An examination of acute physiological and perceptual responses following blood flow restriction exercise using a traditional research device or novel, automated system

Objective. To compare the acute physiological and perceptual responses to blood flow restriction (BFR) exercise using a traditional research device or novel, automated system.Methods. Forty-four resistance trained individuals performed four sets of unilateral elbow flexion exercise (30% one-repetition maximum) to volitional failure using two distinct restrictive devices [SmartCuffs PRO BFR Model (SMARTCUFF), Hokanson E20 Rapid Inflation device (HOKANSON)] and with two levels of BFR [40% limb occlusion pressure (LOP), 80% LOP]. Blood pressure (BP), muscle thickness (MT), and isometric strength (ISO) were assessed prior to and following exercise. Perceptual responses [ratings of perceived exertion (RPE), discomfort] were assessed prior to exercise and following each exercise set.Main results. Data are displayed as means (SD). Immediately following exercise with 40% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 1 of exercise, RPE was greater with SMARTCUFF compared to HOKANSON (p< 0.05). In addition, only following Set 2 of exercise, discomfort was greater with HOKANSON compared to SMARTCUFF (p< 0.001). Immediately following exercise with 80% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 4 of exercise, RPE was greater with HOKANSON compared to SMARTCUFF (p< 0.05). In addition, following all exercise sets, discomfort was greater with HOKANSON compared to SMARTCUFF (p< 0.001). For repetitions completed with 40% LOP there were no statistical differences between SMARTCUFF and HOKANSON across any exercise sets. For repetitions completed with 80% LOP there were no statistical differences between SMARTCUFF and HOKANSON across Set 1 of exercise (p= 0.34), however, for Sets 2-4 of exercise, significantly greater number of repetitions were completed during SMARTCUFF than HOKANSON.Significance. The present study provides valuable insight into the efficacy of a novel, automated BFR system (SMARTCUFF) eliciting comparable acute physiological responses to BFR exercise and in some cases favorable perceptual responses when compared to a traditional research device (HOKANSON).

Blood Flow Restriction Enhances Recovery After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

PURPOSE

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating neuromuscular and clinical outcomes of blood flow restriction (BFR) training after anterior cruciate ligament reconstruction (ACLR) compared to non-BFR rehabilitation protocols.

METHODS

A systematic review was performed in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines by querying PubMed, MEDLINE, Scopus, the Cochrane Database for Systematic Review, and the Cochrane Central Register for Controlled Trials databases from inception through December 2023 to identify Level I-II RCTs evaluating outcomes of BFR training after ACLR compared to non-BFR rehabilitation. A meta-analysis was performed using random-effects models with standardized mean difference (SMD) for pain, muscle strength, and muscle volume, while mean difference (MD) was calculated for patient-reported outcome measures.

RESULTS

Eight RCTs, consisting of 245 patients, met inclusion criteria, with 115 patients undergoing non-BFR rehabilitation versus 130 patients undergoing BFR after ACLR. Mean patient age was 27.2 ± 6.7 years, with the majority of patients being male (63.3%, n=138/218). The length of the BFR rehabilitation protocol was most commonly between 8-12 weeks (range, 14 days - 16 weeks). The majority of studies set the limb/arterial occlusion pressure in the BFR group at 80%. When compared to non-BFR rehabilitation, BFR resulted in significant improvement in isokinetic muscle strength (SMD: 0.77, p=0.02, I2: 58%), IKDC score (MD: 10.97, p=<.00001, I2: 77%), and pain (SMD: 1.52, p=.04, I2: 87%), but not quadriceps muscle volume (SMD: 0.28, p=0.43, I2: 76%).

CONCLUSION

The use of BFR following ACLR led to improvements in pain, IKDC score and isokinetic muscle strength, with variable outcomes based on quadriceps strength, volume and thickness when compared to non-BFR rehabilitation.

Blood flow restriction therapy with exercise are no better than exercise alone in improving athletic performance, muscle strength, and hypertrophy: a systematic review and meta-analysis

BACKGROUND

The benefits of Blood Flow Restriction Therapy (BFRT) have gained attention in recent times.

OBJECTIVE

This review aimed to evaluate the immediate (up to 24 hours), intermediate (up to 6 weeks), and long term (6-10 weeks) effects of BFRT plus exercises (EX) compared to EX only on athletic performance (sprint and jump performance), muscle strength, and hypertrophy in athletes and physically active population.

METHODS

A literature search was conducted to select randomized controlled trials across four electronic databases from inception till April 2021. The search yielded twenty-seven studies in total.

RESULTS

Based on eligibility criteria, twenty-one studies were analyzed. No differences were found between both groups for immediate (standardized mean difference [SMD] -0.02, 95% confidence interval [CI] -0.31, 0.27) and long-term effects (SMD -0.30, 95%CI -0.90, 0.30) on sprint performance. For jump performance, no significant effect was observed immediately (SMD -0.02 (95% CI -1.06, 1.02) and long term (SMD -0.40 (95% CI -1.46, 0.67). Similarly, muscle torque at intermediate (SMD 0.90 (95% CI -1.01, 2.81) and long term (SMD -0.54 (95% CI -1.19, 0.12), muscle strength at intermediate (SMD 1.12 (95% CI 0.20, 2.04), and long term (SMD -0.07 (95% CI -0.56, 0.42) also showed non-significant effects. Muscle hypertrophy at intermediate (SMD 0.16 (95% CI -0.31, 0.63) and long term (SMD -0.20 (95% CI -0.90, 0.50) were not statistically significant.

CONCLUSIONS

There was no significant difference observed in BFRT plus EX group compared to the EX-group on athletic performance, muscle strength, and muscle hypertrophy.

Outcomes of Blood Flow Restriction Training After ACL Reconstruction in NCAA Division I Athletes

Background

Blood flow restriction training (BFRT) is a safe and potentially effective adjunctive therapeutic modality for postoperative rehabilitation related to various knee pathologies. However, there is a paucity of literature surrounding BFRT in high-performance athletes after anterior cruciate ligament reconstruction (ACLR).

Purpose

To (1) compare the overall time to return to sports (RTS) in a cohort of National Collegiate Athletic Association (NCAA) Division I athletes who underwent a standardized rehabilitation program either with or without BFRT after ACLR and (2) identify a postoperative time interval for which BFRT has the maximum therapeutic benefit.

Study Design

Cohort study; Level of evidence, 3.

Methods

A total of 55 student-athletes who underwent ACLR between 2000 and 2023 while participating in NCAA Division I sports at a single institution were included in this study. Athletes were allocated to 1 of 2 groups based on whether they participated in a standardized postoperative rehabilitation program augmented with BFRT (BFRT group; n = 22) or completed the standardized protocol alone (non-BFRT group [control]; n = 33). Our primary outcome measure was time to RTS. The secondary outcome measure was handheld dynamometry quadriceps strength testing at various postoperative time points, converted to a limb symmetry index (LSI). Quadriceps strength was not tested between the BFRT and non-BFRT groups because of the limited amount of data on the control group.

Results

The mean age at the date of surgery was 18.59 ± 1.10 years for the BFRT group and 19.45 ± 1.30 years for the non-BFRT group (P = .011), and the mean RTS time was 409 ± 134 days from surgery for the BFRT group and 332 ± 100 days for the non-BFRT cohort (P = .047). For the BFRT group, the mean quadriceps strength LSI increased by 0.67% (95% CI, 0.53%-0.81%) for every week of rehabilitation, and there was a significantly positive rate of change in quadriceps strength in weeks 13-16 compared with weeks 9-12 (ΔLSI, 8.22%; P < .001).

Conclusion

In elite NCAA Division I athletes, a statistically significant delay was observed in RTS with BFRT compared with standardized physical therapy alone after undergoing ACLR. There also appeared to be an early window during the rehabilitation period where BFRT had a beneficial impact on quadriceps strength.

Daily blood flow restriction does not preserve muscle mass and strength during 2 weeks of bed rest

We measured the impact of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Twelve healthy, male adults (age: 24 ± 3 years, body mass index: 23.7 ± 3.1 kg/m2 ) were subjected to 14 days of strict bed rest with unilateral blood flow restriction performed three times daily in three 5 min cycles (200 mmHg). Participants consumed deuterium oxide and we collected blood and saliva samples throughout 2 weeks of bed rest. Before and immediately after bed rest, lean body mass (dual-energy X-ray absorptiometry scan) and thigh muscle volume (magnetic resonance imaging scan) were assessed in both the blood flow restricted (BFR) and control (CON) leg. Muscle biopsies were collected and unilateral muscle strength (one-repetition maximum; 1RM) was assessed for both legs before and after the bed rest period. Bed rest resulted in 1.8 ± 1.0 kg lean body mass loss (P < 0.001). Thigh muscle volume declined from 7.1 ± 1.1 to 6.7 ± 1.0 L in CON and from 7.0 ± 1.1 to 6.7 ± 1.0 L in BFR (P < 0.001), with no differences between treatments (P = 0.497). In addition, 1RM leg extension strength decreased from 60.2 ± 10.6 to 54.8 ± 10.9 kg in CON and from 59.2 ± 12.1 to 52.9 ± 12.0 kg in BFR (P = 0.014), with no differences between treatments (P = 0.594). Muscle protein synthesis rates during bed rest did not differ between the BFR and CON leg (1.11 ± 0.12 vs. 1.08 ± 0.13%/day, respectively; P = 0.302). Two weeks of bed rest substantially reduces skeletal muscle mass and strength. Blood flow restriction during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. KEY POINTS: Bed rest, often necessary for recovery from illness or injury, leads to the loss of muscle mass and strength. It has been postulated that blood flow restriction may attenuate the loss of muscle mass and strength during bed rest. We investigated the effect of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Blood flow restriction applied during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. Blood flow restriction is not effective in preventing muscle atrophy during a prolonged period of bed rest.

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.

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.

Six weeks of high-load resistance and low-load blood flow restricted training increase Na/K-ATPase sub-units α2 and β1 equally, but does not alter ClC-1 abundance in untrained human skeletal muscle

Contractile function of skeletal muscle relies on the ability of muscle fibers to trigger and propagate action potentials (APs). These electrical signals are created by transmembrane ion transport through ion channels and membrane transporter systems. In this regard, the Cl^- ion channel 1 (ClC-1) and the Na⁺/K^--ATPase (NKA) are central for maintaining ion homeostasis across the sarcolemma during intense contractile activity. Therefore, this randomized controlled trial aimed to investigate the changes in ClC-1 and specific NKA subunit isoform expression in response to six weeks (18 training sessions) of high-load resistance exercise (HLRE) and low-load blood flow restricted resistance exercise (BFRRE), respectively. HLRE was conducted as 4 sets of 12 repetitions of knee extensions performed at 70% of 1 repetition maximum (RM), while BFRRE was conducted as 4 sets of knee extensions at 30% of 1RM performed to volitional fatigue. Furthermore, the potential associations between protein expression and contractile performance were investigated. We show that muscle ClC-1 abundance was not affected by either exercise modality, whereas NKA subunit isoforms [Formula: see text]² and [Formula: see text]¹ increased equally by appx. 80-90% with BFRRE (p < 0.05) and 70-80% with HLRE (p < 0.05). No differential impact between exercise modalities was observed. At baseline, ClC-1 protein expression correlated inversely with dynamic knee extensor strength (r=-0.365, p = 0.04), whereas no correlation was observed between NKA subunit content and contractile performance at baseline. However, training-induced changes in NKA [Formula: see text]² subunit (r = 0.603, p < 0.01) and [Formula: see text]¹ subunit (r = 0.453, p < 0.05) correlated with exercise-induced changes in maximal voluntary contraction. These results suggest that the initial adaptation to resistance-based exercise does not involve changes in ClC-1 abundance in untrained skeletal muscle, and that increased content of NKA subunits may facilitate increases in maximal force production.

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 low-intensity resistance exercise with blood flow restriction after high tibial osteotomy in middle-aged women

BACKGROUND

High tibial osteotomy (HTO) is an effective surgical method for treating medial compartment osteoarthritis. However, in most cases after surgery, muscle strength is decreased, and rapid muscle atrophy is observed. Therefore, the purpose of this study is to verify the effects of low-intensity resistance exercise (LIE) with blood flow restriction (BFR) on the cross-sectional area (CSA) of thigh muscles, knee extensor strength, pain, and knee joint function and investigate proper arterial occlusion pressure (AOP) in middle-aged women who underwent HTO.

METHOD

This study was designed as a prospective randomized controlled trial. Forty-two middle-aged women who underwent HTO were randomly divided into three groups and participated in LIE with (40% or 80% AOP applied) or without BFR. The main outcome was the measurement of the CSA of thigh muscles (at 30% and 50% distal length of the femur) before and 12 weeks after treatment. Additionally, knee extension muscle strength, pain, and joint function were evaluated before and 6 and 12 weeks after treatment.

RESULTS

CSA of thigh muscles at 30% and 50% distal length of the femur decreased in the AOP 40% and control groups and was the largest in the AOP 80% group 12 weeks after treatment. Knee extension strength increased in all groups and was the highest in the AOP 80% group 6 and 12 weeks after treatment. Pain improved in all groups, with no intergroup differences. Knee joint function improved in all groups and was superior in the 80% AOP group 12 weeks after treatment.

CONCLUSION

LIE with BFR at 80% AOP was effective in preventing atrophy of the thigh muscle, increasing muscle strength, and improving function. BFR at 40% AOP had no difference in the results when compared with the group in which BFR was not applied. Therefore, LIE with an AOP of 80% is recommended for patients undergoing HTO.

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 vibration training vs. conventional resistance training among community-dwelling older people with sarcopenia: three-arm randomized controlled trial protocol

Introduction

Sarcopenia is a chronic and progressive disease, which is accompanied by the decline in muscle mass, muscle strength, and physical performance with aging, and it can lead to falls, fracture, and premature death. The prevention and treatment of sarcopenia mainly include exercise therapy and nutritional supplement. Exercise therapy is one of the most potential interventions to prevent and/or delay the progression of sarcopenia. Resistance training (RT), one of the most commonly used exercise types, is widely used in the treatment of sarcopenia, while vibration training (VT) is a prospective strategy for improving sarcopenia in older people. The aim of our study is to compare the effect of VT and RT in older people with sarcopenia on muscle mass, muscle strength, physical performance, blood biomarkers, and quality of life.

Methods and analysis

Our study is a 12-week, three-arm randomized controlled trial with assessor-blinded. The diagnosis criteria for subject recruitment adopt the guidelines for the Asian Working Group for Sarcopenia. A total of 54 subjects who met the criteria were randomized into one of the following three groups: VT group, RT group, and control group. The VT group and RT group received a 12-week whole-body vibration training and a resistance training program three times every week, respectively. The primary outcome is lower limb muscle strength, and the secondary outcomes include muscle mass, upper limb muscle strength, physical performance, blood biomarkers, and quality of life. We then performed assessments three times, at baseline (0 week), after intervention (12 weeks), and follow-up (24 weeks). The adverse events were also be reported. All outcome measurements were performed by the same researchers. Data were saved in the unified database, and the collected data of all subjects were analyzed by intention-to-treat analysis.

Ethics and dissemination

This study was reviewed and approved by the Ethical Committee of Xinhua Hospital Chongming Branch. The findings of the study were authorized in peer-reviewed journals with online access; meanwhile, it will be presented at domestic or international academic congresses.

Clinical trial registration

Chinese Clinical Trial Registry (ChiCTR2100051178), registered on 15 September 2021.

Quadriceps strengthening by the Kaatsu Training method in women with patellofemoral pain

ABSTRACT This is a cross-sectional, comparative, and randomized study aimed to evaluate the effects of the partial vascular occlusion technique (Kaatsu Training) associated with low load exercises in the muscle strengthening of quadriceps in women with patellofemoral pain. We evaluated 18 women with patellofemoral pain, aged from 18 to 35 years, allocated into two groups. The experimental group performed the strengthening with blood flow reduction with the aid of a sphygmomanometer, associated with low load (≅20% RM). Whereas the control group performed exercises with the same load, but without blood flow reduction. The treatment was performed three times a week for six weeks, totaling 18 sessions. We used the numerical pain rating scale (NPRS) and the anterior knee pain scale (AKPS) questionnaire for evaluation; we evaluated the muscle strength of knee extensors by the digital dynamometer. The results showed that the partial vascular occlusion technique significantly improved the values of quadriceps strength gain in the right, 6.22kg (p=0.03) and left limb, 6.98kg (p=0.04), in women with patellofemoral pain. Therefore, training with partial vascular occlusion can be useful for strengthening of the knee extensor musculature in women with patellofemoral pain who, because of the pain, have low tolerance to high load exercises for muscle strengthening. An effective, safe and cost-effective technique, which does not require an investment in a leg extension machine, since, with a cuff, low load exercises can offer significant results.

Fortalecimento do quadríceps através do método Kaatsu Training em mulheres com dor femoropatelar

RESUMO Este é um estudo transversal, comparativo e randomizado, cujo objetivo foi avaliar os efeitos da técnica de oclusão vascular parcial (Kaatsu Training) associada a exercícios de baixa carga no fortalecimento muscular de quadríceps em mulheres com dor femoropatelar. Foram avaliadas 18 mulheres com dor femoropatelar, com idade entre 18 e 35 anos, que foram alocadas em dois grupos. O grupo experimental realizou fortalecimento com redução do fluxo sanguíneo por meio de um esfigmomanômetro, associado com baixa carga (≅20% RM). Enquanto o grupo-controle realizou exercícios com a mesma carga, porém sem redução do fluxo sanguíneo. O tratamento foi realizado três vezes na semana, em um período de seis semanas, totalizando 18 sessões. Para avaliação foram utilizadas a escala numérica de avaliação da dor (NPRS) e o questionário anterior knee pain scale (AKPS); a força muscular de extensores do joelho foi avaliada através do dinamômetro digital. Os resultados mostraram que a técnica de oclusão vascular parcial provocou melhorias significativas nos valores de ganho de força do quadríceps no membro direito, 6,22kg (p=0,03), e esquerdo, 6,98kg (p=0,04), em mulheres com dor femoropatelar. Portanto, treinamento com oclusão vascular parcial pode ser uma alternativa útil para ganho de força da musculatura extensora do joelho em mulheres com dor femoropatelar que, devido à dor, tenham baixa tolerância a exercícios de alta carga para fortalecimento muscular, sendo uma técnica eficaz, segura e com boa relação de custo-benefício, não necessitando a compra de uma cadeira extensora, uma vez que utilizando um manguito é possível obter resultados significativos associados a exercícios de baixa carga.

Differences in the limb blood flow between two types of blood flow restriction cuffs: A pilot study

Introduction: The determination of the optimal occlusion level is a key parameter in blood flow restriction (BFR). This study aimed to compare the effects of elastic (BStrong) vs. nylon (Hokanson) BFR cuffs on blood flow in the lower and upper limbs.

Methods: Eleven healthy participants undertook several BFR sessions with 2 different cuffs of similar width on their lower and upper limbs at different pressures [200, 250, 300, 350, and 400 mmHg for BStrong and 0, 40, and 60% of the arterial occlusion pressure (AOP) for Hokanson]. Doppler ultrasound recorded blood flows through the brachial and femoral artery at rest.

Results: With BStrong, only 350 and 400 mmHg pressures were significantly different from resting values (0% AOP). With Hokanson, both 40% and 60% of the AOP were significantly different from resting values (p < 0.05).

Discussion: While both cuffs elicited BFR, they failed to accurately modulate blood flow. Hokanson is appropriate for research settings while BStrong appears to be a convenient tool for practitioners due to its safety (i.e., the impossibility of completely occluding arteries) and the possibility of exercising freely detached from the pump.

Acute hemodynamic responses from Low- load resistance exercise with blood flow restriction in young and older individuals: A Systematic Review and Meta-Analysis of Cross-Over Trials

OBJECTIVE

To summarize the existing evidence on the acute response of low-load (LL) resistance exercise (RE) with blood flow restriction (BFR) on hemodynamic parameters.

DATA SOURCES

MEDLINE (via PubMed), EMBASE (via Scopus), SPORTDiscus, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Web of Science, and MedRxiv databases were searched from inception to February 2022.

REVIEW METHODS

Cross-over trials investigating the acute effect of LLRE+BFR vs. passive (no exercise) and active control methods (LLRE or HLRE) on heart rate (HR), systolic (SBP), diastolic (DBP), and mean (MBP) blood pressure responses.

RESULTS

The quality of the studies was assessed using the PEDro scale, risk of bias using the RoB 2.0 tool for cross-over trials, and certainty of the evidence using the GRADE method. A total of 15 randomized cross-over studies with 466 participants were eligible for analyses. Our data showed that LLRE+BFR increases all hemodynamic parameters compared to passive control, but not compared to conventional resistance exercise. Subgroup analysis did not demonstrate any differences between LLRE+BFR and low- (LL) or high-load (HL) resistance exercise protocols. Studies including younger volunteers presented higher chronotropic responses (HR) than those with older volunteers.

CONCLUSIONS

Despite causing notable hemodynamic responses compared to no exercise, the short-term low-load resistance exercise with BFR modulates all hemodynamic parameters HR, SBP, DBP, and MBP, similarly to a conventional resistance exercise protocol, whether at low or high-intensity. The chronotropic response is slightly higher in younger healthy individuals despite the similarity regarding pressure parameters. This article is protected by copyright. All rights reserved.

Effect of different recovery modes during resistance training with blood flow restriction on hormonal levels and performance in young men: a randomized controlled trial

BACKGROUND

Resistance training with blood flow restriction (BFR) results in hypertrophy, and its magnitude depends on various training variables. This study aimed to compare the long-term effect of passive recovery (PR) and active recovery (AR) during low-intensity resistance training with BFR on hormonal levels and performance in young men.

METHODS

In the randomized clinical trial, 20 men were randomly divided into PR and AR groups during resistance training with BFR. The intervention consisted of six upper and lower body movements with 30% of one maximum repetition (1RM), three sessions per week for six weeks. Both groups wore pneumatic cuffs on the proximal part of thighs and arms. The cuff pressure was 60% of the calculated arterial blood occlusion and increased 10% every two weeks. The AR group performed seven repetitions in 30 s break between sets by one second for concentric and eccentric phases and two seconds rest, and the other group had passive rest. The blood samples and a series of performance tests were gathered before and after the intervention. A repeated measure ANOVA was used to analyze data.

RESULTS

AR and PR interventions significantly improved the C-reactive protein (CRP) (- 38% vs. - 40%), Lactate dehydrogenase (LDH) (- 11% vs. - 3%), Sargent jump (9% vs. 10%), peak power (20% vs.18%), and average power (14% vs. 14%), upper 1RM (8% vs. 8%) and no significant differences were observed between groups. The AR intervention significantly increased growth hormone (GH) (423% vs. 151%, p = 0.03), lower body 1RM (18% vs. 11%) and muscle endurance (34% vs. 22% for the upper body, p = 0.02 and 32% vs. 24% for the lower body, p = 0.04) than the PR group. The PR intervention further increased the minimum power than the AR group (19% vs. 10%). There were no significant changes in testosterone (p = 0.79) and cortisol (p = 0.34) following interventions.

CONCLUSION

The findings indicated that by increasing muscle activation and higher metabolic load, AR during resistance training with BFR might cause more remarkable improvements in serum GH, muscle strength, and endurance. Thus, to gain further benefits, AR during training with BFR is recommended.

TRIAL REGISTRATION

IRCT20191207045644N1. Registration date: 14/03/2020. URL: https://www.irct.ir/search/result?query=IRCT20191207045644N1.

The Role of Plasma Extracellular Vesicles in Remote Ischemic Conditioning and Exercise-Induced Ischemic Tolerance

Ischemic conditioning and exercise have been suggested for protecting against brain ischemia-reperfusion injury. However, the endogenous protective mechanisms stimulated by these interventions remain unclear. Here, in a comprehensive translational study, we investigated the protective role of extracellular vesicles (EVs) released after remote ischemic conditioning (RIC), blood flow restricted resistance exercise (BFRRE), or high-load resistance exercise (HLRE). Blood samples were collected from human participants before and at serial time points after intervention. RIC and BFRRE plasma EVs released early after stimulation improved viability of endothelial cells subjected to oxygen-glucose deprivation. Furthermore, post-RIC EVs accumulated in the ischemic area of a stroke mouse model, and a mean decrease in infarct volume was observed for post-RIC EVs, although not reaching statistical significance. Thus, circulating EVs induced by RIC and BFRRE can mediate protection, but the in vivo and translational effects of conditioned EVs require further experimental verification.

Effects of Low-Load Blood-Flow Restricted Resistance Training on Functional Capacity and Patient-Reported Outcome in a Young Male Suffering From Reactive Arthritis

Introduction: Reactive arthritis (ReA) is a chronic inflammatory disease usually caused by a preceding gastrointestinal or genitourinary bacterial infection. ReA usually occurs in the lower limbs causing joint pain and joint swelling. Physiotherapy-led exercise is recommended to prevent muscle atrophy. The purpose of this case report is to describe the outcome after 12 weeks of low-load blood flow restricted resistance training (BFR-RT) as a rehabilitation method for a young male suffering from ReA.

Methods and materials: A 17-year-old male suffered from ReA in the both knee joints and the left hip joint. 36 months after the incident, he suffered from another ReA incident in his right knee. Non-steroid anti-inflammatory drugs and a new arthrocentesis added with corticosteroid injection was unsuccessful in treating the ReA. The patient performed 12 weeks of BFR-RT on the right lower limb with a low amount of supervision after the first week of training. Assessment of unilateral 30-sec chair stand test (u30-sec CST), low-thigh circumference above apex patella, The Knee Injury and Osteoarthritis Outcome Score (KOOS), The Forgotten Knee Joint Score (FJS), and Numeric Ranking Scale for pain (NRS) was performed at baseline and after 3,6,9, and 12 weeks of BFR-RT.

Results: The patient completed all planned exercise sessions. u30-sec CST improved with 7 repetitions (reps) on the right limb and 5 reps on the left leg. Low-thigh circumference decreased 1.1 cm on the right leg and 1.0 on the left leg. KOOS symptoms, ADL, quality of life and FJS demonstrated a clinically relevant change on 10, 14 and 23 points.

Conclusion: The present case study indicates that even with low amounts of supervision BFR-RT could increase functional performance, reduce knee joint swelling and improve key patient-reported outcome.

Optimization of Exercise Countermeasures to Spaceflight Using Blood Flow Restriction

INTRODUCTION: During spaceflight missions, astronauts work in an extreme environment with several hazards to physical health and performance. Exposure to microgravity results in remarkable deconditioning of several physiological systems, leading to impaired physical condition and human performance, posing a major risk to overall mission success and crew safety. Physical exercise is the cornerstone of strategies to mitigate physical deconditioning during spaceflight. Decades of research have enabled development of more optimal exercise strategies and equipment onboard the International Space Station. However, the effects of microgravity cannot be completely ameliorated with current exercise countermeasures. Moreover, future spaceflight missions deeper into space require a new generation of spacecraft, which will place yet more constraints on the use of exercise by limiting the amount, size, and weight of exercise equipment and the time available for exercise. Space agencies are exploring ways to optimize exercise countermeasures for spaceflight, specifically exercise strategies that are more efficient, require less equipment, and are less time-consuming. Blood flow restriction exercise is a low intensity exercise strategy that requires minimal equipment and can elicit positive training benefits across multiple physiological systems. This method of exercise training has potential as a strategy to optimize exercise countermeasures during spaceflight and reconditioning in terrestrial and partial gravity environments. The possible applications of blood flow restriction exercise during spaceflight are discussed herein.Hughes L, Hackney KJ, Patterson SD. Optimization of exercise countermeasures to spaceflight using blood flow restriction. Aerosp Med Hum Perform. 2021; 93(1):32-45.

Efficacy of low-load resistance training combined with blood flow restriction vs. high-load resistance training on sarcopenia among community-dwelling older Chinese people: study protocol for a 3-arm randomized controlled trial

BACKGROUND

Sarcopenia is accompanied by a decline in muscle mass, muscle strength, and muscle function. Resistance training is the most potential training method for the prevention and treatment of sarcopenia. However, the conventional high-load resistance training (CRT) recommended by the American College of Sports Medicine is a challenge for older people with sarcopenia. As a novel training method, low-load resistance training combined with blood flow restriction (LRT-BFR) may elicit similar muscle mass and muscle strength gains as CRT but with less effort. The objectives of this study are to assess and compare the efficacy and safety of 12-week LRT-BFR and CRT on muscle strength, muscle performance, body composition, pulmonary function, blood biomarkers, CVD risk factors, and quality of life in community-dwelling older Chinese people with sarcopenia.

METHOD

This is a 12-week, assessor-blinded, 3-arm randomized controlled trial with a non-exercise control group. Community-dwelling people over 65 years will be screened for sarcopenia according to the diagnostic criteria of the Asian Working Group for Sarcopenia (AWGS). Fifty-one subjects will be randomized into a LRT-BFR group (n = 17), a CRT group (n = 17), and a no-strength training control group (n = 17). The primary outcome is lower limb muscle strength. The secondary outcomes are body composition, upper limb muscle strength, pulmonary function, blood biomarkers, CVD risk factors, and quality of life. Post-intervention follow-up will be performed for 12 weeks. These indicators will be assessed at baseline (0 week), after the 12-week intervention (12 weeks), and at follow-up (24 weeks). The adverse events will also be reported. Data will be analyzed for all participants in an intent-to-treat plan.

DISCUSSION

This study is the first RCT that will systematically measure and compare the efficacy and safety of LRT-BFR and CRT in older people with sarcopenia on muscle strength, body composition, pulmonary function, blood biomarkers (inflammatory biomarkers, hormone, and growth factors), CVD risk factors, and quality of life. This study can provide an efficient and safe method to prevent the progression of sarcopenia in older people.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2100042803 . Registered on 28 January 2021.

Blood Flow Restriction Training for Athletes: A Systematic Review

BACKGROUND

Blood flow restriction (BFR) is a novel technique involving the use of a cuff/tourniquet system positioned around the proximal end of an extremity to maintain arterial flow while restricting venous return.

PURPOSE

To analyze the available literature regarding the use of BFR to supplement traditional resistance training in healthy athletes.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. From November to December 2018, studies that examined the effects of BFR training in athletes were identified using PubMed and OVID Medline. Reference lists from selected articles were analyzed for additional studies. The inclusion criteria for full article review were randomized studies with control groups that implemented BFR training into athletes' resistance training workouts. Case reports and review studies were excluded. The following data were extracted: patient demographics, study design, training protocol, occlusive cuff location/pressure, maximum strength improvements, muscle size measurements, markers of sports performance (eg, sprint time, agility tests, and jump measurements), and other study-specific markers (eg, electromyography, muscular torque, and muscular endurance).

RESULTS

The initial search identified 237 articles. After removal of duplicates and screening of titles, abstracts, and full articles, 10 studies were identified that met the inclusion criteria. Seven of 9 (78%) studies found a significant increase in strength associated with use of BFR training as compared with control; 4 of 8 (50%) noted significant increases in muscle size associated with BFR training; and 3 of 4 (75%) reported significant improvements in sport-specific measurements in the groups that used BFR training. Occlusive cuff pressure varied across studies, from 110 to 240 mm HG.

CONCLUSION

The literature appears to support that BFR can lead to improvements in strength, muscle size, and markers of sports performance in healthy athletes. Combining traditional resistance training with BFR may allow athletes to maximize athletic performance and remain in good health. Additional studies should be conducted to find an optimal occlusive pressure to maximize training improvements.

REGISTRATION

CRD42019118025 (PROSPERO).

Evaluation of muscle thickness of the vastus lateralis by ultrasound imaging following blood flow restricted resistance exercise

BACKGROUND

Blood flow restricted (BFR) exercise results in transient muscle growth that may be due to metabolite accumulation, hyperaemia and muscle damage, possibly serving as a stimulus for hypertrophy. Understanding the duration of this growth is important for exercise recovery and measurement of hypertrophy.

PURPOSE

To measure changes in muscle size via ultrasound throughout a 48-h period after a session of BFR knee extension (KE) exercise.

METHODS

Muscle thickness of the vastus lateralis (VL) was measured via ultrasound in 12 participants (six males and six females, age: 20.3 ± 1.1 years) before and immediately, 10 min, 30 min, 1, 3, 8, 24, and 48 h after unilateral exercise. One leg served as a non-exercise control while the other leg performed four sets of unilateral BFR KE at 30% of one-repetition maximum with a pressurized cuff applied to the proximal thigh and inflated to 50% arterial occlusion pressure.

RESULTS

Vastus lateralis thickness was 34.9 ± 7.2% higher immediately after exercise, 28.6 ± 7.9% at 10 min, 25.2 ± 6.1% at 30 min, 14.9 ± 4.8% at 1 h and 11.8 ± 5.6% at 3 h (p < 0.05). There were no changes compared to pre-exercise measurements past 3 h, and the control limb did not change (p > 0.05). The muscle thickness of the exercise leg was significantly greater than that of the control leg from immediately after exercise up to 1 h post-exercise (p < 0.05).

CONCLUSION

Muscle thickness of the VL increases for 3 h post-BFR exercise and returns to normal within 8 h. This timeframe should be considered when prescribing exercise and planning muscle hypertrophy assessments.

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

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

High-frequency blood flow-restricted resistance exercise results in acute and prolonged cellular stress more pronounced in type I than in type II fibers

Myocellular stress with high-frequency blood flow-restricted resistance exercise (BFRRE) was investigated by measures of heat shock protein (HSP) responses, glycogen content, and inflammatory markers. Thirteen participants [age: 24 ± 2 yr (means ± SD), 9 males] completed two 5-day blocks of seven BFRRE sessions, separated by 10 days. Four sets of unilateral knee extensions to failure at 20% of one-repetition maximum (1RM) were performed. Muscle samples obtained before, 1 h after the first session in the first and second block (acute 1 and acute 2), after three sessions (day 4), during the "rest week," and at 3 (post 3) and 10 days postintervention (post 10) were analyzed for HSP70, αB-crystallin, glycogen [periodic acid-Schiff (PAS) staining], mRNAs, miRNAs, and CD68⁺ (macrophages) and CD66b⁺ (neutrophils) cell numbers. αB-crystallin translocated from the cytosolic to the cytoskeletal fraction after acute 1 and acute 2 (P < 0.05) and immunostaining revealed larger responses in type I than in type II fibers (acute 1, 225 ± 184% vs. 92 ± 81%, respectively, P = 0.001). HSP70 was increased in the cytoskeletal fraction at day 4 and post 3, and immunostaining intensities were more elevated in type I than in type II fibers at day 4 (206 ± 84% vs. 72 ± 112%, respectively, P <0.001), during the rest week (98 ± 66% vs. 42 ± 79%, P < 0.001), and at post 3 (115 ± 82% vs. 28 ± 78%, P = 0.003). Glycogen content was reduced in both fiber types, but most pronounced in type I, which did not recover until the rest week (-15% to 29%, P ≤ 0.001). Intramuscular macrophage numbers were increased by ∼65% postintervention, but no changes were observed in muscle neutrophils. We conclude that high-frequency BFRRE with sets performed till failure stresses both fiber types, with type I fibers being most affected.NEW & NOTEWORTHY BFRRE has been reported to preferentially stress type I muscle fibers, as evidenced by HSP responses. We extend these findings by showing that the HSP responses occur in both fiber types but more so in type I fibers and that they can still be induced after a short-term training period. Furthermore, the reductions in glycogen content of type I fibers after strenuous frequent BFRRE in unaccustomed subjects can be prolonged (≥5 days), probably due to microdamage.

Rehabilitation outcomes and parameters of blood flow restriction training in ACL injury: A scoping review

OBJECTIVE

To identify the outcomes of physical function, physical fitness, training, and cuff parameters, used in BFRT in ACL rehabilitation.

METHODS

This scoping review was initiated on April 25th, 2020, according to the PRISMA Extension for Scoping Reviews (PRISMA-ScR). Relevant literature was identified searching three main concepts: BFRT, rehabilitation and ACL injury on MEDLINE (PubMed), CENTRAL of Cochrane Library, Web of Science and PEDro. Studies looking at adults with a primary ACL injury undergoing conservative or pre/post-surgery rehabilitation with BFR or BFRT, with physical fitness and physical function as outcomes or other physical outcomes were included.

RESULTS

Sixty-eight articles were identified and six were included. One article was added through backward tracking. All studies used BFRT in the ACL injury surgical rehabilitation. Most studies evaluated physical fitness (muscular strength and volume) however, physical function was not considered a primary outcome. Training and cuff parameters were heterogeneously prescribed.

CONCLUSION

The existing evidence is not enough to draw definitive conclusions due to the heterogenous reported outcomes and parameters. Future investigation with standardized outcome measures and specific protocols are needed to draw conclusions on patients' physical function, so BFRT can be used more effectively in clinical rehabilitation practice.

Low-Intensity Resistance Training with Moderate Blood Flow Restriction Appears Safe and Increases Skeletal Muscle Strength and Size in Cardiovascular Surgery Patients: A Pilot Study

We examined the safety and the effects of low-intensity resistance training (RT) with moderate blood flow restriction (KAATSU RT) on muscle strength and size in patients early after cardiac surgery. Cardiac patients (age 69.6 ± 12.6 years, n = 21, M = 18) were randomly assigned to the control (n = 10) and the KAATSU RT group (n = 11). All patients had received a standard aerobic cardiac rehabilitation program. The KAATSU RT group additionally executed low-intensity leg extension and leg press exercises with moderate blood flow restriction twice a week for 3 months. RT-intensity and volume were increased gradually. We evaluated the anterior mid-thigh thickness (MTH), skeletal muscle mass index (SMI), handgrip strength, knee extensor strength, and walking speed at baseline, 5-7 days after cardiac surgery, and after 3 months. A physician monitored the electrocardiogram, rate of perceived exertion, and the color of the lower limbs during KAATSU RT. Creatine phosphokinase (CPK) and D-dimer were measured at baseline and after 3 months. There were no side effects during KAATSU RT. CPK and D-dimer were normal after 3 months. MTH, SMI, walking speed, and knee extensor strength increased after 3 months with KAATSU RT compared with baseline. Relatively low vs. high physical functioning patients tended to increase physical function more after 3 months with KAATSU RT. Low-intensity KAATSU RT as an adjuvant to standard cardiac rehabilitation can safely increase skeletal muscle strength and size in cardiovascular surgery patients.

Efficacy of low-load blood flow restricted resistance EXercise in patients with Knee osteoarthritis scheduled for total knee replacement (EXKnee): protocol for a multicentre randomised controlled trial

INTRODUCTION

Up to 20% of patients undergoing total knee replacement (TKR) surgery report no or suboptimal pain relief after TKR. Moreover, despite chances of recovering to preoperative functional levels, patients receiving TKR have demonstrated persistent deficits in quadriceps strength and functional performance compared with healthy age-matched adults. We intend to examine if low-load blood flow restricted exercise (BFRE) is an effective preoperative method to increase functional capacity, lower limb muscle strength and self-reported outcomes after TKR. In addition, the study aims to investigate to which extent preoperative BFRE will protect against surgery-related atrophy 3 months after TKR.

METHODS

In this multicentre, randomised controlled and assessor blinded trial, 84 patients scheduled for TKR will be randomised to receive usual care and 8 weeks of preoperative BFRE or to follow usual care-only. Data will be collected before randomisation, 3-4 days prior to TKR, 6 weeks, 3 months and 12 months after TKR. Primary outcome will be the change in 30 s chair stand test from baseline to 3-month follow-up. Key secondary outcomes will be timed up and go, 40 me fast-paced walk test, isometric knee extensor and flexor strength, patient-reported outcome and selected myofiber properties.Intention-to-treat principle and per-protocol analyses will be conducted. A one-way analysis of variance model will be used to analyse between group mean changes. Preintervention-to-postintervention comparisons will be analysed using a mixed linear model. Also, paired Student's t-test will be performed to gain insight into the potential pretraining-to-post-training differences within the respective training or control groups and regression analysis will be used for analysation of associations between selected outcomes.

ETHICAL APPROVAL

The trial has been accepted by the Central Denmark Region Committee on Biomedical Research Ethics (Journal No 10-72-19-19) and the Danish Data Protection Agency (Journal No 652164). All results will be published in international peer-reviewed scientific journals regardless of positive, negative or inconclusive results.

TRIAL REGISTRATION NUMBER

NCT04081493.

Effects of Blood Flow Restriction at Different Intensities on IOP and Ocular Perfusion Pressure

SIGNIFICANCE

The use of blood flow restriction allows obtaining beneficial physical adaptions when combined with low-intensity exercise or even when used alone. We found that using blood flow restriction may be a potential strategy to avoid IOP and ocular perfusion pressure fluctuations provoked by strength and endurance training.

PURPOSE

The purpose of this study was to assess the influence of bilateral blood flow restriction in the upper and lower body at two different intensities on IOP and ocular perfusion pressure, as well as the possible sex differences.

METHODS

Twenty-eight physically active university students (14 men and 14 women) took part in the study, and blood flow restriction was bilaterally applied with two pressures in the legs and arms. There were five experimental conditions (control, legs-high, legs-low, arms-high, and arms-low). IOP was measured by rebound tonometry before, during (every 4 seconds), and immediately after blood flow restriction. Ocular perfusion pressure was measured before and after blood flow restriction.

RESULTS

We found that only the arms-high condition promoted a statistically significant IOP rise when compared with the rest of the experimental conditions (all Bayes factors10, >100; effect sizes, 1.18, 1.06, 1.35, and 1.73 for the control, arms-low, legs-high, and legs-low conditions, respectively). For ocular perfusion pressure, there was strong evidence for the null hypothesis regarding the type of blood flow restriction (Bayes factor10, 0.012); however, men showed an ocular perfusion pressure reduction after blood flow restriction in the arms-high condition (Bayes factor10, 203.24; effect size, 1.41).

CONCLUSIONS

This study presents preliminary evidence regarding the safety of blood flow restriction in terms of ocular health. Blood flow restriction may be considered as an alternative training strategy to reduce abrupt fluctuations in IOP and ocular perfusion pressure because its use permits a considerable reduction of exercise intensity.

An Updated Panorama of "Living Low-Training High" Altitude/Hypoxic Methods

With minimal costs and travel constraints for athletes, the “living low-training high” (LLTH) approach is becoming an important intervention for modern sport. The popularity of the LLTH model of altitude training is also associated with the fact that it only causes a slight disturbance to athletes' usual daily routine, allowing them to maintain their regular lifestyle in their home environment. In this perspective article, we discuss the evolving boundaries of the LLTH paradigm and its practical applications for athletes. Passive modalities include intermittent hypoxic exposure at rest (IHE) and Ischemic preconditioning (IPC). Active modalities use either local [blood flow restricted (BFR) exercise] and/or systemic hypoxia [continuous low-intensity training in hypoxia (CHT), interval hypoxic training (IHT), repeated-sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH) and resistance training in hypoxia (RTH)]. A combination of hypoxic methods targeting different attributes also represents an attractive solution. In conclusion, a growing number of LLTH altitude training methods exists that include the application of systemic and local hypoxia stimuli, or a combination of both, for performance enhancement in many disciplines.

Muscle fibre activation and fatigue with low-load blood flow restricted resistance exercise-An integrative physiology review

Blood flow-restricted resistance exercise (BFRRE) has been shown to induce increases in muscle size and strength, and continues to generate interest from both clinical and basic research points of view. The low loads employed, typically 20%-50% of the one repetition maximum, make BFRRE an attractive training modality for individuals who may not tolerate high musculoskeletal forces (eg, selected clinical patient groups such as frail old adults and patients recovering from sports injury) and/or for highly trained athletes who have reached a plateau in muscle mass and strength. It has been proposed that achieving a high degree of muscle fibre recruitment is important for inducing muscle hypertrophy with BFRRE, and the available evidence suggest that fatiguing low-load exercise during ischemic conditions can recruit both slow (type I) and fast (type II) muscle fibres. Nevertheless, closer scrutiny reveals that type II fibre activation in BFRRE has to date largely been inferred using indirect methods such as electromyography and magnetic resonance spectroscopy, while only rarely addressed using more direct methods such as measurements of glycogen stores and phosphocreatine levels in muscle fibres. Hence, considerable uncertainity exists about the specific pattern of muscle fibre activation during BFRRE. Therefore, the purpose of this narrative review was (1) to summarize the evidence on muscle fibre recruitment during BFRRE as revealed by various methods employed for determining muscle fibre usage during exercise, and (2) to discuss reported findings in light of the specific advantages and limitations associated with these methods.

Speeding of oxygen uptake kinetics is not different following low-intensity blood-flow-restricted and high-intensity interval training

NEW FINDINGS

What is the central question of this study? Can interval blood-flow-restricted (BFR) cycling training, undertaken at a low intensity, promote a similar adaptation to oxygen uptake ( V ̇ O 2 ) kinetics to high-intensity interval training? What is the main finding and its importance? Speeding of pulmonary V ̇ O 2 on-kinetics in healthy young subjects was not different between low-intensity interval BFR training and traditional high-intensity interval training. Given that very low workloads are well tolerated during BFR cycle training and speed V ̇ O 2 on-kinetics, this training method could be used when high mechanical loads are contraindicated.

ABSTRACT

Low-intensity blood-flow-restricted (BFR) endurance training is effective to increase aerobic capacity. Whether it speeds pulmonary oxygen uptake ( V ̇ O 2 p ), CO₂ output ( V ̇ C O 2 p ) and ventilatory ( V ̇ Ep ) kinetics has not been examined. We hypothesized that low-intensity BFR training would reduce the phase 2 time constant (τ_p ) of V ̇ O 2 p , V ̇ C O 2 p and V ̇ Ep by a similar magnitude to traditional high-intensity interval training (HIT). Low-intensity interval training with BFR served as a control. Twenty-four participants (25 ± 6 years old; maximal V ̇ O 2 46 ± 6 ml kg^-1  min^-1 ) were assigned to one of the following: low-intensity BFR interval training (BFR; n = 8); low-intensity interval training without BFR (LOW; n = 7); or high-intensity interval training without BFR (HIT; n = 9). Training was 12 sessions of two sets of five to eight × 2 min cycling and 1 min resting intervals. LOW and BFR were conducted at 30% of peak incremental power (P_peak ), and HIT was at ∼103% P_peak . For BFR, cuffs were inflated on both thighs (140-200 mmHg) during exercise and deflated during rest intervals. Six moderate-intensity step transitions (30% P_peak ) were averaged for analysis of pulmonary on-kinetics. Both BFR (pre- versus post-training τ_p  = 18.3 ± 3.2 versus 14.5 ± 3.4 s; effect size = 1.14) and HIT (τ_p  = 20.3 ± 4.0 versus 13.1 ± 2.9 s; effect size = 1.75) reduced the V ̇ O 2 p τ_p (P < 0.05). As expected, there was no change in LOW ( V ̇ O 2 p τ_p  = 17.9 ± 6.2 versus 17.7 ± 4.3 s; P = 0.9). The kinetics of V ̇ C O 2 p and V ̇ Ep were speeded only after HIT (38.5 ± 10.6%, P < 0.001 and 31.2 ± 24.7%, P = 0.004, respectively). Both HIT and low-intensity BFR training were effective in speeding moderate-intensity V ̇ O 2 p kinetics. These data support the findings of others that low-intensity cycling training with BFR increases muscle oxidative capacity.

Low intensity blood flow restriction exercise: Rationale for a hypoalgesia effect

Exercise-induced hypoalgesia is characterised by a reduction in pain sensitivity following exercise. Recently, low intensity exercise performed with blood flow restriction has been shown to induce hypoalgesia. The purpose of this manuscript is to discuss the mechanisms of exercise-induced hypoalgesia and provide rationale as to why low intensity exercise performed with blood flow restriction may induce hypoalgesia. Research into exercise-induced hypoalgesia has identified several potential mechanisms, including opioid and endocannabinoid-mediated pain inhibition, conditioned pain modulation, recruitment of high threshold motor units, exercise-induced metabolite production and an interaction between cardiovascular and pain regulatory systems. We hypothesise that several mechanisms consistent with prolonged high intensity exercise may drive the hypoalgesia effect observed with blood flow restriction exercise. These are likely triggered by the high level of intramuscular stress in the exercising muscle generated by blood flow restriction including hypoxia, accumulation of metabolites, accelerated fatigue onset and ischemic pain. Therefore, blood flow restriction exercise may induce hypoalgesia through similar mechanisms to prolonged higher intensity exercise, but at lower intensities, by changing local tissue physiology, highlighting the importance of the blood flow restriction stimulus. The potential to use blood flow restriction exercise as a pain modulation tool has important implications following acute injury and surgery, and for several load compromised populations with chronic pain.

Type 1 Muscle Fiber Hypertrophy after Blood Flow-restricted Training in Powerlifters

PURPOSE

To investigate the effects of blood flow-restricted resistance exercise (BFRRE) on myofiber areas (MFA), number of myonuclei and satellite cells (SC), muscle size and strength in powerlifters.

METHODS

Seventeen national level powerlifters (25 ± 6 yr [mean ± SD], 15 men) were randomly assigned to either a BFRRE group (n = 9) performing two blocks (weeks 1 and 3) of five BFRRE front squat sessions within a 6.5-wk training period, or a conventional training group (Con; n = 8) performing front squats at 60%-85% of one-repetition maximum (1RM). The BFRRE consisted of four sets (first and last set to voluntary failure) at ~30% of 1RM. Muscle biopsies were obtained from m. vastus lateralis (VL) and analyzed for MFA, myonuclei, SC and capillaries. Cross-sectional areas (CSA) of VL and m. rectus femoris were measured by ultrasonography. Strength was evaluated by maximal voluntary isokinetic torque (MVIT) in knee extension and 1RM in front squat.

RESULTS

BFRRE induced selective increases in type I MFA (BFRRE: 12% vs Con: 0%, P < 0.01) and myonuclear number (BFRRE: 18% vs Con: 0%, P = 0.02). Type II MFA was unaltered in both groups. BFRRE induced greater changes in VL CSA (7.7% vs 0.5%, P = 0.04), which correlated with the increases in MFA of type I fibers (r = 0.81, P = 0.02). No group differences were observed in SC and strength changes, although MVIT increased with BFRRE (P = 0.04), whereas 1RM increased in Con (P = 0.02).

CONCLUSIONS

Two blocks of low-load BFRRE in the front squat exercise resulted in increased quadriceps CSA associated with preferential hypertrophy and myonuclear addition in type 1 fibers of national level powerlifters.

Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety

The current manuscript sets out a position stand for blood flow restriction (BFR) exercise, focusing on the methodology, application and safety of this mode of training. With the emergence of this technique and the wide variety of applications within the literature, the aim of this position stand is to set out a current research informed guide to BFR training to practitioners. This covers the use of BFR to enhance muscular strength and hypertrophy via training with resistance and aerobic exercise and preventing muscle atrophy using the technique passively. The authorship team for this article was selected from the researchers focused in BFR training research with expertise in exercise science, strength and conditioning and sports medicine.

Delayed myonuclear addition, myofiber hypertrophy, and increases in strength with high-frequency low-load blood flow restricted training to volitional failure

The purpose of the present study was to investigate muscle hypertrophy, strength, and myonuclear and satellite cell (SC) responses to high-frequency blood flow-restricted resistance exercise (BFRRE). Thirteen individuals [24 ± 2 yr (mean ± SD), 9 men] completed two 5-day blocks of 7 BFRRE sessions, separated by a 10-day rest period. Four sets of unilateral knee extensions to voluntary failure at 20% of one repetition maximum (1RM) were conducted with partial blood flow restriction (90–100 mmHg). Muscle samples obtained before, during, 3 days, and 10 days after training were analyzed for muscle fiber area (MFA), myonuclei, SC, and mRNA and miRNA expression. Muscle size was measured by ultrasonography and magnetic resonance imaging and strength with 1RM knee extension. With the first block of BFRRE, SC number increased in both fiber types (70%–80%, P < 0.05), whereas type I and II MFA decreased by 6 ± 7% and 15 ± 11% ( P < 0.05), respectively. With the second block of training, muscle size increased by 6%–8%, whereas the number of SCs (type I: 80 ± 63%, type II: 147 ± 95%), myonuclei (type I: 30 ± 24%, type II: 31 ± 28%), and MFA (type I: 19 ± 19%, type II: 11 ± 19%) peaked 10 days after the second block of BFRRE, whereas strength peaked after 20 days of detraining (6 ± 6%, P < 0.05). Pax7- and p21 mRNA expression were elevated during the intervention, whereas myostatin, IGF1R, MyoD, myogenin, cyclinD1 and -D2 mRNA did not change until 3–10 days postintervention. High-frequency low-load BFRRE induced robust increases in SC, myonuclei, and muscle size but modest strength gains. Intriguingly, the responses were delayed and peaked 10–20 days after the training intervention, indicating overreaching.

NEW & NOTEWORTHY In line with previous studies, we demonstrate that high-frequency low-load blood flow-restricted resistance exercise (HF-BFRRE) can elicit robust increases in satellite cell and myonuclei numbers, along with gains in muscle size and strength. However, our results also suggest that these processes can be delayed and that with very strenuous HF-BFRRE, there may even be transient muscle fiber atrophy, presumably because of accumulated stress responses. Our findings have implications for the prescription of BFR exercise.

Blood Flow Restriction Resistance Exercise as a Rehabilitation Modality Following Orthopaedic Surgery: A Review of Venous Thromboembolism Risk

Synopsis Restoration of skeletal muscle mass and strength is critical to successful outcomes following orthopaedic surgery. Blood flow restriction (BFR) resistance exercise has emerged as a promising means of augmenting traditional low-intensity physical rehabilitation exercise and has yielded successful outcomes in a wide range of applications. Though BFR is well tolerated and safe for most individuals, patients who have undergone orthopaedic surgery may be an exception, due to their heightened risk for venous thromboembolism (VTE). While the pathogenesis of VTE is multifactorial and specific to the individual, it is commonly described as a combination of blood stasis, endothelial injury, and alterations in the constituents of the blood leading to hypercoagulability. The collective literature suggests that, given the pathogenic mechanisms of VTE, limited use of a wide, partially occluding cuff during resistance exercise should be low risk, and the likelihood that BFR would directly cause a VTE event is remote. Alternatively, it is plausible that BFR may enhance blood flow and promote fibrinolysis. Of greater concern is the individual with pre-existing asymptomatic VTE, which could be dislodged during BFR. However, it is unknown whether the direct risk associated with BFR is greater than the risk accompanying traditional exercise alone. Presently, there are no universally agreed-upon standards indicating which postsurgical orthopaedic patients may perform BFR safely. While excluding all these patients from BFR may be overly cautious, clinicians need to thoroughly screen for VTE signs and symptoms, be cognizant of each patient's risk factors, and use proper equipment and prescription methods prior to initiating BFR. J Orthop Sports Phys Ther 2019;49(1):17-27. Epub 12 Sep 2018. doi:10.2519/jospt.2019.8375.

Blood Flow Restriction Training Reduces Blood Pressure During Exercise Without Affecting Metaboreflex Activity

Objective: Blood flow restriction training (BFRT) has been proposed to induce muscle hypertrophy, but its safety remains controversial as it may increase mean arterial pressure (MAP) due to muscle metaboreflex activation. However, BFR training also causes metabolite accumulation that may desensitize type III and IV nerve endings, which trigger muscle metaboreflex. Then, we hypothesized that a period of BFR training would result in blunted hemodynamic activation during muscle metaboreflex.

Methods: 17 young healthy males aged 18–25 yrs enrolled in this study. Hemodynamic responses during muscle metaboreflex were assessed by means of postexercise muscle ischemia (PEMI) at baseline (T0) and after 1 month (T1) of dynamic BFRT. BFRT consisted of 3-min rhythmic handgrip exercise applied 3 days/week (30 contractions per minute at 30% of maximum voluntary contraction) in the dominant arm. On the first week, the occlusion was set at 75% of resting systolic blood pressure (always obtained after 3 min of resting) and increased 25% every week, until reaching 150% of resting systolic pressure at week four. Hemodynamic measurements were assessed by means of impedance cardiography.

Results: BFRT reduced MAP during handgrip exercise (T1: 96.3 ± 8.3 mmHg vs. T0: 102.0 ± 9.53 mmHg, p = 0.012). However, no significant time effect was detected for MAP during the metaboreflex activation (P > 0.05). Additionally, none of the observed hemodynamic outcomes, including systemic vascular resistance (SVR), showed significant difference between T0 and T1 during the metaboreflex activation (P > 0.05).

Conclusion: BFRT reduced blood pressure during handgrip exercise, thereby suggesting a potential hypotensive effect of this modality of training. However, MAP reduction during handgrip seemed not to be provoked by lowered metaboreflex activity.

Blood Flow Restriction Therapy After Knee Surgery: Indications, Safety Considerations, and Postoperative Protocol

Blood flow restriction (BFR) training involves occluding venous outflow while maintaining arterial inflow by the application of an extremity tourniquet after surgery. BFR ultimately reduces oxygen delivery to muscle cells, similar to an anaerobic environment, and allows patients to exercise with low resistance and stimulates muscle hypertrophy and strength using heavy resistance. Thus orthopaedic surgeons and physical therapists are incorporating this type of training into their postoperative rehabilitation protocols, particularly after injuries or surgical procedures about the knee joint. The purpose of this Technical Note is to describe a BFR clinical application technique and to report on the indications, safety considerations, and postoperative knee surgery rehabilitation protocols for BFR.

Oxygenation time course and neuromuscular fatigue during repeated cycling sprints with bilateral blood flow restriction

The aim was to evaluate changes in peripheral and cerebral oxygenation, cardiorespiratory, and performance differences, as well as neuromuscular fatigue across multiple levels of blood flow restriction (BFR) during a repeated cycling sprint test to exhaustion (RST). Participants performed three RST (10-sec maximal sprints with 20-sec recovery until exhaustion) with measurements of power output and V̇O2peak as well as oxygenation (near-infrared spectroscopy) of the vastus lateralis and prefrontal cortex. Neuromuscular fatigue was assessed by femoral nerve stimulation to evoke the vastus lateralis. Tests were conducted with proximal lower limb bilateral vascular occlusion at 0%, 45%, and 60% of resting pulse elimination pressure. Total work decreased with BFR (52.5 ± 22.9% at 45%, 68.6 ± 32.6% at 60%, P < 0.01 compared with 0%) as V̇O2peak (12.6 ± 9.3% at 45%, 18.2 ± 7.2% at 60%, compared with 0%, P < 0.01). Decreased changes in muscle deoxyhemoglobin (∆[HHb]) during sprints were demonstrated at 60% compared to 0% (P < 0.001). Changes in total hemoglobin concentrations (∆[tHb]) increased at both 45% and 60% compared with 0% (P < 0.001). Cerebral ∆[tHb] increased toward exhaustion (P < 0.05). Maximal voluntary contraction (MVC), voluntary activation level (VAL), and root mean square (RMS)/M-wave ratio decreased at 60% compared with 0% (P < 0.001, all). MVC and VAL decreased between 45% and 60% (P < 0.05, both). The application of BFR during RST induced greater changes in tissue perfusion (via blood volume, ∆[tHb]) suggesting a possible stimulus for vascular blood flow regulation. Additionally, high-intensity sprint exercise with partial ischemia may challenge cerebral blood flow regulation and influence local fatigue development due to protection of cerebral function.

The Role of Blood Flow Restriction Therapy Following Knee Surgery: Expert Opinion

Blood flow restriction (BFR) therapy is becoming increasingly popular in musculoskeletal injury rehabilitation. In particular, this form of therapy is being utilized more often in the postoperative setting following knee surgery, including anterior cruciate ligament reconstruction. BFR therapy provides patients and clinicians an alternative treatment option to standard muscle strengthening and hypertrophy guidelines in the setting of postoperative pain, weakness, and postoperative activity restrictions that contribute to muscle atrophy. The ability to complete exercise in a low load environment and achieve similar physiological adaptations as high-intensity strength training makes this modality appealing. With poor patient-related outcomes associated with continued muscle atrophy, pain, and muscle weakness, some researchers have investigated BFR training postoperatively following arthroscopic knee surgery with promising results. However, owing to the current paucity of research studies, inconsistency among reported protocols, and mixed results, it may be some time before a mass adoption of BFR therapy is made into the world of orthopaedic rehabilitation. Although the current data is inconclusive, we choose to utilize BFR in postoperative knee patients, regardless of weight-bearing status, for whom maintenance of existing muscle mass or improvement of decreased postoperative strength levels is important. Therefore, the purpose of this expert opinion is to review the background of BFR, describe the clinical evidence of BFR following knee surgery, and report the authors' current recommendations for application of BFR postoperatively.

Hemodynamic responses are reduced with aerobic compared with resistance blood flow restriction exercise

The hemodynamics of light‐load exercise with an applied blood‐flow restriction (BFR) have not been extensively compared between light‐intensity, BFR, and high‐intensity forms of both resistance and aerobic exercise in the same participant population. Therefore, the purpose of this study was to use a randomized crossover design to examine the hemodynamic responses to resistance and aerobic BFR exercise in comparison with a common high‐intensity and light‐intensity non‐BFR exercise. On separate occasions participants completed a leg‐press (resistance) or treadmill (aerobic) trial. Each trial comprised a light‐intensity bout (LI) followed by a light‐intensity bout with BFR (80% resting systolic blood pressure (LI+BFR)), then a high‐intensity bout (HI). To characterize the hemodynamic response, measures of cardiac output, stroke volume, heart rate and blood pressure were taken at baseline and exercise for each bout. Exercising hemodynamics for leg‐press LI+BFR most often resembled those for HI and were greater than LI (e.g. for systolic blood pressure LI+BFR = 152 ± 3 mmHg; HI = 153 ± 3; LI = 143 ± 3 P < 0.05). However, exercising hemodynamics for treadmill LI+BFR most often resembled those for LI and were lower than HI (e.g. for systolic pressure LI+BFR = 124 ± 2 mmHg; LI = 123 ± 2; HI = 140 ± 3 P < 0.05). In conclusion, the hemodynamic response for light aerobic (walking) BFR exercise suggests this mode of BFR exercise may be preferential for chronic use to develop muscle size and strength, and other health benefits in certain clinical populations that are contraindicated to heavy‐load resistance exercise.

Delayed Onset Muscle Soreness and Perceived Exertion After Blood Flow Restriction Exercise

Brandner, CR, and Warmington, SA. Delayed onset muscle soreness and perceived exertion after blood flow restriction exercise. J Strength Cond Res 31(11): 3101-3108, 2017-The purpose of this study was to determine the perceptual responses to resistance exercise with heavy loads (80% 1 repetition maximum [1RM]), light loads (20% 1RM), or light loads in combination with blood flow restriction (BFR). Despite the use of light loads, it has been suggested that the adoption of BFR resistance exercise may be limited because of increases in delayed onset muscle soreness (DOMS) and perceived exertion. Seventeen healthy untrained males participated in this balanced, randomized cross-over study. After 4 sets of elbow-flexion exercise, participants reported ratings of perceived exertion (RPE), with DOMS also recorded for 7 days after each trial. Delayed onset muscle soreness was significantly greater for low-pressure continuous BFR (until 48 hours postexercise) and high-pressure intermittent BFR (until 72 hours postexercise) than for traditional heavy-load resistance exercise and light-load resistance exercise. In addition, RPE was higher for heavy-load resistance exercise and high-pressure intermittent BFR than for low-pressure continuous BFR, with all trials greater than light-load resistance exercise. For practitioners working with untrained participants, this study provides evidence to suggest that to minimize the perception of effort and postexercise muscle soreness associated with BFR resistance exercise, continuous low-pressure application may be more preferential than intermittent high-pressure application. Importantly, these perceptual responses are relatively short-lived (∼2 days) and have previously been shown to subside after a few exercise sessions. Combined with smaller initial training volumes (set × repetitions), this may limit RPE and DOMS to strengthen uptake and adherence and assist in program progression for muscle hypertrophy and gains in strength.