Comparing adaptations from blood flow restriction exercise training using regulated or unregulated pressure systems: A systematic review and meta-analysis.

OBJECTIVE: No study has examined outcomes derived from blood flow restriction exercise training interventions using regulated compared with unregulated blood flow restriction pressure systems. Therefore, we used a systematic review and meta-analyses to compare the chronic adaptations to blood flow restriction exercise training achieved with regulated and unregulated blood flow restriction pressure systems. DATA SOURCES: The electronic database search included using the tool EBSCOhost and other online database search engines. The search included Medline, SPORTDiscus, CINAHL, Embase and SpringerLink. METHODS: Included studies utilised chronic blood flow restriction exercise training interventions greater than two weeks duration, where blood flow restriction was applied using a regulated or unregulated blood flow restriction pressure system, and where outcome measures such as muscle strength, muscle size or physical function were measured both pre- and post-training. Studies included in the meta-analyses used an equivalent non-blood flow restriction exercise comparison group. RESULTS: Eighty-one studies were included in the systematic review. Data showed that regulated (n = 47) and unregulated (n = 34) blood flow restriction pressure systems yield similar training adaptations for all outcome measures post-intervention. For muscle strength and muscle size, this was reaffirmed in the included meta-analyses. CONCLUSION: This review indicates that practitioners may achieve comparable training adaptations with blood flow restriction exercise training using either regulated or unregulated blood flow restriction pressure systems. Therefore, additional factors such as device quality, participant comfort and safety, cost and convenience are important factors to consider when deciding on appropriate equipment to use when prescribing blood flow restriction exercise training.

Progression and perceptual responses to blood flow restriction resistance training among people with multiple sclerosis.

PURPOSE: 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% of one-repetition maximum [1RM]) resistance training (RT) with BFR applied intermittently during the exercise intervals (RT + BFR) versus volume-matched heavy-load (65% of 1RM) RT. METHODS: Men and women with MS (n = 16) were randomly assigned to low-load RT + BFR (applied intermittently) or heavy-load RT and completed 12 weeks (2 × /week) of RT that consisted of bilateral chest press, seated row, shoulder press, leg press, leg extension, and leg curl exercises. Exercise load, tonnage, and rating of perceived exertion were assessed at baseline and every 6 weeks. RESULTS: Training load increased to a greater extent and sometimes earlier for RT + BFR (57.7-106.3%) than heavy-load RT (42.3-54.3%) during chest press, seated row, and leg curl exercises, while there were similar increases (63.5-101.1%) for shoulder press, leg extension, and leg press exercises. Exercise tonnage was greater across all exercises for RT + BFR than heavy-load RT, although tonnage only increased during the chest press (70.7-80.0%) and leg extension (89.1%) exercises. Perceptions of exertion (4.8-7.2 au) and compliance (97.9-99.0%) were similar for both interventions. CONCLUSION: The training-induced increases in load, high compliance, and moderate levels of exertion suggested that RT + BFR and heavy-load RT are viable interventions among people with MS. RT + BFR may be a preferred modality if heavy loads are not well tolerated and/or to promote early-phase training responses.

Investigating the autoregulation of applied blood flow restriction training pressures in healthy, physically active adults: an intervention study evaluating acute training responses and safety.

OBJECTIVE: To examine the effects of autoregulated (AUTO) and non-autoregulated (NAUTO) blood flow restriction (BFR) application on adverse effects, performance, cardiovascular and perceptual responses during resistance exercise. METHODS: Fifty-six healthy participants underwent AUTO and NAUTO BFR resistance exercise in a randomised crossover design using a training session with fixed amount of repetitions and a training session until volitional failure. Cardiovascular parameters, rate of perceived effort (RPE), rate of perceived discomfort (RPD) and number of repetitions were investigated after training, while the presence of delayed onset muscle soreness (DOMS) was verified 24 hours post-session. Adverse events during or following training were also monitored. RESULTS: AUTO outperformed NAUTO in the failure protocol (p<0.001), while AUTO scored significantly lower for DOMS 24 hours after exercise (p<0.001). Perceptions of effort and discomfort were significantly higher in NAUTO compared with AUTO in both fixed (RPE: p=0.014, RPD: p<0.001) and failure protocol (RPE: p=0.028, RPD: p<0.001). Sixteen adverse events (7.14%) were recorded, with a sevenfold incidence in the fixed protocol for NAUTO compared with AUTO (NAUTO: n=7 vs AUTO: n=1) and five (NAUTO) vs three (AUTO) adverse events in the failure protocol. No significant differences in cardiovascular parameters were found comparing both pressure applications. CONCLUSION: Autoregulation appears to enhance safety and performance in both fixed and failure BFR-training protocols. AUTO BFR training did not seem to affect cardiovascular stress differently, but was associated with lower DOMS, perceived effort and discomfort compared with NAUTO. TRIAL REGISTRATION NUMBER: NCT04996680.

Muscle growth adaptations to high-load training and low-load training with blood flow restriction in calf muscles.

PURPOSE: To compare muscle growth adaptations between traditional high-load training and low-load training with blood flow restriction (BFR) in the calf muscles over 6 weeks. METHODS: 27 trained individuals performed calf exercise in both legs for 6 weeks. Each leg was randomly assigned to one of the two conditions: (1) Traditional (70% of 1RM) training (TRAD); and (2) Low-load (30% of 1RM) training with BFR. In addition, subjects performed standing calf raises with or without BFR. Measures were taken pre- and post-intervention. RESULTS: For the posterior muscle site, there was no condition (BFR vs. TRAD) × time (pre vs. post) interaction (p = 0.15). In addition, there was no main effect for condition (p = 0.83) or time (p = 0.20). For the lateral muscle site, there was no condition × time interaction (p = 0.47). In addition, there was no main effect for condition (p = 0.10) or time (p = 0.57). For the medial muscle site, there was no condition × time interaction (p = 0.60). In addition, there was no main effect for condition (p = 0.44) or time (p = 0.72). For RPE, there was no condition × time interaction. However, there was a main effect for condition (p < 0.05) with BFR having higher RPE. For discomfort, there was no condition × time interaction. However, there was a main effect for condition (p < 0.001) with the BFR condition displaying higher discomfort. CONCLUSION: No muscle growth was detected in the calf musculature. BFR was not more effective at eliciting muscle hypertrophy compared to traditional training. However, it was accompanied with higher exertion and discomfort.

Clinical use of blood flow restriction in people with neurologic conditions: a cross-sectional survey.

[Purpose] There is little evidence for blood flow restriction (BFR), or Kaatsu, training in people with neurologic conditions. This study's purpose was to survey clinicians on BFR use in people with neurologic conditions. [Participants and Methods] One-hundred twelve physical therapists and other healthcare professionals who reported using BFR in the past 5 years completed an anonymous, online survey. [Results] Eighty-nine percent of respondents thought BFR was safe in people with neurologic conditions. Meanwhile, 38% reported BFR use in people with neurologic conditions. The most common intervention used with BFR was resistance training (n=33) and the most commonly reported benefit was improved strength (n=27). The most common side-effect causing treatment to stop was intolerance to pressure (n=6). No side-effects requiring medical attention were reported. In order to support future BFR use in neurologic populations, the most common response was the need for more research (n=63). [Conclusion] Despite the lack of evidence, clinical use of BFR in people with neurologic conditions may be somewhat common. Although this study had a relatively small sample size and collected data retrospectively, the results support the potential clinical feasibility and safety of BFR use in patients with neurologic conditions and suggest that more research is needed.

Frequent blood flow restricted training not to failure and to failure induces similar gains in myonuclei and muscle mass.

The purpose of the present study was to compare the effects of short-term high-frequency failure vs non-failure blood flow-restricted resistance exercise (BFRRE) on changes in satellite cells (SCs), myonuclei, muscle size, and strength. Seventeen untrained men performed four sets of BFRRE to failure (Failure) with one leg and not to failure (Non-failure; 30-15-15-15 repetitions) with the other leg using knee-extensions at 20% of one repetition maximum (1RM). Fourteen sessions were distributed over two 5-day blocks, separated by a 10-day rest period. Muscle samples obtained before, at mid-training, and 10-day post-intervention (Post10) were analyzed for muscle fiber area (MFA), myonuclei, and SC. Muscle size and echo intensity of m.rectus femoris (RF) and m.vastus lateralis (VL) were measured by ultrasonography, and knee extension strength with 1RM and maximal isometric contraction (MVC) up until Post24. Both protocols increased myonuclear numbers in type-1 (12%-17%) and type-2 fibers (20%-23%), and SC in type-1 (92%-134%) and type-2 fibers (23%-48%) at Post10 (p < 0.05). RF and VL size increased by 5%-10% in both legs at Post10 to Post24, whereas the MFA of type-1 fibers in Failure was decreased at Post10 (-10 ± 16%; p = 0.02). Echo intensity increased by ~20% in both legs during Block1 (p < 0.001) and was ~8 to 11% below baseline at Post24 (p = 0.001-0.002). MVC and 1RM decreased by 5%-10% after Block1, but increased in both legs by 6%-11% at Post24 (p < 0.05). In conclusion, both short-term high-frequency failure and non-failure BFRRE induced increases in SCs, in myonuclei content, muscle size, and strength, concomitant with decreased echo intensity. Intriguingly, the responses were delayed and peaked 10-24 days after the training intervention. Our findings may shed light on the mechanisms involved in resistance exercise-induced overreaching and supercompensation.

Is blood flow-restricted training effective for rehabilitation of a pianist with residual neurological symptoms in the upper limbs? A case study.

[Purpose] We investigated whether blood flow-restricted training known as KAATSU training, was effective for rehabilitation of a pianist with residual neurological symptoms in the upper limbs. [Participant and Methods] A pianist with residual neurological symptoms in the upper body played "Revolutionary Etude" under two conditions: piano performance with (Piano-blood flow-restricted) and without (Piano-control) the restriction of blood flow to the upper limbs. In the Piano-blood flow-restricted exercise, a pressure of 130-170 mmHg was applied around the most proximal portion of both arms. The changes in upper limb circumference and muscle strength were measured before, immediately after, and 15 min after the performance. The impression of the piano performance was recorded after the Piano-blood flow-restricted exercise. [Results] Immediately after the piano performance, the forearm and upper arm circumferences had increased significantly in both arms, and the change was greater in the Piano-blood flow-restricted than in the Piano-control condition. The handgrip strength for the right arm also showed greater changes in the former than the latter. However, there were no significant differences between the two conditions regarding the handgrip strength of the left arm. [Conclusion] There is a high possibility that blood flow-restricted training is effective for rehabilitation of the pianist with residual neurological symptoms in the upper limbs.

Clinical safety of blood flow-restricted training? A comprehensive review of altered muscle metaboreflex in cardiovascular disease during ischemic exercise.

Blood flow restriction training (BFRT) is an increasingly widespread method of exercise that involves imposed restriction of blood flow to the exercising muscle. Blood flow restriction is achieved by inflating a pneumatic pressure cuff (or a tourniquet) positioned proximal to the exercising muscle before, and during, the bout of exercise (i.e., ischemic exercise). Low-intensity BFRT with resistance training promotes comparable increases in muscle mass and strength observed during high-intensity exercise without blood flow restriction. BFRT has expanded into the clinical research setting as a potential therapeutic approach to treat functionally impaired individuals, such as the elderly, and patients with orthopedic and cardiovascular disease/conditions. However, questions regarding the safety of BFRT must be fully examined and addressed before the implementation of this exercise methodology in the clinical setting. In this respect, there is a general concern that BFRT may generate abnormal reflex-mediated cardiovascular responses. Indeed, the muscle metaboreflex is an ischemia-induced, sympathoexcitatory pressor reflex originating in skeletal muscle, and the present review synthesizes evidence that BFRT may elicit abnormal cardiovascular responses resulting from increased metaboreflex activation. Importantly, abnormal cardiovascular responses are more clearly evidenced in populations with increased cardiovascular risk (e.g., elderly and individuals with cardiovascular disease). The evidence provided in the present review draws into question the cardiovascular safety of BFRT, which clearly needs to be further investigated in future studies. This information will be paramount for the consideration of BFRT exercise implementation in clinical populations.

Is there rationale for the cuff pressures prescribed for blood flow restriction exercise? A systematic review.

BACKGROUND: Blood flow restriction exercise has increasingly broad applications among healthy and clinical populations. Ensuring the technique is applied in a safe, controlled, and beneficial way for target populations is essential. Individualized cuff pressures are a favored method for achieving this. However, there remains marked inconsistency in how individualized cuff pressures are applied. OBJECTIVES: To quantify the cuff pressures used in the broader blood flow restriction exercise literature, and determine whether there is clear justification for the choice of pressure prescribed. METHODS: Studies were included in this review from database searches if they employed an experimental design using original data, involved either acute or chronic exercise using blood flow restriction, and they assessed limb or arterial occlusion pressure to determine an individualized cuff pressure. Methodologies of the studies were evaluated using a bespoke quality assessment tool. RESULTS: Fifty-one studies met the inclusion criteria. Individualized cuff pressures ranged from 30% to 100% arterial occlusion pressure. Only 7 out of 52 studies attempted to justify the individualized cuff pressure applied during exercise. The mean quality rating for all studies was 11.1 ± 1.2 out of 13. CONCLUSIONS: The broader blood flow restriction exercise literature uses markedly heterogeneous prescription variables despite using individualized cuff pressures. This is problematic in the absence of any clear justification for the individualized cuff pressures selected. Systematically measuring and reporting all relevant acute responses and training adaptations to the full spectrum of BFR pressures alongside increased clarity around the methodology used during blood flow restriction exercise is paramount.

The blood flow restriction training effect in knee osteoarthritis people: a systematic review and meta-analysis.

OBJECTIVE: To synthesize evidence on the effects of blood flow restriction (BFR) comparing with high (HLT) and low load (LLT), and on the influence of different forms of application in individuals with knee osteoarthritis. DATA SOURCES: The CENTRAL, PEDro, PubMed and BVS, which include Lilacs, Medline and SciELO, until April 2020. REVIEW METHODS: A systematic review and meta-analysis of randomized trials used the PRISMA guidelines, whose main keywords were: Therapeutic Occlusion, Resistance Training, and Knee Osteoarthritie, blood flow restriction and Kaatsu training. Method quality was evaluated with the PEDro scale. When studies demonstrated homogeneity on outcome measures, the mean differences or standardized mean differences with 95% confidence interval were calculated and pooled in a meta-analysis for pooled synthesis. RESULTS: Five articles were eligible in this review with moderate to low risk bias. Our results, showed no difference between BFR and HLT in knee strength (SMD = 0.00, 95% CI, -0.54 to 0.54, P = 1.00), function (SMD = -0.20, 95% CI, -0.45 to 0.06, P = 0.13), pain and volume. But, when compared BFR and LLT, the descriptive analysis demonstrated significant results in favor BFR to muscle strength (71.4% of measurement) and volume (MD = 1.66, 95% CI, 0.93 to 2.38, P < 0.00001), but not in pain or function. CONCLUSION: BFR can be used as a strategy in the rehabilitation of osteoarthritis due to gains in strength and volume with low mechanical stress. However, its application must be safe and individualized, since they can attenuate the stimuli offered by BFR.

Acute cardiovascular response to unilateral, bilateral, and alternating resistance exercise with blood flow restriction.

AIM: Blood flow restriction (BFR) exercise is a common alternative to traditional high-load resistance exercise used to increase muscle size and strength. Some populations utilizing BFR at a low load may wish to limit their cardiovascular response to exercise. Different contraction patterns may attenuate the cardiovascular response, but this has not been compared using BFR. PURPOSE: To compare the cardiovascular response to unilateral (UNI), bilateral (BIL), and alternating (ALT) BFR exercise contraction patterns. METHODS: Twenty healthy participants performed four sets (30 s rest) of knee extensions to failure, using 30% one-repetition maximum, 40% arterial occlusion pressure, and each of the three contraction patterns (on different days, at the same time of day, separated by 2-10 days, randomized). Cardiovascular responses, presented as pre- to post-exercise mean changes (SD), were measured using pulse wave analysis and analyzed with Bayesian RMANOVA. RESULTS: ALT caused greater changes in: aortic systolic [ΔmmHg: ALT = 21(8); UNI = 13(11); BIL = 15(8); BF10 = 29.599], diastolic [ΔmmHg: ALT = 13(8); UNI = 7(11); BIL = 8(8); BF10 = 5.175], and mean arterial [ΔmmHg: ALT = 19(8); UNI = 11(11); BIL = 13(7); BF10 = 48.637] blood pressures. Aortic [ΔmmHg bpm: ALT = 4945(2340); UNI = 3294(1408); BIL = 3428 (1461); BF10 = 113.659] and brachial [ΔmmHg bpm: ALT = 6134(2761); UNI = 4300(1709); BIL = 4487(1701); BF10 = 31.845] rate pressure products, as well as heart rate [Δbpm: ALT = 26(14); UNI = 19(8); BIL = 19(11); BF10 = 5.829] were greatest with ALT. Augmentation index [Δ%: UNI = -6(13); BIL = - 7(11); ALT = - 5(16); BF10 = 0.155] and wave reflection magnitude [Δ%: UNI = - 5(9); BIL = - 4(7); ALT = - 4(7); BF10 = 0.150] were not different. CONCLUSION: Those at risk of a cardiovascular event may choose unilateral or bilateral BFR exercise over alternating until further work determines the degree to which it can be tolerated.

[Application and effects of blood flow restriction training]. / Anwendung und Effekte des "blood flow restriction training".

Blood flow restriction (BFR) limits arterial and venous blood flow and leads to blood pooling, which could increase exercise-induced training effects. Strength training at lower intensities (20-30% of maximum strength) in combination with BFR showed similar effects on muscle hypertrophy as training with 70% without BFR. Low-intensity cycling endurance training with BFR improves muscle hypertrophy and endurance performance and activates angiogenesis. After determination of the complete occlusion pressure on the corresponding extremity, it is recommended that BFR training should be performed with 40-80% of the measured occlusion pressure. During strength training of the upper extremities, an occlusion of 60-80% leads to a reduction in the arterial blood flow by 20-50%. Local ischemia and hypoxia, a stronger metabolic stimulus, swelling of the muscle cells and the increased oxidative stress are discussed as causes for the increased training effects due to BFR. In short-term studies, comparable adjustments to parameters of fibrinolytic activity, coagulation and inflammation could be observed for strength training with and without BFR. So far, thromboses after BFR have been described only rarely but need to be further clarified by appropriate studies. The BFR training leads to a stronger activation of the muscular metabolic reflex and thus to a relatively greater increase in exercise blood pressure, so that cardiovascular parameters should be controlled during BFR training. First meta-analyses with small numbers of healthy people and patients indicate the effectiveness of BFR training. Standardization or guidelines for clinical use are still lacking.

Pelvic floor muscle training with and without supplementary KAATSU for women with stress urinary incontinence - a randomized controlled pilot study.

AIMS: To explore if adding occlusion training of a thigh (KAATSU) to low-intensity pelvic floor muscle training (PFMT) could increase effect of PFMT in women with stress urinary incontinence (SUI). METHODS: Single-blinded randomized controlled pilot study. Women with SUI and an ICIQ-UI-SF (International Consultation on Incontinence Questionnaire-Short form) score of ≥12 were randomized to a low-intensity PFMT program followed by KAATSU (KAATSU + PFMT) or to a low-intensity PFMT program without KAATSU (PFMT group), both performed four times a week for 12 weeks. PRIMARY OUTCOME: Change in the ICIQ-UI-SF score at a 12-week follow-up. SECONDARY OUTCOMES: a 3-day leakage diary, the PGI-I (Patient Global Index of Improvement scale), bother with KAATSU in a numeric rank scale and change in urethral opening pressure (UOP) measured with urethral pressure reflectometry (UPR) at rest, contraction and straining at the 12-week follow-up. RESULTS: Forty-one women with SUI and an ICIQ-UI-SF of 13 (range 12-16) were included. Fourteen in the KAATSU + PFMT and 17 in the PFMT group completed the study. Both groups had a significant and clinically relevant improvement of the ICIQ-UI-SF score and decrease in number of incontinence episodes with no significant between group differences. UOP did not increase significantly in either group. Bother with KAATSU was low but seven of 14 women expressed dislike with KAATSU. CONCLUSIONS: The added KAATSU protocol did not increase the effect of low-intensity PFMT and it was not well tolerated. While subjective effect was significant in both intervention groups this was not reflected in the UPR measures.

Central cardiovascular hemodynamic response to unilateral handgrip exercise with blood flow restriction.

AIM: Exercise training with blood flow restriction (BFR) increases muscle size and strength. However, there is limited investigation into the effects of BFR on cardiovascular health, particularly central hemodynamic load. PURPOSE: To determine the effects of BFR exercise on central hemodynamic load (heart rate-HR, central pressures, arterial wave reflection, and aortic stiffness). METHODS: Fifteen males (age = 25 ± 2 years; BMI = 27 ± 2 kg/m2, handgrip max voluntary contraction-MVC = 50 ± 2 kg) underwent 5-min bouts (counter-balanced, 10 min rest between) of rhythmic unilateral handgrip (1 s squeeze, 2 s relax) performed with a moderate-load (60% MVC) with and without BFR (i.e., 71 ± 5% arterial inflow flow reduction, assessed via Doppler ultrasound), and also with a low-load (40% MVC) with BFR. Outcomes included HR, central mean arterial pressure (cMAP), arterial wave reflection (augmentation index, AIx; wave reflection magnitude, RM%), aortic arterial stiffness (pulse wave velocity, aPWV), and peripheral (vastus lateralis) microcirculatory response (tissue saturation index, TSI%). RESULTS: HR increased above baseline and time control for all handgrip bouts, but was similar between the moderate load with and without BFR conditions (moderate-load with BFR = + 9 ± 2; moderate-load without BFR = + 8 ± 2 bpm, p < 0.001). A similar finding was noted for central pressure (e.g., moderate load with BFR, cMAP = + 14 ± 1 mmHg, p < 0.001). No change occurred for RM% or AIx (p > 0.05) for any testing stage. TSI% increased during the moderate-load conditions (p = 0.01), and aPWV increased above baseline following moderate-load handgrip with BFR only (p = 0.012). CONCLUSIONS: Combined with BFR, moderate load handgrip training with BFR does not significantly augment central hemodynamic load during handgrip exercise in young healthy men.

Limb blood flow and tissue perfusion during exercise with blood flow restriction.

INTRODUCTION: Exercise with blood flow restriction (BFR) is emerging as an effective modality for improving muscular function in clinical and athletic populations. Selection of cuff pressure is critical because it should maximize metabolic stress without completely occluding blood flow or compromising user safety. It is unknown how cuff pressures determined at rest influence blood flow hemodynamics during exercise. PURPOSE: We evaluated changes in blood flow and tissue perfusion before, during, and after exercise with BFR. METHODS: Ten males performed rhythmic handgrip exercise (30 contractions, 30% MVC) at 0%, 60%, 80%, 100%, and 120% of limb occlusion pressure (LOP). Brachial artery blood flow and tissue saturation were assessed using Doppler ultrasound and near-infrared spectroscopy, respectively. RESULTS: At rest blood flow generally decreased with increased pressure (0% > 60% ≈ 80% > 100% ≈ 120% LOP). During 60% and 80% LOP conditions, blood flow increased during exercise from rest and decreased after exercise (all P < 0.05). Compared to 0% LOP, relative blood flow at 60% and 80% LOP decreased by 22-47% at rest, 22-48% during exercise, and 52-71% after exercise (all P < 0.05). Increased LOP decreased tissue saturation during exercise with BFR (P < 0.05). Heart rate, mean arterial pressure, and cardiac output did not differ across LOP. CONCLUSION: At pressures below LOP the cardiovascular system overcame the external pressure and increased blood flow to exercising muscles. Relative reductions in blood flow at rest were similar to those during exercise. Thus, the relative occlusion measured at rest approximated the degree of occlusion during exercise. Moderate cuff pressures increased metabolic stress without completely occluding blood flow.

Perceptual changes to progressive resistance training with and without blood flow restriction.

The purpose was to examine changes in the perceptual responses to lifting a very low load (15% one repetition maximum (1RM)) with and without (15/0) different pressures [40% (15/40) and 80% (15/80) arterial occlusion pressure] and compare that to traditional high load (70/0) resistance exercise. Ratings of perceived exertion (RPE) and discomfort were measured following each set of exercise. In addition, resting arterial occlusion pressure was measured prior to exercise. Assessments were made in training sessions 1, 9, and 16 for the upper and lower body. Data are presented as means and 95% CI. There were changes in RPE in the upper body with condition 15/40 [-2.1 (-3.4, -0.850)] and 15/80 [-2.4 (-3.6, -1.1)] decreasing by the end of training. In the lower body, RPE decreased in condition 15/40 [-1.4 (-2.3, -0.431)] by the end of the training study. There was a main effect of time in the upper body with all conditions decreasing discomfort. In the lower body, all conditions decreased except for 15/80. For arterial occlusion pressure, there were differences across time in the 15/40 condition and the 15/80 condition in the upper body. Repeated exposure to blood flow restriction may dampen the perceptual responses over time.

Blood-Flow Restriction Resistance Exercise Promotes Lower Pain and Ratings of Perceived Exertion Compared With Either High- or Low-Intensity Resistance Exercise Performed to Muscular Failure.

CONTEXT: Given the comparable muscle hypertrophy constantly observed between blood-flow restriction exercise (BFR-RE) and conventional resistance exercise, understanding their particular rating of perceived exertion (RPE) and pain may help to better prescribe exercise at a low-discomfort level, thus increasing its feasibility. DESIGN: Randomized crossover study. OBJECTIVE: To compare the RPE and pain response between conventional high- (HI-RE) and low-intensity resistance exercise (LI-RE) protocols to failure with a nonmuscular failure LI-RE associated with BFR-RE. PARTICIPANTS: A total of 12 men (age: 20 [3] y; body mass: 73.5 [9] kg; height: 174 [6] cm). INTERVENTIONS: Four sets of 45° leg-press exercises in 3 different conditions: (1) BFR-RE (15 repetitions; 30% 1-repetition maximum), (2) HI-RE (80% 1-repetition maximum to muscular failure), and (3) LI-RE (30% 1-repetition maximum to muscular failure). MAIN OUTCOME MEASURES: RPE and pain were assessed immediately before exercise session and after the end of each of the 4 sets. RESULTS: RPE and pain levels increased throughout the exercise sets for all RE protocols (all, Ps < .05). HI-RE and LI-RE protocols showed similar increase in RPE and pain levels during all exercise sets (P < .05); however, both protocols demonstrated higher RPE and pain response compared with BFR-RE after each of the 4 sets (all Ps < .05 between-group comparisons). CONCLUSIONS: Our results demonstrated that both HI-RE and LI-RE to muscular failure resulted in similar and significant increases in RPE and pain levels, regardless of exercise intensity. In addition, nonmuscular failure BFR-RE also increased RPE and pain response, however, to a lower extent compared with either HI-RE or LI-RE.

Muscle fatigue in response to low-load blood flow-restricted elbow-flexion exercise: are there any sex differences?

PURPOSE: This study aimed to determine whether men and women display a different magnitude of muscle fatigue in response to high-load (HL) and low-load blood flow-restricted (LLBFR) elbow-flexion exercise. We also explored to which extent both exercise protocols induce similar levels of muscle fatigue (i.e., torque decrement). METHODS: Sixty-two young participants (31 men and 31 women) performed dynamic elbow flexions at 20 and 75% of one-repetition maximum for LLBFR and HL exercise, respectively. Maximum voluntary isometric contractions were performed before and after exercise to quantify muscle fatigue. RESULTS: Men and women exhibited similar magnitude of relative torque decrement after both exercise protocols (p > 0.05). HL was more fatiguing (∆ torque output: 11.9 and 23 N.m in women and men, respectively) than LLBFR resistance exercise (∆ torque output: 8.3 and 15.4 N.m in women and men, respectively) in both sexes, but this was largely attenuated after controlling for the differences in volume load between protocols (p > 0.05). CONCLUSIONS: These data show that torque decrement in response to LLBFR and HL dynamic elbow-flexion exercise does not follow a sexually dimorphic pattern. Our data also indicate that, if performed in a multiple-set fashion and prescribed for a given volume load, elbow-flexion LLBFR exercise induces similar levels of fatigue as HL acute training. Importantly, this occurs similarly in both sexes.

Moderately heavy exercise produces lower cardiovascular, RPE, and discomfort compared to lower load exercise with and without blood flow restriction.

PURPOSE: To determine the acute cardiovascular and perceptual responses of low-load exercise with or without blood flow restriction and compare those responses to that of moderately heavy exercise. METHODS: Twenty-two participants completed unilateral elbow flexion exercise with a moderately heavy-load- [70% one-repetition maximum (1RM); 70/0] and with three low-load conditions (15% 1RM) in combination with 0% (15/0), 40%, (15/40) and 80% (15/80) arterial occlusion pressure. Participants exercised until failure (or until 90 repetitions per set). The cardiovascular response (arterial occlusion) was measured pre and post exercise and the perceptual responses [ratings of perceived exertion (RPE) and discomfort] were determined before and after each set of exercise. RESULTS: For arterial occlusion pressure, the lower-load conditions had greater change from pre to post compared to 70/00 (e.g., 15/80: 44 vs. 70/0: 34 mmHg). RPE was highest across the sets for the 15/80 condition with the other conditions having similar RPE (e.g., set 4: median rating of 17.2 for 15/80 vs. ~ 15.5 for other conditions). Ratings of discomfort were also greatest for the 15/80 condition (15/80 > 15/40 > 15/0 > 70/0). Exercise volume within the 15/0 and 15/40 conditions were similar but were significantly greater than that observed with the 15/80 and 70/0 conditions. CONCLUSION: Low-load exercise to volitional failure results in a greater cardiovascular response to that of moderately heavy-load exercise. When high pressure is applied to low load exercise, there is a reduction in exercise volume but an elevated perceptual response that may be an important consideration when applying this stimulus in practice.

The systemic myokine response of decorin, interleukin-6 (IL-6) and interleukin-15 (IL-15) to an acute bout of blood flow restricted exercise.

PURPOSE: Blood flow restricted resistance exercise (BFR-RE) is an emerging hypertrophy training modality. A complete profile of its mechanisms of action has yet to be elucidated. Cytokines are universal intercellular messengers. Recent research has implicated certain cytokines (termed "myokines") in skeletal muscle hypertrophy pathways; however, little research has been conducted on the systemic myokine response to BFR-RE as potential hypertrophic biomarkers. Therefore, this project was conducted to determine any differences in the systemic myokine response between BFR-RE and control conditions. METHODS: The appearance of systemic myokines interleukin-6 (IL-6), interleukin-15 (IL-15), and decorin were measured following acute bouts of low-load resistance exercise, BFR-RE, and high-load resistance exercise in physically active young males to determine if BFR-RE modifies the exercise-induced systemic myokine response. RESULTS: No measurable levels of IL-6 were observed during the project. No significant effects were observed for IL-15. A significant time (11.91% increase pre to post exercise; p < 0.05) but no condition or condition by time effect was observed for decorin. CONCLUSION: These findings suggest that BFR-RE does not modify the systemic myokine appearance of IL-6, IL-15, or decorin when compared to control conditions.