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

The purpose of this investigation was to examine muscle excitation at maximal running capacity without blood flow restriction (BFR) relative to submaximal running bouts with BFR. Fourteen college-aged males randomly completed four, three-minute running bouts at 70, 80, and 90% of peak speed with BFR (70% BFR , 80% BFR , and 90% BFR ) and without BFR at 100% of their peak speed (100% NOBFR ). The surface electromyographic amplitudes of the vastus lateralis, rectus femoris, and vastus medialis muscles were assessed. Muscle excitation of the vastus lateralis was similar across most bouts; however, it was lower during the 70% BFR compared to 90% BFR (Meandiff =-4.67 +/-- 0.22%; Bayesian 95% high-density interval [HDI]: - 7.07 to - 2.2) and 100% NOBFR (Meandiff =-2.94 +/-- 0.27%; 95% HDI:-5.33 to-0.50) bouts. For the rectus femoris, muscle excitation largely increased across running speeds (70% BFR <80% BFR < 90% BFR ; 90% BFR < 100% NOBFR ). For the vastus medialis, muscle excitation was lower during the 70% BFR compared to 90% BFR (Meandiff =-8.15 +/-- 0.28%; 95% HDI:-15.3 to-0.89). Submaximal running with BFR increased muscle excitation responses for the vastus lateralis and vastus medialis, such that muscle excitation was similar to 100% BFR , despite 10-20% reductions in running speed. The rectus femoris muscle, however, was not affected by BFR during the submaximal running bouts.

ABSTRACT:Lubiak, SM, Proppe, CE, Rivera, PM, Howard, MA, Prajapati, AJ, Shah, NM, Patel, NN, Hammer, SM, Trevino, MA, Dinyer-McNeely, TK, Richardson, LD, Roth, BL, Zak, RB, and Hill, EC. Acute effects of running and blood flow restriction on gas exchange and perceptual responses. J Strength Cond Res 39(3): e436-e443, 2025-The purpose of this investigation was to examine gas exchange and perceptual responses during discrete running bouts performed at different peak running speeds with and without blood flow restriction (BFR). Twelve college-aged male subjects randomly performed four, 3-minute running bouts at 70%BFR, 80%BFR, and 90%BFR of their running speed at peak V̇o2 with BFR (applied bilaterally and most proximally on each leg) at 40% of total arterial occlusion pressure and 100%NOBFR of their running speed at peak V̇o2 without BFR. Separate 2-way, 4 (Speed [70%BFR, 80%BFR, 90%BFR, and 100%NOBFR]) × 3 (Time [120, 150, and 180 seconds]), Bayesian repeated-measure models were performed to examine differences in oxygen consumption (V̇o2), carbon dioxide production (V̇co2), and minute ventilation (V̇E) as well as ratings of perceived exertion (RPE) and pain. V̇o2, V̇co2, and V̇E increased across running speeds and was similar between the 90%BFR and 100%NOBFR speeds for V̇o2 (Meandiff = -1.49 ± 0.003 ml·kg-1·min-1; 95% HDI: -4.8 to 1.8) and V̇E (Meandiff = -6.97 ± 0.65 L·min-1; 95% HDI: -16.5 to 2.52). Ratings of perceived exertion was highest during the 90%BFR and 100%NOBFR speeds (90%BFR and 100%NOBFR > 80%BFR > 70%BFR), whereas pain was greater during the 90%BFR speed relative to the 70%BFR (Meandiff = -1.31 ± -0.20 au; 95% HDI: -2.63 to -0.0165) and 100%NOBFR (Meandiff = 1.3 ± 0.26 au; 95% HDI: 0.01-2.56) speeds. Applying BFR during 90%BFR of peak running speed induced comparable V̇o2 and V̇E responses as 100%NOBFR but was not associated with lower RPE and provoked more pain. Collectively, BFR exhibits a small, potentially negligible effect on gas exchange, which were largely speed dependent. Coaches and practitioners may consider treadmill running with BFR when reductions in exercise intensity are warranted.

BACKGROUND: There is conflicting evidence regarding the presence and magnitude of exercise-induced muscle damage (EIMD) following low-load resistance training with blood flow restriction (LL+BFR), which may be related to the protocol implemented or exercise volume. Therefore, the purpose of this investigation was to examine the effects of a 75 repetition (BFR-75) (1x30, 3x15) and four sets to volitional failure (BFR-4x) protocols on indices of EIMD among untrained men. METHODS: Twelve males with no history of lower-body resistance training during the previous six months volunteered for this investigation. One leg was randomly assigned to BFR-75, and the other to BFR-4x. Participants performed isokinetic, unilateral, concentric-eccentric, leg extension muscle actions at 30% of maximal strength with BFR. Indices of EIMD (limb circumference, perceived muscle soreness, pain pressure threshold [PPT], passive range of motion, and maximal strength [MVIC]) were recorded before exercise and 0, 24, 48, 72, and 96-hours post-exercise for each protocol. RESULTS: There were no significant changes (P>0.05) in limb circumference, PPT, passive range of motion, or MVIC. For both BFR-75 and BFR-4x, perceived muscle soreness increased (P<0.001) similarly 24- (2.5 +/- 1.7 AU) and 48-hours (1.9 +/- 1.7 AU) post-exercise. CONCLUSIONS: There was an increase in muscle soreness 24-48 hours post-exercise for both conditions, which may be due to metabolic stress, but this did not affect the force-generating capacity of the muscle (MVIC), suggesting minimal EIMD. The conflicting evidence of EIMD following LL+BFR may be related to differences in restriction time or overall exercise time.

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.

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: There is conflicting evidence related to the prevalence and magnitude of exercise-induced muscle damage (EIMD) following four sets to volitional failure with BFR (BFR-F) or 75 total repetitions with BFR (1 x 30, 3 x 15, BFR-75). The purpose of this investigation was to examine muscle swelling, peak torque, and neuromuscular responses following BFR-75 and BFR-F. Methods: Thirteen untrained women completed unilateral isokinetic (120 degrees s-1) leg extensions concentric-eccentric at 30% of their maximal voluntary isometric contraction (MVIC) using BFR-75 and BFR-F protocols, separated by 15 minutes. Ultrasound was used to assess muscle thickness, cross sectional area, and echo intensity of the rectus femoris and vastus lateralis before, 0-, 24-, 48-, 72-, and 96-hours post-exercise. Peak torque and surface electromyography (sEMG) were recorded during MVICs before, 24-, 48-, 72-, and 96-hours post-exercise to determine sEMG amplitude, frequency, and neuromuscular efficiency. Results: There were no differences between conditions. Collapsed across conditions, muscle thickness and cross-sectional area increased at 0-hours for the rectus femoris (2.5 +/- 0.4, 2.8 +/- 0.4 cm, 10.6 +/- 1.8, 12.1 +/- 1.8 cm2, respectively) and vastus lateralis (2.1 +/- 0.5, 2.5 +/- 0.7 cm; 22.2 +/- 3.9, 25.1 +/- 4.5 cm2, respectively), but returned to baseline at 24-hours. There were no changes in echo intensity, sEMG amplitude, sEMG frequency, or neuromuscular efficiency. MVIC peak torque increased relative to pre-exercise at 24-, 48-, 72-, and 96-hours (159.9 +/- 34.9, 171.4 +/- 30.1-179.1 +/- 35.6 Nm). Conclusion: These results suggest that BFR-75 and BFR-F did not cause EIMD but caused an acute increase in muscle swelling that returned to baseline 24-hours post-exercise.

The purpose of this investigation was to examine neuromuscular function, muscle fatigue, rating of perceived exertion (RPE), and muscle swelling between isokinetic and isotonic leg extensions with blood flow restriction (BFR). Fourteen (21 ± 2years; 160cm ± 3.8; 61kg ± 9.1) trained women performed 75 (1 × 30,3 × 15) submaximal (30% of maximal strength), unilateral, isokinetic and isotonic leg extensions with BFR (60% of total arterial occlusion pressure). Before and after exercise, subjects performed maximal voluntary isometric contractions (MVIC) and muscle thickness (MT) was assessed with ultrasound. RPE was recorded across all sets and surface electromyography (EMG) was assessed during the MVIC muscle actions. Separate repeated measures ANOVAs were used to examine MVIC, MT, RPE and neuromuscular function. There were greater reductions in MVIC torque and EMG mean power frequency following isotonic (46.2 ± 17.1%; 16.4 ± 7.9%) than isokinetic (17.9 ± 10.9%;6.5 ± 6.3%). RPE was also higher during isotonic (7.5 ± 2.2), than isokinetic (5.7 ± 1.9). There were no differences in EMG amplitude or MT increases (20 ± 2.1%) between conditions. Isotonic BFR elicited greater fatigue-induced decreases in muscular strength and greater RPE than isokinetic BFR, but similar MT and muscle excitation responses for both conditions. Therefore, both isokinetic and isotonic may induce similar acute physiological responses, but isotonic BFR was associated with greater muscle fatigue and perceived effort.HighlightsExercise modality affects the fatigue and perceptual responses when applying blood flow restriction.Despite greater utility, isotonic blood flow restriction was associated greater fatigue and perceived effort.Isotonic and isokinetic blood flow restriction elicited comparable neural changes.

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.

Surface electromyography (EMG) and mean force can be used to identify motor unit excitation and fatigue. Low-load resistance training with blood flow restriction (LL+BFR) may result in earlier fatigue and maximal muscle fibre recruitment compared to low-load resistance training (LL). The purpose of this investigation was to examine EMG and force responses during LL versus LL+BFR. Thirteen males (mean ± standard deviation = 24±4 years) completed a bout (1×30) of leg extension muscle actions at 30% of their 1 repetition maximum LL and LL+BFR while force, EMG amplitude, and EMG mean power frequency (EMG MPF) were recorded. EMG amplitude increased (74.2%) and EMG MPF decreased (22.6%) similarly during both conditions. There was no significant difference in mean force during the first 3 repetitions between LL+BFR (477.3±132.3 N) and LL (524.3±235.1 N) conditions, but mean force was lower during the last 3 repetitions for LL+BFR (459.7±179.3 N) compared to LL (605.4±276.4 N). The results of the present study indicated that a fatiguing bout of leg extension muscle actions performed LL and LL+BFR elicited similar neuromuscular responses. There was a significant difference in mean force during the last 3 repetitions (LL>LL+BFR) that may have been due to differences in the time spent near peak force.

Applying blood flow restriction (BFR) during resistance exercise is a potent stimulus of muscular adaption, but there is little direct comparison of its effect on neuromuscular function. The purpose of this investigation was to compare surface electromyography amplitude and frequency responses during a 75 (1 × 30, 3 × 15) repetition bout (BFR-75) of BFR to 4 sets to failure (BFR-F). Twelve women (mean ± SD age = 22 ± 4 years; body mass = 72 ± 14.4 kg; height = 162.1 ± 4.0 cm) volunteered for the investigation. One leg was randomly assigned to complete BFR-75 and the other to BFR-F. Each leg performed isokinetic, unilateral, concentric-eccentric, leg extension at 30% of maximal strength while surface electromyographic (sEMG) data was recorded. More repetitions (p = 0.006) were completed during set 2 for BFR-F (21.2 ± 7.4) than BFR-75 (14.7 ± 1.2), but there were no other between condition differences for set 1 (29.8 ± 0.9 vs 28.9 ± 10.1), set 3 (14.4 ± 1.4 vs 17.1 ± 6.9), or set 4 (14.8 ± 0.9 vs 16.3 ± 7.0). Collapsed across condition, normalized sEMG amplitude increased (p = 0.014, 132.66 ± 14.03% to 208.21 ± 24.82%) across the first three sets of exercise then plateaued, while normalized sEMG frequency decreased (p = 0.342, 103.07 ± 3.89% to 83.73 ± 4.47%) across the first two sets then plateaued. The present findings indicated that BFR-75 and BFR-F elicited similar acute neuromuscular fatigue responses. The plateau in amplitude and frequency suggested that maximal motor unit excitation and metabolic buildup may be maximized after two to three sets of BFR-75 and BFR-F.

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.

Wizenberg, AM, Gonzalez-Rojas, D, Rivera, PM, Proppe, CE, Laurel, KP, Stout, JR, Fukuda, DH, Billaut, F, Keller, JL, and Hill, EC. Acute effects of continuous and intermittent blood flow restriction on sprint interval performance and muscle oxygen responses. J Strength Cond Res 37(10): e546-e554, 2023-This investigation aimed to examine the acute effects of continuous and intermittent blood flow restriction (CBFR and IBFR, respectively) during sprint interval training (SIT) on muscle oxygenation, sprint performance, and ratings of perceived exertion (RPE). Fifteen men (22.6 & PLUSMN; 2.4 years; 176 & PLUSMN; 6.3 cm; 80.0 & PLUSMN; 12.6 kg) completed in random order a SIT session with CBFR, IBFR (applied during rest), and no blood flow restriction (NoBFR). Each SIT session consisted of two 30-second all-out sprint tests separated by 2 minutes. Peak power (PP), total work (TW), sprint decrement score (Sdec), RPE, and muscle oxygenation were measured during each sprint. A p value & LE;0.05 was considered statistically significant. PP decreased to a greater extent from sprint 1 to sprint 2 during CBFR (25.5 & PLUSMN; 11.9%) and IBFR (23.4 & PLUSMN; 9.3%) compared with NoBFR (13.4 & PLUSMN; 8.6%). TW was reduced similarly (17,835.6 & PLUSMN; 966.2 to 12,687.2 & PLUSMN; 675.2 J) from sprint 1 to sprint 2 for all 3 conditions, but TW was lower (collapsed across time) for CBFR (14,320.7 & PLUSMN; 769.1 J) than IBFR (15,548.0 & PLUSMN; 840.5 J) and NoBFR (15,915.4 & PLUSMN; 771.5 J). There were no differences in Sdec (84.3 & PLUSMN; 1.7%, 86.1 & PLUSMN; 1.5%, and 87.2 & PLUSMN; 1.1% for CBFR, IBFR, and NoBFR, respectively) or RPE, which increased from sprint 1 (8.5 & PLUSMN; 0.3) to sprint 2 (9.7 & PLUSMN; 0.1). Collective muscle oxygenation responses increased across time and were similar among conditions, whereas increases in deoxy[heme] and total[heme] were greatest for CBFR. Applying BFR during SIT induced greater decrements in PP, and CBFR resulted in greater decrements in work across repeated sprints. The larger increases in deoxy[heme] and total[heme] for CBFR suggested it may induce greater metabolite accumulation than IBFR and NoBFR when combined with SIT.

ABSTRACTThere is conflicting evidence regarding the prevalence and magnitude of exercise-induced muscle damage (EIMD) following low-load resistance exercise with blood flow restriction (LL + BFR) that may be related to exercise protocols. The purpose of this investigation was to examine the effects of 75-repetition (BFR-75) (1 × 30, 3 × 15) and 4 sets to failure (BFR-4x) protocols on indices of EIMD among untrained women. Thirteen women completed this investigation. One leg was randomly assigned to BFR-75 and the other to BFR-4x. Each leg performed isokinetic, unilateral, concentric-eccentric, leg extension muscle actions at 30% of maximal strength. Indices of EIMD (muscle soreness, range of motion [ROM], limb circumference, pain pressure threshold [PPT], and maximal voluntary isometric contraction [MVIC]) were recorded before exercise, 0-, 24-, 48-, 72-, and 96-hours post-exercise. There were no changes for ROM, circumference, or PPT. Muscle soreness increased similarly in both conditions 0-, 24-, and 48-hours post-exercise and MVIC increased 24-, 48-, 72-, and 96-hours post-exercise. These findings suggested BFR-75 and BFR-4x were not associated with EIMD and elicited similar physiological responses. The increases in muscle soreness may be due to metabolic stress associated with LL + BFR protocols apart from EIMD.

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.

PURPOSE: The application of blood flow restriction (BFR) with resistance training has been applied to various exercise modalities, but no previous investigations have examined isotonic BFR versus isokinetic BFR. Therefore, the purpose of this investigation was to examine the acute effects of isotonic versus isokinetic BFR on performance and perceptual outcomes under load-matched conditions. METHODS: Thirteen (21 ± 1.9 years) recreationally women randomly performed (on separate days) 75 (1x30, 3x15) submaximal (30% of maximal strength) leg extensions with BFR (60% of total arterial occlusion pressure). Before and immediately after each exercise, subjects performed MVICs and torque was recorded for the first 30 repetitions and examined across 10 time points (average of every 3 repetitions). RPE was recorded during all 4 sets. A 2 (Condition [isotonic, isokinetic]) × 2 (Time [pretest, posttest]) repeated measures ANOVA was used to examine changes in MVIC torque. A 2 (Condition [isotonic, isokinetic]) × 10 (Time Point [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) repeated measures ANOVA was used to examine changes in torque across the first 30 repetitions. A 2 (Condition [isotonic, isokinetic]) × 2 (Time [set 1, set 2, set 3, set 4]) repeated measures ANOVA was used to examine differences in RPE RESULTS: : For MVIC torque, there was a significant Condition × Time (p = 0.042) interaction indicating greater decreases in torque from pretest to posttest for the isotonic (46.6% ± 17.7) than isokinetic (17.6% ± 9.5) condition. For the 30 repetitions, there was a significant (p = 0.029) Condition × Repetition interaction that indicated torque was greater during time points 1-6 (repetitions 1-18) for the isotonic (69.4 -73.2 Nm) than isokinetic (48.5 - 49.7 Nm) condition. For RPE, there was no significant (p = 0.328) interaction but there were significant (p < 0.001) main effects for Time (set 4 > set 3 > set 2 > set 1) and Condition (isotonic > isokinetic) (p = 0.015). CONCLUSIONS: Isotonic BFR exercise elicited greater fatigue-induced decreases in MVIC torque that was associated with greater perceived effort. Despite load-matched conditions, average torque was higher during isotonic than isokinetic. Therefore, there are clear and prevalent differences between isokinetic and isotonic BFR resistance exercise that affects performance and perception.

PURPOSE: The purpose of this investigation was to examine the chronic effects of low-load blood flow restricted (LLBFR) and traditional (TRAD) moderate-load resistance training on neuromuscular and muscle function among people living with multiple sclerosis (PwMS). METHODS: Seven women (mean age ± SD = 39 ± 14 yrs; body mass = 70.2 ± 15.2 kg; height = 164.3 ± 6.8 cm) with relapsing-remitting multiple sclerosis participated in 12 weeks (2/wk) of LLBFR (n = 4) or TRAD (n = 3) consisting of bilateral upper body (chest press, seated row, shoulder press) and bilateral lower body (leg press, leg extension, leg curl) exercises. LLBFR performed 75 repetitions (1 × 30, 3 × 15) at 30% of one-repetition maximum (1RM) with a pneumatic cuff pressurized to 60% of total arterial occlusion pressure and applied to the most proximal portion of the upper arms or legs. TRAD performed 35-40 repetitions (4 × 8-12) at 65% of 1RM. Every four weeks, surface electromyography (sEMG) of the vastus lateralis and maximal strength of the dominant and non-dominant legs were assessed, separately, during unilateral, concentric, isokinetic, leg extensions at 90°·s-1 using 2 (Group [LLBFR, TRAD]) × 4 (Time [baseline, 4-, 8-, 12-wks]) mixed factorial ANOVAs. RESULTS: There were no significant (p = 0.228-0.787) interactions or main effects for Group, but there were significant main effects for Time (p < 0.001-0.035). Normalized (to baseline) sEMG amplitude of the non-dominant leg increased from baseline, 4-wks (mean ± SD = 106.2 ± 7.4%), and 8-wks (118.6 ± 15.9%) to 12-wks (138.9 ± 26.8%). There were non-significant (p > 0.05) increases in sEMG amplitude at 12-wks (141.1 ± 36.6%) of the dominant leg. Concentric peak torque of the dominant and non-dominant legs increased from baseline (88.6 ± 12.5 Nm and 92.2 ± 15.5 Nm, respectively) to 8-wks (103.9 ± 14.7 Nm and 98.8 ± 15.2 Nm, respectively) and to 12-wks (123.5 ± 14.1 Nm and 106.1 ± 16.5 Nm, respectively). CONCLUSIONS: Bilateral resistance exercise (LLBFR and TRAD) was effective at improving unilateral muscle strength, while local muscle excitation increased for only the non-dominant leg. These findings highlight the utility of LLBFR and TRAD resistance exercise to improve muscle outcomes among PwMS, but bilateral resistance exercise may exhibit non-homogenous adaptations between limbs.