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

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.

Blood-flow-restricted exercise: Strategies for enhancing muscle adaptation and performance in the endurance-trained athlete

NEW FINDINGS

What is the topic of this review? Blood-flow-restricted (BFR) exercise represents a potential approach to augment the adaptive response to training and improve performance in endurance-trained individuals. What advances does it highlight? When combined with low-load resistance exercise, low- and moderate-intensity endurance exercise and sprint interval exercise, BFR can provide an augmented acute stimulus for angiogenesis and mitochondrial biogenesis. These augmented acute responses can translate into enhanced capillary supply and mitochondrial function, and subsequent endurance-type performance, although this might depend on the nature of the exercise stimulus. There is a requirement to clarify whether BFR training interventions can be used by high-performance endurance athletes within their structured training programme.

ABSTRACT

A key objective of the training programme for an endurance athlete is to optimize the underlying physiological determinants of performance. Training-induced adaptations are governed by physiological and metabolic stressors, which initiate transcriptional and translational signalling cascades to increase the abundance and/or function of proteins to improve physiological function. One important consideration is that training adaptations are reduced as training status increases, which is reflected at the molecular level as a blunting of the acute signalling response to exercise. This review examines blood-flow-restricted (BFR) exercise as a strategy for augmenting exercise-induced stressors and subsequent molecular signalling responses to enhance the physiological characteristics of the endurance athlete. Focus is placed on the processes of capillary growth and mitochondrial biogenesis. Recent evidence supports that BFR exercise presents an intensified training stimulus beyond that of performing the same exercise alone. We suggest that this has the potential to induce enhanced physiological adaptations, including increases in capillary supply and mitochondrial function, which can contribute to an improvement in performance of endurance exercise. There is, however, a lack of consensus regarding the potency of BFR training, which is invariably attributable to the different modes, intensities and durations of exercise and BFR methods. Further studies are needed to confirm its potential in the endurance-trained athlete.

Acute Effects of Interset Rest Duration on Physiological and Perceptual Responses to Resistance Exercise in Hypoxia

Lockhart, C, Scott, BR, Thoseby, B, and Dascombe, BJ. Acute effects of interset rest duration on physiological and perceptual responses to resistance exercise in hypoxia. J Strength Cond Res 34(8): 2241-2249, 2020-This study aimed to determine whether manipulating interset rest periods during resistance training in hypoxia impacts on physiological and perceptual responses to exercise. Twelve healthy males completed 1 repetition maximum (1RM) testing for the bilateral leg extension, before completing 4 separate randomized trials comprising 5 × 10 repetitions of leg extensions at 70% 1RM. Experimental trials were completed in both moderate hypoxia (FIO2 = 15%) and normoxia (FIO2 = 21%), using interset rest periods of both 60 and 180 seconds for each environmental condition. Near-infrared spectroscopy was used to quantify muscle oxygenation of vastus lateralis , and surface electromyography assessed the activation of vastus lateralis and medialis. Blood lactate concentration ([BLa]) and midthigh circumference were assessed before and immediately after each trial. Heart rate (HR) responses, blood oxygen saturation, and rating of perceived exertion (RPE) were also assessed after each set and the whole session RPE (sRPE). Perceived quadriceps soreness was reported before, immediately after, and at 24 and 48 hours after each trial. Muscle activation (sets 4-5), RPE (sets 3-5), and sRPE were significantly (p < 0.05) higher in the 60-second trials of the resistance exercise protocol. Significant increases (p < 0.01) were observed for [BLa] and midthigh circumference across sets within each condition. No significant main effect was observed for interset rest duration or environmental condition for muscle oxygenation, HR, or perceived quadriceps soreness. These findings indicate that performing resistance exercise in hypoxia or normoxia with shortened interset rest periods increases muscle activation and perceived exertion, without exacerbating muscle soreness.

Strength Training: In Search of Optimal Strategies to Maximize Neuromuscular Performance

Training with low-load exercise performed under blood flow restriction can augment muscle hypertrophy and maximal strength to a similar extent as the classical high-load strength training method. However, the blood flow restriction method elicits only minor neural adaptations. In an attempt to maximize training-related gains, we propose using other protocols that combine high voluntary activation, mechanical tension, and metabolic stress.

EFFECTS OF BLOOD FLOW RESTRICTION TRAINING ON HANDGRIP STRENGTH AND MUSCULAR VOLUME OF YOUNG WOMEN

Background

High-intensity training methods are generally recommended to increase muscle mass and strength, with training loads of 60-70% 1RM for novice and 80-100% 1RM for advanced individuals. Blood flow restriction training, despite using lower intensities (30-50% 1RM), can provide similar improvements in muscle mass and strength. However, studies commonly investigate the effects of blood flow restriction training in large muscular groups, whereas there are few studies that investigated those effects in smaller muscle groups, such as the muscles involved in grasping (e.g, wrist flexors; finger flexors). Clinically, smaller muscular groups should also be considered in intervention programs, given that repetitive stress, such as repeated strain injuries, affects upper limbs and may lead to chronic pain and incapacity for work. The purpose of the present study was to examine the effects of blood flow restriction training in strength and anthropometric indicators of muscular volume in young women.

Hypothesis

The effect of blood flow restriction training in handgrip strength (HGS) and muscular volume of young women can be similar to traditional training, even with lower loads.

Methods

Twenty-eight university students, 18 to 25 years of age, were randomly assigned into two groups, blood flow restriction training (BFR, n = 14) and traditional training (TRAD, n = 14). The anthropometric measures and maximum handgrip strength (MHGS) test were performed before and after the intervention. The participants did three weekly sessions of dynamic concentric contraction exercises on a dynamometer for four weeks (12 sessions). Each session had a time length of five minutes and the intensity was established from a percentage of MHGS at 30-35% in the first week, 40-45% in the second and 50-55% in third/fourth weeks. Three sets of 15-25 handgrip repetitions were performed until a failure with a 30 seconds rest for BFR training and three sets of 8-12 repetitions with one-minute rest for TRAD training.

Results

A significant increase was found in the arm muscle circumference (20.6 ± 2.2 vs 21.6 ± 1.7cm) and right MHGS (32.7 ± 4.5 vs 34.3 ± 4.1 kgf) and left MHGS (28.0 ± 5.5 vs 30.9 ± 4.1 kgf) for the BFR training, and the left MHGS (27.6 ± 5.0 vs 31.0 ± 6.1 kgf) for the TRAD training.

Conclusion

Dynamometer training with blood flow restriction, performed with low to moderate loads, was more effective than the traditional training in increasing HGS and muscle volume in young women.

Level of evidence

2b.

Quadriceps strengthening with blood flow restriction for the rehabilitation of patients with knee conditions: A systematic review with meta-analysis

OBJECTIVE

The purpose of this systematic review with meta-analysis was to compare the effects of low load resistance combined with blood flow restriction (BFR) versus conventional quadriceps strengthening on knee symptoms and function as well as knee extensor strength and muscle thickness in adults with knee conditions.

LITERATURE SURVEY

Guidelines based on the latest evidence highlight the importance of quadriceps strengthening to reduce pain and improve function in patients with knee conditions. Blood flow restriction is based on brief periods of vascular occlusion which cause muscle hypertrophy and increased strength. Before it can be recommended for individuals with knee conditions, quadriceps strengthening with low load resistance combined with BFR (LL-BFR) must show beneficial effects on clinical outcomes in addition to quadriceps strength and mass.

METHODS

A systematic review with meta-analysis was conducted to identify relevant studies through PubMed, PEDro, and ScienceDirect up to January 2019. The protocol was registered on PROSPERO (CRD42019121306). Differences in pre- and post-intervention means and standard deviations were extracted to calculate the standardized mean difference for each intervention in each included study.

SYNTHESIS

Eight studies were included. Limited evidence suggests that LL-BFR is more beneficial on quadriceps strength and thickness in patients with knee conditions than LL training alone or in addition to a rehabilitation program. Limited evidence indicates that LL-BFR training is equally effective in improving function and muscle thickness compared with a HL quadriceps strengthening program but elicits less knee pain, corresponding to additional benefits of 22 (95% confidence interval 1 to 43) mm on a 0-100 mm visual analogue scale.

CONCLUSIONS

BFR could be a useful option for patients with knee conditions where conventional quadriceps strengthening program exacerbate knee symptoms. Future investigations should compare different BFR protocols to help establish better guidelines for clinicians.

Feasibility and estimated efficacy of blood flow restricted training in female patients with rheumatoid arthritis: a randomized controlled pilot study

Objectives: The study aimed to evaluate the feasibility of a blood flow restriction (BFR) training regimen in patients with rheumatoid arthritis (RA); and to compare the effects of 4 weeks of BFR training with low-intensity strength training on muscle strength, muscle endurance, and joint pain in patients with RA.Method: In this non-blinded pilot randomized controlled trial, 18 women with RA aged 18-65 years performed low-intensity strength training for the lower limbs three times a week for 4 weeks, and were randomized to train with or without occlusion bands. The primary outcomes were registration of the recruitment process, compliance with training sessions, side effects, perceived pain, and a satisfaction survey. The secondary outcomes were changes in muscle strength, muscle endurance, and joint pain.Results: The findings of this pilot study included a challenging recruitment process, well tolerated training and test protocols, overall good patient satisfaction, no serious side effects, and high compliance. Both groups achieved significant improvements in knee extensor strength from baseline to follow-up, with a change of 11.5 kg [interquartile range (IQR) 9.8;13.0] in the intervention group and 8.4 kg (IQR 5.5;12.4) in the control group, and a significant between-group difference in favour of the intervention group (p = 0.0342).Conclusions: The feasibility results of this study indicated a challenging recruitment process, general satisfaction with the BFR and exercises, good compliance, and only expected non-serious side effects. BFR training may improve knee extensor strength in women with RA, compared low-intensity strength training without BFR.

EFFECT OF BLOOD FLOW RESTRICTION TRAINING ON MUSCULAR PERFORMANCE, PAIN AND VASCULAR FUNCTION

Background

Blood flow restriction (BFR) training enhances muscular strength and hypertrophy in several populations including older adults and injured athletes. However, the efficacy of emerging BFR technologies on muscular adaptations, vascular health, and pain is unclear.

Purpose

The purpose of this study was to examine muscular performance, pain and vascular function in response to eight weeks of BFR compared to traditional resistance training and a control group.

Study Design

Randomized control trial.

Methods

Thirty-one overtly healthy participants (age: 23 ± 4y, 65% female) underwent eight weeks of supervised high load resistance training (RES), low load resistance training with BFR (BFR) or no training (control, CON). RES and BFR (with pneumatic bands) performed seven upper and lower body exercises, two to three sessions per week at 60% and 30% of one-repetition maximum (1RM), respectively. Twenty-four hours post-exercise, general muscle soreness was assessed via a visual analog scale (VAS) and present pain intensity (PPI) of the McGill Pain Questionnaire. At baseline and after eight weeks, participants underwent one-repetition maximum (1RM), and flow-mediated dilation (FMD) testing.

Results

At baseline all groups exhibited similar muscle strength and endurance and vascular function. At the end of training, RES and BFR groups significantly increased muscle strength (1RM) to a similar magnitude as compared to the CON group (p < 0.0001), but did not alter body composition. FMD significantly increased in RES and BFR groups compared to CON group (p = 0.006). VAS and PPI were similar between RES and BFR groups throughout the exercise sessions until VAS decreased in the BFR group after the last session compared to the RES group (p = 0.02).

Conclusion

Compared to RES, BFR resulted in similar muscular performance (strength and endurance) and vascular improvements at a lower exercise intensity, suggesting BFR is an effective alternative to high load resistance training. Further longitudinal studies may gain greater understanding regarding general muscle pain and soreness when using BFR.

Level of Evidence

Therapy, Level 2.

Approaches to determining occlusion pressure for blood flow restricted exercise training: Systematic review

Low-intensity exercise with blood flow restriction (BFR) is an increasingly common method of improving muscular strength and hypertrophy, and improving aerobic fitness, in clinical and athletic populations. The aim of this systematic review was to describe common approaches to determining occlusion pressures for BFR exercise. A comprehensive literature search yielded 1389 results, of which 129 were included. Studies were predominantly randomised control trials (86.7%) with modest sample sizes (average number of 11.4 ± 6.2 participants per BFR group/s) of young adults (average age of 34.6 ± 17.9). Five different approaches for determining occlusion pressure were identified: arbitrary pressures (56.6%), percentage of limb occlusion pressure (25.6%), brachial systolic blood pressure (10.9%), perceived tightness (3.9%) and other (3%). From 2016 to 2018, the number of published papers using a percentage of limb occlusion pressure increased yearly, paralleling a decrease use of arbitrary pressures. Of the studies included in this review, the most common approach to determining occlusion pressure was using a non-individualised, arbitrary pressure. Given the safety concerns associated with arbitrary pressures, continual dissemination regarding the optimal applications of BFR for safety and efficacy is required.

Local and Systemic Effects of Blood Flow Restriction Therapy in an Animal Model

BACKGROUND

Blood flow restriction therapy (BFRT) has been increasingly applied to improve athletic performance and injury recovery. Validation of BFRT has lagged behind commercialization, and currently the mechanism by which this therapy acts is unknown. BFRT is one type of ischemic therapy, which involves exercising with blood flow restriction. Repetitive restriction of muscle blood flow (RRMBF) is another ischemic therapy type, which does not include exercise.

HYPOTHESIS/PURPOSE

The purpose was to develop a rat model of ischemic therapy, characterize changes to muscle contractility, and evaluate local and systemic biochemical and histologic responses of 2 ischemic therapy types. We hypothesized that ischemic therapy would improve muscle mass and strength as compared with the control group.

STUDY DESIGN

Controlled laboratory study.

METHODS

Four groups of 10 Sprague-Dawley rats were established: control, stimulation, RRMBF, and BFRT. One hindlimb of each subject underwent 8 treatment sessions over 4 weeks. To simulate exercise, the stimulation group underwent peroneal nerve stimulation for 2 minutes. The RRMBF group used a pneumatic cuff inflated to 100 mm Hg with a 48-minute protocol. The BFRT group involved 100-mm Hg pneumatic cuff inflation and peroneal nerve stimulation for a 5-minute protocol. Four methods of evaluation were performed: in vivo contractility testing, histology, immunohistochemistry, and ELISA. Analysis of variance with post hoc Tukey test and linear mixed effects modeling were used to compare the treatment groups.

RESULTS

There was no difference in muscle mass among groups (P = .40) or between hindlimbs (P = .73). In vivo contractility testing showed no difference in maximum contractile force among groups (P = .64) or between hindlimbs (P = .30). On histology, myocyte cross-sectional area was not different among groups (P = .55) or between hindlimbs (P = .44). Pax7 immunohistochemistry demonstrated no difference in muscle satellite cell density among groups (P = .06) or between hindlimbs (P = .046). ELISA demonstrated the RRMBF group as eliciting elevated GH levels as compared with the other groups (P < .001).

CONCLUSION

Ischemic therapy did not induce gains in muscle mass, contractility strength, fiber cross-sectional area, or satellite cell density locally or systemically in this model, although the RRMBF group did have elevated GH levels on ELISA.

CLINICAL RELEVANCE

This animal model does not support ischemic therapy as a method to improve muscle mass, function, or satellite cell density.

RESIDENTS CASE REPORT: MUSCULOCUTANEOUS NERVE INJURY IN A COLLEGIATE BASEBALL PITCHER

Background

Literature regarding musculocutaneous nerve injuries among the athletic population is scarce, with only several reported clinical cases among baseball and softball pitchers.

Purpose

To present a unique case of a musculocutaneous nerve injury to aid in clinician awareness and propose innovative rehabilitation practices that may facilitate improved patient outcomes during recovery.

Case Description

A 23-year-old Division 1 NCAA collegiate baseball pitcher presented with vague anterior arm pain following a pre-season game. The athlete described the pain as an "intense stretch" of his right arm that occurred during his last pitch. The initial evaluation identified tenderness over the right distal bicep. All shoulder and elbow orthopedic tests to assess shoulder impingement, labral pathologies, and glenohumeral instability were unremarkable. Increased neural tension was also noted with upper limb neurodynamic testing of the median and ulnar nerves on the right arm compared bilaterally. Electromyography (EMG) testing confirmed a right upper and mid-brachial plexus stretch injury with the primary involvement of the musculocutaneous nerve. Rehabilitation focused on restoring strength deficits and diminishing neural tension. Blood flow restriction (BFR) was introduced on the uninvolved limb to reduce deficits in bicep musculature strength. Once the athlete regained bicep strength and forearm sensation, he was progressed from flat-ground throwing activities to throwing off the mound.

Outcomes

A reduction in neural tension during neurodynamic testing of the right arm, improvement of bicep brachii deficits seen between the right and left limbs, and restoration of sensation in the right lateral forearm enabled a progressive return to sport.

Discussion

Due to vague reports and inconclusive findings, the initial presentation of musculocutaneous nerve injuries may be mistaken for other conditions such as a biceps brachii strain. Further -documentation of this injury and rehabilitation procedures are needed to enhance patient outcomes.

Blood Flow Restriction and Its Function in Post-Operative Anterior Cruciate Ligament Reconstruction Therapy: Expert Opinion

An increasingly popular method for post-operative rehabilitation of an ACL reconstruction, as a substitute for traditional therapy, is blood flow restriction therapy (BFR). BFR therapy utilizes a pneumatic cuff to simulate strenuous exercise in an effort to stimulate muscle recruitment, mitigate atrophy, and promote hypertrophy in patients with load-bearing limitations. Because this is a relatively new form of therapy, there is a lack of established literature and protocol that is preventing widespread use of the therapy. This article will seek to confirm the value and validity of the utilization of BFR therapy. In order to validate the utilization of BFR, an evaluation of the science underlying BFR will be discussed as well as the technique and exercises preformed during therapy. Furthermore, analysis of other BFR literature will be utilized to lend further credence to the obtained conclusions. Based on the literature, BFR therapy mitigates atrophy through type II muscle recruitment while also stimulating hypertrophy in patients, supporting its use post-operatively. Moreover, positive results from BFR case series also lend credence to its value as a substitute for traditional therapy in patients who have weight-bearing limitations, specifically those who are recovering from anterior cruciate ligament reconstructions.

Physiological responses of human skeletal muscle to acute blood flow restricted exercise assessed by multimodal MRI

Important physiological quantities for investigating muscle hypertrophy include blood oxygenation, cell swelling, and changes in blood flow. The purpose of this study was to compare the acute changes of these parameters in human skeletal muscle induced by low-load (20% 1-RM) blood flow-restricted (BFR-20) knee extensor exercise compared with free-flow work-matched (FF-20_WM) and free-flow 50% 1-RM (FF-50) knee extensor exercise using multimodal magnetic resonance imaging (MRI). Subjects (n = 11) completed acute exercise sessions for each exercise mode in an MRI scanner, where interleaved measures of muscle R₂ (indicator of edema), [Formula: see text] (indicator of deoxyhemoglobin), macrovascular blood flow, and diffusion were performed before, between sets, and after the final set for each exercise protocol. BFR-20 exercise resulted in larger acute decreases in R₂ and greater increases in cross-sectional area than FF-20_WM and FF-50 (P < 0.01). Blood oxygenation decreased between sets during BFR-20, as indicated by a 13.6% increase in [Formula: see text] values (P < 0.01)), whereas they remained unchanged for FF-20_WM and decreased during FF-50 exercise. Quadriceps blood flow between sets was highest for the heavier load (FF-50), averaging 305 mL/min, and lowest for BFR-20 at 123 ± 73 mL/min until post-exercise cuff release, where blood flow rates in BFR-20 exceeded both FF protocols (P < 0.01). Acute changes in diffusion rates were similar for all exercise protocols. This study was able to differentiate the acute exercise response of selected physiological factors associated with skeletal muscle hypertrophy. Marked differences in these parameters were found to exist between BFR and FF exercise conditions, which contribute to explain the anabolic potential of low-load blood flow restricted muscle exercise.NEW & NOTEWORTHY Acute changes in blood flow, diffusion, blood oxygenation, cross-sectional area, and the "T₂ shift" are evaluated in human skeletal muscle in response to blood flow-restricted (BFR) and conventional free-flow knee extensor exercise performed in an MRI scanner. The acute physiological response to exercise was dependent on the magnitude of load and the application of BFR. Physiological variables changed markedly and established a steady state rapidly after the first of four exercise sets.

The Acute Physiological Responses to Traditional vs. Practical Blood Flow Restriction Resistance Exercise in Untrained Men and Women

This study compared the acute physiological responses of traditional and practical blood flow restriction resistance exercise (tBFR and pBFR, respectively) and high- and low-load resistance exercise without BFR (HL and LL, respectively), as well as the potential sex differences within the aforementioned exercise methods. Fourteen men and fifteen women randomly completed the following experimental conditions: (1) tBFR, consisting of four sets of 30-15-15-15 repetitions of the bilateral horizontal leg press and knee extension exercises, at 30% of one-repetition maximum (1-RM), with a 13.5 cm wide pneumatic cuff placed at the most proximal portion of each thigh and inflated to a pressure equivalent to 50% of the participant’s total occlusion pressure; (2) pBFR, which was the same as the tBFR condition, except that an elastic band wrapped around the proximal portion of each thigh at a tightness of 7 on a 0 to 10 perceived pressure scale was used to reduce blood flow; (3) LL, same as the tBFR and pBFR protocols, except that no BFR was applied; and (4) HL, consisting of 3 sets of 10 repetitions at 80% of 1-RM, with the same 1-min rest interval between sets and a 3-min rest period between exercises. At baseline, immediately post-, 5 min post-, and 15 min post-exercise, whole-blood lactate (WBL), indices of muscle swelling (muscle thickness and thigh circumference), hematocrit and plasma volume changes, were measured as well as superficial electromyography (sEMG) amplitude during exercise. There were no significant (p > 0.05) differences between the tBFR and pBFR exercise protocols for any of the physiological parameters assessed. However, significantly greater (p < 0.05) WBL and sEMG values were observed for HL compared to the remaining exercise conditions. Finally, males displayed greater WBL levels than females at 15 min post-exercise. Interestingly, males also displayed significantly (p < 0.05) greater sEMG amplitude than females within the low-load trials during leg press, but no significant (p < 0.05) sex differences were observed during knee extension. In conclusion, tBFR and pBFR seemed to be capable of inducing the same acute physiological responses. Furthermore, males displayed greater responses than females for some of the physiological parameters measured.

Feasibility and safety of 4 weeks of blood flow-restricted exercise in an individual with tetraplegia and known autonomic dysreflexia: a case report

INTRODUCTION

Blood flow-restricted exercise (BFRE) appears to hold considerable potential in spinal cord injury (SCI) rehabilitation, due to its ability to induce beneficial functional changes and morphological alterations from low-intensity, low-load exercise. However, it remains unclear if this training approach is feasible and safe in individuals with autonomic dysreflexia (AD).

CASE PRESENTATION

A 23-year-old male with traumatic, cervical (C6), motor-complete (AIS: B) SCI and diagnosed AD completed eight sessions of BFRE for the upper extremities over 4 weeks. Blood pressure and heart rate recordings and perceptual pain responses were collected repeatedly during exercise. Blood samples were drawn pre- and post-training. Training was carried out in a neurorehabilitation hospital setting with appertaining medical staff readiness, and was supervised by a physiotherapist with expertise in AD in general as well as prior knowledge of the present patient's triggers and symptoms. Four incidences of AD (defined as systolic blood pressure increase >20 mmHg) were recorded across all training sessions, of which one was symptomatic. The patient's blood profile did not change considerably from pre- to post-training sessions. Self-reported average pain during training corresponded from "mild" to "moderate".

DISCUSSION

The patient was able to perform 4 weeks of BFRE, but encountered episodes of AD. Similarly, two AD episodes were registered during a single conventional, free-flow resistance training session. Evidence from clinically controlled safety studies is needed in order to establish if and how BFRE can be applied in a rehabilitation strategy in SCI individuals with neurological level of injury at or above T6 level.

Perceptual responses: Clinical versus practical blood flow restriction resistance exercise

The purpose of the current investigation was to compare the acute perceptual responses during low-load resistance exercise (RE) with clinical blood flow restriction (cBFR-RE) and practical blood flow restriction (pBFR-RE), and during conventional low- (LL-RE) and high-load resistance exercise (HL-RE), to determine if these responses differed between young males and females. Twenty-nine participants (14 males: 23.6±2.7years, 25.3±3.1kg/m² and 15 females: 20.3±1.6years, 23.4±1.9kg/m²) completed the following exercise conditions in a randomized design: 1) cBFR-RE, 2) pBFR-RE, 3) HL-RE, and 4) LL-RE. Low-load conditions consisted of 30-15-15-15 repetitions of two-leg press (LP) and knee extension (KE) exercises with 30% one-repetition maximum (1-RM), and HL-RE consisted of 3 sets of 10 repetitions at 80% 1-RM, all with 60s rest intervals. Ratings of perceived exertion (RPE) and discomfort were assessed before exercise and immediately following each set. RPE was significantly higher in HL-RE compared to all low-load conditions for both exercises after each set (all p<0.05). cBFR-RE resulted in significantly greater RPE than pBFR-RE and LL-RE for both exercises for sets 1-4 for LP and sets 2-3 for KE (all p<0.05). Levels of discomfort were similar between cBFR-RE and HL-RE, which tended to be significantly higher than pBFR-RE and LL-RE (p<0.05). Men reported significantly greater RPE than women following sets 2-4 during KE with cBFR-RE and sets 2 and 3 during KE for HL-RE (all p<0.05). Males also reported significantly greater discomfort than women following sets 2-4 for KE LL-RE (p<0.05). Altogether, these data suggest that pBFR-RE may provide a more favorable BFR condition based on perceptual responses and that perceptual responses may differ between sexes across varying resistance exercise conditions.

Blood Flow Restriction Exercise: Effects of Sex, Cuff Width, and Cuff Pressure on Perceived Lower Body Discomfort

Narrow cuffs cause less discomfort than wide cuffs immediately following elbow flexion exercise in combination with blood flow restriction, possibly due to a balling up effect of the bicep underneath the cuff. In this study, we sought to examine the impact of cuff width, sex, and pressure on perceived discomfort in the quadriceps, following knee extensions. One hundred participants completed three separate experiments. In Experiment 1, we compared participants' discomfort at rest after using a 5 and a 12 cm cuff. In Experiment 2, we compared the discomfort from these two cuffs after four sets of exercise. In Experiment 3, we used the same exercise protocol as in Experiment 2, but we compared the discomfort between a 12 cm cuff inflated to an inappropriate pressure and a 12 cm cuff inflated to the recommended pressure. We found no sex differences in Experiments 1 and 3. In Experiment 1, the narrow cuff had higher discomfort (16 vs 12 AU). In Experiment 2, men reported higher discomfort than women, with no discomfort differences related to cuff width, though narrow cuffs were most preferred. In Experiment 3, cuffs inflated to a pressure intended for narrow cuffs were associated with higher discomfort, and participants preferred to use it less. In summary, we found no strong evidence for discomfort differences due to cuff width. There was some indication that participants preferred narrow cuffs with pressures inflated to the recommended relative pressure. Muscle shape may influence how cuff width affects discomfort.

Acute Neuromuscular Electrical Stimulation (NMES) With Blood Flow Restriction: The Effect of Restriction Pressures

CONTEXT

Neuromuscular electrical stimulation (NMES) combined with blood flow restriction (BFR) has been shown to improve muscular strength and size better than NMES alone. However, previous studies used varied methodologies not recommended by previous NMES or BFR research.

OBJECTIVE

The present study investigated the acute effects of NMES combined with varying degrees of BFR using research-recommended procedures to enhance understanding and the clinical applicability of this combination.

DESIGN

Randomized crossover.

SETTING

Physiology laboratory.

PARTICIPANTS

A total of 20 healthy adults (age 27 [4] y; height 177 [8] cm; body mass 77 [13] kg).

INTERVENTIONS

Six sessions separated by at least 7 days. The first 2 visits served as familiarization, with the experimental conditions performed in the final 4 sessions: NMES alone, NMES 40% BFR, NMES 60% BFR, and NMES 80% BFR.

MAIN OUTCOME MEASURES

Maximal voluntary isometric contraction, muscle thickness, blood pressure, heart rate, rating of perceived exertion, and pain were all recorded before and after each condition.

RESULTS

The NMES 80% BFR caused greater maximal voluntary isometric contraction decline than any other condition (-38.9 [22.3] N·m, P < .01). Vastus medialis and vastus lateralis muscle thickness acutely increased after all experimental conditions (P < .05). Pain and ratings of perceived exertion were higher after NMES 80% BFR compared with all other experimental conditions (P < .05). No cardiovascular effects were observed between conditions.

CONCLUSION

The NMES combined with 80% BFR caused greater acute force decrement than the other conditions. However, greater perceptual ratings of pain and ratings of perceived exertion were observed with NMES 80% BFR. These acute observations must be investigated during chronic interventions to corroborate any relationship to changes in muscle strength and size in clinical populations.

The effect of blood flow on tibialis anterior motor unit firing rates during sustained low-intensity isometric contractions

Low-intensity contractions with blood flow occlusion (BFO) result in neuromuscular adaptations comparable with high-intensity (>70% maximal voluntary contraction, MVC) exercise. Because BFO exercise can only be applied to limb muscles, it is of interest to explore whether muscles proximal to the occlusion site are affected. Therefore, the purpose of this study was to assess neural activation of the tibialis anterior (TA) when flow is occluded proximal and distal to the active muscle. Five males completed three protocols to observe the effect of BFO on motor unit firing rates (MUFR) of the TA at a fatiguing contraction intensity of ∼15% MVC. Two occlusion protocols, one proximal (BFO_prox) to and one distal (BFO_dis) to the TA, were compared with a control (free-flow) protocol time-matched to BFO_dis. MVC was significantly reduced following the BFO_prox (∼41%; P < 0.001) and BFO_dis (∼27%, P < 0.001), but not following the control protocol (∼15%; P = 0.13). Surface electromyography (EMG) during BFO_dis and BFO_prox increased ∼14% and ∼28%, respectively, but was not different among protocols. MUFRs for BFO_dis and BFO_prox were significantly reduced (by ∼33% and ∼23%, respectively; P < 0.01) at task failure. Results indicate that although BFO_prox results in the largest reductions of MUFRs, BFO_dis shows greater impairments compared with the free-flow control condition. Novelty Effects on motor unit firing rates of proximal versus distal blood flow occlusion were compared during low-intensity fatiguing task. Proximal occlusion results in greatest fatigue and reduction in motor unit rates, but distal occlusion elicits more fatigue and rate reduction than a control task.

The Effects of Blood Flow Restriction on Muscle Activation and Hypoxia in Individuals With Chronic Ankle Instability

CONTEXT

Muscle dysfunction is common in patients with chronic ankle instability (CAI). Blood flow restriction (BFR) may enhance muscle responses during exercise and provide an opportunity to enhance muscle adaptations to ankle rehabilitation exercises; however, there is no evidence examining the effect of BFR on muscle function in CAI patients.

OBJECTIVE

Examine the effects of BFR on muscle activation and oxygen saturation during submaximal ankle eversion and dorsiflexion exercises in individuals with CAI.

DESIGN

Cross-over study design.

SETTING

Laboratory setting. Patients (or Other Participants): Nineteen young adults with a history of CAI.

INTERVENTIONS

Participants performed 4 sets (30, 15, 15, and 15) of eversion and dorsiflexion resistance exercises at 30% of maximum voluntary isometric contraction during 2 conditions, BFR and control. For BFR, a cuff was applied above the knee at 80% of blood flow occlusion. For control, the cuff was not inflated.

MAIN OUTCOME MEASURES

Fibularis longus and tibialis anterior electromyography muscle activation, lower-leg muscle oxygen saturation, and ratings of perceived exertion were recorded during exercises.

RESULTS

Average grand mean muscle activation was 5.6% greater during eversion (P = .03) and 7.7% greater during dorsiflexion (P = .01) resistance exercises with BFR compared with control; however, the magnitudes of the effects of BFR were only clinically important during the dorsiflexion exercises. Lower-leg muscle oxygen saturation was 31% to 44% lower (P < .001) during BFR exercises. Ratings of perceived exertion were significantly higher during BFR exercises (P < .001).

CONCLUSIONS

Greater muscle activation and hypoxia were present during submaximal resistance exercise with BFR in participants with CAI. Greater muscle activation and hypoxia during BFR exercises may be important acute responses mediating the training-related muscle adaptations that have been observed with BFR. The presence of these acute responses in CAI patients supports further research examining BFR as a potential ankle rehabilitation tool.

The Acute Impact of External Compression on Back Squat Performance in Competitive Athletes

The aim of the present study was to evaluate the effects of external compression with blood flow restriction on power output and bar velocity changes during the back-squat exercise (SQ). The study included 10 judo athletes (age = 28.4 ± 5.8 years; body mass = 81.3 ± 13.1 kg; SQ one-repetition maximum (1-RM) 152 ± 34 kg; training experience 10.7 ± 2.3 years).

METHODS

The experiment was performed following a randomized crossover design, where each participant performed three different exercise protocols: (1) control, without external compression (CONT); (2) intermittent external compression with pressure of 100% arterial occlusion pressure (AOP) (EC-100); and (3) intermittent external compression with pressure of 150% AOP (EC-150). To assess the differences between conditions, the participants performed 3 sets of 3 repetitions of the SQ at 70% 1-RM. The differences in peak power output (PP), mean power output (MP), peak bar velocity (PV), and mean bar velocity (MV) between the three conditions were examined using repeated measures two-way ANOVA.

RESULTS

The post hoc analysis for the main effect of conditions showed a significant increase in PP (p = 0.03), PV (p = 0.02), MP (p = 0.04), and MV (p = 0.03), for the EC-150, compared to the CONT. Furthermore, a statistically significant increase in PP (p = 0.04), PV (p = 0.03), MP (p = 0.02), and MV (p = 0.01) were observed for the EC-150 compared to EC-100. There were no significant changes in PP, PV, MP, and MV, between EC-100 and CONT conditions.

CONCLUSION

The results indicate that the use of extremely high-pressure external compression (150% AOP) during high-loaded (70% 1-RM) lower limb resistance exercise elicits an acute increase in power output and bar velocity.

Skeletal Muscle Microvascular Changes in Response to Short-Term Blood Flow Restricted Training-Exercise-Induced Adaptations and Signs of Perivascular Stress

Aim: Previous reports suggest that low-load muscle exercise performed under blood flow restriction (BFR) may lead to endurance adaptations. However, only few and conflicting results exist on the magnitude and timing of microvascular adaptations, overall indicating a lack of angiogenesis with BFR training. The present study, therefore, aimed to examine the effect of short-term high-frequency BFR training on human skeletal muscle vascularization.

Methods: Participants completed 3 weeks of high-frequency (one to two daily sessions) training consisting of either BFR exercise [(BFRE) n = 10, 22.8 ± 2.3 years; 20% one-repetition maximum (1RM), 100 mmHg] performed to concentric failure or work-matched free-flow exercise [(CON) n = 8, 21.9 ± 3.0 years; 20% 1RM]. Muscle biopsies [vastus lateralis (VL)] were obtained at baseline, 8 days into the intervention, and 3 and 10 days after cessation of the intervention to examine capillary and perivascular adaptations, as well as angiogenesis-related protein signaling and gene expression.

Results: Capillary per myofiber and capillary area (CA) increased 21–24 and 25–34%, respectively, in response to BFRE (P < 0.05–0.01), while capillary density (CD) remained unchanged. Overall, these adaptations led to a consistent elevation (15–16%) in the capillary-to-muscle area ratio following BFRE (P < 0.05–0.01). In addition, evaluation of perivascular properties indicated thickening of the perivascular basal membrane following BFRE. No or only minor changes were observed in CON.

Conclusion: This study is the first to show that short-term high-frequency, low-load BFRE can lead to microvascular adaptations (i.e., capillary neoformation and changes in morphology), which may contribute to the endurance effects previously documented with BFR training. The observation of perivascular membrane thickening suggests that high-frequency BFRE may be associated with significant vascular stress.

The Acute Effects of External Compression With Blood Flow Restriction on Maximal Strength and Strength-Endurance Performance of the Upper Limbs

The main goal of the present study was to evaluate the acute effects external compression with blood flow restriction (BFR) at 100 and 150% of full arterial occlusion pressure (AOP) on maximal strength and strength-endurance performance during the bench press (BP) exercise. The study included 12 strength-trained male subjects (age = 23.2 ± 2.66 years; body mass = 75.3 ± 6.33 kg; height = 179.1 ± 3.82 cm), experienced in resistance training (5.7 ± 2.93 years). During the experimental sessions in a randomized crossover design, the subjects performed a 1 repetition maximum (1RM) test and three sets of the BP using 60% 1RM to failure with three different conditions: without BFR (NO-BFR); BFR with a pressure of 100% AOP (BFR₁₀₀); and BFR with a pressure of 150% AOP (BFR₁₅₀). The differences between the NO-BFR, BFR₁₀₀, and BFR₁₅₀ conditions were examined using repeated measures ANOVA. The ANOVA indicated significant main effect for condition in 1RM, number of performed repetitions (REP), and time under tension (TUT) (p < 0.01). Post hoc analyses for the main effect indicated significant increases in 1RM (p < 0.01; 95.00 ± 15.37 vs 91.87 ± 15.99), REP (p < 0.01; 17.56 ± 3.36 vs 15.67 ± 5.24), and TUT (p < 0.01; 32.89 ± 6.40 vs 28.72 ± 6.18) for the BFR₁₅₀ condition compared to NO-BFR. Furthermore, significant increases in REP (p = 0.03; 17.56 ± 3.36 vs 16.47 ± 4.01) and TUT (p = 0.03; 32.89 ± 6.40 vs 30.00 ± 6.45) were observed for the BFR₁₅₀ condition compared to the BFR₁₀₀. The results of the present study indicate that high external compression increases maximal strength evaluated by the 1RM test, as well as endurance performance during three sets of the BP exercise.

Upper-extremity blood flow restriction: the proximal, distal, and contralateral effects-a randomized controlled trial

BACKGROUND

Blood flow restriction (BFR) training with low weight is purported to induce similar physiological changes to high-weight regimens with the benefit of less tissue stress. We hypothesized that low-weight training with BFR would produce increased gains in strength and hypertrophy for muscle groups proximal, distal, and contralateral to tourniquet placement compared with low-weight training alone.

METHODS

In this prospective, randomized controlled trial, healthy subjects were randomized into a 6-week low-weight training program either with or without BFR on 1 extremity. Outcome measures included limb circumference and strength. Comparisons were made between the BFR and non-BFR extremities, BFR and control groups, and non-BFR extremity and control groups.

RESULTS

A total of 24 subjects (14 BFR and 10 control subjects) completed the protocol. Significantly greater gains were observed in dynamometric strength both proximal (shoulder scaption [30% greater], flexion [23%], and abduction [22%]) and distal (grip strength [13%]) to the tourniquet in the BFR limb compared with both the non-BFR extremity and the control group (P < .05). Arm and forearm circumferences significantly increased in the BFR limb compared with the non-BFR limb and control group (P = .01). The non-BFR extremity demonstrated greater grip strength than the control group (9%, P < .01). No adverse events were reported.

CONCLUSION

Low-weight BFR training provided a greater increase in strength and hypertrophy in the upper-extremity proximal and distal muscle groups compared with the control group. The non-BFR extremity showed a significant increase in grip strength compared with the control group, indicating a potential systemic effect.

Walking With Leg Blood Flow Restriction: Wide-Rigid Cuffs vs. Narrow-Elastic Bands

Background

Blood flow restriction (BFR) training is becoming a popular form of exercise. Walking exercise in combination with pressurized wide-rigid (WR) cuffs elicits higher cardiac workload and a vascular dysfunction due presumably to reperfusion injury to the endothelium. In contrast, narrow-elastic (NE) BFR bands may elicit different hemodynamic effects. Therefore, we compared the acute cardiovascular responses to two distinct forms of BFR training during light-intensity exercise.

Methods and Results

15 young healthy participants (M = 9, F = 6) performed five bouts of 2-min walking intervals at 0.9 m/s with a 1-min rest and deflation period with either WR, NE, or no bands placed on upper thighs. Cuff pressure was inflated to 160 mmHg in WR cuffs and 300 mmHg in NE bands while no cuffs were used for the control. Increases in heart rate and arterial blood pressure were greater (p < 0.05) in the WR than the NE and control conditions. Double product increased to a greater extent in the WR than in the NE and control conditions. Increases in perceived exertion and blood lactate concentration were greater (p < 0.05) in the WR compared with the NE and control conditions (p < 0.05), while no differences emerged between the NE and control conditions. There were no changes in arterial stiffness or brachial artery flow-mediated dilation (FMD) after all three trials.

Conclusion

Use of WR BFR cuffs resulted in a marked increase in blood pressure and myocardial oxygen demand compared with NE BFR bands, suggesting that NE bands present a safer alternative for at-risk populations to perform BFR exercise.

Clinical Trial Registration

This study was registered in the Clinicaltrials.gov (NCT03540147).

Does Post-Activation Performance Enhancement Occur During the Bench Press Exercise under Blood Flow Restriction?

Background: The aim of the present study was to evaluate the effects of post-activation performance enhancement (PAPE) during successive sets of the bench press (BP) exercise under blood flow restriction (BFR). Methods: The study included 10 strength-trained males (age = 29.8 ± 4.6 years; body mass = 94.3 ± 3.6 kg; BP 1-repetition maximum (1RM) = 168.5 ± 26.4 kg). The experiment was performed following a randomized crossover design, where each participant performed two different exercise protocols: under blood flow restriction (BFR) and control test protocol (CONT) without blood flow restriction. During the experimental sessions, the study participants performed 3 sets of 3 repetitions of the BP exercise at 70%1RM with a 5 min rest interval between sets. The differences in peak power output (PP), mean power output (MP), peak bar velocity (PV), and mean bar velocity (MV) between the CONT and BFR conditions were examined using 2-way (condition × set) repeated measures ANOVA. Furthermore, t-test comparisons between conditions were made for the set 2-set 1, set 3-set 1, and set 3-set 2 delta values for all variables. Results: The post hoc results for condition × set interaction in PP showed a significant increase in set 2 compared to set 1 for BFR (p < 0.01) and CONT (p = 0.01) conditions, a significant increase in set 3 compared to set 1 for the CONT (p = 0.01) condition, as well as a significant decrease in set 3 compared to set 1 for BFR condition occurred (p < 0.01). The post hoc results for condition × set interaction in PV showed a significant increase in set 2 compared to set 1 for BFR (p < 0.01) and CONT (p = 0.01) conditions, a significant increase in set 3 compared to set 1 for CONT (p = 0.03) condition, as well as a significant decrease in set 3 compared to set 1 for BFR condition (p < 0.01). The t-test comparisons showed significant differences in PP (p < 0.01) and PV (p = 0.01) for set 3-set 2 delta values between BFR and CONT conditions. Conclusion: The PAPE effect was analyzed through changes in power output and bar velocity that occurred under both the CONT and BFR conditions. However, the effects of PAPE have different kinetics in successive sets for BFR and for CONT conditions.

Short-Term Blood Flow Restriction Increases Power Output and Bar Velocity During the Bench Press

Wilk, M, Krzysztofik, M, Filip, A, Zajac, A, Bogdanis, GC, and Lockie, RG. Short-term blood flow restriction increases power output and bar velocity during the bench press. J Strength Cond Res XX(X): 000-000, 2020-This study examined the effect of blood flow restriction (BFR) with 2 different types of cuffs on peak power output (PP), mean power output (MP), peak bar velocity (PV), and mean bar velocity (MV) in the bench press exercise (BP). Fourteen healthy strength-trained male athletes (age = 27.6 ± 3.5 years; body mass = 84.1 ± 8.0 kg; height = 175.8 ± 6.7 cm; BP 1 repetition maximum [RM] = 138.6 ± 17.8 kg) performed 3 different testing protocols as follows: without BFR (NO-BFR), BFR with a narrow cuff (BFRNARROW), and BFR with a wide cuff (BFRWIDE) in a randomized crossover design. During all sessions, subjects performed one set of 3 repetitions of the BP exercise using 70% 1RM. Cuff pressure was set to approximately 90% full arterial occlusion pressure of the upper limb at rest. Analyses of variance showed an increase in PP (by 21%, p < 0.01; effect size [ES] = 1.67), MP (by 16%, p < 0.01; ES = 0.93), PV (by 22%, p < 0.01; ES = 1.79), and MV (by 21%, p < 0.01; ES = 1.36) during BFRWIDE compared with NO-BFR and a significant increase in PP (by 15%, p < 0.01; ES = 1.07), MP (by 17%, p < 0.01; ES = 0.78), PV (by 18%, p < 0.01; ES = 1.65), and MV (by 13% p < 0.01; ES = 1.00) during BFRWIDE compared with BFRNARROW. There were no significant differences in any of the variable between NO-BFR and BFRNARROW. The results of the study indicate that short-term BFR training increases power output and bar velocity during the BP exercise. However, only BFRWIDE significantly influenced bar velocity and power output, which indicates that the width of the cuff is a critical factor determining acute exercise adaptation during BFR resistance training.

Nerve conduction during acute blood-flow restriction with and without low-intensity exercise Nerve conduction and blood-flow restriction

Despite being apparently safe for most individuals, the impact of low intensity (LI) blood-flow restricted (BFR) exercise on nerve function and integrity is still obscure. We explored whether BFR (with and without exercise) alters the properties of nerve conduction measured at the level of the restricted limb. Thirteen healthy, young men (22.0 ± 1.7 years) were included in this study. Arterial occlusion pressure was taken at rest. Soleus M- and H-recruitment curves were constructed for all participants. H-wave latencies and amplitudes were obtained in three testing conditions (non-BFR vs. 60 vs. 80% BFR) at four different time points: [#1] non-restricted baseline, [#2] time control either with or without BFR, [#3] non-restricted pre-exercise, [#4] LI exercise either with or without BFR. Nerve conduction was estimated using the difference between the latency of H and M wave. BFR did not affect H-wave amplitude, either with or without exercise. The changes in the difference between H- and M-wave latency of over time were similar between all conditions (condition-by-time interaction: F = 0.7, p = 0.47). In conclusion, our data indicate that performing LI exercise with BFR, set at 60 or 80% BFR, does not exert a negative impact on sciatic-tibial nerve function. Thus, from a neurological standpoint, we provide preliminary evidence that LI BFR exercise may be regarded as a safe mode of resistance training in healthy young men.

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

BACKGROUND

Blood flow restriction exercise has increasingly broad applications among healthy and clinical populations. Ensuring the technique is applied in a safe, controlled, and beneficial way for target populations is essential. Individualized cuff pressures are a favored method for achieving this. However, there remains marked inconsistency in how individualized cuff pressures are applied.

OBJECTIVES

To quantify the cuff pressures used in the broader blood flow restriction exercise literature, and determine whether there is clear justification for the choice of pressure prescribed.

METHODS

Studies were included in this review from database searches if they employed an experimental design using original data, involved either acute or chronic exercise using blood flow restriction, and they assessed limb or arterial occlusion pressure to determine an individualized cuff pressure. Methodologies of the studies were evaluated using a bespoke quality assessment tool.

RESULTS

Fifty-one studies met the inclusion criteria. Individualized cuff pressures ranged from 30% to 100% arterial occlusion pressure. Only 7 out of 52 studies attempted to justify the individualized cuff pressure applied during exercise. The mean quality rating for all studies was 11.1 ± 1.2 out of 13.

CONCLUSIONS

The broader blood flow restriction exercise literature uses markedly heterogeneous prescription variables despite using individualized cuff pressures. This is problematic in the absence of any clear justification for the individualized cuff pressures selected. Systematically measuring and reporting all relevant acute responses and training adaptations to the full spectrum of BFR pressures alongside increased clarity around the methodology used during blood flow restriction exercise is paramount.

Acute Effects of Tissue Flossing on Ankle Range of Motion and Tensiomyography Parameters

CONTEXT

Recently, a few papers have suggested that tissue flossing (TF) acutely improves range of motion (ROM) and neuromuscular performance. However, the effects of TF on muscle contractile properties are yet to be defined.

OBJECTIVE

To investigate the acute effects of TF on ankle ROM and associated muscle gastrocnemius medialis displacement and contraction time assessed with tensiomyography.

DESIGN

Crossover design in a single session.

SETTING

University laboratory.

PARTICIPANTS

Thirty recreationally trained volunteers (age 23.00 [4.51] y).

INTERVENTION

Active ankle plantar flexion and dorsiflexion were performed for the duration of 2 minutes (3 sets, 2-min rest between sets), while a randomly selected ankle was wrapped using TF elastic band (BAND) and the other ankle served as a control condition (CON).

MAIN OUTCOME MEASURES

Participants performed an active ankle plantar flexion and dorsiflexion ROM test and muscle gastrocnemius medialis tensiomyography displacement and contraction time measurement pre, 5, 15, 30, and 45 minutes after the floss band application.

RESULTS

There were no statistically significant differences between BAND and CON conditions (active ankle plantar flexion ROM: P = .09; active ankle dorsiflexion ROM: P = .85); however, all ROM measurements were associated with medium or large effect sizes in favor of BAND compared with CON. No significant changes were observed in the tensiomyography parameters.

CONCLUSIONS

The results of this study suggest that TF applied to the ankle is a valid method to increase ROM and at the same time maintaining muscular stiffness.

Effects of Blood Flow Restriction Training on Muscular Strength and Hypertrophy in Older Individuals: A Systematic Review and Meta-Analysis

Background

The combination of low-load resistance training with blood flow restriction (BFR) has recently been shown to promote muscular adaptations in various populations. To date, however, evidence is sparse on how this training regimen influences muscle mass and strength in older adults.

Purpose

The purpose of this systematic review and meta-analysis was to quantitatively identify the effects of low-load BFR (LL-BFR) training on muscle mass and strength in older individuals in comparison with conventional resistance training programmes. Additionally, the effectiveness of walking with and without BFR was assessed.

Methods

A PRISMA-compliant systematic review and meta-analysis was conducted. The systematic literature research was performed in the following electronic databases from inception to 1 June 2018: PubMed, Web of Science, Scopus, CINAHL, SPORTDiscus and CENTRAL. Subsequently, a random-effects meta-analysis with inverse variance weighting was conducted.

Results

A total of 2658 articles were screened, and 11 studies with a total population of N = 238 were included in the meta-analysis. Our results revealed that during both low-load training and walking, the addition of BFR elicits significantly greater improvements in muscular strength with pooled effect sizes (ES) of 2.16 (95% CI 1.61 to 2.70) and 3.09 (95% CI 2.04 to 4.14), respectively. Muscle mass was also increased when comparing walking with and without BFR [ES 1.82 (95% CI 1.32 to 2.32)]. In comparison with high-load training, LL-BFR promotes similar muscle hypertrophy [ES 0.21 (95% CI − 0.14 to 0.56)] but lower strength gains [ES − 0.42 (95% CI − 0.70 to − 0.14)].

Conclusion

This systematic review and meta-analysis reveals that LL-BFR and walking with BFR is an effective interventional approach to stimulate muscle hypertrophy and strength gains in older populations. As BFR literature is still scarce with regard to potential moderator variables (e.g. sex, cuff pressure or training volume/frequency), further research is needed for strengthening the evidence for an effective application of LL-BFR training in older people.

Electronic supplementary material

The online version of this article (10.1007/s40279-018-0994-1) contains supplementary material, which is available to authorized users.

Does Blood Flow Restriction Therapy in Patients Older Than Age 50 Result in Muscle Hypertrophy, Increased Strength, or Greater Physical Function? A Systematic Review

BACKGROUND

Blood flow restriction (BFR) is a process of using inflatable cuffs to create vascular occlusion within a limb during exercise. The technique can stimulate muscle hypertrophy and improve physical function; however, most of these studies have enrolled healthy, young men with a focus on athletic performance. Furthermore, much of the information on BFR comes from studies with small samples sizes, limited follow-up time, and varied research designs resulting in greater design, selection, and sampling bias. Despite these limitations, BFR's popularity is increasing as a clinical rehabilitation tool for aging patients. It is important for practitioners to have a clear understanding of the reported effects of BFR specifically in older adults while simultaneously critically evaluating the available literature before deciding to employ the technique.

QUESTIONS/PURPOSES

(1) Does BFR induce skeletal muscle hypertrophy in adults older than 50 years of age? (2) Does BFR improve muscle strength and/or physical function in adults older than 50 years?

METHODS

Using PubMed, Google Scholar, Web of Science, and Science Direct, we conducted a systematic review of articles using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to assess the reported effects of BFR on skeletal muscle in older adults. Included articles enrolled participants 50 years of age or older and used BFR in conjunction with exercise to study the effects of BFR on musculoskeletal outcomes and functionality. The following search terms were used: "blood flow restriction" OR "KAATSU" OR "ischemic training" AND "clinical" AND "elderly." After duplicates were removed, 1574 articles were reviewed for eligibility, and 30 articles were retained with interventions duration ranging from cross-sectional to 16 weeks. Sample sizes ranged from 6 to 56 participants, and exercise tasks included passive mobilization or electrical stimulation; walking; resistance training using machines, free weights, body weight, or elastic bands; and water-based activities. Furthermore, healthy participants and those with cardiovascular disease, osteoarthritis, osteoporosis, sporadic inclusion body myositis, spinal cord injuries, and current coma patients were studied. Lastly, retained articles were assigned a risk of bias score using aspects of the Risk of Bias in Nonrandomized Studies of Interventions and the Cochrane Collaboration's tool for assessing the risk of bias in randomized trials.

RESULTS

BFR, in combination with a variety of exercises, was found to result in muscle hypertrophy as measured by muscle cross-sectional area, thickness, volume, mass, or circumference. Effect sizes for BFR's ability to induce muscle hypertrophy were calculated for 16 of the 30 papers and averaged 0.75. BFR was also shown to improve muscle strength and functional performance. Effect sizes were calculated for 21 of the 30 papers averaging 1.15.

CONCLUSIONS

Available evidence suggests BFR may demonstrate utility in aiding rehabilitation efforts in adults older than 50 years of age, especially for inducing muscle hypertrophy, combating muscle atrophy, increasing muscle strength, and improving muscle function. However, most studies in this systematic review were at moderate or high risk of bias; that being so, the findings in this systematic review should be confirmed, ideally using greater sample sizes, randomization of participants, and extended follow-up durations.

LEVEL OF EVIDENCE

Level II, systematic review.

Blood Flow Restricted Exercise and Discomfort: A Review

Spitz, RW, Wong, V, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. Blood flow restricted exercise and discomfort: A Review. J Strength Cond Res XX(X): 000-000, 2020-Blood flow restriction exercise involves using a pneumatic cuff or elastic band to restrict arterial inflow into the muscle and block venous return out of the muscle during the exercise bout. The resultant ischemia in conjunction with low-load exercise has shown to be beneficial with increasing muscle size and strength. However, a limitation of using blood flow restriction (BFR) is the accompanying discomfort associated with this type of exercise. Factors that may influence discomfort are applied pressure, width of the cuff, cuff material, sex, and training to failure. The goal of this review was to evaluate the existing literature and elucidate how these factors can be manipulated to reduce discomfort during exercise as well as provide possible directions for future research. Thirty-eight different studies were located investigating BFR and discomfort. It was found that BFR training causes more discomfort than exercise without BFR. However, chronic use of BFR may increase tolerability, but discomfort may still be elevated over traditional non-blood flow restricted exercise. Discomfort can be attenuated by the application of lower applied pressures and stopping short of task failure. Finally, in the upper body, wider cuffs seem to increase ratings of discomfort compared with more narrow cuffs. In conclusion, applying the proper-sized cuff and making the applied pressure relative to both the individual and the cuff applied may attenuate discomfort. Reducing discomfort during exercise may help increase adherence to exercise and rehabilitation programs.

[Effectiveness of blood flow restriction training in competitive sports]

BACKGROUND

Training under conditions of blood flow restriction (BFR) has recently been advocated as an option for alternative training in athletes.

OBJECTIVE

Does BFR make sense in athlete training?

MATERIAL AND METHODS

An overview of the currently available literature is given.

RESULTS

The use of BFR appears to be a possibility to achieve muscle hypertrophy and an increase in muscular strength and can also improve parameters of cardiocirculatory function.

CONCLUSION

Various approaches for implementation of BFR in athletes can be found in the literature. These approaches differ in the frequency, force used, duration and finally type of implementation of BFR itself. Clear recommendations for training cannot be given to date and the individual weighing up of possibilities and supervised implementation of BFR in athlete training by the trainer are still necessary.

Lunge exercises with blood-flow restriction induces post-activation potentiation and improves vertical jump performance

PURPOSE

This study examined the post-activation potentiation effects of body-weight lunge exercises with blood-flow restriction on jump performance. Eighteen anaerobically trained men took part in this study across 3 weeks.

METHODS

During the first week, participants were familiarised with the lunge exercises with blood-flow restriction and the drop-jump protocol. In the second and third week, participants were randomly allocated to complete body-weight lunges (three sets of eight repetitions) either with or without blood-flow restriction (occlusion set at 130% of systolic blood pressure) to induce post-activation potentiation. Drop-jump performance was assessed between blood-flow conditions, and prior to, and at the third, sixth, ninth, twelfth and fifteenth minute following each lunge exercise. Relationships between mechanical contributors of jump performance and final jump performance were examined via Pearson correlation coefficients.

RESULTS

Lunges with blood-flow restriction significantly improved jump height (~ 4.5% ± 0.8%), flight time (~ 3.4% ± 0.3%) and power (~ 4.1% ± 0.3%) within 6-15 min post-exercise (p < 0.05) with the magnitude of effect between blood-flow conditions, moderate-large (0.54-1.16). No significant changes (p > 0.05) were found in jump performance measures following lunge exercises without blood-flow restriction. Significant correlations (p < 0.05) between mechanical contributors of jump performance and jump performance highlighted the potential of blood-flow restriction to enhance stretch-shortening cycle mechanics in the current study.

CONCLUSION

Lunge exercises with blood-flow restriction improved subsequent jump performance in anaerobically trained men. The use of blood-flow restriction may be a practical alternative to heavy resistance training equipment during warm-up protocols.

Eccentric and blood flow restriction exercises in women induce hypertrophy

BACKGROUND

The purpose of the study was to assess the mechanical and metabolic effects of eccentric (ECC) resistance training and blood flow restriction (BFR) exercise on the elbow flexors in recreationally trained females.

METHODS

Seventeen females (ECC: 30.0±7.6 years, 165.6±5.4 cm, 67.1±8.5 kg; ECC+BFR: 24.4±2.2 years, 163.7±9.3 cm, 67.6±12.2 kg) were randomized to two groups and trained twice weekly for four weeks. The ECC+BFR group trained at 30% 1-rep max (1-RM), 3x20 repetitions, and the ECC group trained at 60% 1-RM, 3×10 repetitions. The BFR cuff was pressurized to 60% of maximal occlusion. Both groups performed the ECC portion of a bicep curl with assistance to return the arm back to starting position. Rate of perceived exertion (RPE) and blood lactate were measured each week. Testing was conducted at baseline and post-training and included: body composition, thickness and cross-sectional area (CSA) of the elbow flexors, arm circumference, bicep curl 1-RM, and inverted rows to exhaustion.

RESULTS

There was no significant group difference for any of the variables (P>0.05). A training effect was shown with both groups increasing right arm circumference (P=0.004), muscle thickness (P<0.001), CSA (P=0.001), 1-RM for the right (P=0.001) and left arms (P=0.014), and inverted rows (P=0.001). Both groups showed significant decreases in lactate (P=0.047) and RPE (P<0.001).

CONCLUSIONS

Females can produce muscular gains with ECC and BFR training similar to previous results seen in males.

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.

Scientific Basis for Eccentric Quasi-Isometric Resistance Training: A Narrative Review

Oranchuk, DJ, Storey, AG, Nelson, AR, and Cronin, JB. The scientific basis for eccentric quasi-isometric resistance training: A narrative review. J Strength Cond Res 33(10): 2846-2859, 2019-Eccentric quasi-isometric (EQI) resistance training involves holding a submaximal, yielding isometric contraction until fatigue causes muscle lengthening and then maximally resisting through a range of motion. Practitioners contend that EQI contractions are a powerful tool for the development of several physical qualities important to health and sports performance. In addition, several sports involve regular quasi-isometric contractions for optimal performance. Therefore, the primary objective of this review was to synthesize and critically analyze relevant biological, physiological, and biomechanical research and develop a rationale for the value of EQI training. In addition, this review offers potential practical applications and highlights future areas of research. Although there is a paucity of research investigating EQIs, the literature on responses to traditional contraction types is vast. Based on the relevant literature, EQIs may provide a practical means of increasing total volume, metabolite build-up, and hormonal signaling factors while safely enduring large quantities of mechanical tension with low levels of peak torque. Conversely, EQI contractions likely hold little neuromuscular specificity to high velocity or power movements. Therefore, EQI training seems to be effective for improving musculotendinous morphological and performance variables with low injury risk. Although speculative due to the limited specific literature, available evidence suggests a case for future experimentation.

PREDICTIVE EQUATION FOR BLOOD FLOW RESTRICTION TRAINING

ABSTRACT Introduction No research has investigated predictive equations for application in blood flow restriction (BFR) training using a cuff with a circumference of 18 cm for the lower limbs, and including age and sex as predictor variables. Objectives To develop an equation to predict cuff pressure levels for use in BFR training for the lower limbs. Methods A total of 51 adults (age 23.23 ± 5.24 years) of both sexes (males, n= 32; females, n= 19) underwent a series of tests and anthropometric (body mass, height, body mass index – BMI, and thigh circumference – TC) and hemodynamic (brachial systolic – SBP – and diastolic – DBP – blood pressure) measurements. The arterial occlusion pressure (AOP) of the lower limbs was measured using a Doppler probe. Results The predictive equation was developed based on a hierarchical linear regression model consisting of six blocks, corresponding to TC (β = 0.380; p = 0.005), SBP (β = 0.091; p = 0.482), age (β = 0.320; p = 0.015), and sex (β = -0.207; p = 0.105), which explained 39.7% of the variation in arterial occlusion pressure. DBP and BMI were not associated with AOP. As a result, the predictive equation is as follows: AOP (mmHg) = 65.290 + 1.110 (TC in cm) + 0.178 (SBP in mmHg) + 1.153 (age in years) – 7.984 (sex, 1 – male and 2 – female), reporting values of r = 0.630, r2 = 0.397 and SEE = 15,289. Conclusion Cuff pressure for BFR training of the lower limbs may be selected based on TC, SBP, age and sex, and thigh circumference is considered the main predictor. Level of Evidence III, Non-consecutive studies, or studies without consistently applied reference standard.