Blood Flow Restriction Protocol Research Articles

Implementation and Clinical Outcomes of Blood Flow Restriction Training on Adults With Cerebral Palsy: A Case Series.

Cerebral palsy (CP) is a congenital neurological disorder that causes musculoskeletal weakness and biomechanical dysfunctions. Strength training guidelines recommend at least 70% of 1-repetition maximum to increase muscle strength and mass. However, individuals with CP may not tolerate such high exercise intensity. Blood flow restriction (BFR) can induce similar gains in strength and muscle mass using loads as low as 20% to 30% 1-repetition maximum. This case series described the safety, feasibility, and acceptability of BFR in adults with CP and examined changes in muscle mass and strength. Three male participants with gross motor function classification system level 3 CP underwent strength training using a periodized 8-week BFR protocol. Outcomes included: Safety via blood pressure during and post-BFR exercises in addition to adverse event tracking; Feasibility via number of support people and time-duration of BFR exercises; Acceptability via rate of perceived discomfort (0-10) and qualitative interviews; Muscle Mass via ultrasonographic cross-sectional area of the quadriceps and hamstring; and Strength via (1) 3-repetition maximum in the leg press and knee extension, (2) isometric knee flexor and extensor muscle force measured with a hand-held dynamometer, and (3) 30-second sit-to-stand test. Participants replaced 2 exercises from their current regimen with seated knee extension and leg press exercises using progressively higher limb occlusion pressure and exercise intensity. Limb occlusion pressure started at 60%, by week 4 progressed to 80%, and then remained constant. The exercise repetition scheme progressed from fixed nonfailure repetition sets to failure-based repetition sets. Blood pressure never exceeded safety threshold, and no adverse events were reported. The BFR training was time-consuming and resource-intensive, but well-tolerated by participants (rate of perceived discomfort with a mean value of 5.8, 100% protocol adherence). Strength, as measured by 3-repetition maximum testing and 30-second sit-to-stand test, increased, but isometric muscle force and muscle mass changes were inconsistent. Blood flow restriction may be an effective means to increase strength in adults with CP who cannot tolerate high-intensity resistance training. Future research should compare BFR to traditional strength training and investigate mediators of strength changes in this population. for more insights from the authors (see the Video, Supplemental Digital Content available at: http://links.lww.com/JNPT/A473).

Innovations in the Assessment of Skeletal Muscle Health: A Glimpse into the Future.

Skeletal muscle is the largest organ system in the human body and plays critical roles in athletic performance, mobility, and disease pathogenesis. Despite growing recognition of its importance by major health organizations, significant knowledge gaps remain regarding skeletal muscle health and its crosstalk with nearly every physiological system. Relevant public health challenges like pain, injury, obesity, and sarcopenia underscore the need to accurately assess skeletal muscle health and function. Feasible, non-invasive techniques that reliably evaluate metrics including muscle pain, dynamic structure, contractility, circulatory function, body composition, and emerging biomarkers are imperative to unraveling the complexities of skeletal muscle. Our concise review highlights innovative or overlooked approaches for comprehensively assessing skeletal muscle in vivo. We summarize recent advances in leveraging dynamic ultrasound imaging, muscle echogenicity, tensiomyography, blood flow restriction protocols, molecular techniques, body composition, and pain assessments to gain novel insight into muscle physiology from cellular to whole-body perspectives. Continued development of precise, non-invasive tools to investigate skeletal muscle are critical in informing impactful discoveries in exercise and rehabilitation science.

Acute effect of different blood flow restriction protocols on muscle damage

The aim of this study is to examine the acute effect of different blood flow restriction (BFR) protocols on muscle damage. Thirty (age 19.77±1.30 years) healthy young men were included in the study. Participants were randomly divided into three groups: Experiment 1 (continuous BFR+ barbell squat, n=10), Experiment 2 (intermittent BFR + barbell squat, n=10), and Control (only barbell squats without BFR, n=10). In 80% of their 1RMs, they performed barbell squat exercises for a total of six sets, with two repetitions in each set and a 3-minute rest interval between sets. For markers of muscle damage creatine kinase (CK), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alanine transaminase (ALT), blood was drawn from the individuals twice before and immediately after the exercise. Analysis of variance in repeated measures (Repeated Measures ANOVA) test was used to analyze the data. In statistical analysis, the level of significance was accepted as p

Equine blood flow restriction training: Safety validation.

Blood flow restriction (BFR) has become a key rehabilitative tool for human orthopaedic conditions. With modernised technology and evolution of clinical application, patient-specific delivery of occlusion percentages is now considered the standard of care in human patients due to improved therapeutic outcomes and minimised safety risks. Safety validation and limb occlusion pressure (LOP) data for horses, however, are lacking. (1) To determine if BFR exposure resulted in forelimb biomechanical gait dysfunction as safety validation and (2) to investigate inter-horse and inter-limb LOP differences. Controlled in vivo experiment. Daily unilateral forelimb BFR was performed in four horses over 56 days. Clinical examinations and objective gait analyses were performed on Days 0, 28 and 56. Daily LOP values were determined by Doppler evaluation to deliver 80% vascular occlusion at a walk. A linear mixed model evaluated for differences in lameness, kinetic and kinematic gait parameters. There were no significant differences in forelimb lameness (range of Grades 0-2 across all forelimbs), kinematic or kinetic gait parameters over time or between BFR-exposed and control (contralateral) limbs (p > 0.05). Clinically apparent complications related to BFR such as thrombosis or dermatitis were not appreciated. Significant differences in mean LOP values between various horses (p < 0.001) and measured left (204.48 mmHg) and right (173.78 mmHg) forelimbs (p < 0.001) were observed. Mean LOP and standard deviation across all readings was 189.1 ± 22.2 mmHg. Optimal BFR occlusion percentages and protocols with documented clinical efficacy are unknown. Small study population. Exposure to BFR did not result in forelimb biomechanical dysfunction in four horses. Applied pressures of 75-151 mmHg would likely simulate a range of 50%-80% vascular occlusion in horses, but inherent physiological variation between horses and forelimbs warrants incorporation of individual pressures.

Subject factors influencing blood flow restriction in the arm at low cuff pressures.

Limb circumference predicts the pressure needed for complete occlusion. However, that relationship is inconsistent at moderate pressures typical of effective blood flow restriction (BFR) training. The purpose of this study was to investigate the influence of subject factors on BFR at low restriction pressures in the arm. Fifty subjects had arm anthropometrics assessed by peripheral quantitative computed tomography (pQCT), sum of skinfold thickness (sumSKF) and Gulick tape (Gulick tape circumference [Gulick Circ.]) at cuff level. Blood flow (BF) was measured with ultrasound at baseline and five restrictive pressures (20, 30, 40, 50 and 60 mmHg). Relationships between subject characteristics and BFR were assessed using Pearson's correlations and hierarchical regression. BF decreased (p < 0.05) at each incremental pressure. Regression models including percent muscle composition (%Muscle), pQCT circumference and systolic blood pressure (SBP), were significant at all five pressures (R2 = 0.18-0.49). %Muscle explained the most variance at each pressure. Regression models including sumSKF, Gulick Circ. and SBP, were significant at 30-60 mmHg (R2 = 0.28-0.49). SumSKF explained the most variance at each pressure. At low pressures (20-60 mmHg), there is considerable variability in the magnitude of BFR across individuals. Arm composition factors (muscle and fat) explained the greatest variance at each cuff pressure and may be the most important consideration when using BFR protocols.

The Effects of Blood Flow Restriction in Patients Undergoing Knee Surgery: A Systematic Review and Meta-analysis

Background: Blood flow restriction (BFR) training has been shown to have beneficial effects in reducing quadriceps muscle atrophy and improving strength in patients with various knee pathologies. Furthermore, the effectiveness of BFR training in patients undergoing knee surgery has been investigated to determine if its use can improve clinical outcomes. Purpose/Hypothesis: The purpose of this study was to conduct a systematic review and meta-analysis to examine the effectiveness of BFR training in patients undergoing knee surgery. We hypothesized that BFR, before or after surgery, would improve clinical outcomes as well as muscle strength and volume. Study Design: Systematic review and meta-analysis; Level of evidence, 4. Methods: This systematic review and meta-analysis of peer-reviewed literature was conducted using PubMed, Embase, and Cochrane databases from 1980 to present. Search results were limited to those assessing BFR training in patients undergoing knee surgery published in a scientific peer-reviewed journal in English. Selected studies subsequently underwent data extraction, methodological quality assessment, and data analysis. Results: Eleven studies were eligible, including anterior cruciate ligament reconstruction (n = 10) and knee arthroscopy (n = 1). Two studies specifically assessed BFR use in the preoperative time frame. For the meta-analysis, including 4 studies, the primary outcome variables included the cross-sectional area of the quadratus femoris muscle group assessed with magnetic resonance imaging or ultrasonography, and patient-reported outcome measure scores. The results demonstrated that BFR use in the postoperative time period can lead to a significant improvement in the cross-sectional area when quantifying muscle atrophy. However, there were no significant differences found for patient-reported outcome measures between the included studies. It should be noted that 4 of the included papers in this review reported increases in clinical strength when using BFR in the postoperative setting. Last, preoperative BFR training did not show any significant clinical benefit between the 2 studies. Conclusion: This is the first systematic review and meta-analysis to study the effects of BFR in patients undergoing knee surgery. The results of this analysis show that BFR in the postoperative period after knee surgery can improve quadriceps muscle bulk compared with a control group. However, future research should examine the effects of preconditioning with BFR before surgery. Lastly, BFR protocols need to be further investigated to determine which provide the best patient outcomes. This will help standardize this type of treatment modality for future studies.

Acute Effects of Different Blood Flow Restriction Protocols on Bar Velocity During the Squat Exercise.

The main goal of the present study was to evaluate the effects of different blood flow restriction (BFR) protocols (continuous and intermittent) on peak bar velocity (PV) and mean bar velocity (MV) during the squat exercise at progressive loads, from 40 to 90% 1RM. Eleven healthy men (age = 23.4 ± 3.1 years; body mass = 88.5 ± 12.1 kg; squat 1RM = 183.2 ± 30.7 kg; resistance training experience, 5.7 ± 3.6 years) performed experimental sessions once a week for 3 weeks in random and counterbalanced order: without BFR (NO-BFR), with intermittent BFR (I-BFR), and with continuous BFR (C-BFR). During the experimental session, the participants performed six sets of the barbell squat exercise with loads from 40 to 90% 1RM. In each set, they performed two repetitions. During the C-BFR session, the cuffs were maintained throughout the training session. During the I-BFR, the cuffs were used only during the exercise and released for each rest interval. The BFR pressure was set to ∼80% arterial occlusion pressure (AOP). Analyses of variance showed a statistically significant interaction for MV (p < 0.02; η2 = 0.18). However, the post hoc analysis did not show significant differences between particular conditions for particular loads. There was no significant condition × load interaction for PV (p = 0.16; η2 = 0.13). Furthermore, there were no main effects for conditions in MV (p = 0.38; η2 = 0.09) as well as in PV (p = 0.94; η2 = 0.01). The results indicate that the different BFR protocols used during lower body resistance exercises did not reduce peak bar velocity and mean bar velocity during the squat exercise performed with various loads.

Similar Morphological and Functional Training Adaptations Occur Between Continuous and Intermittent Blood Flow Restriction.

Davids, CJ, Raastad, T, James, L, Gajanand, T, Smith, E, Connick, M, McGorm, H, Keating, S, Coombes, JS, Peake, JM, and Roberts, LA. Similar morphological and functional training adaptations occur between continuous and intermittent blood flow restriction. J Strength Cond Res 35(7): 1784-1793, 2021-The aim of the study was to compare skeletal muscle morphological and functional outcomes after low-load resistance training using 2 differing blood flow restriction (BFR) protocols. Recreationally active men and women (n = 42 [f = 21], 24.4 ± 4.4 years) completed 21 sessions over 7 weeks of load-matched and volume-matched low-load resistance training (30% 1 repetition maximum [1RM]) with either (a) no BFR (CON), (b) continuous BFR (BFR-C, 60% arterial occlusion pressure [AOP]), or (c) intermittent BFR (BFR-I, 60% AOP). Muscle mass was assessed using peripheral quantitative computed tomography before and after training. Muscular strength, endurance, and power were determined before and after training by assessing isokinetic dynamometry, 1RM, and jump performance. Ratings of pain and effort were taken in the first and final training session. An alpha level of p < 0.05 was used to determine significance. There were no between-group differences for any of the morphological or functional variables. The muscle cross sectional area (CSA) increased pre-post training (p = 0.009; CON: 1.6%, BFR-C: 1.1%, BFR-I: 2.2%). Maximal isometric strength increased pre-post training (p < 0.001; CON: 9.6%, BFR-C: 14.3%, BFR-I: 19.3%). Total work performed during an isokinetic endurance task increased pre-post training (p < 0.001, CON: 3.6%, BFR-C: 9.6%, BFR-I: 11.3%). Perceptions of pain (p = 0.026) and effort (p = 0.033) during exercise were higher with BFR-C; however, these reduced with training (p = 0.005-0.034). Overall, these data suggest that when 30% 1RM loads are used with a frequency of 3 times per week, the addition of BFR does not confer superior morphological or functional adaptations in recreationally active individuals. Furthermore, the additional metabolic stress that is proposed to occur with a continuous BFR protocol does not seem to translate into proportionally greater training adaptations. The current findings promote the use of both intermittent BFR and low-load resistance training without BFR as suitable alternative training methods to continuous BFR. These approaches may be practically applicable for those less tolerable to pain and discomfort associated with ischemia during exercise.

Comparison Of The Effects Of Two Different Resistance Training Programs On Strength In Older Males

PURPOSE: The purpose of this study was to compare the effects of 8 weeks of blood flow restriction (BFR) training and traditional endurance resistance training on isotonic, isokinetic, isometric strength in older males. METHODS: A total of 17 males (57.0 yr ± 4.6 yr) completed the study. Subjects were randomly assigned to two training groups: blood flow restriction (BFR; n= 9) or endurance resistance training (END; n = 8). Prior to exercise training, baselines measurements were recorded, including height, weight, one repetition maximum (1RM), and unilateral knee extension testing to determine maximal voluntary contraction (MVC) and isokinetic torque at 60°/sec and 180°/sec. Training was held three times a week in a training room under laboratory settings and under the supervision of an experienced and certified strength and conditioning specialist, who ensured that subjects used proper exercise form and provided verbal encouragement. The following machine-based exercises were performed: Leg press, leg extension, leg curl, chest press, and shoulder press. Following a warm-up consisting of a 5-minute walk or jog, the BFR group performed 4 sets of 20 repetitions of the 5 exercises at 20-30% 1RM, while the END group performed 4 sets of 15 repetitions of the 5 exercises at 40-65% 1RM, with 30-60 seconds of rest between exercises. Cuffs were placed at the upper most portion of the limbs. Initial cuff tightness was kept between 30 and 40 mmHg for upper and lower limbs, and final pressure of the cuffs was between 140 to 160 mmHg for upper body 160 to 200 mmHg for lower body. BFR group rested 3-5 minutes between upper and lower body exercises. Following completion of the 8-week training, the measurements at baseline were re-recorded. RESULTS: One-way ANOVA resulted in no difference between groups at baseline. Time main effects were seen in 1RM (p ≤0.05), isokinetic torque at 60°/sec (p ≤0.05) and 80°/sec (p ≤0.05), and MVC (p ≤0.05) tests. CONCLUSION: The BFR and END training protocols resulted in similar results on improving strength after 8 weeks of resistance training. It could be speculated that even though half the weight was lifted during the BFR sessions compared to the END sessions, the BFR-related local and systemic changes elicited similar improvements in isotonic, isokinetic, and isometric strength in older males.

Central And Systemic Haematological Responses Are Similar Between Continuous And Intermittent Blood Flow Restricted Resistance Exercise

Resistance training (RT) with blood flow restriction (BFR) induces similar adaptations to traditional RT but uses markedly lower training loads. However, information about the acute exercise pressor, hemodynamic, and local metabolic cost of this training approach is sparse. These data are needed to understand the acute safety implications of this training approach and help identify an optimal BFR protocol. PURPOSE: To compare the acute central and systemic cardiovascular, and local metabolic responses to resistance exercise performed with continuous (BFR-C) and intermittent (BFR-I) BFR. METHODS: 12 resistance-trained males (mean ± SD) aged 22.3 ± 3.2yrs, 1.82 ± 0.06m, and 84.1 ± 9.0kg performed 4 separate acute resistance training sessions in a random order, each separated by 7 days. Training sessions involved four sets of squat-based RT at 30% of individuals’ 1 repetition maximum with 1) no BFR (CON), 2) BFR-C, 3) BFR-I, and 4) traditional high load training at 70% of 1 repetition maximum with no BFR (HL). Systemic blood pressure and derivatives of cardiac output, central aortic blood pressure pulse wave characteristics, and local blood volume and metabolism were assessed periodically during, and after each training session. Data were assessed by two-way ANOVA with Bonferroni-corrected post-hoc comparisons. RESULTS: All sessions similarly increase average metabolic demand, seen by a decreased tissue saturation index (-15%, 95% CI 13.3 to 17.4, p<0.0001) with no difference between conditions (p>0.05). Whilst changes in haemoglobin-derived Vastus Lateralis blood volumes were similar between conditions, they were higher with BFR-C than CON (6.97 μmol/L, 95% CI 0.2 to 13.6, p=0.04) and HL (7.9 μmol/L, 95% CI 1.2 to 14.8, p=0.01). Training equally increased mean systemic mean arterial pressure (MAP) (+70.5 to 76.6 mmHg, p<0.001) and cardiac output (+0.74 to 0.96 L, p<0.001) above baseline, with no difference between conditions. Training also equally increased mean aortic MAP (+14.8 to 24.2 mmHg, p<0.001) above baseline across conditions. CONCLUSIONS: BFR-C and BFR-I cause similar exercise pressor responses comparable with both traditional resistance training, and training without BFR. Adding BFR to resistance training didn’t exacerbate the magnitude or duration of the associated cardiovascular stress.

Functional strength exercise and blood-flow restriction protocols: a systematic review

Objective: To assess current literature focused on the influence of functional training with blood flow restriction (BFR) on muscular adaptation in adults below the age of 65 years. Methods: A systematic literature search was performed with the following databases: PubMed, CINAHL Complete EBSCOhost, and ScienceDirect. Two researchers filtered the articles according to the criteria and quality, supported by the Consolidated Standards of Reporting Trials (CONSORT) tool. Studies were limited to those with participants with a mean age between18 and 65 years. Articles were peer-reviewed, available in English, and utilized either multi-joint resistance exercises or functional exercise as the intervention. Results: The search yielded 16 studies on uninjured, older adult, injured and athletic subjects. Regardless of the population, the studies tended to favor BFR training for improvements of strength, but this was highly dependent on cuff pressure and training load. Conclusions: Current literature suggests that BFR with functional and or multi-joint strength training is successful in improving strength, hypertrophy, function and in pain reduction. Favorable results with functional BFR included procedures using relative and well-controlled occlusion pressure. More research is necessary to understand the effect of BFR on self-reported outcomes and hypertrophy in athletic and older adults.

Blood Flow Restriction Does Not Attenuate Short-Term Detraining-Induced Muscle Size and Strength Losses After Resistance Training With Blood Flow Restriction.

Teixeira, EL, de Salles Painelli, V, Silva-Batista, C, de Souza Barros, T, Longo, AR, Lasevicius, T, Schoenfeld, BJ, Aihara, AY, and de Almeida Peres, B. Blood flow restriction does not attenuate short-term detraining-induced muscle size and strength losses after resistance training with blood flow restriction. J Strength Cond Res 35(8): 2082-2088, 2021-After a short-term resistance training with blood flow restriction (BFR), we investigated the effects of 12 days of detraining (DET), without an exercise stimulus, on quadriceps cross-sectional area (QCSA) and muscle strength (1 repetition maximum [1RM]), with 1 leg receiving daily intermittent BFR during DET vs. the same nonexercise condition without BFR (CON) in the contralateral leg. Both subjects' legs were evaluated for QCSA and 1RM before (PRE) and after (POST) both legs being unilaterally submitted to 3 weeks (4 days per week) of low-load (3 sets of 15 repetitions, 30% 1RM) resistance training with BFR. The DET period started immediately after POST, where each leg was randomly submitted to a daily intermittent BFR protocol or CON, without any associated exercise stimulus. Quadriceps cross-sectional area and 1RM were reassessed after DET. Both legs at CON and BFR conditions increased QCSA (6.3 and 6.8%, respectively; both p < 0.0001) and 1RM (9.5 and 10.1%, respectively; both p < 0.05) from PRE to POST. Both legs at CON and BFR conditions reduced QCSA (-4.6 and 4.9%, respectively; both p < 0.0001) and 1RM (-9.0 and -8.2%, respectively; both p < 0.05) from POST to DET, with no significant differences between conditions (p > 0.05). We conclude that muscle strength and hypertrophy gains obtained in 3 weeks of resistance training with BFR are not maintained after 12 days of DET. Moreover, the application of BFR, without an associated exercise stimulus, does not attenuate such losses.

Lower occlusion pressure during resistance exercise with blood-flow restriction promotes lower pain and perception of exercise compared to higher occlusion pressure when the total training volume is equalized.

Low-intensity resistance exercise with blood-flow restriction (BFR) promotes similar adaptations to high-intensity resistance exercise (HI-RE). Interestingly, BFR has been demonstrated to be effective for a wide range of occlusion pressures. However, the occlusion pressure magnitude may alter the psychophysiological stress related to BFR as measured by rating of perceived exertion scale (RPE) and rating of pain. We aimed to compare the RPE and pain levels across different magnitudes of occlusion pressures, promoting new knowledge regarding occlusion pressure on stress related to BFR. All BFR protocols ranging between 40% and 80% of total arterial occlusion (BFR40, BFR50, BFR60, BFR70, and BFR80) were compared to HI-RE in 12 participants using a randomized and crossover design 72h apart. BFR protocols and HI-RE were performed with 30% and 80% of one-repetition maximum (1RM) test value, respectively. RPE and pain levels were measured before exercise and immediately after each set. BFR protocols (i.e.,BFR40 and BFR50) presented overall lower RPE response compared to higher-pressure BFR (i.e.,BFR70 and BFR80) and HI-RE conditions. For pain levels, low-pressure BFRs (i.e.,BFR40 and BFR50), and HI-RE showed lower values than high-pressure BFR protocols (i.e.,BFR60, BFR70, and BFR80). In conclusion, low-pressure BFR protocols promote lower RPE and pain compared to high-pressure BFR protocols (between 60% and 80% of occlusion pressure), when total training volume (TTV) is equalized. In addition, HI-RE promotes similar levels of pain, but higher RPE than low-pressure BFR, probably due to the higher TTV.

Acute responses of hemodynamic and oxidative stress parameters to aerobic exercise with blood flow restriction in hypertensive elderly women.

Systemic arterial hypertension has been associated with the majority deaths from cardiovascular disease, especially among the elderly population, and the imbalance between antioxidant and pro-oxidants has been associated with hypertension. This study analyzed the acute responses of cardiorespiratory and oxidative stress parameters to low intensity aerobic exercise (LIAE) with blood flow restriction (BFR) in hypertensive elderly women. The experimental group consisted of 16 hypertensive women (67.2 ± 3.7years) who underwent a progressive treadmill test and performed three exercise protocols in random order: high intensity (HIAE), low intensity aerobic exercise (LIAE) and low intensity aerobic exercise with blood flow restriction (LIAE + BFR). Data analysis showed that blood pressure and heart rate augmented from rest to post effort (p < 0.05) and reduced from post effort to recovery (p < 0.05) in all protocols. The values of lipid peroxidation were higher after 30min of recovery when compared to the moment at rest in the LILIAE + BFR (p < 0.05). The same occurred with glutathione-S-transferase and superoxide dismutase activity. However, non-protein thiols levels (NPSH) reduced after 30min of recovery when compared to the moment at rest in the LILIAE + BFR protocol (p < 0.05). In the HIAE and LIAE + BFR protocols, the levels of NPSH were lower at 30min of recovery when compared to the same moment in the LIAE protocol (p < 0.05). LIAE + RBF produces an oxidative status and hemodynamic stimulus similar to HIAE. Taken together, these results support the indication of LIAE with BFR in chronic intervention protocols, with potential benefits for the hypertensive elderly population.

Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery.

The present study was designed to provide mechanistic insight into the time course and etiology of muscle fatigue development and recovery during and after low-intensity exercise when it is combined with blood flow restriction (BFR). Seventeen resistance-trained males completed four sets of low-intensity isotonic resistance exercise under two experimental conditions: knee extension exercise (i) with BFR and (ii) without BFR (CON). Neuromuscular tests were performed before, during (immediately after each set of knee extension exercise), and 1, 2, 4, and 8 min after each experimental condition. Maximal voluntary torque, quadriceps twitch torque in response to paired electrical stimuli at 10 Hz (PS10) and 100 Hz (PS100), PS10·PS100 ratio as an index of low-frequency fatigue, and voluntary activation were measured under isometric conditions. Perceptual and EMG data were recorded during each exercise condition. After the first set of exercise, BFR induced significantly greater reductions in maximal voluntary torque, PS100, and PS10·PS100 ratio compared with CON. These parameters progressively declined throughout the BFR protocol but recovered substantially within 2 min postexercise when blood flow was restored. Neither a progressive decline in the course of the exercise protocol nor a substantial recovery of these parameters occurred during and after CON. Only at exercise termination, voluntary activation differed significantly between BFR and CON with greater reductions during BFR. At the early stage of exercise, BFR exacerbated the development of muscle fatigue mainly due to a pronounced impairment in contractile function. Despite the high level of muscle fatigue during BFR exercise, the effect of BFR on muscle fatigue was diminished after 2 min of reperfusion, suggesting that BFR has a strong but short-lasting effect on neuromuscular function.

Influence of muscle mass on hemodynamic responses during different resistance exercises with and without blood flow restriction

Summary Introduction We investigated acute hemodynamic responses during resistance exercises performed with small and large muscle mass, comparing high intensity resistance exercises and low intensity resistance exercise with blood flow restriction. Summary of facts and results In a randomized crossover design, 15 sedentary men aged 40–60 years performed four exercise sessions: 45° hip angle leg-press (80% 1-RM), 45° hip angle leg-press (20% 1-RM) with blood flow restriction, knee extension (80% 1-RM), knee extension (20% 1-RM) with blood flow restriction. Blood pressure and heart rate were measured before and at the end of each set of exercise sessions. Blood pressure values were higher for sessions with blood flow restriction (systolic peak of 170.27 mmHg in knee extension and diastolic peak of 92.40 mmHg in leg press) compared to high intensities sessions whereas heart rate (peak of 140.53 bpm for leg press) and double product (peak of 23,688 mmHg bpm for leg press) were significantly increased at high intensities compared to blood flow restriction protocols. The results are achieved regardless of the size of muscle mass involved in the exercises. Conclusion BFR method consists of a deciding factor for increase hemodynamic variables during exercise regardless of the size the muscle mass involved and should be prescribed with carefully for population.

Influence of Blood Flow Restriction During Low-Intensity Resistance Exercise on the Postexercise Hypotensive Response.

Low-intensity resistance exercise (RE) combined with blood flow restriction (BFR) has been shown to promote similar increases in strength and hypertrophy as traditional high-intensity RE without BFR. However, the effect of BFR on the acute postexercise hypotensive response has received limited examination. Therefore, the purpose of this study was to compare high-intensity exercise (HIE) vs. low-intensity RE with BFR on the postexercise hypotensive response in normotensive young subjects. Fifteen men (age: 23.4 ± 3.4 years) performed the following 2 experimental protocols in randomized order: (a) 3 sets of biceps curls (BCs) at 80% of 1 repetition maximum (RM) and 120-second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60-second rest between sets. Analysis of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was conducted for 60 minutes after both protocols. The values for SBP, DBP, and mean blood pressure (MBP) at baseline and postexercise were not significantly different between the HIE vs. the BFR protocol. However, within the BFR protocol, significant decreases (p ≤ 0.05) in SBP occurred at 30 minutes (125.86 ± 9.33 mm Hg) and 40 minutes (125.53 ± 10.19 mm Hg) after exercise when compared with baseline (132.86 ± 9.12 mm Hg) and significant decreases in DBP and MBP occurred at 20 minutes, 30 minutes, and 40 minutes after exercise vs. baseline (p ≤ 0.05). Therefore, we conclude that exercises engaging a relatively small amount of muscle mass, such as the BC (or other similar single joint exercises), might be performed at a lower intensity with BFR to promote a postexercise hypotensive response.

Hypotensive effects of resistance exercises with blood flow restriction.

The effects of low-intensity resistance exercise (RE) combined with blood flow restriction (BFR) on blood pressure (BP) are an important factor to be considered because of the acute responses imposed by training. The aim of this study was to compare the hypotensive effect of RE performed with and without BFR in normotensive young subjects. After 1 repetition maximum (1RM) tests, 24 men (21.79 ± 3.21 years; 1.72 ± 0.06 m; 69.49 ± 9.80 kg) performed the following 4 experimental protocols in a randomized order: (a) high-intensity RE at 80% of 1RM (HI), (b) low-intensity RE at 20% of 1RM (LI), (c) low-intensity RE at 20% of 1RM combined with partial BFR (LI + BFR), and (d) control. Analysis of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was conducted over a 60-minute period. The 3 RE protocols resulted in hypotensive SBP (HI = -3.8%, LI = -3.3%, LI + BFR = -5.5%) responses during the 60 minutes (p ≤ 0.05). The LI + BFR protocol promoted hypotensive (-11.5%) responses in DBP during the 60 minutes (p ≤ 0.05), and both the HI and LI + BFR protocols resulted in mean blood pressure (MBP) hypotension between 30 (-7.0%, -7.7%) and 60 minutes (-3.6%, -8.8%), respectively. In conclusion, postexercise hypotension may occur after all 3 exercise protocols with greater reductions in SBP after HI and LI + BFR, in DBP after LI + BFR, and in MBP after HI and LI + BFR protocols.

The acute muscle swelling effects of blood flow restriction

The purpose of this study was to investigate the potential mechanisms behind the blood flow restriction (BFR) stimulus in the absence of exercise. Nine participants completed a 10 minute time control and then a BFR protocol. The protocol was five, 5-minute bouts of inflation with 3-minutes of deflation between each bout. The pressure was set relative to each individual's thigh circumference. Significant increases in muscle thickness were observed for both the vastus lateralis (VL) [6%, p = 0.027] and rectus femoris (RF) [22%, p = 0.001] along with a significant decrease in plasma volume [15%, p = 0.001]. Ratings of discomfort during the BFR protocol peaked at 2.7 (light discomfort). There were no significant changes with whole blood lactate, electromyography (EMG), or heart rate (HR), however, there was a trend for a significant increase in HR during the 5th inflation (p = 0.057). In conclusion, this is the first study to demonstrate that the attenuation of both muscle atrophy and declines in strength previously observed with brief applications of BFR may have been mediated through an acute fluid shift induced increase in muscle size. This is supported by our finding that the changes in muscle thickness are maintained even after the cuffs have been removed.

The acute hemodynamic effects of blood flow restriction in the absence of exercise

The purpose was to investigate the acute effects of blood flow restriction (BFR) on arterial and venous hemodynamic parameters. Nine participants completed a 10-min time control (resting condition) and then a lower body BFR protocol. The protocol was five, 5-min bouts of restrictive cuff inflation with 3-min of deflation between each bout. The pressure was set relative to each individual's thigh circumference. There were no significant differences between resting and BFR conditions for blood pressure or wave reflection. There was, however, a significant decrease in venous compliance and maximal venous outflow following BFR. Acute BFR with pressures relative to thigh circumference does not result in acute changes in blood pressure or wave reflection. There is, however, an acute decrease in venous compliance and maximal venous outflow, the significance of which is currently unknown. These results suggest that an acute BFR protocol affects venous but not arterial hemodynamics.