Application Of Blood Flow Restriction Research Articles

The Effectiveness of Blood Flow Restriction Training on Upper Extremity Muscle Strength: A Systematic Review

Abstract Objective This systematic review aims to investigate the effect of blood flow restriction training (BFRT) on upper extremity muscle strength in pathological conditions of the upper extremity musculoskeletal system or in healthy individuals. Materials and Methods This study was conducted in accordance with the PRISMA guideline statement. The randomized controlled studies which published from January 2000 to May 2022 were searched in the PubMed, Web of Science, MEDLINE, Scopus, and Cochrane Library databases. Inclusion criteria were healthy clinical population or musculoskeletal pathology related to the upper extremity, participants aged 18 and above, application of blood flow restriction to the arm, a randomized controlled study design, and publication in English. Additionally, the presentation of upper extremity muscle strength as an outcome measurement was required. The quality of the studies was evaluated using The Physiotherapy Evidence Database (PEDro) scale. Articles that were non-randomized, inaccessible in full text, and scored 4 or below on the PEDro scale were excluded. Results Five studies were included with 219 participants. The included studies had PEDro scores ranging from 5 to 8, with an average score of 6.4. This review demonstrated a positive or neutral effect of BFRT on grip strength and shoulder strength. Conclusion Although some studies have reported positive effects of BFRT on upper extremity muscle strength, there is no conclusive evidence regarding the protocol to be used for increasing upper extremity muscle strength.

Blood flow restriction attenuates surface mechanomyography lateral and longitudinal, but not transverse oscillations during fatiguing exercise.

Objective. Surface mechanomyography (sMMG) can measure oscillations of the activated muscle fibers in three axes (i.e.X,Y, andZ-axes) and has been used to describe motor unit activation patterns (X-axis). The application of blood flow restriction (BFR) is common in exercise studies, but the cuff may restrict muscle fiber oscillations. Therefore, the purpose of this investigation was to examine the acute effects of submaximal, fatiguing exercise with and without BFR on sMMG amplitude in theX,Y, andZ-axes among female participants.Approach. Sixteen females (21 ± 1 years) performed two separate exercise bouts to volitional exhaustion that consisted of unilateral, submaximal (50% maximal voluntary isometric contraction [MVIC]) intermittent, isometric, leg extensions with and without BFR. sMMG was recorded and examined across percent time to exhaustion (%TTE) in 20% increments. Separate 2-way repeated measures ANOVA models were constructed: (condition [BFR, non-BFR]) × (time [20, 40, 60, 80, and 100% TTE]) to examine absolute (m·s-2) and normalized (% of pretest MVIC) sMMG amplitude in theX-(sMMG-X),Y-(sMMG-Y), andZ-(sMMG-Z) axes.Main results. The absolute sMMG-X amplitude responses were attenuated with the application of BFR (mean ± SD = 0.236 ± 0.138 m·s-2) relative to non-BFR (0.366 ± 0.199 m·s-2, collapsed across time) and for sMMG-Y amplitude at 60%-100% of TTE (BFR range = 0.213-0.232 m·s-2versus non-BFR = 0.313-0.445 m·s-2). Normalizing sMMG to pretest MVIC removed most, but not all the attenuation which was still evident for sMMG-Y amplitude at 100% of TTE between BFR (72.9 ± 47.2%) and non-BFR (98.9 ± 53.1%). Interestingly, sMMG-Z amplitude was not affected by the application of BFR and progressively decreased across %TTE (0.332 ± 0.167 m·s-2to 0.219 ± 0.104 m·s-2, collapsed across condition.)Significance. The application of BFR attenuated sMMG-X and sMMG-Y amplitude, although normalizing sMMG removed most of this attenuation. Unlike theXandY-axes, sMMG-Z amplitude was not affected by BFR and progressively decreased across each exercise bout potentially tracking the development of muscle fatigue.

Distinct adaptations of muscle endurance but not strength or hypertrophy to low-load resistance training with and without blood flow restriction.

Low-load resistance training promotes muscle strength and hypertrophic adaptations when combined with blood flow restriction (BFR). However, the effect of BFR on muscle endurance remains unclear. The aim of this study was to clarify the effects of BFR on muscle performance and adaptation, with special reference to local muscle endurance. In experiment1, eight healthy men performed unilateral elbow flexion exercise to failure at 30% of one-repetition maximum with BFR (at 40% of estimated arterial occlusion pressure) and free blood flow (FBF). During the exercise, muscle activity and tissue oxygenation were measured from the biceps brachii. In experiment 2, another eight healthy men completed 6weeks of elbow flexion training with BFR and FBF. The number of repetitions to failure at submaximal load (Rmax ), the estimated time for peak torque output to decay by 50% during repetitive maximum voluntary contractions (half-time), one-repetition maximum, isometric strength and muscle thickness of elbow flexors were measured pre- and post-training. Blood flow restriction resulted in fewer repetitions and lower muscle tissue oxygenation at the end of exercise than FBF, while the muscle activity increased similarly to repetition failure. Blood flow restriction also resulted in a smaller post-training Rmax , which was strongly correlated with the total exercise volume over the 6week period. Despite the smaller exercise volume, BFR resulted in similar improvements in half-time, muscle strength and thickness compared with FBF. These results suggest that the application of BFR can attenuate muscle endurance adaptations to low-load resistance training by decreasing the number of repetitions during exercise, both acutely and chronically.

Blood flow restriction augments the cross-education effect of isometric handgrip training.

The application of blood flow restriction (BFR) to low-intensity exercise may be able to increase strength not only in the trained limb but also in the homologous untrained limb. Whether this effect is repeatable and how that change compares to that observed with higher intensity exercise is unknown. Examine whether low-intensity training with BFR enhances the cross-education of strength compared to exercise without BFR and maximal efforts. A total of 179 participants completed the 6-week study, with 135 individuals performing isometric handgrip training over 18 sessions. Participants were randomly assigned to one of four groups: 1) low-intensity (4 × 2min of 30% MVC; LI, n = 47), 2) low-intensity with blood flow restriction (LI + 50% arterial occlusion pressure; LI-BFR, n = 41), 3) maximal effort (4 × 5s of 100% MVC; MAX, n = 47), and 4) non-exercise control (CON, n = 44). LI-BFR was the only group that observed a cross-education in strength (CON: 0.64 SD 2.9kg, LI: 0.95 SD 3.6kg, BFR-LI: 2.7 SD 3.3kg, MAX: 0.80 SD 3.1kg). In the trained hand, MAX observed the greatest change in strength (4.8 SD 3.3kg) followed by LI-BFR (2.8 SD 4.0kg). LI was not different from CON. Muscle thickness did not change in the untrained arm, but ulna muscle thickness was increased within the trained arm of the LI-BFR group (0.06 SD 0.11cm). Incorporating BFR into low-intensity isometric training led to a cross-education effect on strength that was greater than all other groups (including high-intensity training).

Effect of low-intensity resistance training with blood flow restriction on functional status in knee osteoarthritis

Background: Knee osteoarthritis is a joint pathology with high prevalence, resulting from the increase of aging and obesity in the world population. Articular cartilage destruction can cause pain and eventually reduces activities of daily living and affects functional status in subjects with knee osteoarthritis. Exercise interventions in knee-OA aimed at increasing knee extensor muscle strength involve high-intensity resistance training but may result in joint pain due to high-compressive forces. Other alternative method includes low-intensity resistance training performed with blood flow restriction, a potential intervention for a patient who does not tolerate high loads due to lower mechanical stress. This study aims to determine the effects of blood flow restriction with low-intensity resistance training on the quadriceps for six weeks on functional status in knee-OA patients. Methods: Twenty-eight patients aged 50-70 years old with knee-OA in Physical Medicine and Rehabilitation Outpatient Clinic Soetomo Hospital Surabaya were randomized into control and treatment groups. Both groups underwent a 6-week supervised training program consisting of LI-RT (30% 1-RM) two sessions/week. The treatment group received an additional application of blood flow restriction using a cuff on 1/3 of the upper thigh with 50 mmHg occlusion pressure. Both groups were assessed for functional status by self-reported WOMAC questionnaire before and after the protocol. Results: Both training methods were able to reduce WOMAC pain and improve physical function subscales significantly, but WOMAC stiffness subscales only reduced significantly in low-intensity resistance training with blood flow restriction. There were no significant differences between groups for any domain from WOMAC, nor any significant differences between delta scores (all P > 0.05). Conclusion: Low-intensity resistance training with and without blood flow restriction was similarly effective in enhancing functional status in subjects with knee osteoarthritis.

Effects of blood flow restriction on mechanical properties of the rectus femoris muscle at rest.

Introduction: This study examined the effects of blood flow restriction (BFR) and reperfusion on the mechanical properties of the rectus femoris muscle at rest (frequency and stiffness). Methods: Fourteen trained men (body weight = 81.0 ± 10.3kg; BMI = 25 ± 3.0m/kg2; height = 181 ± 4cm; training experience = 6.0 ± 2.2years) participated in an experimental session involving their dominant (BFR) and non-dominant leg (control). Muscle mechanical properties were measured using Myoton's accelerometer at the midpoint of the rectus femoris muscle at five time points. In the BFR leg, an 80% arterial occlusion pressure was applied by a cuff for 5min. No cuff was applied in the control leg. Femoral Myoton measurements were taken from both legs 2 and 4min after the start of BRF as well as 30s and 2min after the end of the occlusion period. Results: The two-way ANOVA revealed a statistically significant interaction effect for stiffness and frequency (p < 0.001; η2 > 0.67). The post hoc analysis showed that both stiffness and frequency increased during BFR compared with rest and then dropped to the resting levels post BFR period. Also, stiffness and frequency were higher than control only during the BFR period, and similar during rest and post BFR. Conclusion: These results indicate that the application of BFR at rest leads to significant changes in mechanical properties of the rectus femoris muscle.

Blood flow restricted walking alters gait kinematics

ABSTRACT This study investigated the impact of blood flow restriction (BFR) during treadmill walking on gait kinematics. Twenty-one participants completed one familiarisation and four experimental sessions, including two walking speeds (moderate [5.0 ± 0.3km·h−1] and fast [6.4 ± 0.4km·h−1]) and two occlusion conditions (BFR [60% of arterial occlusion pressure] and unrestricted). For each exercise intensity, the BFR session was performed first. Participants were instructed to walk as long as possible, with sessions capped at 20 min. Unrestricted sessions were time-matched, and the order of exercise intensity was randomised. Kinematics were collected over 10s every minute using retro-reflective markers affixed to specific body landmarks. Ratings of perceived exertion and discomfort were collected every two minutes. Blood samples were collected from the fingertip pre-exercise and the finger and toe post-exercise, and were analysed for lactate, electrolytes, and markers of cell-membrane damage. During the BFR sessions the cuffs remained inflated while the blood samples were collected. Fast-walk BFR sessions exhibited higher anterior trunk flexion (p = 0.001) and knee flexion during stance (p = 0.001) compared to all other sessions. Step width was increased during BFR sessions (p = 0.001), but no difference in step length (p = 0.300) or cadence (p = 0.922) were observed. The time required to elicit change in anterior trunk flexion and plantar-flexion angle at toe-off was shorter during BFR sessions (p = 0.024). The BFR sessions elicited the highest ratings of perceived exertion and discomfort, as well as blood lactate concentration (p ≤ 0.001). Application of BFR during moderate and fast treadmill walking modifies gait kinematics and exacerbates exercise-related sensations as well as blood lactate concentration.

Application of blood flow restriction in hypoxic environment augments muscle deoxygenation without compromising repeated sprint exercise performance.

What is the central question of this study? Does applying blood flow restriction during the rest periods of repeated sprint exercise in a hypoxic environment lead to greater local hypoxia within exercising muscles without compromising training workload? What is the main finding and its importance? Repeated sprint exercise with blood flow restriction administered during rest periods under systemic hypoxia led to severe local hypoxia within the exercised muscles without a reduction in power output. The maintained power output might be due to elevated neuromuscular activation. Accordingly, the proposed repeated sprint exercise in the current study may be an effective training modality. Repeated sprint exercise (RSE) is a popular training modality for a wide variety of athletic activities. The purpose of this study was to assess the combined effects of systemic hypoxia and blood flow restriction (BFR) on muscle deoxygenation and RSE performance. Twelve healthy young men performed a standard RSE training modality (five sets of 10s maximal sprint with a 60s rest) under four different conditions: (1) normoxic control (NC), normoxia (N, 20.9%) + control BFR (C, 0mmHg); (2) normoxic BFR (NB), normoxia (N, 20.9%) + BFR (B, 140mmHg); (3) hypoxic control (HC), hypoxia (H, 13.7%) + control BFR (C, 0mmHg); and (4) hypoxic BFR (HB): hypoxia (H, 13.7%) + BFR (B, 140mmHg). BFR was only administered during the rest period of the respective RSE trials. In the local exercising muscles, muscle oxygen saturation ( ) and neuromuscular activity were measured using near-infrared spectroscopy and surface electromyography, respectively. SmO2 was lower in systemic hypoxia conditions relative to normoxia conditions (P<0.05). A rther decrease in SmO2 was observed in HB relative to HC (Set 1: HC 70.0±17.5vs. HB 57.4±11.3%, P=0.001; Set 4: HC 67.5±14.6vs. HB 57.0±12.0%, P=0.013; Set 5: HC 61.0±15.3vs. HB 47.7±11.9%, P<0.001). No differences in RSE performance were observed between any of the conditions (P>0.05). Interestingly, an elevated neuromuscular activity was seen in response to the BFR, particularly during conditions of systemic hypoxia (P<0.05). Thus, RSE with BFR administered during rest periods under systemic hypoxia led to severe local hypoxia without compromising training workload.

Application of Current Knowledge of Blood Flow Restriction Training for Use on Upper Extremity Injuries

Blood flow restriction (BFR) utilizes a cuff or tourniquet to induce muscle hypoxia by maintaining arterial flow, while restricting venous return. This technique has recently gained popularity in healthy patients and patients undergoing rehabilitation. Two studies have shown that patients who use BFR, in addition to the standard therapy protocol, following an upper extremity injury (UEI) have reduced pain and improved Patient-Reported Wrist Evaluation scores. The use of BFR in the upper extremity of healthy patients and patients with a prior lower extremity injury have shown statistically significant improvements in muscle strength and muscle hypertrophy. Further studies focusing on BFR training following various upper extremity injuries are needed to determine the potential impact on clinical outcomes. The purpose of this review was to analyze the use of BFR following lower extremity injuries, summarize the literature of BFR for upper extremity injuries, and consider the application of BFR following upper extremity injuries in the future.

Use of Blood Flow Restriction Training Between North American Sports Medicine Practitioners: A Questionnaire-Based Survey

<h3>Research Objectives</h3> To profile current clinical application of blood flow restriction (BFR) training among active sports medicine practitioners in North America using an online questionnaire. To compare responses to position stand recommendations regarding BFR training methodology. <h3>Design</h3> Survey distributed through August and September of 2021. <h3>Setting</h3> Online. <h3>Participants</h3> Convenience sample of 72 clinicians actively practicing in the United States (n=67) and Canada (n=5) were included. Experience applying or prescribing BFR training was required. Individuals unfamiliar with written English were excluded. The survey link was distributed electronically through professional organizations, email list servs, and social media. <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> Demographics (profession, practice setting, years of experience), type of equipment, treatment parameters, observed side effects, and personal opinions on the efficacy and value of BFR training. <h3>Results</h3> Athletictrainers (48.6%) and physical therapists (41.7%) primarily completed the survey. Automatic inflated cuffs and KAATSU airbands were the most common units employed. Parameters varied between respondents for exercise prescription (e.g. load and volume) and occlusion settings. Populations for BFR implementation ranged from injured (93.1%) and post-surgery cases (88.4%) to healthy individuals for performance enhancement (9.4%). Respondents primarily followed position statement recommendations with individualized pressure selections specific to blood pressure for resistance (80.9%) and aerobic BFR (69.6%) modes. Side effects reported included delayed onset muscle soreness (66.2%), inability to continue treatment due to pain (28%), numbness (22.5%), and cold feeling in the extremity (19.7%). Physical therapists indicated higher confidence in safety (t= -2.291, p=0.026), understanding of practice recommendations (t= -2.615, p=0.011) and theoretical principles (t=-3.056, p=0.004) compared with athletic trainers. <h3>Conclusions</h3> BFR is a common modality in contemporary sports medicine settings. Variations in BFR application is evident in devices, exercise and occlusion parameters selected, and side effects observed. Practitioners appear to be compliant with practice recommendations regarding the adoption of individualized pressure prescription. <h3>Author(s) Disclosures</h3> N/A.

Acutemuscular and cardiovascular responses to high load training with pre-exercise blood flow restriction.

The purpose of this study is to examine the acute muscular and cardiovascular responses to applying blood flow restriction (BFR) before high-load training. Forty trained individuals visited the lab on three occasions. On Visit 1, participants completed paperwork and performed strength assessments. During Visits 2 and 3, participants completed four exercise conditions (one in each arm during each visit) as follows: (1) traditional resistance training (TRAD),(2) low load training with BFR (LLBFR),(3) low repetition high load training with pre-exercise BFR (PreBFR),and (4) low repetition traditional training (LRTRAD). Blood pressure, muscle thickness (MT), and isometric strength (ISO) were measured before and after exercise. Data aredisplayed as means (SD). Immediately following exercise, MT in TRAD was greater compared withPreBFR (mean difference = 0.18[0.30] cm, p < 0.001) and LRTRAD (mean difference = 0.28[0.30] cm, p < 0.001). In addition, LLBFR demonstrated greater MT compared withPreBFR (mean difference = 0.24[0.30] cm,p < 0.001]. Immediately following exercise, ISO was lower in TRAD compared withPreBFR (mean difference = 33.8[46.9]N,p < 0.001) and the LRTRAD condition (mean difference = 32.8[50.4]N,p < 0.001). In addition, ISO was lower in LLBFR compared withPreBFR (mean difference = 43.9 [47.4]N,p < 0.001)and LRTRAD (mean difference = 42.9 [43.8]N, p < 0.001). Immediately following exercise, systolic blood pressure was greater in TRAD compared withPreBFR and LRTRAD. The application of BFR before engaging in high-load training does not seem to augment the muscular responses to exercise when compared withtraditional high loads alone; however, it may pose less demand on the cardiovascular system.

Blood Flow Restriction Prevents The Drop In Blood Pressure Upon Head-up Tilt

Many astronauts develop orthostatic intolerance following spaceflight and this change may be more prevalent in females. Although the blood pressure response to standing should normalize in the weeks following their return to Earth, there may be emergencies where an immediate short-term solution is necessary. PURPOSE: To examine the effects of different levels of blood flow restriction on blood pressure and heart rate when a person is transitioned from supine to an upright position and determine whether this change differs based on sex. METHODS: 45 men and 44 women partook in this four-visit study. The first visit included the determination of the applied pressure for the different conditions, and familiarization with the tilt table protocol. Visits 2-4 were the experimental visits completed in a randomized order on the tilt table: 1) Sham, 2) Moderate, or 3) High pressure. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and 8 more times separated by 45 seconds. RESULTS: Data are presented as mean (SD) and as a change from the baseline measurement. Changes in systolic blood pressure were pressure dependent (High > Moderate > Sham). Notably, the application of blood flow restriction was able to prevent the drop in systolic blood pressure when moving from a supine to the head-up tilt position [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4), and Moderate vs Sham: 2.4 (8.4) mmHg]. Diastolic blood pressure increased following head-up tilt and changes were greatest with the High pressure with no differences between Moderate and Sham [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3), and Moderate vs Sham: 0.6 (5.1) mmHg]. Heart rate increased following head-up tilt and the change was initially greatest in the Sham condition [High vs Sham: -3.5 (9.1) mmHg, High vs Moderate: 0.5 (9.1), and Moderate vs Sham: -3.6 (9.3) mmHg]. However, heart rate changed the most in the High pressure condition by the end of the head-up tilt period. CONCLUSIONS: The application of blood flow restriction prevented the initial drop in blood pressure when transitioning from the supine to the upright position. This could be useful when astronauts need to exit the spacecraft quickly upon landing, where a failure to maintain blood pressure could be fatal.

Neuromuscular, Swelling, And Perceived Effort Responses Following Isotonic Versus Isokinetic Blood Flow Restriction Exercise

PURPOSE: The application of blood flow restriction (BFR) with resistance training has been applied to various exercise modalities, but no previous investigations have examined isotonic BFR vs isokinetic BFR. Therefore, the purpose of this study was to examine the neuromuscular, swelling, and rating of perceived exertion (RPE) responses following isotonic and isokinetic BFR exercise. METHODS: Fifteen (22 ± 2 years) women randomly performed (on separate days) 75 (1x30, 3x15) submaximal (30% of one repetition maximum [isotonic] or 30% maximal voluntary isometric contraction (MVIC) [isokinetic]) unilateral leg extensions with BFR (60% of total arterial occlusion pressure). Before and immediately after each exercise, subjects performed MVICs while electromyography (EMG) was simultaneously recorded from the vastus lateralis (VL) muscle. Ultrasound muscle thickness (MT) was assessed from the VL prior to and after the MVICs. RPE was recorded during all 4 sets. Separate 2 (Condition [Isotonic, Isokinetic]) × 2 (Time [pretest, posttest]) repeated measures ANOVAs were used to examine the EMG and MT responses. A separate 2 (Condition [Isotonic, Isokinetic]) × 4 (Time [set 1, set 2, set 3, set 4]) repeated measures ANOVAs was used to assess RPE. Paired samples t-tests were used to analyze percent change in MVIC torque. RESULTS: There was no significant (p = 0.294-0.823) interaction or main effect for normalized EMG amplitude. For EMG frequency and MT there were significant interactions (p = 0.008) that indicated greater decreases in EMG frequency following isotonic (13%) than isokinetic (6%) but similar increases in MT (22%). For RPE, there was no significant (p = 0.368) interaction, but there were significant (p = 0.004) main effects for Time (set 4 > set 3 > set 2 > set 1) and Condition (isotonic > isokinetic) (p = 0.018). Additionally, there was a greater (34.9%) decrease in MVIC following the isotonic than isokinetic (15.2%) condition. CONCLUSIONS: Isotonic BFR exercise elicited greater fatigue-induced changes in EMG frequency, MVIC, and perceived effort than isokinetic condition. Therefore, relative to isokinetic, isotonic BFR exercise may provide a more potent acute exercise response and discomfort, but this may not translate to chronic adaptations as there were similar EMG amplitude responses between conditions.

A narrative review of the effects of blood flow restriction on vascular structure and function.

Blood flow restriction is growing in popularity as a tool for increasing muscular size and strength. Currently, guidelines exist for using blood flow restriction alone and in combination with endurance and resistance exercise. However, only about 1.3% of practitioners familiar with blood flow restriction applications have utilized it for vascular changes, suggesting many of the guidelines are based on skeletal muscle outcomes. Thus, this narrative review is intended to explore the literature available in which blood flow restriction, or a similar application, assess the changes in vascular structure or function. Based on the literature, there is aknowledge gap in how applying blood flow restriction with relative pressures may alter the vasculature when applied alone, with endurance exercise, and with resistance exercise. In many instances, the application of blood flow restriction was not in accordance with the current guidelines, making it difficult to drawdefinitive conclusions as to how the vascular system would be affected. Additionally, several studies report no change in vascular structure or function, but few studies look at variables for both outcomes. By examining outcomes for both structure and function, investigators would be able to generate recommendations for the use of blood flow restriction to improve vascular structure and/or function in the future.

Greater neuromuscular fatigue following low-load blood flow restriction than non-blood flow restriction resistance exercise among recreationally active men.

The purpose of this study was to examine the acute effects of low-load blood flow restriction (LLBFR) and low-load non-BFR (LL) on neuromuscular function after a bout of standardized fatiguing leg extension muscle actions. Fourteen men (mean age ± SD = 23 ± 4 yr) volunteered to participate in this investigation and randomly performed LLBFR and LL on separate days. Resistance exercise consisted of 75 isotonic unilateral leg extension muscle actions performed at 30% of one-repetition maximum. Before (pretest) and after (posttest) performance of each bout of exercise, strength and neural assessments were determined. There were no pretest to posttest differences between LLBFR and LL for maximal voluntary isometric contraction (MVIC) torque or V wave/M wave responses (muscle compound action potentials assessed during a superimposed MVIC muscle action), which exhibited decreases (collapsed across condition) of 41.2% and 26.2%, respectively. There were pretest to posttest decreases in peak twitch torque (36.0%) and surface electromyography amplitude (sEMG) (29.5%) for LLBFR but not LL and larger decreases in voluntary activation for LLBFR (11.3%) than for LL (4.5%). These findings suggested that LLBFR elicited greater fatigue-induced decreases in several indexes of neuromuscular function relative to LL. Despite this, both LLBFR and LL resulted in similar decrements in performance as assessed by maximal strength.NEW & NOTEWORTHY The application of blood flow restriction induces greater acute neuromuscular fatigue relative to nonrestricted conditions. Resistance exercise with blood flow restriction elicited a greater reduction in twitch responses. These neuromuscular differences might explain the more favorable adaptations achieved with blood flow restriction that are likely a function of metabolic stress and subsequent changes in efferent neural drive.

Blood Flow Restriction Training for the Intervention of Sarcopenia: Current Stage and Future Perspective.

Sarcopenia is a geriatric syndrome that is characterized by a progressive and generalized skeletal muscle disorder and can be associated with many comorbidities, including obesity, diabetes, and fracture. Its definitions, given by the AWGS and EWGSOP, are widely used. Sarcopenia is measured by muscle strength, muscle quantity or mass and physical performance. Currently, the importance and urgency of sarcopenia have grown. The application of blood flow restriction (BFR) training has received increased attention in managing sarcopenia. BFR is accomplished using a pneumatic cuff on the proximal aspect of the exercising limb. Two main methods of exercise, aerobic exercise and resistance exercise, have been applied with BFR in treating sarcopenia. Both methods can increase muscle mass and muscle strength to a certain extent. Intricate mechanisms are involved during BFRT. Currently, the presented mechanisms mainly include responses in the blood vessels and related hormones, such as growth factors, tissue hypoxia-related factors and recruitment of muscle fiber as well as muscle satellite cells. These mechanisms contribute to the positive balance of skeletal muscle synthesis, which in turn mitigates sarcopenia. As a more suited and more effective way of treating sarcopenia and its comorbidities, BFRT can serve as an alternative to traditional exercise for people who have marked physical limitations or even show superior outcomes under low loads. However, the possibility of causing stress or muscle damage must be considered. Cuff size, pressure, training load and other variables can affect the outcome of sarcopenia, which must also be considered. Thoroughly studying these factors can help to better determine an ideal BFRT scheme and better manage sarcopenia and its associated comorbidities. As a well-tolerated and novel form of exercise, BFRT offers more potential in treating sarcopenia and involves deeper insights into the function and regulation of skeletal muscle.

Does the application of blood flow restriction during walking exercise influence the accuracy of indirect calorimetry?

ObjectivesIdentify whether the application of blood flow restriction (BFR) during walking influences fraction of expired oxygen (FeO2) and carbon dioxide (FeCO2) measures, key variables in the calculation of oxygen consumption (V̇O2) via indirect calorimetry. DesignRandomised cross-over. MethodsOn separate visits, sixteen participants completed four experimental sessions (order randomised), each comprising 10 min of treadmill exercise; i.e., with or without BFR (60% arterial occlusion pressure) combined with two different intensity levels (100% or 120% comfortable walking speed). For data analysis, walking speeds within the same condition (with or without BFR) were pooled, and the speed variance was controlled within the statistical model. The FeO2, FeCO2, V̇O2, volume of carbon dioxide production, minute ventilation (V̇E) and respiratory exchange ratio were extracted from the metabolic cart from the fifth min of the exercise period to the 3 min post-exercise. Measures were averaged across 2 min increments during exercise and 1 min increments post-exercise. ResultsCondition × time interactions were observed for FeO2 (p < 0.01) and FeCO2 (p < 0.01). Post hoc analysis identified within the BFR condition an increase in FeO2 (p < 0.01) during the exercise period and for 2 min post-exercise, while FeCO2 was decreased (p < 0.01) during the exercise period and 1 min post-exercise. A main effect of BFR and time was observed for V̇E (p ≤ 0.044) and V̇O2 (p ≤ 0.01). ConclusionsThe increase of FeO2 and decrease of FeCO2 during BFR walking likely reduces the validity of V̇O2 values calculated via indirect calorimetry.

Acute Effects of Local Ischemic Hypoxia and Systemic Hypoxemia on Neuromuscular and Cognitive Function

Rivera, Paola M., Chris E. Proppe, Esther Beltran, and Ethan C. Hill. Acute effects of local ischemic hypoxia and systemic hypoxemia on neuromuscular and cognitive function. High Alt Med Biol. 23:18-25, 2022. Background: The application of blood flow restriction (BFR) induces local ischemic hypoxia within the muscle(s) distal to the restriction device. Systemic hypoxemia via oxygen or barometric pressure manipulation achieves whole-body hypoxia and thus may be a more potent exercise adjunct than BFR. Therefore, the purpose of this study was to examine the acute effects of local ischemic hypoxia versus systemic hypoxemia on maximal voluntary isometric contraction (MVIC) torque, electromyographic amplitude (EMG AMP), EMG mean power frequency (MPF), and cognition. Materials and Methods: Twelve recreationally trained women (mean age ± standard deviation = 21 ± 1.6 years) performed 75 submaximal (1 × 30, 3 × 15) unilateral leg extension muscle actions under normoxia, local ischemic hypoxia, and systemic hypoxemia. Before and immediately after the 75 repetitions, MVIC muscle actions were performed, and surface EMG was simultaneously assessed from the vastus lateralis. Cognitive function was assessed immediately after each exercise using the Automated Neuropsychological Assessment Metrics (ANAM). Separate repeated-measures analyses of variance (ANOVAs) were performed to examine changes in MVIC, reaction time, EMG AMP, and EMG MPF responses during the MVIC muscle actions. Results: There were no significant (p = 0.21-0.953) Condition × Time interactions for MVIC, EMG AMP, or EMG MPF but a significant (p < 0.001-0.005) main effect for the Time collapsed across Condition for MVIC torque (pretest 238.8 ± 19.5, posttest 212.7 ± 20.1 Nm) and EMG MPF (88.5% ± 1.4% of pretest). There were no significant (p = 0.503) differences in reaction time among Conditions. Conclusions: The findings of the present study suggest that all three conditions elicited comparable acute changes in performance as assessed by MVIC torque that were associated with no changes in muscle activation but decrease in action potential conduction velocity. Therefore, the application of local ischemic hypoxia or systemic hypoxemia during low-load resistance exercise can be used to elicit similar acute physiological responses and not adversely affect cognitive function relative to nonhypoxic conditions.

Effects of blood flow restriction and neuromuscular electrical stimulation on muscle hypertrophy in adults: a meta-analysis

Background: Skeletal muscle mass is a key determinant for the preservation of an individual’s health throughout the life span. The application of blood flow restriction (BFR) alone has been shown to attenuate skeletal muscle atrophy in the lower limb following periods of immobilisation. However, it has not been found to provide a sufficient stimulus to promote hypertrophy without the addition of low-load resistance training (20-30% of 1-repetition maximum). Neuromuscular electrical stimulation (NMES) has been used extensively as a rehabilitation technique to attenuate muscle atrophy.

Blood Flow Restriction Training for the Shoulder: A Case for Proximal Benefit

Background: Although blood flow restriction (BFR) is becoming increasingly popular in physical therapy and athletic training settings, little is known about the effects of BFR combined with low-intensity exercise (LIX) on muscles proximal to the site of occlusion. Hypothesis/Purpose: Determine whether LIX combined with BFR applied distally to the shoulder on the brachial region of the arm (BFR-LIX) promotes greater increases in shoulder lean mass, rotator cuff strength, endurance, and acute increases in shoulder muscle activation compared with LIX alone. We hypothesized that BFR-LIX would elicit greater increases in rotator cuff strength, endurance, and muscle mass. We also hypothesized that the application of BFR would increase EMG amplitude in the shoulder muscles during acute exercise. Study Design: Controlled laboratory study. Methods: 32 healthy adults were randomized into 2 groups (BFR group, 13 men, 3 women; No-BFR group, 10 men, 6 women) who performed 8 weeks of shoulder LIX (2 times per week; 4 sets [30/15/15/fatigue]; 20% maximum) using common rotator cuff exercises (cable external rotation [ER], cable internal rotation [IR], dumbbell scaption, and side-lying dumbbell ER). The BFR group also trained with an automated tourniquet placed at the proximal arm (50% occlusion). Regional lean mass (dual-energy x-ray absorptiometry), isometric strength, and muscular endurance (repetitions to fatigue [RTF]; 20% maximum; with and without 50% occlusion) were measured before and after training. Electromyographic amplitude (EMGa) was recorded from target shoulder muscles during endurance testing. A mixed-model analysis of covariance (covaried on baseline measures) was used to detect within-group and between-group differences in primary outcome measures (α = .05). Results: The BFR group had greater increases in lean mass in the arm (mean ± 95% CI: BFR, 175 ± 54 g; No BFR, –17 ± 77 g; P < .01) and shoulder (mean ± 95% CI: BFR, 278 ± 90 g; No BFR, 96 ± 61 g; P < .01), isometric IR strength (mean ± 95% CI: BFR, 2.9 ± 1.3 kg; No BFR, 0.1 ± 1.3 kg; P < .01), single-set RTF volume (repetitions × resistance) for IR (~1.7- to 2.1-fold higher; P < .01), and weekly training volume (weeks 4, 6-8, ~5%-22%; P < .05). Acute occlusion (independent of group or timepoint) yielded increases in EMGa during RTF (~10%-20%; P < .05). Conclusion: Combined BFR-LIX may yield greater increases in shoulder and arm lean mass, strength, and muscular endurance compared with fatiguing LIX alone during rotator cuff exercises. These findings may be due, in part, to a greater activation of shoulder muscles while using BFR. Clinical Relevance: The present study demonstrates that BFR-LIX may be a suitable candidate for augmenting preventive training or rehabilitation outcomes for the shoulder.