Adaptation of Perceptual Responses to Low-Load Blood Flow Restriction Training

Comparison of enjoyment and energy expenditure of exergame with and without blood flow restriction in men and women

This study compared the effects of blood flow restriction (BFR) on intensity and perceived enjoyment during an exergame. Fourteen healthy young participants engaged in a boxing exergame for 20 min, with or without BFR, across two sessions. Perceived enjoyment levels were assessed using the Physical Activity Enjoyment Scale. Heart rate was monitored, and energy expenditure (EE) during exercise was calculated. A mixed model analysis of variance with repeated measures was used to evaluate differences in EE and enjoyment between exergame conditions (with and without BFR) as well as the interaction effects of these protocols with gender. Although not statistically significant, perceived enjoyment decreased with BFR inclusion for both genders. No significant differences were observed between men and women for both protocols. Regarding EE, there was no significant difference between the two groups (with and without BFR). However, a significant main effect of gender was found, with men exhibiting higher EE values in both protocols compared to women. In conclusion, exergames incorporating BFR impact perceptual responses, particularly perceived enjoyment. Furthermore, significant gender differences in EE were found, with men displaying higher values.

BFR Training Improves Patients' Reported Outcomes, Strength, and Range of Motion After Casting for Colles' Fracture

PURPOSE

This study compared traditional rehabilitation as a treatment modality after plaster cast treatment of Colles' fracture with a combination of individualized blood flow restriction (BFR) and traditional rehabilitation.

METHODS

Twenty-eight participants were randomized into a BFR group and a non-BFR group after plaster cast treatment of Colles' fracture. The BFR group completed traditional rehabilitation with a medical grade tourniquet applied to the upper arm, and the non-BFR group underwent traditional rehabilitation only. Patients were followed up with radiographic outcomes (palmar tilt and radial inclination) to ensure the stability of the fracture. Clinical assessment of patient-rated wrist evaluation (PRWE) score, grip strength, pinch strength, wrist range of motion (ROM), and muscle stiffness was conducted at cast removal and 6 wk after cast removal. Two-way repeated-measures ANOVA determined significant interactions between time and group in the aforementioned variables. An independent-sample t -test assessed the differences in baseline variables and radiographic outcomes.

RESULTS

Significant interactions between time and group were noted for PRWE score ( F = 11.796, P = 0.002, η2p = 0.339), grip strength ( F = 5.445, P = 0.029, η2p = 0.191), and wrist ROM (ulnar deviation; F = 7.856, P = 0.010, η2p = 0.255). No significant interactions between time and group were found in measurements of pinch strength or wrist ROM (flexion, extension, radial deviation, pronation, supination). An independent-sample t -test showed no significant difference in baseline variables and radiographic outcomes between the groups before or after intervention.

CONCLUSIONS

This study found that combining individualized BFR with traditional rehabilitation resulted in greater increases in PRWE score, grip strength, and wrist ROM (ulnar deviation) than traditional rehabilitation alone. Therefore, adding individualized BFR to traditional rehabilitation might be a better option for treatment for similar patients.

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

CONTEXT

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

OBJECTIVES

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

DATA SOURCES

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

STUDY SELECTION

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

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 2.

DATA EXTRACTION

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

RESULTS

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

CONCLUSION

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

Comparative Perceptual, Affective, and Cardiovascular Responses between Resistance Exercise with and without Blood Flow Restriction in Older Adults

Older adults and patients with chronic disease presenting with muscle weakness or musculoskeletal disorders may benefit from low-load resistance exercise (LLRE) with blood flow restriction (BFR). LLRE-BFR has been shown to increase muscle size, strength, and endurance comparable to traditional resistance exercise but without the use of heavy loads. However, potential negative effects from LLRE-BFR present as a barrier to participation and limit its wider use. This study examined the perceptual, affective, and cardiovascular responses to a bout of LLRE-BFR and compared the responses to LLRE and moderate-load resistance exercise (MLRE). Twenty older adults (64.3 ± 4.2 years) performed LLRE-BFR, LLRE and MLRE consisting of 4 sets of leg press and knee extension, in a randomised crossover design. LLRE-BFR was more demanding than LLRE and MLRE through increased pain (p ≤ 0.024, d = 0.8-1.4) and reduced affect (p ≤ 0.048, d = -0.5--0.9). Despite this, LLRE-BFR was enjoyed and promoted a positive affective response (p ≤ 0.035, d = 0.5-0.9) following exercise comparable to MLRE. This study supports the use of LLRE-BFR for older adults and encourages future research to examine the safety, acceptability, and efficacy of LLRE-BFR in patients with chronic disease.

Acute and chronic cardiometabolic responses induced by resistance training with blood flow restriction in HIV patients

Resistance training with blood flow restriction (RTBFR) allows physically impaired people living with HIV (PWH) to exercise at lower intensities than traditional resistance training (TRT). But the acute and chronic cardiac and metabolic responses of PWH following an RTBFR protocol are unknown. The objective was to compare the safety of acute and chronic effects on hemodynamic and lipid profiles between TRT or RTBFR in PWH. In this randomized control trial, 14 PWH were allocated in RTBFR (G_RTBFR; n = 7) or TRT (G_TRT; n = 7). Both resistance training protocols had 36 sessions (12 weeks, three times per week). Protocol intensity was 30% (G_RTBFR) and 80% (G_TRT). Hemodynamic (heart rate, blood pressure) and lipid profile were acutely (rest and post exercise 7th, 22nd, and 35th sessions) and chronically (pre and post-program) recorded. General linear models were applied to determine group * time interaction. In the comparisons between groups, the resistance training program showed acute adaptations: hemodynamic responses were not different (p > 0.05), regardless of the assessment session; and chronicles: changes in lipidic profile favors G_RTBFR, which significantly lower level of total cholesterol (p = 0.024), triglycerides (p = 0.002) and LDL (p = 0.030) compared to G_TRT. RTBFR and TRT induced a similar hemodynamic adaptation in PWH, with no significant risks of increased cardiovascular stress. Additionally, RTBFR promoted better chronic adequacy of lipid profile than TRT. Therefore, RTBFR presents a safe resistance training alternative for PWH.Trial registration: ClinicalTrials.gov ID: NCT02783417; Date of registration: 26/05/2016.

Blood Flow Restriction Therapy: An Evidence-Based Approach to Postoperative Rehabilitation

➢

Blood flow restriction therapy (BFRT) involves the application of a pneumatic tourniquet cuff to the proximal portion of the arm or leg. This restricts arterial blood flow while occluding venous return, which creates a hypoxic environment that induces many physiologic adaptations.

➢

BFRT is especially useful in postoperative rehabilitation because it produces muscular hypertrophy and strength gains without the need for heavy-load exercises that are contraindicated after surgery.

➢

Low-load resistance training with BFRT may be preferable to low-load or high-load training alone because it leads to comparable increases in strength and hypertrophy, without inducing muscular edema or increasing pain.

Blood Flow Restriction Resistance Training in Tendon Rehabilitation: A Scoping Review on Intervention Parameters, Physiological Effects, and Outcomes

Objective

To identify current evidence on blood flow restriction training (BFRT) in tendon injuries and healthy tendons, evaluating physiological tendon effects, intervention parameters, and outcomes.

Methods

This scoping review was reported in accordance with the PRISMA Extension for Scoping Reviews (PRISMA-ScR). Databases searched included MEDLINE, CINAHL, AMED, EMBase, SPORTDiscus, Cochrane library (Controlled trials, Systematic reviews), and five trial registries. Two independent reviewers screened studies at title/abstract and full text. Following screening, data was extracted and charted, and presented as figures and tables alongside a narrative synthesis. Any study design conducted on adults, investigating the effects of BFRT on healthy tendons or tendon pathology were included. Data were extracted on physiological tendon effects, intervention parameters and outcomes with BFRT.

Results

Thirteen studies were included, three on tendinopathy, two on tendon ruptures, and eight on healthy Achilles, patellar, and supraspinatus tendons. A variety of outcomes were assessed, including pain, function, strength, and tendon morphological and mechanical properties, particularly changes in tendon thickness. BFRT intervention parameters were heterogeneously prescribed.

Conclusion

Despite a dearth of studies to date on the effects of BFRT on healthy tendons and in tendon pathologies, preliminary evidence for beneficial effects of BFRT on tendons and clinical outcomes is encouraging. As BFRT is a relatively novel method, definitive conclusions, and recommendations on BFRT in tendon rehabilitation cannot be made at present, which should be addressed in future research, due to the potential therapeutic benefits highlighted in this review.

Effects of low load exercise with and without blood-flow restriction on microvascular oxygenation, muscle excitability and perceived pain

This paper aimed to examine the acute effect of low-load (LL) exercise with blood-flow restriction (LL-BFR) on microvascular oxygenation and muscle excitability of the vastus medialis (VM) and vastus lateralis (VL) muscles during a single bout of unilateral knee extension exercise performed to task failure. Seventeen healthy recreationally resistance-trained males were enrolled in a within-group randomized cross-over study design. Participants performed one set of unilateral knee extensions at 20% of one-repetition maximum (1RM) to task failure, using a LL-BFR or LL free-flow (LL-FF) protocol in a randomized order on separate days. Changes in microvascular oxygenation and muscle excitability in VL and VM were assessed using near-infrared spectroscopy (NIRS) and surface electromyography (sEMG), respectively. Pain measures were collected using the visual analog scale (VAS) before and following set completion. Within- and between- protocol comparisons were performed at multiple time points of set completion for each muscle. During LL-BFR, participants performed 43% fewer repetitions and reported feeling more pain compared to LL-FF (p<0.05). Normalized to time to task failure, LL-BFR and LL-FF generally demonstrated similar progression in microvascular oxygenation and muscle excitability during exercise to task failure. The present results demonstrate that LL-BFR accelerates time to task failure, compared with LL-FF, resulting in a lower dose of mechanical work to elicit similar levels of oxygenation, blood-pooling, and muscle excitability. LL-BFR may be preferable to LL-FF in clinical settings where high workloads are contraindicated, although increased pain experienced during BFR may limit its application.HighlightsCompared to free flow (FF), neuromuscular fatigue mechanisms are accelerated during blood flow restricted (BFR) training. This can be observed as changes in microvascular oxygenation and muscle excitability occurring at a ∼43% faster mean rate during BFR compared to FF.BFR exercise seems to elicit the same level of neuromuscular fatigue as FF training within a shorter timeframe. This reduces total joint load and may be especially helpful in cases where high training volumes may be contraindicated (e.g. recovering from a sports injury or orthopedic surgery).

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.

Perceived Barriers to Blood Flow Restriction Training

Blood flow restriction (BFR) training is increasing in popularity in the fitness and rehabilitation settings due to its role in optimizing muscle mass and strength as well as cardiovascular capacity, function, and a host of other benefits. However, despite the interest in this area of research, there are likely some perceived barriers that practitioners must overcome to effectively implement this modality into practice. These barriers include determining BFR training pressures, access to appropriate BFR training technologies for relevant demographics based on the current evidence, a comprehensive and systematic approach to medical screening for safe practice and strategies to mitigate excessive perceptual demands of BFR training to foster long-term compliance. This manuscript attempts to discuss each of these barriers and provides evidence-based strategies and direction to guide clinical practice and future research.

Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7

BACKGROUD

Blood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training.

METHODS

A total of 7 healthy young men performed squats, and between sets BFR was carried out on one leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mmHg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training.

RESULTS

Doppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. microRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-β serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg.

CONCLUSION

BFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

Blood Flow Restriction Training: To Adjust or Not Adjust the Cuff Pressure Over an Intervention Period?

Blood flow restriction (BFR) training combines exercise and partial reduction of muscular blood flow using a pressured cuff. BFR training has been used to increase strength and muscle mass in healthy and clinical populations. A major methodological concern of BFR training is blood flow restriction pressure (BFRP) delivered during an exercise bout. Although some studies increase BFRP throughout a training intervention, it is unclear whether BFRP adjustments are pivotal to maintain an adequate BFR during a training period. While neuromuscular adaptations induced by BFR are widely studied, cardiovascular changes throughout training intervention with BFR and their possible relationship with BFRP are less understood. This study aimed to discuss the need for BFRP adjustment based on cardiovascular outcomes and provide directions for future researches. We conducted a literature review and analyzed 29 studies investigating cardiovascular adaptations following BFR training. Participants in the studies were healthy, middle-aged adults, older adults and clinical patients. Cuff pressure, when adjusted, was increased during the training period. However, cardiovascular outcomes did not provide a plausible rationale for cuff pressure increase. In contrast, avoiding increments in cuff pressure may minimize discomfort, pain and risks associated with BFR interventions, particularly in clinical populations. Given that cardiovascular adaptations induced by BFR training are conflicting, it is challenging to indicate whether increases or decreases in BFRP are needed. Based on the available evidence, we suggest that future studies investigate if maintaining or decreasing cuff pressure makes BFR training safer and/or more comfortable with similar physiological adaptation.

Exercise-induced hypoalgesia and pain reduction following blood flow restriction: A brief review

OBJECTIVE

To review past literature regarding exercise-induced hypoalgesia and pain reduction following blood flow restriction interventions, and to discuss potential mechanisms as well as future considerations towards the efficacy of blood flow restriction in pain reduction following exercise.

METHODS

To be eligible for inclusion, studies had to include acute exercise, or long-term training interventions, with blood flow restriction, along with including pre and post intervention pain measurements.

RESULTS

A total of 13 studies met the inclusion criteria. Among these 13 studies, 3 studies examined exercise-induced hypoalgesia after an acute bout of resistance exercise with blood flow restriction, and 10 studies investigated pain reduction following long-term blood flow restriction training.

CONCLUSIONS

Existing literature suggests that low load resistance exercise with blood flow restriction may serve as an effective pain management method for those who are unable or unwilling to train with high loads. Several potential mechanisms have been suggested, however, the roles of these mechanisms are still unclear and require further clarification. Future research should consider implementing different methods of blood flow restriction application, and research study design to clarify the utility and efficacy of blood flow restriction as a pain management tool, by itself or in combination with exercise.

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.

Comparison of blood flow restriction devices and their effect on quadriceps muscle activation

OBJECTIVES

Blood flow restriction training (BFRT) provides an alternative approach to traditional strength training. The purpose of this study was to determine differences in quadriceps muscle activation, subject reported pain, and perceived exertion between three exercise conditions: low-load resistance BFRT with (1) regulated and (2) standardized devices, and (3) high-load resistance exercise without BFRT.

DESIGN

Randomized cross over study.

SETTING

XX University Biomechanics laboratory.

PARTICIPANTS

Thirty-four healthy subjects (18 male/16 female) each completed three randomized sessions of knee extensions using Delfi's Personalized Tourniquet System (R) at 30% of 1 repetition maximum (1RM), the B-Strong™ device (S) at 30% 1RM, and high-load resistance exercise (HL) at 80% 1RM.

MAIN OUTCOME MEASURES

Quadriceps EMG activity, numeric pain rating scale (NPRS), and perceived exertion (OMNI-RES) were recorded.

RESULTS

Average and peak EMG were greater in HL sessions than both S and R (p < .001). NPRS was greater in the R sessions compared to both S (p < .001) and HL (p < .001). OMNI-RES was greater in the R sessions compared to S (p < .02) and HL (p < .001). No differences (p > .05) in average or peak EMG activation were found between S and R sessions.

CONCLUSIONS

Quadriceps EMG amplitude was greater during high-load resistance exercise versus low-load BFR exercise and there were no differences in EMG findings between BFRT devices.

Isometric blood flow restriction exercise: acute physiological and neuromuscular responses

Background

Numerous studies have demonstrated that the addition of blood flow restriction (BFR) to low-load (LL) resistance exercise leads to elevated levels of muscle hypertrophy and strength gains. In terms of main underlying mechanisms, metabolic accumulation and increased neuromuscular adaptations seem to play a primary role. However, this evidence is largely based on dynamic exercise conditions. Therefore, the main objective was to investigate the acute physiological adaptations following isometric LL-BFR exercise.

Methods

Fifteen males participated in this cross-over trial and completed the following sessions in a random and counterbalanced order: isometric LL-BFR exercise (20% maximum voluntary contraction, MVC) and load matched LL exercise without BFR. Lactate levels, muscle activation as well as muscle swelling were recorded during the whole exercise and until 15 min post completion. Additionally, changes in maximal voluntary torque and ratings of perceived exertion (RPE) were monitored.

Results

During exercise, EMG amplitudes (72.5 ± 12.7% vs. 46.3 ± 6.7% of maximal EMG activity), muscle swelling and RPE were significantly higher during LL-BFR compared to LL (p < 0.05). Lactate levels did not show significant group differences during exercise but revealed higher increases 15 min after completion in the LL-BFR condition (LL-BFR: + 69%, LL: + 22%) (p < 0.05). Additionally, MVC torque significantly decreased immediately post exercise only in LL-BFR (~ − 11%) (p < 0.05) but recovered after 15 min.

Conclusions

The present results demonstrate that isometric LL-BFR causes increased metabolic, neuromuscular as well as perceptual responses compared to LL alone. These adaptations are similar to dynamic exercise and therefore LL-BFR represents a valuable type of exercise where large joint movements are contraindicated (e.g. rehabilitation after orthopedic injuries).

The perceptual responses of individuals with multiple sclerosis to blood flow restriction versus traditional resistance exercise

BACKGROUND

Low-load resistance exercise with blood flow restriction (_LLBFR-RE) has been shown capable of improving neuromuscular parameters in several clinical populations, however, its tolerability and effects on individuals with multiple sclerosis (MS) remains unknown.

OBJECTIVE

To investigate the perceptual responses of individuals with MS to _LLBFR-RE versus traditional high-load resistance exercise (HL-RE).

METHODS

Four men and eleven women diagnosed with relapsing-remitting MS randomly completed the following experimental trials: 1) _LLBFR-RE four sets of 30-15-15-15 repetitions, at 20% of one-repetition maximum (1-RM) of leg-press (LP) and knee-extension (KE), with 50% of BFR, and a 1-min rest interval between sets; 2) HL-RE- four sets of 8-10 repetitions, at 70% 1-RM of LP and KE, with the same rest intervals. Ratings of perceived exertion (RPE) were measured after each set, pain was measured before and after sets, and delayed-onset muscle soreness (DOMS) was measured at 5, 30, 60 min, and 24-h post-exercise.

RESULTS

HL-RE elicited significantly (p<0.05) greater RPE compared to _LLBFR-RE during all sets. Additionally, there were no significant (p>0.05) differences between _LLBFR-RE and HL-RE for pain immediately after all sets, although pain measured before sets were significantly (p<0.05) greater for _LLBFR-RE. Finally, both protocols resulted in similar DOMS, however, it was significantly (p<0.05) elevated 24-h post-exercise compared to 1-h after for HL-RE but not for _LLBFR-RE.

CONCLUSION

Altogether, these data demonstrate that _LLBFR-RE is well tolerated by individuals with MS, requires less muscular exertion than HL-RE, and does not cause exaggerated pain during exercise or elevated DOMS up to 24 h post-exercise.

Perceptual and Neuromuscular Responses Adapt Similarly Between High-Load Resistance Training and Low-Load Resistance Training With Blood Flow Restriction

Teixeira, EL, Painelli, VdS, Schoenfeld, BJ, Silva-Batista, C, Longo, AR, Aihara, AY, Cardoso, FN, Peres, BdA, and Tricoli, V. Perceptual and neuromuscular responses adapt similarly between high-load resistance training and low-load resistance training with blood flow restriction. J Strength Cond Res XX(X): 000-000, 2020-This study compared the effects of 8 weeks of low-load resistance training with blood flow restriction (LL-BFR) and high-load resistance training (HL-RT) on perceptual responses (rating of perceived exertion [RPE] and pain), quadriceps cross-sectional area (QCSA), and muscle strength (1 repetition maximum [RM]). Sixteen physically active men trained twice per week, for 8 weeks. One leg performed LL-BFR (3 sets of 15 repetitions, 20% 1RM), whereas the contralateral leg performed HL-RT (3 sets of 8 repetitions, 70% 1RM). Rating of perceived exertion and pain were evaluated immediately after the first and last training sessions, whereas QCSA and 1RM were assessed at baseline and after training. Rating of perceived exertion was significantly lower (6.8 ± 1.1 vs. 8.1 ± 0.8, p = 0.001) and pain significantly higher (7.1 ± 1.2 vs. 5.8 ± 1.8, p = 0.02) for LL-BFR than that for HL-RT before training. Significant reductions in RPE and pain were shown for both protocols after training (both p < 0.0001), although no between-protocol differences were shown in absolute changes (p = 0.10 and p = 0.48, respectively). Both LL-BFR and HL-RT were similarly effective in increasing QCSA (7.0 ± 3.8% and 6.3 ± 4.1%, respectively; both p < 0.0001) and 1RM (6.9 ± 4.1% and 13.7 ± 5.9%, respectively; both P < 0.0001), although absolute changes for 1RM in HL-RT were greater than LL-BFR (p = 0.001). In conclusion, LL-BFR produces lower RPE values and a higher pain perception than HL-RT. However, consistent application of these approaches result in chronic adaptations so that there are no differences in perceptual responses over the course of time. In addition, muscle strength is optimized with HL-RT despite similar increases in muscle hypertrophy between conditions.

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.

Effectiveness of a 2-Week Strength Training Learning Intervention on Self-selected Weight-Training Intensity

Glass, SC, Ahmad, S, and Gabler, T. Effectiveness of a 2-week strength training learning intervention on self-selected weight-training intensity. J Strength Cond Res 34(9): 2443-2448, 2020-The purpose of this study was to determine the effectiveness of an imposed (IM) vs. self-selected (SS) 2-week strength training intervention on SS resistance training intensity. Subjects 18-40 years (SS n = 10 and IM n = 10) were provided resistance training orientation (chest press, leg press, triceps extension, bicep curl, and shoulder press). On 6 different training days, subjects completed 2 sets on each machine while blinded to the load. The SS group SS loads without any intensity or effort feedback. Load, repetitions, and ratings of perceived exertion (RPE) were recorded. The IM group was encouraged to lift to fatigue, and if they exceeded 12 repetitions, subsequent load was increased (goal-attain 70% one repetition maximum [1RM]). After training, SS and IM SS loads and repetitions for all lifts, plus 3 novel lifts (pec fly, leg extension, and shoulder raise). One repetition maximum was assessed last. Comparisons between groups were made using 2-way analysis of variance. There were significant main effects for % 1RM for the condition and day (day 1 IM = 57.2 ± 12.0%, SS = 47.2 ± 13.7% and day 6 IM = 74.7 ± 10.8%, SS = 66.2 ± 13.4%). There were significant effects across days for reps (day 1 IM = 10.8 ± 4.8, SS = 12.3 ± 4.0 and day 6 IM = 9.3 ± 3.6, SS = 10.0 ± 3.0) and RPE (day 1 = 15.4 ± 2.0 and day 6 = 16.5 ± 1.9). For both SS and IM post-training SS loads exceeded 60% 1RM. However, among the novel lifts, only the pec fly was greater than 60% 1RM (pec fly 63.0 ± 11.0%, leg extension 39.8 ± 12.5%, and shoulder raise 53.1 ± 12.8%). Two weeks of supervised resistance training resulted in both IM and SS self-selecting loads greater than 60% 1RM. There were no differences after 2-weeks of training between IM load and SS load groups.

The effect of blood flow restriction exercise on exercise-induced hypoalgesia and endogenous opioid and endocannabinoid mechanisms of pain modulation

This study aimed to investigate and compare the magnitude of exercise-induced hypoalgesia (EIH) with low-intensity blood flow restriction (BFR) resistance exercise (RE) at varying pressures to other intensities of resistance exercise and examine endogenous mechanisms of pain reduction. Twelve individuals performed four experimental trials involving unilateral leg press exercise in a randomized crossover design: low-load RE at 30% of one repetition maximum (1RM), high-load RE (70% 1RM), and BFR-RE (30% 1RM) at a low and high pressure. BFR pressure was prescribed relative to limb occlusion pressure at 40% and 80% for the low- and high-pressure trials. Pressure pain thresholds (PPT) were assessed before and 5 min and 24 h following exercise in exercising and nonexercising muscles. Venous blood samples were collected at the same timepoints to determine plasma concentrations of beta-endorphin and 2-arachidonoylglycerol. High-pressure BFR-RE increased PPTs in the exercising limb to a greater extent than all other trials. Comparable systemic EIH effects were observed with HLRE and both BFR-RE trials. PPTs in the exercising limb remained elevated above baseline at 24 h postexercise following both BFR-RE trials. Postexercise plasma beta-endorphin concentration was elevated during the BFR-RE trials. No changes to 2-arachidonoylglycerol concentration were observed. High pressure BFR-RE causes a greater EIH response in the exercising limb that persists for up to 24 h following exercise. The reduction in pain sensitivity with BFR-RE is partly driven by endogenous opioid production of beta-endorphin. BFR-RE should be investigated as a possible pain-modulation tool in individuals with acute and chronic pain.

NEW & NOTEWORTHY High-pressure blood flow restriction (BFR) causes a greater hypoalgesia response in the exercising limb (48%) compared with light and heavy load resistance exercise (10–34%). Performing light load resistance exercise with BFR causes systemic hypoalgesia comparable with heavy load resistance exercise (10–18%). BFR resistance exercise prolonged the exercise-induced hypoalgesia response for 24 h in the exercising limb (15% and 24%, respectively). Activation of endogenous opioid production and a conditioned pain modulation effect partly mediate the relationship between exercise and hypoalgesia.

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.

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.

Examination of the comfort and pain experienced with blood flow restriction training during post-surgery rehabilitation of anterior cruciate ligament reconstruction patients: A UK National Health Service trial

OBJECTIVE

Examine the comfort and pain experienced with blow flow restriction resistance training (BFR-RT) compared to standard care heavy load resistance training (HL-RT) during anterior cruciate ligament reconstruction (ACLR) patient rehabilitation.

DESIGN

Randomised controlled trial.

SETTING

United Kingdom National Health Service.

PARTICIPANTS

Twenty eight patients undergoing unilateral ACLR surgery with hamstring autograft were recruited. Following surgery participants were block randomised to either HL-RT at 70% repetition maximum (1RM) (n = 14) or BFR-RT (n = 14) at 30% 1RM and completed 8 weeks of twice weekly unilateral leg press training on both limbs.

MAIN OUTCOME MEASURES

Perceived knee pain, muscle pain and rating of perceived exertion (RPE) were assessed using Borg's (1998) RPE and pain scales during training. Knee pain was also assessed 24 h post-training.

RESULTS

There were no adverse events. Knee pain was lower with BFR-RT during (p < 0.05) and at 24 h post-training (p < 0.05) with BFR-RT for all sessions. Muscle pain was higher (p < 0.05) with BFR-RT compared to HL-RT during all sessions. RPE remained unchanged (p > 0.05) for both BFR-RT and HL-RT.

CONCLUSION

ACLR patients experienced less knee joint pain and reported similar ratings of perceived exertion during and following leg press exercise with BFR-RT compared to traditional HL-RT. BFR-RT may be more advantageous during the early phases of post-surgery ACLR rehabilitation.

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

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

Is Postexercise Blood Flow Restriction a Viable Alternative to Other Resistance Exercise Protocols?

PURPOSE

The purpose of this study was to identify whether post-resistance exercise (REx) blood flow restriction (BFR) can elicit a similar acute training stimulus to that offered by either heavy REx or traditional low-load BFR REx.

METHOD

Ten men completed trials with 30% one-repetition maximum (1RM) for 5 sets of 15 repetitions without BFR (30%), with BFR during exercise (30% RD), and with postexercise BFR (30% RP) and at 75% 1RM for 3 sets of 10 repetitions. Lactate and cortisol were measured before and up to 60 min after exercise. Thigh circumference, ratings of perceived exertion (RPE), and pain were measured before and after exercise. Surface electromyography was measured during exercise.

RESULTS

All conditions had a large effect (effect size [ES] > 0.8) on lactate, with the largest effects observed with the 75% condition; no differences were observed between the 30% conditions. All conditions had a moderate effect (ES > 0.25 ≤ 0.4) on increasing thigh circumference. This effect was maintained (ES = 0.35) with the application of BFR after REx (30% RP). Change in RPE, from the first to last set, was significantly greater with 30% RD compared with other conditions (all p < .05). Electromyography amplitude was higher and percentage change was greater for the 75% condition compared with the other conditions (both p < .05).

CONCLUSIONS

The application of BFR immediately post-REx altered several of the responses associated with REx that is aimed at inducing muscular hypertrophy. Additionally, these changes occurred with less pain and perceived exertion suggesting that this form of REx may offer an alternative, tolerable method of REx.

Higher Training Frequency Is Important for Gaining Muscular Strength Under Volume-Matched Training

Background: This study investigated the effect of volume-matched strength training programs with different frequency and subsequent detraining on muscle size and strength.

Methods: During a training period of 11 weeks, untrained subjects (age: 22.3 ± 0.9 years, height: 173.1 ± 4.8 cm and body mass: 66.8 ± 8.4 kg) performed knee-extension exercise at 67% of their estimated one-repetition maximum either one session per week (T1 group: 6 sets of 12 repetitions per session; n = 10) or three sessions per week (T3 group: 2 sets of 12 repetitions per session; n = 10). Rating of perceived exertion (RPE) and muscle stiffness were measured as an index of muscle fatigue and muscle damage, respectively. The magnitude of muscle hypertrophy was assessed with thigh circumference and the quadriceps muscle thickness. The changes in muscle strength were measured with isometric maximum voluntary contraction torque (MVC).

Results: During the training period, RPE was significantly higher in the T1 than in the T3 (p < 0.001). After 11 weeks of training, both groups exhibited significant improvements in thigh circumference, muscle thickness, and MVC compared with baseline values. However, there was a significant group difference in MVC improvement at week 11 (T1: 43.5 ± 15.5%, T3: 65.2 ± 23.2%, p < 0.05). After 6 weeks of detraining, both groups showed the significant decreases in thigh circumference and muscle thickness from those at the end of training period, while no significant effect of detraining was observed in MVC.

Conclusion: These results suggest that three training sessions per week with two sets are recommended for untrained subjects to improve muscle strength while minimizing fatigue compared to one session per week with six sets.

Perceptual and arterial occlusion responses to very low load blood flow restricted exercise performed to volitional failure

PURPOSE

Studies examining perceptual and arterial occlusion responses between blood flow restricted exercise and high load exercise often prescribe an arbitrary number of repetitions, making it difficult for direct comparisons. Therefore, the purpose of this study was to compare these protocols when performed to volitional failure.

METHODS

Individuals completed four exercise conditions varying in load and pressure: (i) 15% 1RM; no restrictive pressure, (ii) 15% 1RM; 40% arterial occlusion pressure, (iii) 15% 1RM; 80% arterial occlusion pressure, and (iv) 70% 1RM; no pressure. Four sets of knee extension exercises were performed until volitional failure (or until 90 repetitions per set) was completed.

RESULTS

A total of 23 individuals completed the study. While all conditions increased arterial occlusion pressure, the greatest increases (~30%) were observed in the blood flow restriction conditions. All lower load conditions resulted in greater RPE and discomfort than that of the high load condition, but only discomfort was increased further when adding blood flow restriction.

CONCLUSION

High load exercise will likely be perceived more favourably than lower load exercise to volitional failure; however, those who are incapable or unwilling to lift heavier loads may use blood flow restriction to help reduce the volume needed to reach volitional failure, although this will likely increase discomfort.

Effects of local versus remote ischemic preconditioning on repeated sprint running performance

BACKGROUND

The aim of this study was to compare the effect of local and remote ischemic preconditioning (IPC) on repeated sprint exercise.

METHODS

Twelve males (age 22±2 years; stature 1.79±0.07 m; body mass 77.8±8.4 kg; mean±SD) completed four trials consisting of remote (arm) and local (leg) IPC and SHAM interventions prior to repeated sprint exercise (3x[6x15+15-m] shuttle sprints), in a double-blind, randomized, crossover designed study. These tests were immediately preceded by IPC (4x5-minute intervals at 220 mmHg bilateral occlusion) or SHAM treatment (4x5-minute intervals at 20 mmHg bilateral occlusion). Sprint performance and percentage decrement score alongside measurement of Tissue Saturation Index, blood lactate and RPE were measured throughout the intervention.

RESULTS

During the IPC/SHAM intervention there was a large decrease in TSI for IPC-arm in comparison to IPC-leg (P<0.05), however IPC-legs resulted in greater soreness compared with the other three conditions (P<0.05). There was no main effects or interaction effects for sprint performance. There was a significant effect of condition (P=0.047, r=0.56) on percentage decrement score across all 18 sprints with IPC demonstrating less fatigue than SHAM. There were no other effects of IPC during the sprint trials for any other physiological measure.

CONCLUSIONS

In conclusion local IPC resulted in more pain/soreness during the IPC/SHAM intervention but both remote and local IPC reduced the fatigue associated with repeated sprint exercise.