, neuromuscular efficiency, and average torque.METHODS:Eleven men (age±SD=22±3yrs) randomly performed LLBFR and LL that consisted of 30 unilateral leg extensions at 30% of one-repetition maximum while surface electromyography (sEMG) and torque were simultaneously assessed. Polynomial regression analyses and slope comparisons were performed to examine patterns of responses and rates of change.RESULTS:sEMG amplitude increased for LLBFR (9 of 11) and LL (8 of 11) and between composite responses (R2=0.939-0.981). For LLBFR, sEMG amplitude increased to a greater extent for 5 of the 11 individual and for the composite responses. Similarly, neuromuscular efficiency decreased for LLBFR (8 of 11) and LL (5 of 11) as well as the composite responses r2=0.902-0.929, but the decrease was larger for LLBFR than LL for the individual (4 of 11) responses. For average submaximal concentric torque, there were individual increases, decreases, and no changes for the composite responses (R2=0.198-0.325).CONCLUSION:LLBFR elicited greater fatigue-induced increases in muscle excitation and decreases in neuromuscular efficiency than LL, but neither LLBFR nor LL affected average submaximal concentric torque.