Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans

Microvascular Reactivity Is Greater Following Blood Flow Restriction Resistance Exercise Compared with Traditional Resistance Exercise

ABSTRACT

Perlet, MR, Hosick, PA, Licameli, N, and Matthews, EL. Microvascular reactivity is greater following blood flow restriction resistance exercise compared with traditional resistance exercise. J Strength Cond Res XX(X): 000-000, 2024-Chronic blood flow restriction (BFR) resistance exercise can improve muscular strength, hypertrophy, and microvasculature function, but the acute microvascular effects are unknown. We aimed to test the effects of acute BFR resistance exercise on postexercise microvascular reactivity in an exercising muscle and nonexercising muscle compared with traditional resistance exercise (TRE). Twenty-five adults (men = 14, women = 11, age: 22 ± 3 years, body mass: 71.69 ± 14.49 kg, height: 170 ± 10 cm) completed barbell back squat 1-repetition maximum (1RM) testing followed by 2 randomized and counterbalanced resistance exercise visits separated by ≥48 hours. The 2 visits involved either BFR (4 sets of 30-15-15-15 repetitions at 30% 1RM, with 60-second rest intervals) or TRE (4 sets of 10 repetitions at 70% 1RM, 60-second rest intervals). During each exercise visit, a pre- and postbarbell back squat vascular occlusion test was performed using near-infrared spectroscopy to measure skeletal muscle oxygen (SmO2) in the vastus lateralis (VL) and flexor carpi radialis (FCR). Two-way repeated-measures ANOVA found an interaction effect (p = 0.020) for SmO2 reactivity in the VL. Post hoc analysis found greater reactive hyperemia postexercise in the VL for the BFR condition (p < 0.001) but not the TRE condition (p ≥ 0.05). There were no time, condition, or interaction effects (all p > 0.05) for the same analysis in the FCR. This analysis suggests that BFR, but not TRE, lead to acutely improved microvasculature function. Moreover, it suggests that the effects of BFR resistance exercise are local to the exercised or occluded limb and not systemic.

Effects of blood flow restriction training on physical fitness among athletes: a systematic review and meta-analysis

Blood flow restriction training (BFRT) is an effective, scientific and safe training method, but its effect on the overall quality of athletes remains unclear. The aim of this systematic review with meta-analysis was to clarify the effects of BFRT on the physical fitness among athletes. Based on the PRISMA guidelines, searches were performed in PubMed, Web of Science, SPORTDiscus, and SCOUPS, the Cochrane bias risk assessment tool was used to assess methodological quality, and RevMan 5.4 and STATA 15.0 software were used to analyze the data. A meta-analysis of 28 studies with a total sample size of 542 athletes aged 14-26 years and assessed as low risk for quality was performed. Our results revealed that the BFRT intervention had small to large improvements in the athletes' strength (ES = 0.74-1.03), power (ES = 0.46), speed (ES = 0.54), endurance (ES = 1.39-1.40), body composition (ES = 0.28-1.23), while there was no significant effect on body mass (p > 0.05). Subgroup analyses revealed that moderator variables (training duration, frequency, load, cuff pressure, and pressurization time) also had varying degrees of effect on athletes' physical fitness parameters. In conclusion, BFRT had a positive effect on the physical fitness parameters of the athletes, with significantly improved strength, power, speed, endurance and body composition, but not body mass parameters. When the training frequency ≥ 3 times/week, cuff pressure ≥ 160 mmHg, and pressurization time ≥ 10 min, the BFRT group was more favorable for the improvement of physical fitness parameters.

Acute resistance exercise combined with whole body vibration and blood flow restriction: Molecular and neurocognitive effects in late-middle-aged and older adults

Limited research exists regarding the effects of resistance exercise (RE) combined with whole body vibration (WBV), blood flow restriction (BFR), or both on the neuropsychological performance of working memory (WM) in late-middle-aged and older adults and regarding the physiological mechanisms underlying this effect. This study thus explored the acute molecular and neurophysiological mechanisms underlying WM performance following RE combined with WBV, BFR, or both. Sixty-six participants were randomly assigned into a WBV, BFR, or WBV + BFR group. Before and after the participants engaged in a single bout of isometric RE combined with WBV, BFR, or both, this study gathered data on several neurocognitive measures of WM performance, namely, accuracy rate (AR), reaction time (RT), and brain event-related potential (specifically P3 latency and amplitude), and data on biochemical indices, such as the levels of insulin-like growth factor-1 (IGF-1), norepinephrine (NE), and brain-derived neurotrophic factor (BDNF). Although none of the RE modalities significantly affected RTs and P3 latencies, ARs and P3 amplitudes significantly improved in the WBV and WBV + BFR groups. The WBV + BFR group exhibited greater improvements than the WBV group did. Following acute RE combined with WBV, BFR, or both, IGF-1 and NE levels significantly increased in all groups, whereas BDNF levels did not change. Crucially, only the changes in NE levels were significantly correlated with improvements in ARs in the WBV + BFR and WBV groups. The findings suggest that combining acute RE with WBV, BFR, or both could distinctively mitigate neurocognitive decline in late-middle-aged and older adults.

Lower limb blood flow occlusion increases systemic pressor response without increasing brachial arterial blood flow redistribution in women

This study was conducted to investigate the systemic hemodynamic and vascular changes in women during and after two commonly used clinical blood flow restriction (BFR) pressures at rest. There are minimal data regarding the independent effects of BFR on hemodynamic and systemic vascular changes due to pressor response, particularly among women. Therefore, this study investigated BFR-induced alterations in pressor response and systemic flow redistribution at rest during two commonly used pressures (50% and 80% limb occlusion pressure [LOP]). Fifteen women (22.1 ± 4.2 years) completed two randomised sessions involving 8-min of bilateral, lower limb restriction at 50% or 80% LOP followed by 8-min of recovery post-deflation. Changes in vascular (arterial diameter [DIA], time-averaged mean velocity [TAMV], volume flow [VF], and area) and hemodynamic (heart rate [HR] and blood pressure) measures over time (pre-, during, post-occlusion) and by session (50% vs. 80% LOP) were tested using repeated measures analysis of variance. Repeated measures correlations (rrm) quantified common intraindividual associations between BFR-induced hemodynamic and vascular responses. HR increased from baseline during 50% LOP and remained elevated during recovery (p < 0.05). HR increased from baseline during 80% LOP, while tibial VF and TAMV decreased (p < 0.03 for all). HR and TAMV values returned to baseline during recovery, while brachial artery VF decreased (p < 0.05). Changes in HR, brachial VF, and brachial TAMV were similar between 50% and 80% LOP (rrm = 0.32-0.70, p < 0.05 for all). At 80% LOP, changes in HR were positively correlated with brachial VF (rrm = 0.38) and TAMV (rrm = 0.43) and negatively correlated with tibial VF (rrm = -0.36) and TAMV (rrm = -0.30) (p < 0.05 for all). Results suggest that BFR at 80% LOP elicits an acute systemic pressor reflex without concomitant increases in brachial arterial flow, while 50% LOP elicits a subdued response.

Validity and reliability of a wearable blood flow restriction training device for arterial occlusion pressure assessment

Purpose

The blood flow restriction (BFR) training is an effective approach to promoting muscle strength, muscle hypertrophy, and regulating the peripheral vascular system. It is recommended to use to the percentage of individual arterial occlusion pressure (AOP) to ensure safety and effectiveness. The gold standard method for assessing arterial occlusive disease is typically measured using Doppler ultrasound. However, its high cost and limited accessibility restrict its use in clinical and practical applications. A novel wearable BFR training device (Airbands) with automatic AOP assessment provides an alternative solution. This study aims to examine the reliability and validity of the wearable BFR training device.

Methods

Ninety-two participants (46 female and 46 male) were recruited for this study. Participants were positioned in the supine position with the wearable BFR training device placed on the proximal portion of the right thigh. AOP was measured automatically by the software program and manually by gradually increasing the pressure until the pulse was no longer detected by color Doppler ultrasound, respectively. Validity, inter-rater reliability, and test-retest reliability were assessed by intraclass correlation coefficients (ICC) and Bland-Altman analysis.

Results

The wearable BFR training device demonstrated good validity (ICC = 0.85, mean difference = 4.1 ± 13.8 mmHg [95% CI: -23.0 to 31.2]), excellent inter-rater reliability (ICC = 0.97, mean difference = -1.4 ± 6.7 mmHg [95% CI: -14.4 to 11.7]), and excellent test-retest reliability (ICC = 0.94, mean difference = 0.6 ± 8.6 mmHg [95% CI: -16.3 to 17.5]) for the assessment of AOP. These results were robust in both male and female subgroups.

Conclusion

The wearable BFR training device can be used as a valid and reliable tool to assess the AOP of the lower limb in the supine position during BFR training.

Cerebral cortex activation and functional connectivity during low-load resistance training with blood flow restriction: An fNIRS study

Despite accumulating evidence that blood flow restriction (BFR) training promotes muscle hypertrophy and strength gain, the underlying neurophysiological mechanisms have rarely been explored. The primary goal of this study is to investigate characteristics of cerebral cortex activity during BFR training under different pressure intensities. 24 males participated in 30% 1RM squat exercise, changes in oxygenated hemoglobin concentration (HbO) in the primary motor cortex (M1), pre-motor cortex (PMC), supplementary motor area (SMA), and dorsolateral prefrontal cortex (DLPFC), were measured by fNIRS. The results showed that HbO increased from 0 mmHg (non-BFR) to 250 mmHg but dropped sharply under 350 mmHg pressure intensity. In addition, HbO and functional connectivity were higher in M1 and PMC-SMA than in DLPFC. Moreover, the significant interaction effect between pressure intensity and ROI for HbO revealed that the regulation of cerebral cortex during BFR training was more pronounced in M1 and PMC-SMA than in DLPFC. In conclusion, low-load resistance training with BFR triggers acute responses in the cerebral cortex, and moderate pressure intensity achieves optimal neural benefits in enhancing cortical activation. M1 and PMC-SMA play crucial roles during BFR training through activation and functional connectivity regulation.

Potential Moderators of the Effects of Blood Flow Restriction Training on Muscle Strength and Hypertrophy: A Meta-analysis Based on a Comparison with High-Load Resistance Training

BACKGROUND

While it has been examined whether there are similar magnitudes of muscle strength and hypertrophy adaptations between low-load resistance training combined with blood-flow restriction training (BFR-RT) and high-load resistance training (HL-RT), some important potential moderators (e.g., age, sex, upper and lower limbs, frequency and duration etc.) have yet to be analyzed further. Furthermore, training status, specificity of muscle strength tests (dynamic versus isometric or isokinetic) and specificity of muscle mass assessments (locations of muscle hypertrophy assessments) seem to exhibit different effects on the results of the analysis. The role of these influencing factors, therefore, remains to be elucidated.

OBJECTIVES

The aim of this meta-analysis was to compare the effects of BFR- versus HL-RT on muscle adaptations, when considering the influence of population characteristics (training status, sex and age), protocol characteristics (upper or lower limbs, duration and frequency) and test specificity.

METHODS

Studies were identified through database searches based on the following inclusion criteria: (1) pre- and post-training assessment of muscular strength; (2) pre- and post-training assessment of muscular hypertrophy; (3) comparison of BFR-RT vs. HL-RT; (4) score ≥ 4 on PEDro scale; (5) means and standard deviations (or standard errors) are reported or allow estimation from graphs. In cases where the fifth criterion was not met, the data were requested directly from the authors.

RESULTS

The main finding of the present study was that training status was an important influencing factor in the effects of BFR-RT. The trained individuals may gain greater muscle strength and hypertrophy with BFR-RT as compared to HL-RT. However, the results showed that the untrained individuals experienced similar muscle mass gains and superior muscle strength gains in with HL-RT compared to BFR-RT.

CONCLUSION

Compared to HL-RT, training status is an important factor influencing the effects of the BFR-RT, in which trained can obtain greater muscle strength and hypertrophy gains in BFR-RT, while untrained individuals can obtain greater strength gains and similar hypertrophy in HL-RT.

Vertical Strength Transfer Phenomenon Between Upper Body and Lower Body Exercise: Systematic Scoping Review

BACKGROUND

There are a myriad of exercise variations in which upper body (UB) and lower body (LB) exercises have been intermittently used. However, it is still unclear how training of one body region (e.g. LB) affects adaptations in distant body areas (e.g. UB), and how different UB and LB exercise configurations could help facilitate physiological adaptations of either region; both referred to in this review as vertical strength transfer.

OBJECTIVE

We aimed to investigate the existence of the vertical strength transfer phenomenon as a response to various UB and LB exercise configurations and to identify potential mechanisms underpinning its occurrence.

METHODS

A systematic search using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for Scoping Reviews protocol was conducted in February 2024 using four databases (Web of Science, MEDLINE, Scopus and CINAHL) to identify peer-reviewed articles that investigated the vertical strength transfer phenomenon.

RESULTS

Of the 5242 identified articles, 24 studies met the inclusion criteria. Findings suggest that the addition of UB strength training to LB endurance exercise may help preserve power-generating capacity for the leg muscle fibres. Furthermore, systemic endocrine responses to high-volume resistance exercise may beneficially modulate adaptations in precedingly or subsequently trained muscles from a different body region, augmenting their strength gains. Last, strength training for LB could result in improved strength of untrained UB, likely due to the increased central neural drive.

CONCLUSIONS

Vertical strength transfer existence is enabled by neurophysiological mechanisms. Future research should involve athletic populations, examining the potential of vertical strength transfer to facilitate athletic performance and preserve strength in injured extremities.

Minimum velocity threshold in response to the free-weight back squat: reliability and validity of different submaximal loading schemes

PURPOSE

To explore if mean concentric velocity (MCV) of the last repetition before set failure differs between free-weight back squat protocols with greater emphasis on metabolic accumulation vs. mechanical loading. The between-set and between-day reliability of terminal MCV obtained with these different loading schemes was also determined.

METHODS

Fifteen healthy male participants (18-30 years) were included. They all were required to exhibit a relative strength ≥ 1.5 times their body mass. MCVs were obtained at one-repetition maximum (1RM) and with two submaximal protocols (metabolic emphasis: three sets of 40%1RM with blood-flow restriction vs. mechanical emphasis: three sets 80%1RM without blood-flow restriction). Participants were instructed to reach maximal intended concentric velocity in each repetition up to failure.

RESULTS

Set failure was achieved at a faster MCV with the metabolic protocol (p < 0.05). The reliability of MCV at failure reached higher values for the metabolic loading scheme. However, while the MCV achieved at failure during the metabolic protocol was systematically higher than the MCV at 1RM (p < 0.05), this was not entirely the case for the mechanical protocol (similar to 1RM MCV during the last sets in both testing days). Finally, the absolute error derived from estimating the MCV at 1RM based on the MCV obtained at set failure with the mechanical protocol was considerably high (≥ 0.05 m/s).

CONCLUSION

This study indicates that MCV obtained at set failure is dependent on the specificity of the physiological demands of exercise. Thus, MCVs obtained at failure with submaximal loads should not be used to estimate 1RM MCV.

The effects of low-intensity resistance training with blood flow restriction versus traditional resistance exercise on lower extremity muscle strength and motor functionin ischemic stroke survivors: a randomized controlled trial

BACKGROUND

Blood flow restriction (BFR) training can temporarily reduce cortical GABA concentrations and increase the size of motor volleys to deafferented muscles, which can promote motor recovery in stroke survivors.

OBJECTIVE

To determine the effect of low-intensity resistance training with BFR (LIRT-BFR) on lower extremity muscle strength, balance, functional mobility, walking capacity, gait speed, anxiety, and depression in stroke survivors and to compare the results with high-intensity resistance training (HIRT).

METHOD

It was a two-arm, single-blinded, randomized controlled trial in which 32 ischemic stroke participants were randomly allocated to LIRT-BFR or HIRT group. The LIRT-BFR group received low load resistance training (40% of 1-Repetition Maximum (1-RM)) with BFR, whereas HIRT group   received high load resistance training (80% of 1-RM). The 6-Minute Walk Test (6-MWT), five-time sit-to-stand test (5TSTST), Timed Up and Go (TUG) test, and Barthel index were the primary outcome measures. The secondary outcome measures included gait speed (m/s), stride length (cm), cadence (steps/min), and Hospital Anxiety and Depression.

RESULTS

All the primary and secondary outcome measures were significantly improved in both groups (p < 0.05). The LIRT-BFR group showed a slightly greater, but non-significant, improvement as compared to the HIRT group in terms of mean change observed in 6-MWT (81 m vs 62 m), 5TSTST (-5.27 vs -4.81), gait speed (0.19 vs 0.12), stride length (18 vs 13), and cadence (8 vs 6). No adverse event was reported.

CONCLUSION

LIRT-BFR produced a significant improvement in muscle strength, balance, walking capacity, and anxiety and depression in ischemic stroke patients, and the improvement are comparable to HIRT.

CLINICAL TRIAL REGISTRATION

NCT05281679.

Survey of Blood Flow Restriction Training Applications in Sports Medicine and Performance Practice Across North America

Colapietro, MA, Lee, JZ, and Vairo, GL. Survey of blood flow restriction training applications in sports medicine and performance practice across North America. J Strength Cond Res 38(5): 856–863, 2024—This study profiled current clinical applications of blood flow restriction (BFR) training and observed side effects by surveying active sports medicine and performance personnel across North America. An online survey consisting of questions derived from a related position statement was distributed through professional organizations, email listservs, and social media. Personnel with experience applying or prescribing BFR training with permanent residence within the United States or Canada were eligible to participate. Variables captured included demographics (profession, practice setting), BFR equipment, treatment parameters, observed side effects, and personal perceptions regarding BFR training. An alpha level of p < 0.05 determined significance. A convenience sample included 72 clinicians with 67 being from the United States. Athletic trainers (n = 35) and physical therapists (n = 30) primarily participated. Chi-square test of independence indicated that a higher proportion of physical therapists (90.3%) report receiving formal education in BFR training compared with athletic trainers (65.7%) ( = 4.1, p = 0.043). Parameters varied between respondents for exercise prescription and occlusion settings. Respondents primarily followed position statement recommendations with individualized pressure selections for resistance (80.9%) and aerobic (84.8%) BFR modes. Side effects reported included delayed onset muscle soreness (66.2%), inability to continue because of pain (28%), and numbness (22.5%). Personal perceptions between athletic trainers and physical therapists were compared using independent t-tests. Physical therapists indicated higher confidence in safety (difference = 0.37 ± 0.32, p = 0.026), understanding recommendations (difference = 0.47 ± 0.37, p = 0.011), and theoretical principles (difference = 0.80 ± 0.53, p = 0.004). Despite variation in BFR parameters used, sports medicine personnel demonstrate compliance with position statement recommendations and report mild side effects.

Effects of Static Stretching on the Blood Circulation of Human Tendon In Vivo

The purpose of this study is to compare the effects of 2- and 5 min of static stretching protocols on the changes in blood circulation of tendon (as well as muscle) and heart rate. Twelve healthy males (age: 26.2 ± 9.1 yrs) volunteered for this study. Before, during stretching, during the recovery period (30 min), blood circulation (oxyhemoglobin; oxy, deoxyhemoglobin; deoxy, blood volume; THb, oxygen saturation; StO2) of the Achilles tendon and medial gastrocnemius muscle were measured using red laser lights and near-infrared spectroscopy. In addition, heart rate was measured during the experimental period. For 2- and 5 min of static stretching, oxy, deoxy, THb, and StO2 of the tendon did not change during or after stretching. Regarding muscle blood circulation, oxy and StO2 decreased, and deoxy and THb increased during 2- and 5 min of static stretching but returned immediately upon completion. In addition, heart rate significantly reduced during and after stretching, whereas the changes in blood volume of tendon and muscle during stretching were not associated with those in heart rate (except for the relationship between tendon THb and heart rate in 2 min of static stretching). These results suggest that static stretching showed no change in tendon blood circulation, although muscle blood circulation during stretching was altered. In addition, significant heart rate reduction with static stretching was not associated with changes in tendon and muscle blood circulation.

Muscular stress is equal when resistance exercise with blood flow restriction is matched in total work volume: A cross-sectional, cross-over study

AIM

We compared muscular metabolic stress during exercise performed at multiple intensities, from very low to moderate, with blood flow restriction (BFR) adjusted by the same work volume.

METHODS

Twenty-five healthy young adults performed unilateral plantar flexion at 1 repetition/2 s in a magnetic resonance system. The BFR exercise protocols were as follows: (A) exercise with 10% of one repetition maximum (1-RM) for 360 s, (B) 15% 1-RM for 240 s, (C) 20% 1-RM for 180 s, (D) 30% 1-RM for 120 s, and (E) 40% 1-RM for 90 s. All protocols had the same total work volume (load × repetitions = 1800). A high-intensity protocol at 65% 1-RM without BFR (60 s) was also performed for comparison. We used 31 P-magnetic resonance spectroscopy to evaluate the muscular metabolic stress in the subjects' calf muscle, defined as decreases in phosphocreatine and intramuscular pH.

RESULTS

The phosphocreatine depletion (A: 15.6 ± 0.7, B: 14.8 ± 0.8, C: 15.2 ± 0.6, D: 14.3 ± 0.6, E: 10.9 ± 0.5 mM; no significant difference [ns]) and the intramuscular pH decrease (A: 6.82 ± 0.02, B: 6.84 ± 0.01, C: 6.83 ± 0.02, D: 6.83 ± 0.02, E: 6.77 ± 0.02; ns) at the end of each exercise were similar and greater than those produced by the 65% 1-RM without BFR.

CONCLUSION

If the total work volumes are equal, the metabolic stress in exercising muscle may reach similar levels at the end of exercise with BFR and could provide similar successful training effects.

Quadriceps vascular occlusion does not alter muscle action or balance: A cross-sectional study

Background

Partial vascular occlusion (PVO) can increase muscle strength and hypertrophy without joint overload. However, PVO could increase the possibility of imbalances and injuries during physical activity.

Objectives

To identify changes in strength, muscle activation, and postural control during the use of PVO in young women.

Method

A total of 14 healthy women aged between 18 and 30 years were evaluated. Dynamometry was used to analyse the strength of the quadriceps muscle, and surface electromyography to evaluate quadriceps muscle activity. A force platform was utilised to assess postural control, static single-legged support, single-legged squat, and climbing and descending stairs. Participants were randomly assigned to the evaluations either with or without PVO. The results were compared and correlated.

Results

The performance of static, dynamic, or stair exercises, with or without PVO, did not indicate differences in muscle strength and recruitment (p > 0.05). The use of PVO improved the velocity of anteroposterior (AP) oscillation of static postural control (p = 0.001). We found a moderate negative correlation between muscle strength and postural control during the ascending stairs task with the use of PVO (r = -0.54; r = -0.59), while in the group without PVO, the correlation was moderate to high (r = -0.55; r = -0.76).

Conclusion

The use of PVO did not impair muscle strength and recruitment of the quadriceps or postural control in healthy women.

Clinical Implications

Partial vascular occlusion can be used during dynamic exercises without impairing the balance and muscle strength of the quadriceps during its execution.

Use of blood flow restriction for increasing the strength of the ischiocrural muscles in anterior cruciate ligament rehabilitation: A case report

BACKGROUND

The hamstring muscles have a key function in the stability of the knee, limiting the anterior translation of the tibia. Therefore, to better perform rehabilitation after anterior cruciate ligament (ACL) surgery, it is important to develop a specific program based on hamstring strength recovery. It is possible to increase strength and muscle hypertrophy through high load exercises (HL); the recommended load is about 60%-80% of a maximum repetition (MR). Although low-load resistance training (LL) is ineffective at reproducing these values, the use of Blood Flow Restriction (BFR) with LL exercises appears to allow athletes to increase strength and muscle hypertrophy. This could limit functional decline and mitigate muscle atrophy allowing to optimize the recovery path and load management in post-operative patients. Recent scientific evidence, as far as the increasingly frequent use of BFR in rehabilitation and sports rehabilitation is concerned, suggests that these devices could represent one of the most significant innovations in the physiotherapy field. The aim of this study was to increase the strength of the hamstrings in the early phases of ACL rehabilitation with an LL-BFR training protocol for speeding up the development of adequate muscle strength.

CASE DESCRIPTIONS

The patient, a 25-year-old male professional footballer, suffered from ACL injury during a football match, and after three months, he underwent a reconstruction ACL surgery with medial Hamstring tendon autograft. The athlete engaged a pre-operative program to restore a full active and passive knee range of motion and increase muscular strength. The first rehabilitation phase was supported by the adoption of BFR for hamstring strengthening, starting from the sixth week post-surgery (T0). A complete assessment of posterior hamstring muscles was performed through a hand-held dynamometer and load detection platforms. Three different types of exercises, focusing on the hamstring muscles, were chosen. Two further assessments were performed over time (T1 ant T2), highlighting different changes that occurred.

RESULTS

Interesting results showed a significant increase between T0 and T1 for all the assessed outcomes; in this case an average increase in strength of 59.87% between the beginning and the end of 4 weeks rehabilitation protocol was obtained in the first interval (T0-T1), while only 25.26% resulted in the second interval (T1-T2). However, the collected data should be considered with caution due to some limitations: the single experience of a single patient can hardly be generalized. Moreover, the reliance on isometric measurement of maximal strength and the absence of a direct strength measurement of the hamstrings during squat remain questionable.

CONCLUSION

The final results suggest the capacity of the LL-BFR exercises to recreate a condition of a high intensity muscular effort with respect to load management, especially after surgery. This highlights the need to further investigate BFR adoption as it allows the patients to speed up their rehabilitation goals in developing adequate muscle strength.

Effects of Blood Flow Restriction Resistance Training on Autonomic and Endothelial Function in Persons with Parkinson's Disease

Background

Autonomic dysfunction precedes endothelial dysfunction in Parkinson's disease (PD) and causes blood pressure and circulation abnormalities that are highly disruptive to one's quality of life. While exercise interventions have proven helpful for motor symptoms of PD, improving associated non-motor symptoms is limited. Low-intensity resistance training with blood flow restriction (LIRT-BFR) improves autonomic dysfunction in non-PD patients and high-intensity resistance training (HIRT) is recommended for motor symptom improvements for people with PD (PwPD).

Objective

To determine the effects of LIRT-BFR and HIRT on homocysteine and autonomic and endothelial function in PwPD and to determine the hemodynamic loads during LIRT-BFR and HIRT in PwPD using a novel exercise protocol.

Methods

Thirty-eight PwPD were assigned LIRT-BFR, HIRT or to a control (CNTRL) group. The LIRT-BFR and HIRT groups exercised three days per week for four weeks. The LIRT-BFR protocol used 60% limb occlusion pressure (LOP) and performed three sets of 20 repetitions at 20% of the one-repetition maximum (1RM). The HIRT group performed three sets of eight repetitions at 80% 1RM. The CNTRL group was asked to continue their normal daily routines.

Results

LIRT-BFR significantly improved orthostatic hypotension (p = 0.026), homocysteine levels (p < 0.001), peripheral circulation (p = 0.003), supine blood pressure (p = 0.028) and heart rate variability (p = 0.041); LIRT-BFR improved homocysteine levels (p < 0.018), peripheral circulation (p = 0.005), supine blood pressure (p = 0.007) and heart rate variability (p = 0.047) more than HIRT; and hemodynamic loads for LIRT-BFR and HIRT were similar.

Conclusions

LIRT-BFR may be more effective than HIRT for autonomic and endothelial function improvements in PwPD and hemodynamic loads may be lessened in LIRT-BFR protocols using single-joint exercises with intermittent blood flow restriction. Further research is needed to determine if non-motor symptoms improve over time and if results are sustainable.

The Influence of Interval Training Combined with Occlusion and Cooling on Selected Indicators of Blood, Muscle Metabolism and Oxidative Stress

There is increasing evidence to support the use of interval training and/or low-impact blood flow restriction exercises in musculoskeletal rehabilitation. The aim of the study was to assess the effect of interval training combined with occlusion and cooling in terms of changes in selected blood parameters affecting the development and progression of atherosclerosis of the lower limbs, as well as selected parameters of muscle metabolism and oxidative stress affecting the growth of muscle mass and regeneration after training.

MATERIAL AND METHODS

The study included 30 young, healthy and untrained people. The VASPER (Vascular Performance) training system was used-High-Intensity Interval Training with the simultaneous use of occlusion and local cryotherapy. Blood from the project participants was collected six times (2 weeks before the start of training, on the day of training, after the first training, after the 10th training, after the 20th training and two weeks after the end of training). The subjects were randomly divided into three groups: exercises only (controlled), with occlusion and with occlusion and local cryotherapy.

RESULTS

Statistical analysis of changes in the average values of indicators in all study groups showed a significant change increase due to the time of testing IGF-1 (F = 2.37, p = 0.04), XOD (F = 14.26, p = 0.00), D-Dimer (F = 2.90, p = 0.02), and decrease in MDA (F = 7.14, p = 0.00), T-AOC (F = 11.17, p = 0.00), PT Quick (F = 26.37, p = 0.00), INR (F = 8.79, p = 0.00), TT (F = 3.81, p = 0.00). The most pronounced changes were observed in the occlusion and cooling group.

CONCLUSIONS

Both interval training without and with the modifications used in the study influences coagulation and oxidative stress parameters and, to a small extent, muscle metabolism. It seems reasonable to use occlusion and local cryotherapy in combination with occlusion.

No Differences in Exercise Performance, Perceptual Response, or Safety Were Observed Among 3 Blood Flow Restriction Devices

Purpose

To compare 3 separate blood flow restriction (BFR) systems in their capacity to reduce repetitions to failure, impact perceptual responses, and cause adverse events during a low-load free-flow exercise.

Methods

The study included healthy subjects aged 18 years or older who presented to an ambulatory-care sports medicine clinic. On day 1, participants' demographic characteristics and anthropomorphic measurements were recorded. Each participant performed dumbbell biceps curl repetitions to failure using 20% of his or her 1-repetition maximum weight with each arm. Participants were exposed to 3 different tourniquet systems for familiarization. On day 2, each participant's arm was randomized to a cuff system, and the participant performed 2 sets of biceps curl repetitions to failure with the cuff inflated. Repetitions to failure, rating of perceived effort (RPE), rating of perceived discomfort, and pulse oxygenation levels were recorded after each set. On day 3, participants completed a survey of their perceived delayed-onset muscle soreness.

Results

The final analysis was performed on 42 arms, with 14 limbs per system. The study population had a mean age of 28.7 ± 2.4 years and a mean body mass index of 24.9 ± 4.3. All 3 systems successfully reduced repetitions to failure compared with unrestricted low-load exercise from baseline to BFR set 1 and from baseline to BFR set 2. There were no significant between-group differences among BFR systems regarding the number of repetitions to failure performed at baseline versus BFR set 1 or BFR set 2. The Delfi Personalized Tourniquet System (PTS) cohort had the greatest reductions in repetitions to failure from BFR set 1 to BFR set 2 (P = .002) and reported the highest RPE after set 2 (P = .025).

Conclusions

The Delfi PTS, SmartCuffs Pro, and BStrong BFR systems were each safe and were able to significantly reduce repetitions to failure compared with a low-load free-flow condition when used in a BFR exercise protocol. The Delfi PTS system may produce a higher RPE with prolonged use in comparison to the other systems.

Level of Evidence

Level II, prospective cohort study.

Skeletal Muscle Adaptations to High-Load Resistance Training With Pre-Exercise Blood Flow Restriction

ABSTRACT

Hammert, WB, Moreno, EN, Martin, CC, Jessee, MB, and Buckner, SL. Skeletal muscle adaptations to high-load resistance training with pre-exercise blood flow restriction. J Strength Cond Res 37(12): 2381-2388, 2023-This study aimed to determine if blood flow restriction (BFR) could augment adaptations to a high-load training protocol that was inadequate for muscle growth. Forty nontrained individuals had each arm assigned to 1 of 3 elbow flexion protocols: (a) high-load resistance training [TRAD; 4 sets to muscular failure at 70% 1 repetition maximum (1RM)], (b) low repetition high-load resistance training with pre-exercise BFR (PreBFR; 4 sets of 3 repetitions at 70% 1RM + 3 min of pre-exercise BFR), and (c) low repetition high-load resistance training (LRTRAD); 4 sets of 3 repetitions at 70% 1RM). Muscle thickness (MT), 1RM strength, and local muscular endurance (LME) of the elbow flexors were measured before and after 8 weeks. An alpha level of 0.05 was used for all comparisons. For the 50% site, MT increased for TRAD (0.211 cm, 95% confidence interval [95% CI]: 0.143-0.280), PreBFR (0.105 cm, 95% CI: 0.034-0.175), and LRTRAD (0.073 cm, 95% CI: 0.000-0.146). The change for TRAD was greater than PreBFR and LRTRAD. For the 60% site, MT increased for TRAD (0.235 cm, 95% CI: 0.153-0.317), PreBFR (0.097 cm, 95% CI: 0.014-0.180), and LRTRAD (0.082 cm, 95% CI: 0.000-0.164). The change for TRAD was greater than PreBFR and LRTRAD. For the 70% site MT increased for TRAD (0.308 cm, 95% CI: 0.247-0.369), PreBFR (0.103 cm, 95% CI: 0.041-0.166), and LRTRAD (0.070 cm, 95% CI: 0.004-0.137). The change for TRAD was greater than PreBFR and LRTRAD. One repetition maximum and LME significantly increased for each condition, with no differences between conditions. Collapsed across conditions 1RM strength increased 2.094 kg (95% CI: 1.771-2.416) and LME increased 7.0 repetitions (95% CI: 5.7-8.3). In conclusion, the application of BFR to low-repetition, high-load training did not enhance the adaptative response.

Low-load blood flow restriction reduces time-to-minimum single motor unit discharge rate

Resistance training with low loads in combination with blood flow restriction (BFR) facilitates increases in muscle size and strength comparable with high-intensity exercise. We investigated the effects of BFR on single motor unit discharge behavior throughout a sustained low-intensity isometric contraction. Ten healthy individuals attended two experimental sessions: one with, the other without, BFR. Motor unit discharge rates from the tibialis anterior (TA) were recorded with intramuscular fine-wire electrodes throughout the duration of a sustained fatigue task. Three 5-s dorsiflexion maximal voluntary contractions (MVC) were performed before and after the fatigue task. Each participant held a target force of 20% MVC until endurance limit. A significant decrease in motor unit discharge rate was observed in both the non-BFR condition (from 13.13 ± 0.87 Hz to 11.95 ± 0.43 Hz, P = 0.03) and the BFR condition (from 12.95 ± 0.71 Hz to 10.9 ± 0.75 Hz, P = 0.03). BFR resulted in significantly shorter endurance time and time-to-minimum discharge rates and greater end-stage motor unit variability. Thus, low-load BFR causes an immediate steep decline in motor unit discharge rate that is greater than during contractions performed without BFR. This shortened neuromuscular response of time-to-minimum discharge rate likely contributes to the rapid rate of neuromuscular fatigue observed during BFR.

Effect of continuous and intermittent blood flow restriction deep-squat training on thigh muscle activation and fatigue levels in male handball players

We aimed to investigate acute changes before and after low-intensity continuous and intermittent blood flow restriction (BFR) deep-squat training on thigh muscle activation characteristics and fatigue level under suitable individual arterial occlusion pressure (AOP). Twelve elite male handball players were recruited. Continuous (Program 1) and intermittent (Program 2) BFR deep-squat training was performed with 30% one-repetition maximum load. Program 1 did not include decompression during the intervals, while Program 2 contained decompression during each interval. Electromyography (EMG) was performed before and after two BFR training programs in each period. EMG signals of the quadriceps femoris, posterior femoral muscles, and gluteus maximus, including the root mean square (RMS) and normalized RMS and median frequency (MF) values of each muscle group under maximum voluntary contraction (MVC), before and after training were calculated. The RMS value under MVC (RMSMVC) of the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), and gluteus maximus (GM) decreased after continuous and intermittent BFR training programs, and those of the biceps femoris (BF) and semitendinosus (SEM) increased; The RMS standard values of the VL, BF, and SEM were significantly increased after continuous and intermittent BFR training (P < 0.05), The RMS value of GM significantly decreased after cuff inflating (P < 0.05). The MF values of RF, VM, VL, and GM decreased significantly after continuous BFR training (P < 0.05). Continuous BFR deep-squat training applied at 50% AOP was more effective than the intermittent BFR training program. Continuous application of BFR induces greater levels of acute fatigue than intermittent BFR that may translate into greater muscular training adaptations over time.

Effects of Resistance Training with Blood Flow Restriction on Explosive Power of Lower Limbs: A Systematic Review and Meta-Analysis

The purpose of this systematic review and meta-analysis was to compare changes in explosive power between blood flow restriction training and traditional resistance training protocols. Searches of PubMed, Scopus, Web of Science, and OVID Medline were conducted for studies. Inclusion criteria were: (a) healthy people; (b) randomized controlled or controlled trials; (c) outcome measures of explosive performance (peak power, rate of force development, jump performance, sprint performance, etc.); (d) involving a comparison between blood flow restriction training and traditional resistance training. Quality assessment was conducted using the Physiotherapy Evidence Database (PEDro) scale. A total of 12 studies (262 subjects) were finally included for analysis. The PEDro scale score had a median of 5 of 10 points (range: 3-6 points). Significant small to moderate improvements were observed in blood flow restriction training [jump: standard mean difference (SMD) of 0.36 (95% CI: 0.02; 0.69); sprint: SMD of 0.54 (95% CI: 0.00; 1.07); power: SMD of 0.72 (95% CI: 0.17; 1.27)] when compared to traditional resistance training. The findings indicate that blood flow restriction training is more effective in improving explosive power of lower limbs compared to traditional resistance training in healthy people. In addition, blood flow restriction with a wide cuff (≥ 10 cm) during training improved explosive power better than with a narrow cuff or during the rest interval. Blood flow restriction training is very suitable for athletes in short competitive seasons and those who are not able to tolerate high loads (i.e., rehabilitators and the elderly).

The effect of four weeks blood flow restricted resistance training on macro- and micro-vascular function in healthy, young men

PURPOSE

To determine the macrovascular and microvascular function responses to resistance training with blood flow restriction (BFR) compared to high-load resistance training (HLRT) control group.

METHODS

Twenty-four young, healthy men were randomly assigned to BFR or HLRT. Participants performed bilateral knee extensions and leg presses 4 days per week, for 4 weeks. For each exercise, BFR completed 3 X 10 repetitions/day at 30% of 1-repetition max (RM). The occlusive pressure was applied at 1.3 times of individual systolic blood pressure. The exercise prescription was identical for HLRT, except the intensity was set at 75% of one repetition maximum. Outcomes were measured pre-, at 2- and 4-weeks during the training period. The primary macrovascular function outcome was heart-ankle pulse wave velocity (haPWV), and the primary microvascular function outcome was tissue oxygen saturation (StO2) area under the curve (AUC) response to reactive hyperemia.

RESULTS

Knee extension and leg press 1-RM increased by 14% for both groups. There was a significant interaction effect for haPWV, decreasing - 5% (Δ-0.32 m/s, 95% confidential interval [CI] - 0.51 to - 0.12, effect size [ES] =  - 0.53) for BFR and increasing 1% (Δ0.03 m/s, 95%CI - 0.17 to 0.23, ES = 0.05) for HLRT. Similarly, there was an interaction effect for StO2 AUC, increasing 5% (Δ47%･s, 95%CI - 3.07 to 98.1, ES = 0.28) for HLRT and 17% (Δ159%･s, 95%CI 108.23-209.37, ES = 0.93) for BFR group.

CONCLUSION

The current findings suggest that BFR may improve macro- and microvascular function compared to HLRT.

Acute Effect of Resistance Training With Blood Flow Restriction on Perceptual Responses: A Systematic Review and Meta-Analysis

CONTEXT

Several studies have compared perceptual responses between resistance exercise with blood flow restriction and traditional resistance exercise (non-BFR). However, the results were contradictory.

OBJECTIVES

To analyze the effect of RE+BFR versus non-BFR resistance exercise [low-load resistance exercise (LL-RE) or high-load resistance exercise (HL-RE)] on perceptual responses.

DATA SOURCES

CINAHL, Cochrane Library, PubMed®, Scopus, SPORTDiscus, and Web of Science were searched through August 28, 2021, and again on August 25, 2022.

STUDY SELECTION

Studies comparing the effect of RE+BFR versus non-BFR resistance exercise on rate of perceived exertion (RPE) and muscle pain/discomfort were considered. Meta-analyses were conducted using the random effects model.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 2.

DATA EXTRACTION

All data were reviewed and extracted independently by 2 reviewers. Disagreements were resolved by a third reviewer.

RESULTS

Thirty studies were included in this review. In a fixed repetition scheme, the RPE [standardized mean difference (SMD) = 1.04; P < 0.01] and discomfort (SMD = 1.10; P < 0.01) were higher in RE+BFR than in non-BFR LL-RE, but similar in sets to voluntary failure. There were no significant differences in RPE in the comparisons between RE+BFR and non-BFR HL-RE; after sensitivity analyses, it was found that the RPE was higher in non-BFR HL-RE in a fixed repetition scheme. In sets to voluntary failure, discomfort was higher in RE+BFR versus non-BFR HL-RE (SMD = 0.95; P < 0. 01); however, in a fixed scheme, the results were similar.

CONCLUSION

In sets to voluntary failure, RPE is similar between RE+BFR and non-BFR exercise. In fixed repetition schemes, RE+BFR seems to promote higher RPE than non-BFR LL-RE and less than HL-RE. In sets to failure, discomfort appears to be similar between LL-RE with and without BFR; however, RE+BFR appears to promote greater discomfort than HL-RE. In fixed repetition schemes, the discomfort appears to be no different between RE+BFR and HL-RE, but is lower in non-BFR LL-RE.

Activation of Lactate Receptor Positively Regulates Skeletal Muscle Mass in Mice

G protein-coupled receptor 81 (GPR81), a selective receptor for lactate, expresses in skeletal muscle cells, but the physiological role of GPR81 in skeletal muscle has not been fully elucidated. As it has been reported that the lactate administration induces muscle hypertrophy, the stimulation of GPR81 has been suggested to mediate muscle hypertrophy. To clarify the contribution of GPR81 activation in skeletal muscle hypertrophy, in the present study, we investigated the effect of GPR81 agonist administration on skeletal muscle mass in mice. Male C57BL/6J mice were randomly divided into control group and GPR81 agonist-administered group that received oral administration of the specific GPR81 agonist 3-Chloro-5-hydroxybenzoic acid (CHBA). In both fast-twitch plantaris and slow-twitch soleus muscles of mice, the protein expression of GPR81 was observed. Oral administration of CHBA to mice significantly increased absolute muscle weight and muscle weight relative to body weight in the two muscles. Moreover, both absolute and relative muscle protein content in the two muscles were significantly increased by CHBA administration. CHBA administration also significantly upregulated the phosphorylation level of p42/44 extracellular signal-regulated kinase-1/2 (ERK1/2) and p90 ribosomal S6 kinase (p90RSK). These observations suggest that activation of GRP81 stimulates increased the mass of two types of skeletal muscle in mice in vivo. Lactate receptor GPR81 may positively affect skeletal muscle mass through activation of ERK pathway.

Muscle strength adaptation between high-load resistance training versus low-load blood flow restriction training with different cuff pressure characteristics: a systematic review and meta-analysis

Purpose: In this systematic review and meta-analysis, blood flow restriction (BFR) with low-load resistance training (BFR-RT) was compared with high-load resistance training (HL-RT) on muscle strength in healthy adults. The characteristics of cuff pressure suitable for muscle strength gain were also investigated by analyzing the effects of applying different occlusion pressure prescriptions and cuff inflation patterns on muscle strength gain. Methods: Literature search was conducted using PubMed, Ovid Medline, ProQuest, Cochrane Library, Embase, and Scopus databases to identify literature published until May 2023. Studies reporting the effects of BFR-RT interventions on muscle strength gain were compared with those of HL-RT. The risk of bias in the included trials was assessed using the Cochrane tool, followed by a meta-analysis to calculate the combined effect. Subgroup analysis was performed to explore the beneficial variables. Results: Nineteen articles (42 outcomes), with a total of 458 healthy adults, were included in the meta-analysis. The combined effect showed higher muscle strength gain with HL-RT than with BFR-RT (p = 0.03, SMD = -0.16, 95% CI: -0.30 to -0.01). The results of the subgroup analysis showed that the BFR-RT applied with incremental and individualized pressure achieved muscle strength gain similar to the HL-RT (p = 0.8, SMD = -0.05, 95% CI: -0.44 to 0.34; p = 0.68, SMD = -0.04, 95% CI: -0.23 to 0.15), but muscle strength gain obtained via BFR-RT applied with absolute pressure was lower than that of HL-RT (p < 0.05, SMD = -0.45, 95% CI: -0.71 to -0.19). Furthermore, muscle strength gain obtained by BFR-RT applied with intermittent pressure was similar to that obtained by HL-RT (p = 0.88, SMD = -0.02, 95% CI: -0.27 to 0.23), but muscle strength gain for BFR-RT applied with continuous pressure showed a less prominent increase than that for HL-RT (p < 0.05, SMD = -0.3, 95% CI: -0.48 to -0.11). Conclusion: In general, HL-RT produces superior muscle strength gains than BFR-RT. However, the application of individualized, incremental, and intermittent pressure exercise protocols in BFR-RT elicits comparable muscle strength gains to HL-RT. Our findings indicate that cuff pressure characteristics play a significant role in establishing a BFR-RT intervention program for enhancing muscle strength in healthy adults. Clinical Trial Registration: https://www.crd.york.ac.uk/PROSPERO/#recordDetails; Identifier: PROSPERO (CRD42022364934).

Acute Effects of Blood Flow Restriction Training on Movement Velocity and Neuromuscular Signal during the Back Squat Exercise

The aim of this study was to verify the effects of blood flow restriction on movement velocity and muscle activity during the back squat exercise.

METHODS

Twenty-four university students participated in this study. In two randomized sessions 72 h apart, participants performed a 4-set protocol consisting of 30-15-15-15 repetitions performed at 30% of their one-repetition maximum in the back squat exercise. In both sessions, neuromuscular function was monitored by surface electromyography (EMG) and movement velocity (mean propulsive velocity (MPV), peak concentric velocity (Vmax), and the effort index (EI)). Blood flow restriction (BFR) was applied during exercise in one of the experimental sessions with 80% of full arterial occlusion pressure over lower limbs.

RESULTS

The BFR condition showed higher (p < 0.05) EI, peak, and rooted mean square normalized EMG in Set 1 compared to Set 2. Similar MPV and Vmax were observed in each set for both the BFR and control conditions. No significant differences were observed between conditions in any set.

CONCLUSIONS

BFR did not imply changes in neuromuscular performance during low-intensity resistance training, but it might induce greater intra-series velocity loss and less excitation of the muscles involved.

The Effect of Skeletal Muscle Oxygenation on Hemodynamics, Cerebral Oxygenation and Activation, and Exercise Performance during Incremental Exercise to Exhaustion in Male Cyclists

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m^-1), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O_2max (-17 ± 2%, p < 0.001), peak power output (-28 ± 2%, p < 0.001), and time to exhaustion (-28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O₂Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions (p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC (p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition (p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar (p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and V˙O_2max. In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction.

Effects of 4-Week Low-Load Resistance Training with Blood Flow Restriction on Muscle Strength and Left Ventricular Function in Young Swimmers: A Pilot Randomized Trial

Low-load resistance training combined with blood flow restriction (BFR) is known to result in muscle hypertrophy and strength similar to that observed with higher loads. However, the effects of resistance training with BFR on cardiac structure and cardiac function remain largely unknown. Therefore, the purpose of this randomized study was to compare the effects of conventional high-load resistance training (HL-RT) with the effects of low-load resistance training with BFR (LL-BFR) on muscle strength and left ventricular function. Sixteen young swimmers (mean ± standard deviation: age = 19.7 ± 1.6 years, body mass = 78.9 ± 9.7 kg, body height = 180.8 ± 5.8 cm) were randomly allocated to a conventional HL-RT group (n = 8) or a LL-BFR group (n = 8) with a pressure band (200 mmHg) placed on both thighs of participants for 4 weeks (3 days•week-1). Outcome measures were taken at baseline and after 4 weeks of training, and included body composition, one-repetition maximum (1RM) back squat, and echocardiography measures. The 1RM back squat significantly improved (partial eta squared (Ƞ2) = 0.365; p = 0.013) in HL-RT (mean difference (Δ) = 6.6 kg; [95% confidence interval (CI) -7.09 to 20.27]) and LL-BFR groups (Δ = 14.7 kg; [95% CI 3.39 to 26.10]), with no main effect of group or group × time interaction (p > 0.05). Interventricular septum end-systolic thickness showed a slight but statistically significant increase in LL-BFR and HL-RT groups (Ƞ2 = 0.253; p = 0.047), yet there was no main effect of group or group × time interaction (p > 0.05). There were no statistically significant changes (p > 0.05) in other cardiac structure or function parameters (e.g., left ventricular (LV) mass, LV cardiac output, LV ejection fraction, LV stroke volume) after the training programs. Results suggest that 4 weeks of HL-RT and LL-BFR improve muscle strength similarly with limited effects on left ventricular function in young swimmers.

Semi-Squat Exercises with Varying Levels of Arterial Occlusion Pressure during Blood Flow Restriction Training Induce a Post-Activation Performance Enhancement and Improve Vertical Height Jump in Female Football Players

Low-load blood flow restriction training (BFRT) has been shown to induce a significant increase in muscle activation. However, low-load BFRT to augment the post-activation performance enhancement (PAPE) has not been previously examined. This study aimed to examine the PAPE of low-intensity semi-squat exercises with varying pressure BFRT on vertical height jump performance. Twelve elite athletes from the Shaanxi Province women's football team volunteered to participate in this study for 4 weeks. Participants completed four testing sessions that included one of the following at random: (1) non-BFRT, (2) 50% arterial occlusion pressure (AOP), (3) 60% AOP, or (4) 70% AOP. Muscle activity of the lower thigh muscles was recorded using electromyography (EMG). Jump height, peak power output (PPO), vertical ground reaction forces (vGRF), and rate of force development (RFD) were recorded for four trials. Two-factor repeated measures analysis of variance (ANOVA) showed that semi-squat with varying pressure BFRT had a significant impact on the measured muscle EMG amplitude and MF value of vastus medialis, vastus lateralis, rectus femoris, and biceps femoris (P < 0.05), and MF value decreased with increasing pressure. Muscle activation (EMG amplitude) did not change further. The EMG amplitude of the gluteus maximus was significantly decreased by semi-squat training with different pressures (P < 0.05), while that of the gluteus maximus muscle was gradually increased by non-BFR with semi-squat training (P > 0.05). The 50% and 60% AOP BFRTs significantly increased jump height, peak power, and force increase rate (RFD) after 5 min and 10 min of rest (P < 0.05). This study further confirmed that low-intensity BFRT can significantly increase lower limb muscle activation, induce PAPE, and improve vertical height jump in female footballers. In addition, 50% AOP continuous BFRT is recommended for warm-up activities.

Effect of quadriceps training at different levels of blood flow restriction on quadriceps strength and thickness in the mid-term postoperative period after anterior cruciate ligament reconstruction: a randomized controlled external pilot study

BACKGROUND

More than 2 million anterior cruciate ligament (ACL) injuries occur worldwide each year. Most surgeons suggest that athletes and active persons with significant knee functional demands, including cutting motions, require and should be offered ligament reconstruction surgery. Despite concentrated rehabilitation efforts, deficits in quadriceps size and strength can persist for years after surgery. Blood flow restriction (BFR) training can help overcome disuse muscular atrophy in the mid-term postoperative period after anterior cruciate ligament reconstruction (ACLR) surgery. The purpose of this study was to evaluate the effects of quadriceps training with different levels of blood flow restriction on quadriceps strength and thickness of participants after ACLR.

METHODS

In this study, 30 post-ACL reconstruction participants were randomly divided into three groups (control, 40% Arterial Occlusion Pressure [AOP] and 80% AOP groups). All patients were subjected to different levels of BFR, combined with conventional quadriceps rehabilitation, for 8 weeks. Assessments included scaled maximal isokinetic knee extension strength at 60°/s and 180°/s, the sum of the thickness of the affected femoris rectus and vastus intermedius, Y-balance test performance, and International Knee Documentation Committee questionnaire responses before and after the intervention.

RESULTS

In total, 23 participants completed the entire study. The 80% AOP compression group showed an increase in quadriceps femoris muscle strength and muscle thickness (p < 0.01). As compared with the control group, outcome indicators in the 40% AOP and 80% AOP group were improved (p < 0.05). After 8 weeks of experimental BFR intervention, the results were better for the 80% AOP compression group than for the 40% AOP compression group in quadriceps peak torque to body weight at 60°/s and 180°/s angular velocity, as well as the sum of the thickness of the rectus femoris and vastus intermedius.

CONCLUSION

The combination of BFR and low-intensity quadriceps femoris training can effectively improve the muscle strength and thickness of knee extensors in participants with ACLR and help reduce the difference between the healthy and surgical sides of the knee joint while improving knee-joint function. Choosing quadriceps training with 80% AOP compression intensity could provide the most benefits. Meanwhile, BFR can accelerate the rehabilitation process of patients and allow early entry into the next rehabilitation cycle.

REGISTRATION

Trial registration Chinese Clinical Trial Registry, registration number ChiCTR2100050011, date of registration: 15/08/2021.

The effect of blood flow restriction training combined with electrical muscle stimulation on neuromuscular adaptation: a randomized controlled trial

Objective: Low-intensity resistance training (≤25% 1RM) combined with blood flow restriction training (BFRT) is beneficial to increasing muscle mass and muscle strength, but it cannot produce increased muscle activation and neuromuscular adaptation, as traditional high-intensity strength training does. The purpose of this study is to investigate the effects of independently applying BFRT and electrical muscle stimulation (EMS), as well as combining the two methods, on muscle function. Methods: Forty healthy participants with irregular exercise experiences were randomly assigned to four groups: BFRT-alone group (BFRT, n = 10), EMS-alone group (EMS, n = 10), BFRT combined with EMS group (CMB, n = 10), and the control group (CTR, n = 10). All participants received low-intensity squat training at a load of 25% 1RM 5 times/week for 6 weeks. Cross-sectional area (CSA) and electromyographic root mean square (RMS) in the rectus femoris, as well as peak torque (PT) of the knee extensor, were measured before and following a 6-week intervention. Results: Following the 6-week intervention, the increases in muscle activation in the CMB group were statistically higher than those in the BFRT group (p < 0.001), but not different from those in the EMS group (p = 0.986). Conclusion: These data suggest that the combination of BFRT and EMS for low-intensity squat training improved the muscle strength of the lower limbs by promoting muscle hypertrophy and improving muscle activation, likely because such a combination compensates for the limitations and deficiencies of the two intervention methods when applied alone.

Low-Intensity Blood Flow Restriction Exercises Modulate Pain Sensitivity in Healthy Adults: A Systematic Review

Low-intensity exercise with blood flow restriction (LIE-BFR) has been proposed as an effective intervention to induce hypoalgesia in both healthy individuals and patients with knee pain. Nevertheless, there is no systematic review reporting the effect of this method on pain threshold. We aimed to evaluate the following: (i) the effect of LIE-BFR on pain threshold compared to other interventions in patients or healthy individuals; and (ii) how different types of applications may influence hypoalgesic response. We included randomized controlled trials assessing the effectiveness of LIE-BFR alone or as an additive intervention compared with controls or other interventions. Pain threshold was the outcome measure. Methodological quality was assessed using the PEDro score. Six studies with 189 healthy adults were included. Five studies were rated with 'moderate' and 'high' methodological quality. Due to substantial clinical heterogeneity, quantitative synthesis could not be performed. All studies used pressure pain thresholds (PPTs) to assess pain sensitivity. LIE-BFR resulted in significant increases in PPTs compared to conventional exercise at local and remote sites 5 min post-intervention. Higher-pressure BFR results in greater exercise-induced hypoalgesia compared to lower pressure, while exercise to failure produces a similar reduction in pain sensitivity with or without BFR. Based on our findings, LIE-BFR can be an effective intervention to increase pain threshold; however, the effect depends on the exercise methodology. Further research is necessary to investigate the effectiveness of this method in reducing pain sensitivity in patients with pain symptomatology.

Blood Flow Restricted Cycling Impairs Subsequent Jumping But Not Balance Performance Slightly More Than Non-Restricted Cycling: An Acute Randomized Controlled Cross-Over Trial

Chronic blood flow restriction (BFR) training has been shown to improve drop jumping (DJ) and balance performance. However, the acute effects of low intensity BFR cycling on DJ and balance indices have not yet been examined. 28 healthy young adults (9 female; 21.8 ± 2.7years; 1.79 ± 0.08m; 73.9 ± 9.5kg) performed DJ and balance testing before and immediately after 20min low intensity cycling (40% of power at maximal oxygen uptake) with (BFR) and without BFR (noBFR). For DJ related parameters, no significant mode × time interactions were found (p ≥ 0.221, η_p ² ≤ 0.06). Large time effects for DJ heights and the reactive strength index were observed (p < 0.001, η_p ² ≥ 0.42). Pairwise comparison revealed notably lower values for both DJ jumping height and reactive strength index at post compared to pre (BFR: -7.4 ± 9.4%, noBFR: -4.2 ± 7.4%). No statistically significant mode × time interactions (p ≥ 0.36; η_p ² ≤ 0.01) have been observed for balance testing. Low intensity cycling with BFR results in increased (p ≤ 0.01; SMD ≥ 0.72) mean heart rate (+14 ± 8bpm), maximal heart rate (+16 ± 12 bpm), lactate (+0.7 ± 1.2 mmol/L), perceived training intensity (+2.5 ± 1.6au) and pain scores (+4.9 ± 2.2au) compared to noBFR. BFR cycling induced acutely impaired DJ performance, but balance performance was not affected, compared to noBFR cycling. Heart rate, lactate, perceived training intensity, and pain scores were increased during BFR cycling.

Acute Responses to High-Intensity Back Squats with Bilateral Blood Flow Restriction

This study examined the acute effects of high-intensity resistance exercise with blood flow restriction (BFR) on performance and fatigue, metabolic stress, and markers of inflammation (interleukin-6 (IL-6)), muscle damage (myoglobin), angiogenesis (vascular endothelial growth factor (VEGF)). Thirteen resistance-trained participants (four female, 24.8 ± 4.7 years) performed four sets of barbell back-squats (75% 1RM) to failure under two conditions: blood flow restriction (BFR, bilateral 80% occlusion pressure) and control (CTRL). Completed repetitions and pre-post-exercise changes in maximal voluntary isometric contractions, countermovement jump, barbell mean propulsive velocity, and surface electromyography were recorded. Pre-post blood lactate (BLa) and venous blood samples for analysis of IL-6, myoglobin, and VEGF were collected. Ratings of perceived exertion (RPE) and pain were recorded for each set. Fewer repetitions were performed during BFR (25.5 ± 9.6 reps) compared to CTRL (43.4 ± 14.2 reps, p < 0.001), with greater repetitions performed during sets 1, 2, and 4 (p < 0.05) in CTRL. Although RPE between conditions was similar across all sets (p > 0.05), pain was greater in BFR across all sets (p < 0.05). Post-exercise fatigue was comparable between conditions. BLa was significantly greater in CTRL compared to BFR at two minutes (p = 0.001) but not four minutes post-exercise (p = 0.063). IL-6 was significantly elevated following BFR (p = 0.011). Comparable increases in myoglobin (p > 0.05) and no changes in VEGF were observed (p > 0.05). BFR increases the rate of muscular fatigue during high-intensity resistance exercise and acutely enhances IL-6 response, with significantly less total work performed, but increases pain perception, limiting implementation.

Novel Orthobiologic Preparation and Regenerative Rehabilitation of a Complex Shoulder Injury in a Competitive Adolescent Female Athlete

Background

Platelet-rich plasma (PRP) and prolotherapy have resulted in promising outcomes in patients with various types of shoulder injuries. However, there is a lack of preliminary evidence supporting preparation of PRP production, timely application of these therapies and regenerative rehabilitation protocols. The purpose of this case report is to describe the distinct method including orthobiologic preparation, tissue-specific treatment and regenerative rehabilitation of an athlete with a complex shoulder injury.

Case Presentation

A 15y/o competitive female wrestler with a complex shoulder injury presented to the clinic after unsuccessful conservative rehabilitation. Unique methods were incorporated to optimize PRP production, specific tissue healing and regenerative rehabilitation. Multiple injuries required different orthobiologic interventions at different time frames, in order to promote optimal healing and stability of the shoulder.

Outcomes

The described interventions resulted in successful outcomes including pain, disability, full return to sport, and regenerative tissue healing confirmed with diagnostic imaging.

Level of Evidence

5.

A non-volitional skeletal muscle endurance test measures functional changes associated with impaired blood flow

Introduction: An electrically stimulated intermittent fatigue test using mechanomyography was recently proposed as a possible tool for detecting clinically relevant changes in muscle function. This study was designed to determine whether the proposed test can detect additional fatigue when it should be present. Methods: Subjects (n = 10) underwent two trials each (occluded and normal blood flow) with a standardized fatigue protocol on the Ankle Dorsiflexors (AD) and Wrist Extensors (WE) using a clinical electrical stimulator. Results: Mean normalized twitch acceleration was strongly predictive of mean normalized torque (R ² = 0.828). The WE experienced lower twitch magnitudes throughout the tourniquet trial (10.81 ± 1.25 m/s²) compared to normal blood flow (18.05 ± 1.06 m/s²). The AD twitches were overall reduced in the tourniquet trial (3.87 ± 0.48 m/s²) compared with the control trial (8.57 ± 0.91 m/s²). Conclusion: Occluding blood flow to a muscle should cause greater muscle fatigue. The ability to detect reduced contraction magnitudes during an electrically stimulated fatigue protocol resulting from low blood flow suggests the proposed test may be capable of detecting clinically relevant muscle deficits.

Effects of blood flow restriction on spine postural control using a robotic platform: A pilot randomized cross-over study

BACKGROUND

Blood flow restriction (BFR) training improves muscle strength and functional outcomes, but the proprioceptive implications of this technique in the rehabilitation field are still unknown.

OBJECTIVE

The present study aimed at assessing the effects of BFR in terms of stabilometric and balance performance.

METHODS

In this pilot randomized cross-over study, healthy young adults were included and randomly assigned to Groups A and B. Both groups underwent a postural assessment with and without wearing a BFR device. Study participants of Group A underwent postural baseline assessment wearing BFR and then removed BFR for further evaluations, whereas subjects in Group B performed the baseline assessment without BFR and then with BFR. Stabilometric and balance performance were assessed by the robotic platform Hunova, the Balance Error Scoring System (BESS), the self-reported perceived balance (7-point Likert scale), and discomfort self-rated assessment. Moreover, the safety profile was recorded.

RESULTS

Fourteen subjects were included and randomly assigned to Group A (n: 7) and Group B (n: 7). Significant differences were shown in balance tests in static conditions performed on the Hunova robot platform in terms of average distance RMS (root-mean-square) with open eyes (OE), anteroposterior (AP) trunk oscillation range with OE, mediolateral (ML) average speed of oscillation with OE, and total excursion AP range with closed eyes (CE) (BFR: 3.44 ± 1.06; without BFR: 2.75 ± 0.72; p= 0.041). Moreover, elastic balance test showed differences in Romberg index (BFR: 0.16 ±0.16; without BFR: 0.09 ± 0.07; p= 0.047). No adverse events were reported.

CONCLUSION

Taken together, our data showed that BFR affects balance performance of healthy subjects. Further studies are needed to better characterize the possible role of BFR treatment in the context of a specific rehabilitation protocol.

The effects of upper body blood flow restriction training on muscles located proximal to the applied occlusive pressure: A systematic review with meta-analysis

BACKGROUND

Blood flow restriction combined with low load resistance training (LL-BFRT) is associated with increases in upper limb muscle strength and size. The effect of LL-BFRT on upper limb muscles located proximal to the BFR cuff application is unclear.

OBJECTIVE

The aim of this systematic review was to evaluate the effect of LL-BFRT compared to low load, or high load resistance training (LL-RT, HL-RT) on musculature located proximal to cuff placement.

METHODS

Six electronic databases were searched for randomized controlled trials (RCTs). Two reviewers independently evaluated the risk of bias using the PEDro scale. We performed a meta-analysis using a random effects model, or calculated mean differences (fixed-effect) where appropriate. We judged the certainty of evidence using the GRADE approach.

RESULTS

The systematic literature searched yielded 346 articles, of which 9 studies were eligible. The evidence for all outcomes was of very low to low certainty. Across all comparisons, a significant increase in bench press and shoulder flexion strength was found in favor of LL-BFRT compared to LL-RT, and in shoulder lean mass and pectoralis major thickness in favor of the LL-BFRT compared to LL-RT and HL-RT, respectively. No significant differences were found between LL-BFRT and HL-RT in muscle strength.

CONCLUSION

With low certainty LL-BFRT appears to be equally effective to HL-RT for improving muscle strength in upper body muscles located proximal to the BFR stimulus in healthy adults. Furthermore, LL-BFRT may induce muscle size increase, but these adaptations are not superior to LL-RT or HL-RT.

Physiological adaptations and myocellular stress in short-term, high-frequency blood flow restriction training: A scoping review

BACKGROUND

High frequency (1-2 times per day) low-intensity blood flow restriction (BFR) training has been recommended as a prescription approach for short durations of time to maximize relevant physiological adaptations. However, some studies demonstrate negative physiological changes after short periods of high-frequency BFR training, including prolonged strength decline and muscle fiber atrophy.

OBJECTIVES

To provide a comprehensive overview of short-term, high-frequency blood flow restriction training, including main adaptations, myocellular stress, limitations in the literature, and future perspectives.

METHODS

A systematic search of electronic databases (Scopus, PubMed®, and Web of Science) was performed from the earliest record to April 23, 2022. Two independent reviewers selected experimental studies that analyzed physical training protocols (aerobic or resistance) of high weekly frequency (>4 days/week) and short durations (≤3 weeks).

RESULTS

In total, 22 studies were included in this review. The samples were composed exclusively of young predominantly male individuals. Muscle strength and hypertrophy were the main outcomes analyzed in the studies. In general, studies have demonstrated increases in strength and muscle size after short term (1-3 weeks), high-frequency low-intensity BFR training, non-failure, but not after control conditions (non-BFR; equalized training volume). Under failure conditions, some studies have demonstrated strength decline and muscle fiber atrophy after BFR conditions, accompanying increases in muscle damage markers. Significant limitations exist in the current HF-BFR literature due to large heterogeneities in methodologies.

CONCLUSION

The synthesis presented indicates that short-term, high-frequency BFR training programs can generate significant neuromuscular adaptations. However, in resistance training to failure, strength declines and muscle fiber atrophy were reported. Currently, there are no studies analyzing low-frequency vs. high-frequency in short-term BFR training. Comparisons between resistance exercises of similar intensities (e.g., combined effort) are lacking, limiting conclusions on whether the effect is a product of proximity to failure or a specific effect of BFR.

Exercised-Induced Hypoalgesia following An Elbow Flexion Low-Load Resistance Exercise with Blood Flow Restriction: A Sham-Controlled Randomized Trial in Healthy Adults

We aimed to evaluate the hypoalgesic effect of an elbow flexion low-load resistance exercise with blood flow restriction (LLRE-BFR) when compared to high-load resistance exercise (HLRE) with sham-BFR in healthy individuals. Forty healthy young adults (17 women), with a mean age ± SD: 26.6 ± 6.8 years, and mean body mass index ± SD: 23.6 ± 2.7 were randomly assigned to either an LLRE-BFR (30% 1 repetition maximum, RM) or an HLRE with sham-BFR group (70% of 1 RM). Blood pressure and pressure pain thresholds (PPTs) were measured pre- and post-exercise intervention. The rating of perceived exertion (RPE) was recorded after each set. There were non-significant between-group changes in PPT at the dominant biceps (-0.61, 95%CI: -1.92 to 0.68) with statistically significant reductions between pre- and post-exercise in LLRE-BFR (effect size, d = 0.88) and HLRE-BFR (effect size, d = 0.52). No within- or between-group differences were recorded in PPT at non-exercising sites of measurement. No mediating effects of changes in blood pressure or RPE on the changes in pressure pain threshold were observed. LLRE-BFR produced a similar hypoalgesic effect locally compared to HLRE and can be used as an alternative intervention to decrease pain sensitivity when HLRE is contraindicated or should be avoided.

Effectiveness of Blood Flow Restriction in Neurological Disorders: A Systematic Review

There is scientific evidence that Blood Flow Restriction (BFR) is beneficial in healthy people, the elderly and patients with musculoskeletal disorders. A systematic review was conducted to evaluate the effectiveness of BFR in patients with neurological disorders. The literature search was conducted up until July 2022 in the following databases: PubMed, Web of Science (WOS), Physiotherapy Evidence Database (PEDro), LILACS, Scopus, Cumulative Index of Nursing and Allied Literature Complete (CINAHL), the Cochrane Library and Scientific Electronic Library Online (SciELO). The PEDro scale was used to analyze the methodological quality of the studies, and the Cochrane Collaboration's tool was employed to evaluate the risk of bias. A total of seven articles were included. BFR seems to be beneficial in neurological disorders. Improvements have been found in sensorimotor function, frequency and step length symmetry, perceived exertion, heart rate and gait speed, walking endurance, fatigue, quality of life, muscles thickness, gluteus density and muscle edema. No improvements were found in lower limb strength or balance. However, results must be taken with caution due to the small number of articles and to the large heterogeneity. More clinical trials are needed. These studies should homogenize the protocols used in larger samples, as well as improve their methodological quality.

A Comparison between High and Low Cuff Pressures on Muscle Oxygen Saturation and Recovery Responses Following Blood-Flow Restriction Resistance Exercise

The aim of the study was to compare the recovery response and muscle oxygenation of a blood-flow restriction resistance exercise (BFR) session with high [HP: 80% of the arterial occlusion pressure (AOP)] and low cuff pressure (LP: 40% of AOP). Both exercise sessions included 4 sets to failure at the barbell preacher curl exercise. Twelve resistance trained men (27.4 ± 5.0 years; 83.5 ± 11.6 kg; 176.6 ± 7.0 cm) performed each protocol in a counterbalanced, randomized order. Maximal isometric force, muscle morphology and muscle soreness of the biceps brachii muscle were assessed at baseline, 15-min, 60-min and 24-h post each testing session. In addition, muscle oxygen saturation (SmO2) was assessed during each training session. A lower number of repetitions (p = 0.013) was detected in HP compared to LP. A lower SmO2 (p < 0.001) was detected in the recovery time between the sets in HP (mean: 47.6 ± 15.7%) compared to LP (mean: 68.9 ± 7.2%). No differences between the two trials (p > 0.05) were noted for isometric force, muscle architecture and soreness at any timepoint. Results indicate that, despite a high cuff pressure may induce a more hypoxic condition compared to a lower cuff pressure, recovery responses may not be affected.

Blood Flow Restriction Training preserves knee flexion and extension torque following anterior cruciate ligament reconstruction: A systematic review

Background

There is inconsistency in the literature comparing the outcomes of Blood Flow Restriction Training versus Traditional Post-Operative Rehabilitation after anterior cruciate ligament reconstruction.

Purpose

This study aimed to determine if Blood Flow Restriction Training can limit the loss of knee extension and knee flexion muscle torque during early recovery from anterior cruciate ligament reconstruction better than Traditional Post-Operative Rehabilitation.

Methods

Three databases (PubMed, Embase, and Scopus) were searched for level 1 randomized controlled trials pertaining to Blood Flow Restriction Training after anterior cruciate ligament reconstruction. To maximize consistency among included studies, only studies which used knee flexion and knee extension muscle torque as the primary outcome measures were included. Search terms included "cruciate + occlusion", "cruciate + blood flow restriction", and "cruciate + occlusion training".

Results

Two level 1 trials with training protocols of 8 and 16 weeks yielded isokinetic knee flexion torque data in support of Blood Flow Restriction Training. Both trials demonstrated that Blood Flow Restriction Training also yielded significantly increased isokinetic knee extension torque compared to control groups.

Conclusion

The highest-quality level 1 trials evaluating knee extension and knee extension strength via isokinetic torque agree that Blood Flow Restriction Training limits post-operative losses of knee flexion and extension strength. No adverse events were reported in either study. Except for patients of whom Blood Flow Restriction is contraindicated, clinicians may consider utilizing Blood Flow Restriction Training from week 2 of the post-operative period through the conclusion of outpatient rehabilitation using low intensities, multiple times per week; however, further studies comparing Blood Flow Restriction Training protocols are necessary before an optimal protocol could be confidently recommended.

Effects of Low Intensity Blood Flow Restriction Training on Muscle Volume, Strength and Power in Healthy Middle-Aged Females

OBJECTIVES The purpose of this study is to investigate the efficacy of weight training with controlled blood flow occlusion compared to conventional resistance training, in the ageing population.METHODS Twenty-three healthy female subjects (aged 40-55) were randomly assigned to one of three groups; low intensity blood flow restriction training (LI-BFRT) (n = 9), conventional resistance training (RT) (n = 7) and control (CON) (n = 7). The RT group trained between 65-70% one repetition maximum (1RM) and the LI-BFRT group trained at 30% 1RM while wearing pressure cuffs inflated to 100-120% of brachial systolic blood pressure (bSBP). Relative appendicular skeletal muscle mass (ASM/weight), isokinetic strength and power were tested pre and post 8 weeks of training.RESULTS Upper limb ASM/weight increased significantly in the LI-BFRT and RT groups (both p < 0.001). Only LI-BFRT showed significant difference compared with the CON group (p < 0.01). Lower limb ASM/weight improved in both the LI-BFRT (p < 0.01) and CON (p < 0.01) groups without group differences. Lower limb flexion strength increased in the LI-BFRT and RT groups (both p < 0.01), with differences between groups (p < 0.01, LI-BFRT > RT > CON). Only RT increased extension muscle strength (p < 0.05). Lower limb flexion and extension power improved following LI-BFRT (p < 0.05 and p < 0.01, respectively), significantly greater than RT in both flexion (p < 0.001) and extension (p < 0.01).CONCLUSIONS LI-BFRT may be as, if not more effective than RT for increasing muscle volume, strength and power in middle-aged women.

Blood flow restriction accelerates aerobic training-induced adaptation of [Formula: see text] kinetics at the onset of moderate-intensity exercise

It is unclear whether blood flow restriction (BFR) accelerates the adaptation of the time constant (τ) of phase II oxygen uptake ([Formula: see text]) kinetics in the moderate-intensity exercise domain via moderate-intensity aerobic training. Therefore, healthy participants underwent moderate-intensity [45-60% [Formula: see text] Reserve] aerobic cycle training with or without BFR (BFR group, n = 9; CON group, n = 9) for 8 weeks to evaluate [Formula: see text] kinetics during moderate-intensity cycle exercise before (Pre) and after 4 (Mid) and 8 (Post) weeks of training. Both groups trained for 30 min, 3 days weekly. BFR was performed for 5 min every 10 min by applying cuffs to the upper thighs. The τ significantly decreased by Mid in the BFR group (23.7 ± 2.9 s [Pre], 15.3 ± 1.8 s [Mid], 15.5 ± 1.4 s [Post], P < 0.01) and by Post in the CON group (27.5 ± 2.0 s [Pre], 22.1 ± 0.7 s [Mid], 18.5 ± 1.9 s [Post], P < 0.01). Notably, the BFR group's τ was significantly lower than that of the CON group at Mid (P < 0.01) but not at Post. In conclusion, BFR accelerates the adaptation of the [Formula: see text] kinetics of phase II by moderate-intensity aerobic training.

Can Blood Flow Restriction Training Benefit Post-Activation Potentiation? A Systematic Review of Controlled Trials

(1) Background: post-activation potentiation (PAP) plays an essential role in enhancing athletic performance. Various conditioning activities (CAs) have been developed to generate PAP before training or competitions. However, whether extra equipment can enhance the effectiveness of CAs is understudied. Hence, this systematic review aims to introduce and examine the effectiveness of blood flow restriction-based conditioning activities (BFR-CAs). (2) Methods: a literature search was conducted via Web of Science, PubMed, SPORTDiscus, and CNKI (a Chinese academic database). The systematic review included the literature concerning BFR-CAs and non-BFR-CAs. The methodological quality of included studies was considered to be "moderate quality" and "good quality" based on the Physiotherapy Evidence Database Scale. (3) Results: five studies were included in this study. Four studies were on lower limb strength training, and three of them suggested a greater PAP in BFR-CAs than in non-BFR counterparts. One study on upper limb strength training also supported the advantage of BFR-CAs. (4) Conclusions: BFR-CAs may be an emerging and promising strategy to generate PAP. Compared with non-BFR-CAs, BFR-CAs might be more efficient and practical for inexperienced sports people or athletes in non-power sports.

Blood-Flow-Restriction-Training-Induced Hormonal Response is not Associated with Gains in Muscle Size and Strength

The aim of this study was to determine whether increases in post-exercise endocrine response to low-load resistance exercise with blood flow restriction and high-load resistance exercise would have association with increases in muscle size and strength after an 8-week training period. Twenty-nine untrained men were randomly allocated into three groups: low-load resistance exercise with (LL-BFR) or without blood flow restriction (LL), and high-load resistance exercise (HL). Participants from LL-BFR and LL groups performed leg extension exercise at 20% of one repetition maximum (1RM), four sets of 15 repetitions and the HL group performed four sets of eight repetitions at 80% 1RM. Before the first training session, growth hormone (GH), insulin-like growth factor 1 (IGF-1), testosterone, cortisol, and lactate concentration were measured at rest and 15 min after the exercise. Quadriceps CSA and 1RM knee extension were assessed at baseline and after an 8-week training period. GH increased 15 min after exercise in the LL-BFR (p = 0.032) and HL (p < 0.001) groups, with GH concentration in the HL group being higher than in the LL group (p = 0.010). There was a time effect for a decrease in testosterone (p = 0.042) and an increase in cortisol (p = 0.005), while IGF-1 remained unchanged (p = 0.346). Both muscle size and strength were increased after training in LL-BFR and HL groups, however, these changes were not associated with the acute post-exercise hormone levels (p > 0.05). Our data suggest that other mechanisms than the acute post-exercise increase in systemic hormones induced by LL-BFR and HL produce changes in muscle size and strength.

Safety and Feasibility Assessment of Repetitive Vascular Occlusion Stimulus (RVOS) Application to Multi-Organ Failure Critically Ill Patients: A Pilot Randomised Controlled Trial

Muscle wasting is implicated in the pathogenesis of intensive care unit acquired weakness (ICU-AW), affecting 40% of patients and causing long-term physical disability. A repetitive vascular occlusion stimulus (RVOS) limits muscle atrophy in healthy and orthopaedic subjects, thus, we explored its application to ICU patients. Adult multi-organ failure patients received standard care +/- twice daily RVOS {4 cycles of 5 min tourniquet inflation to 50 mmHg supra-systolic blood pressure, and 5 min complete deflation} for 10 days. Serious adverse events (SAEs), tolerability, feasibility, acceptability, and exploratory outcomes of the rectus femoris cross-sectional area (RFCSA), echogenicity, clinical outcomes, and blood biomarkers were assessed. Only 12 of the intended 32 participants were recruited. RVOS sessions (76.1%) were delivered to five participants and two could not tolerate it. No SAEs occurred; 75% of participants and 82% of clinical staff strongly agreed or agreed that RVOS is an acceptable treatment. RFCSA fell significantly and echogenicity increased in controls (n = 5) and intervention subjects (n = 4). The intervention group was associated with less frequent acute kidney injury (AKI), a greater decrease in the total sequential organ failure assessment score (SOFA) score, and increased insulin-like growth factor-1 (IGF-1), and reduced syndecan-1, interleukin-4 (IL-4) and Tumor necrosis factor receptor type II (TNF-RII) levels. RVOS application appears safe and acceptable, but protocol modifications are required to improve tolerability and recruitment. There were signals of possible clinical benefit relating to RVOS application.