The Application of Blood Flow Restriction

Measurements of Arterial Occlusion Pressure Using Hand-Held Devices

ABSTRACT

Vehrs, PR, Reynolds, S, Allen, J, Barrett, R, Blazzard, C, Burbank, T, Hart, H, Kasper, N, Lacey, R, Lopez, D, and Fellingham, GW. Measurements of arterial occlusion pressure using hand-held devices. J Strength Cond Res 38(5): 873-880, 2024-Arterial occlusion pressure (AOP) of the brachial artery was measured simultaneously using Doppler ultrasound (US), a hand-held Doppler (HHDOP), and a pulse oximeter (PO) in the dominant (DOM) and nondominant (NDOM) arms of males ( n = 21) and females ( n = 23) using continuous (CONT) and incremental (INCR) cuff inflation protocols. A mixed-model analysis of variance revealed significant ( p < 0.05) overall main effects between AOP measured using a CONT (115.7 ± 10.9) or INCR (115.0 ± 11.5) cuff inflation protocol; between AOP measured using US (116.3 ± 11.2), HHDOP (115.4 ± 11.2), and PO (114.4 ± 11.2); and between males (120.7 ± 10.6) and females (110.5 ± 9.4). The small overall difference (1.81 ± 3.3) between US and PO measures of AOP was significant ( p < 0.05), but the differences between US and HHDOP and between HHDOP and PO measures of AOP were not significant. There were no overall differences in AOP between the DOM and NDOM arms. Trial-to-trial variance in US measurements of AOP was not significant when using either cuff inflation protocol but was significant when using HHDOP and PO and a CONT cuff inflation protocol. Bland-Altman plots revealed reasonable limits of agreement for both HHDOP and PO measures of AOP. The small differences in US, HHDOP, and PO measurements of AOP when using CONT or INCR cuff inflation protocols are of minimal practical importance. The choice of cuff inflation protocol is one of personal preference. Hand-held Doppler of PO can be used to assess AOP before using blood flow restriction during exercise.

Blood Flow Restriction during Walking Does Not Impact Body Composition or Performance Measures in Highly Trained Runners

Blood flow restriction (BFR) is a commonly used training modality that has been demonstrated to enhance muscle characteristics such as size and function. The purpose of this study was to determine if a 4-week walking program with or without BFR in healthy, active adults has an effect on body composition, anaerobic, and aerobic running performance. Thirty-three participants, randomized among three groups, completed the walking program, which included five sets of 2 min walking intervals with 1 min rest, with or without BFR, or 10 min walking with BFR. Assessments completed before and after the walking program included body composition, 40-yard sprints, and a VO2MAX test on a treadmill. A two-way ANOVA revealed no changes among the groups nor for any variables at any time (p > 0.05). Additionally, one main effect for time indicated the VO2 at V-slope threshold was greater following training for all groups combined (p = 0.001). The results demonstrate that low volume and intensity walking with BFR for 4 weeks did not provide a sufficient stimulus for changing body composition or performance metrics in a group of very active adults. Longer or more isolated exposure of BFR on the limbs may contribute to more pronounced adaptations.

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

BACKGROUND

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

CASE DESCRIPTIONS

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

RESULTS

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

CONCLUSION

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

Influence of cuff stiffness on hemodynamics and perceived cuff pressure in the upper extremities in males and females: implications for practical blood flow restriction training

BACKGROUND

Practical blood flow restriction (pBFR) during exercise is a cost-saving alternative to traditional blood flow restriction using pneumatic cuffs, particularly when exercising in a group setting. Depending on the pBFR technique, several factors (e.g., cuff width, limb circumference) have already been shown to be of importance when applying the pBFR pressure. Given that elastic cuffs are often used for pBFR, the cuff stiffness might be an additional influencing factor. Therefore, the present study compared the acute effects of three elastic cuffs with identical width but different stiffness (high stiffness (HS), medium stiffness (MS), and low stiffness (LS)) on hemodynamic measures and perceived cuff pressure at rest.

METHODS

In a randomized, counter-balanced cross-over study, 36 young and normotensive participants completed three experimental trials. After a 10-min rest period in supine position, the cuff was loosely and proximally applied to the right upper arm. Following baseline data recording, the cuff was successively tightened in 10%-increments with respect to the limb circumference (%overlap) until arterial blood flow was occluded. At baseline and during each %overlap, systolic peak blood flow velocity of the brachial artery, rating of perceived cuff pressure, as well as muscle oxygen saturation and total hemoglobin concentration of the biceps brachii muscle were recorded.

RESULTS

The %overlap required to occlude arterial blood flow was different between the three cuffs (HS: 30.9 ± 3.8%, MS: 43.9 ± 6.1%, LS: 54.5 ± 8.3%). Furthermore, at 30% overlap, systolic peak blood flow velocity was lower when applying the HS (9.0 ± 10.9 cm∙s- 1) compared to MS (48.9 ± 21.9 cm∙s- 1) and LS cuff (62.9 ± 19.1 cm∙s- 1). Rating of perceived cuff pressure at 30% overlap was higher when using the HS (6.5 ± 1.5 arbitrary unit (a.u.)) compared to MS (5.1 ± 1.4 a.u.) and LS cuff (4.9 ± 1.5 a.u.) with no difference between the MS and LS cuff. However, muscle oxygen saturation and total hemoglobin concentration were not different between the three cuffs.

CONCLUSIONS

The present study revealed that the cuff stiffness influenced blood flow velocity and arterial occlusion pressure. Therefore, cuff stiffness seems an important factor for the application of pBFR.

Improved interference control after exercise with blood flow restriction and cooling is associated with but not mediated by increased lactate

BACKGROUND

To evaluate the effects of recumbent sprint interval exercise with and without blood flow restriction and body cooling on interference control and whether the changes in interference control can be explained by the changes in blood lactate.

METHODS

85 participants (22 SD 3 years old) completed 1 familiarization visit and then 5 experimental visits in a randomized order: exercise only (Ex), exercise with blood flow restriction (ExB), exercise with cooling (ExC), and exercise with blood flow restriction and cooling (ExBC), and non-exercise control (Con). Measurements of blood lactate and the Stroop Color Word Test were performed before and after exercise. Each bout began with a 15-minute low-moderate intensity warm-up, followed by five 20-second "all out" sprints separated by 40 s of active recovery. Bayes Factors (BF10) quantified evidence for or against the null hypothesis. Within-subject mediation analysis quantified the indirect effect of changes in blood lactate (mediator) on the change in interference control (each exercise condition vs. Con).

RESULTS

Bayesian pairwise comparisons found that only ExC [σ: -0.37 (-0.59, -0.15)] and ExBC [σ: -0.3 (-0.53, -0.09)] produced changes in incongruent reaction time different from that of Con. There was also evidence that all exercise conditions increased blood lactate (BF10 = 8.65e+29 - 1.9e+32) and improved congruent reaction time (BF10 = 4.01 - 15.371) compared to that of Con. There was no evidence to show that changes in lactate mediated the change in incongruent reaction time.

CONCLUSIONS

Both exercise with body cooling and when body cooling was combined with blood flow restriction presented favorable changes in incongruent reaction time (a marker of interference control), which might not be explained by the changes in systemic blood lactate concentration.

Use of a handheld Doppler to measure brachial and femoral artery occlusion pressure

Objective: Measurement of arterial occlusion pressure (AOP) is essential to the safe and effective use of blood flow restriction during exercise. Use of a Doppler ultrasound (US) is the "gold standard" method to measure AOP. Validation of a handheld Doppler (HHDOP) device to measure AOP could make the measurement of AOP more accessible to practitioners in the field. The purpose of this study was to determine the accuracy of AOP measurements of the brachial and femoral arteries using an HHDOP. Methods: We simultaneously measured AOP using a "gold standard" US and a HHDOP in the dominant and non-dominant arms (15 males; 15 females) and legs (15 males; 15 females). Results: There were no differences in limb circumference or limb volume in the dominant and non-dominant arms and legs between males and females or between the dominant and non-dominant arms and legs of males and females. The differences between US and HHDOP measures of AOP in the dominant and non-dominant arms and legs were either not significant or small (<10 mmHg) and of little practical importance. There were no sex differences in AOP measurements of the femoral artery (p > 0.60). Bland-Altman analysis yielded an average bias (-0.65 mmHg; -2.93 mmHg) and reasonable limits of agreement (±5.56 mmHg; ±5.58 mmHg) between US and HHDOP measures of brachial and femoral artery AOP, respectively. Conclusion: HHDOP yielded acceptable measures of AOP of the brachial and femoral arteries and can be used to measure AOP by practitioners for the safe and effective use of blood flow restriction. Due to the potential differences in AOP between dominant and non-dominant limbs, AOP should be measured in each limb.

Effects of Sex and Cuff Pressure on Physiological Responses during Blood Flow Restriction Resistance Exercise in Young Adults

PURPOSE

The purpose of this study was to examine the physiological responses resulting from an acute blood flow restriction resistance exercise bout with two different cuff pressures in young, healthy men and women.

METHODS

Thirty adults (18-30 yr) completed a bilateral leg extension blood flow restriction bout consisting of four sets (30-15-15-15 repetitions), with cuffs applied at pressures corresponding to 40% and 60% of the minimum arterial occlusion pressure (AOP) needed to completely collapse the femoral arteries. During each of these conditions (40% and 60% AOP), physiological measures of near-infrared spectroscopy (NIRS) and EMG amplitude (EMG AMP) were collected from the dominant or nondominant vastus lateralis. After each set, ratings of perceived exertion (RPE) were collected, whereas only at baseline and at the end of the bout, mean arterial pressure (MAP) was assessed. Separate mixed-factorial ANOVA models were used to examine mean differences in the change in EMG AMP and NIRS parameters during each set. The absolute RPE and MAP values were also examined with separate ANOVAs. A P value ≤0.05 was considered statistically significant.

RESULTS

Regardless of sex or cuff pressure, the change in EMG AMP was lower in set 1 (14.8%) compared with the remaining sets (22.6%-27.0%). The 40% AOP condition elicited the greatest changes in oxy[heme] and deoxy[heme], while also providing lower RPEs. For MAP, there was an effect for time such that MAP increased from preexercise (87.5 ± 4.3 mm Hg) to postexercise (104.5 ± 4.1 mm Hg).

CONCLUSIONS

The major findings suggested that the 40% AOP condition permitted the greatest amount of recovery during the interset rest. In addition, there did not seem to be any meaningful sex-related difference in this sample of young healthy adults.

Acute muscular and cardiovascular responses to high load training with pre-exercise blood flow restriction

PURPOSE

The purpose of this study is to examine the acute muscular and cardiovascular responses to applying blood flow restriction (BFR) before high-load training.

METHODS

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.

RESULTS

Data are displayed as means (SD). Immediately following exercise, MT in TRAD was greater compared with PreBFR (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 with PreBFR (mean difference = 0.24[0.30] cm, p < 0.001]. Immediately following exercise, ISO was lower in TRAD compared with PreBFR (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 with PreBFR (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 with PreBFR and LRTRAD.

CONCLUSION

The application of BFR before engaging in high-load training does not seem to augment the muscular responses to exercise when compared with traditional high loads alone; however, it may pose less demand on the cardiovascular system.

Blood flow restriction during high-intensity interval cycling exacerbates psychophysiological responses to a greater extent in females than males

This study aimed to characterize neuromuscular, perceptual, and cardiorespiratory responses to high-intensity interval training (HIIT) with superimposed blood flow restriction in males and females. Twenty-four, healthy individuals (n = 12 females) completed two cycling HIIT protocols to task failure (1-min work phases at 90% of peak power output interspersed by 1-min rest phases). The blood flow restriction (BFR) and control (CON) protocols were identical except for the presence and absence of BFR during rest phases, respectively. The interpolated twitch technique, including maximal voluntary isometric knee extension (MVC) and femoral nerve electrical stimuli, was performed at baseline, every six intervals, and task failure. Perceptual and cardiorespiratory responses were recorded every three intervals and continuously during exercise, respectively. Bayesian inference was used to obtain the joint posterior distribution for all parameters and evidence of an effect was determined via the marginal posterior probability (PP). The BFR shortened task duration by 57.3% compared with CON (PP > 0.99), without a sex difference. The application of BFR exacerbated the rate of decline in neuromuscular measures (MVC and twitch force output), increase of perceptual responses (perceived effort, pain, dyspnea, fatigue), and development of cardiorespiratory parameters (minute ventilation and heart rate), compared with CON (PP > 0.95). In addition, BFR exacerbated the neuromuscular, perceptual, and cardiorespiratory responses to a greater extent in females than males (PP > 0.99). Our results suggest that superimposition of blood flow restriction exacerbates psychophysiological responses to a HIIT protocol to a greater extent in females than males.NEW & NOTEWORTHY To our knowledge, no study has explored sex differences in the neuromuscular, perceptual, and cardiorespiratory indices characterizing exercise tolerance during high-intensity interval training (HIIT) with blood flow restriction (BFR) applied only during rest periods. Our results suggest that BFR elicited a decline in exercise performance that could be attributed to integration of psychophysiological responses. However, this integration was sex-dependent where females demonstrated an exacerbated rate of change in these responses compared with males.

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

Background

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

Purpose

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

Methods

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

Results

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

Conclusion

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

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.

The Effects of Blood Flow Restriction in Patients Undergoing Knee Surgery: A Systematic Review and Meta-analysis

BACKGROUND

Blood flow restriction (BFR) training has been shown to have beneficial effects in reducing quadriceps muscle atrophy and improving strength in patients with various knee pathologies. Furthermore, the effectiveness of BFR training in patients undergoing knee surgery has been investigated to determine if its use can improve clinical outcomes.

PURPOSE/HYPOTHESIS

The purpose of this study was to conduct a systematic review and meta-analysis to examine the effectiveness of BFR training in patients undergoing knee surgery. We hypothesized that BFR, before or after surgery, would improve clinical outcomes as well as muscle strength and volume.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

This systematic review and meta-analysis of peer-reviewed literature was conducted using PubMed, Embase, and Cochrane databases from 1980 to present. Search results were limited to those assessing BFR training in patients undergoing knee surgery published in a scientific peer-reviewed journal in English. Selected studies subsequently underwent data extraction, methodological quality assessment, and data analysis.

RESULTS

Eleven studies were eligible, including anterior cruciate ligament reconstruction (n = 10) and knee arthroscopy (n = 1). Two studies specifically assessed BFR use in the preoperative time frame. For the meta-analysis, including 4 studies, the primary outcome variables included the cross-sectional area of the quadratus femoris muscle group assessed with magnetic resonance imaging or ultrasonography, and patient-reported outcome measure scores. The results demonstrated that BFR use in the postoperative time period can lead to a significant improvement in the cross-sectional area when quantifying muscle atrophy. However, there were no significant differences found for patient-reported outcome measures between the included studies. It should be noted that 4 of the included papers in this review reported increases in clinical strength when using BFR in the postoperative setting. Last, preoperative BFR training did not show any significant clinical benefit between the 2 studies.

CONCLUSION

This is the first systematic review and meta-analysis to study the effects of BFR in patients undergoing knee surgery. The results of this analysis show that BFR in the postoperative period after knee surgery can improve quadriceps muscle bulk compared with a control group. However, future research should examine the effects of preconditioning with BFR before surgery. Lastly, BFR protocols need to be further investigated to determine which provide the best patient outcomes. This will help standardize this type of treatment modality for future studies.

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

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

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

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

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

Does Blood Flow Restriction Therapy Improve Leg Strength in Patients With a Painful Total Knee Arthroplasty?

BACKGROUND

Blood flow restriction (BFR) therapy has been proposed to help patients build strength with fewer repetitions than standard physical therapy (PT). We sought to determine if BFR would improve quadriceps and hamstring strength in patients with instability and perceived weakness >1 year after primary total knee arthroplasty (TKA).

METHODS

We retrospectively reviewed 48 patients with painful TKAs and flexion instability as well as quadriceps and hamstring weakness who performed a 6-week PT program and received isokinetic strength measurements (ISMs). Thirty-six patients completed a standard PT program (non-BFR) and 12 patients completed a BFR regimen. ISMs were taken before and after PT to quantify quadriceps and hamstring power, torque, and work compared to the contralateral leg. Statistical analysis was conducted on pre-PT and post-PT ISMs and decisions for revision surgery.

RESULTS

There were no differences in ISMs after PT between the BFR and non-BFR groups. The non-BFR group showed statistically significant strength improvements in flexion but not extension (+28.7%-32.8%, P = .0145-.255). Although no significant difference was found in the BFR group, they saw improvements in all extension strength metrics (19.4%-23.4%, P = .3315-.3901) and flexion (25.7%-29.9%, P = .1994-.2392). No difference was observed between the groups in the rates of subsequent revision TKA (8.3% vs 16.7%, P = .3362).

CONCLUSION

BFR did not improve quadriceps and hamstring strength compared to PT alone in patients with instability and weakness after TKA. Over 80% of total patients chose to avoid revision TKA after completion of focused PT with or without BFR.

Physiological Adaptations to High-Intensity Interval Training Combined with Blood Flow Restriction in Masters Road Cyclists

PURPOSE

High-intensity interval training (HIIT) and blood flow restriction (BFR) training have been used to enhance athletic performance and cardiovascular health. Combining these training modalities might be an effective training modality for masters athletes who seek to enhance athletic performance and to reduce cardiovascular risks.

METHODS

Fifty masters road cyclists age 35-49 yr were randomly assigned to the continuous exercise training (n = 16), continuous plus HIIT (n = 17), and continuous plus BFR training combined with HIIT (BFRIT; n = 17) for 12 wk. Both HIIT and BFRIT were performed on a cycle ergometer twice a week.

RESULTS

Maximal oxygen consumption (V̇O2max) increased in the HIIT and BFRIT groups (P < 0.05). This was accompanied by significant improvements in maximal cardiac output and stroke volume (P < 0.05). Forty-kilometer time trial performance improved in all three groups (P < 0.05). Peak power output increased in both HIIT and BFRIT groups (P < 0.05). Flow-mediated dilation in both brachial and popliteal arteries increased in all three groups (all P < 0.05). There were no significant changes in carotid intima-media thickness and arterial stiffness in any of the groups. Total lean mass, muscle cross-sectional area and thickness in rectus femoris and vastus lateralis, and peak torque of isokinetic knee extension increased only in the BFRIT group (all P < 0.05). Tissue saturation index decreased only in the BFRIT group (P < 0.05). Changes in 40-km time trial performance were associated with corresponding changes in V̇O2max (r = -0.312, P = 0.029) and peak isokinetic extensor torque (r = -0.432, P = 0.002).

CONCLUSIONS

Including HIIT particularly with BFR in the routine continuous training may be more effective in enhancing performance and physiological functions in masters road cyclists.

A comparison of variability between absolute and relative blood flow restriction pressures

Recommendations are that blood flow restriction (BFR) be applied relative to arterial occlusion pressure (AOP) to provide a similar stimulus.

PURPOSE

Compare variability of the change in blood flow, shear rate, and discomfort between recommended relative pressures and an absolute pressure.

METHODS

During one visit, brachial arterial blood flow was measured in 91 participants using pulse-wave Doppler ultrasonography. After 5-min seated rest, AOP was measured. Following another 5-min rest, blood flow and discomfort were assessed twice before cuff inflation as controls (C1 and C2), then again with a cuff inflated to each BFR pressure (all measures separated by 1-min). Change scores from C1 to all subsequent measures were calculated (i.e., C2-C1; 40%AOP-C1; 80%AOP-C1; 100mmHg-C1). Variability of the changes were compared via pairwise modified Pitman-Morgan tests (α=.008).

RESULTS

Variance (95%CI) of the change for blood flow (mL/min), shear rate (1/sec), and discomfort (AU) had similar trends. C2-C1 differed from all conditions (all p<.001), 40%AOP-C1 differed from 80%AOP-C1 and 100mmHg-C1 (all p<.001), which did not differ (both p≥.117). Blood flow: C2-C1=469.79 (357.90, 644.07), 40%AOP-C1=1263.18 (962.34, 1731.80), 80%AOP-C1=1752.90 (1335.42, 2403.18), 100mmHg-C1=1603.18 (1221.36, 2197.92); Shear rate: C2-C1=6248.24 (4760.10, 8566.15), 40%AOP-C1=14625.30 (11142.06, 20050.95), 80%AOP-C1=22064.02 (16809.13, 30249.27), 100mmHg-C1=20778.76 (15829.98, 28487.21); Discomfort: C2-C1=0.07 (0.05, 0.08), 40%AOP-C1=2.03 (1.55, 2.78), 80%AOP-C1=4.26 (3.25, 5.84), 100mmHg-C1=4.50 (3.43, 6.17).

CONCLUSION

Contrary to previous suggestions, applying relative pressures does not necessarily guarantee a similar stimulus. It seems that higher pressures produce more variable changes even if the external pressure applied is made relative to each individual. This article is protected by copyright. All rights reserved.

An Overview of Blood Flow Restriction Physiology and Clinical Considerations

ABSTRACT

The utilization of blood flow restriction has garnished considerable attention due to its widespread application and benefits that include strength enhancement, muscle hypertrophy, and increased level of function for specific populations. Blood flow restriction induces a hypoxic environment within a muscle group, initiating a metabolic cascade that stimulates muscle protein synthesis, altered gene regulation of muscle satellite cells, and increased muscle fiber recruitment, ultimately resulting in improved strength and endurance. When using blood flow restriction, consideration of the individual patient, occlusion pressure, cuff width, and cuff size are paramount. Blood flow restriction has been proven to be a consistently safe and effective tool for augmenting rehabilitative regimens for the upper and lower extremity.

The feasibility, safety, and efficacy of upper limb garment-integrated blood flow restriction training in healthy adults

Background

Blood flow restriction training (BFR) has been demonstrated to increase muscle hypertrophy and strength, but has logistical and cost barriers. Garment-integrated BFR has the potential to reduce these barriers by lowering equipment demands and cost. The primary aim of the study was to explore the feasibility of garment-integrated BFR in the upper limb of healthy adults, with a secondary aim of exploring safety and efficacy.

Methods

Physically active and otherwise healthy participants with no previous experience with BFR were sought. Eligible participants completed a five-week garment-integrated BFR programme that involved completing two sessions per week. Feasibility was determined by a priori defined thresholds for recruitment, adherence to the garment-integrated BFR programme, and data collection. Safety was determined by recording adverse events and by monitoring for total arterial occlusion pressure using a fingertip pulse oximeter. Efficacy was determined by measuring push-ups to volitional failure, arm girth, and number of prescribed repetitions completed. Feasibility and safety outcomes were reported descriptively or as a proportion with associated 95% confidence intervals (95% CI). Mean change, 95% CIs, and associated effect sizes were calculated for efficacy outcomes.

Results

Twenty-eight participants were included (15 men, 13 women; mean age 31.6 years [±9.1]) and 27 successfully completed the study. Participants were successfully recruited within three months and 278/280 sessions were successfully completed (adherence=99.3%, 95% CI 97.4%, 99.9%). Minimal adverse events were reported; one incident of localised bruising (0.36%, 95% CI 0.06%, 2.0%) and three incidences of excessive pain during or post-exercise from two separate participants (1.07%, 95% CI 0.03%, 3.1%). 82/2240 pulse oximeter readings were not recorded (3.7%, 95% CI 2.9%, 4.5%). Mean push-ups to volitional failure increased by 40% (mean change=8.0, 95% CI 6, 10, d=1.40). Mean arm girth and number of prescribed repetitions completed were unchanged.

Conclusions

Garment-integrated BFR is feasible and has no signal of important harm in the upper limb of healthy adults, and could proceed to a future trial with stop/go criteria for randomisation. Further work is required to investigate the efficacy of garment-integrated BFR and determine its equivalence or superiority compared to existing BFR methods.

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

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

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

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

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

Rotator cuff strength is not augmented by blood flow restriction training

OBJECTIVE

Blood flow restriction (BFR) training utilizes a tourniquet applied to the upper or lower extremities (UE or LE) to occlude blood flow while exercising. BFR training may help augment strength in muscles that are proximal to BFR cuff application. However, prior studies have failed to demonstrate augmented strength gains in the rotator cuff when the tourniquet is applied to the UE. The purpose of this study was to evaluate if a protocol consisting of LE exercises, performed with BFR, followed by rotator cuff exercises was superior in augmenting strength, and cross-sectional area (CSA) of the rectus femoris, in untrained subjects when compared to a non-BFR training group.

DESIGN

Randomized controlled trial.

SETTING

University.

PARTICIPANTS

Thirty-five subjects (mean age 25.8 ± 1.6 y) randomized to a BFR or non-BFR group.

MAIN OUTCOME MEASURES

Muscular strength measured via hand held dynamometer and the CSA of the dominant rectus femoris was measured by diagnostic ultrasound.

RESULTS

Both groups experienced significant gains in LE and rotator cuff strength. Strength increased in the BFR group by 11.6% for the supraspinatus, 34.1% for shoulder ER, 23.4% for the quadriceps, and 17.1% for the hamstrings. Strength increased in the non-BFR group by 7.3% for the supraspinatus, 20% for shoulder ER, 12.8% for the quadriceps, and 10.7% for the hamstrings. However, there were no differences in strength gains between groups. Neither group experienced a significant increase in CSA for the rectus femoris.

CONCLUSION

The BFR protocol used in this study did not augment strength for the rotator cuff in subjects who also performed LE exercises under occlusion.

Current Techniques Used for Practical Blood Flow Restriction Training: A Systematic Review

ABSTRACT

Bielitzki, R, Behrendt, T, Behrens, M, and Schega, L. Current techniques used for practical blood flow restriction training: a systematic review. J Strength Cond Res 35(10): 2936-2951, 2021-The purpose of this article was to systematically review the available scientific evidence on current methods used for practical blood flow restriction (pBFR) training together with application characteristics as well as advantages and disadvantages of each technique. A literature search was conducted in different databases (PubMed, Web of Science, Scopus, and Cochrane Library) for the period from January 2000 to December 2020. Inclusion criteria for this review were (a) original research involving humans, (b) the use of elastic wraps or nonpneumatic cuffs, and (c) articles written in English. Of 26 studies included and reviewed, 15 were conducted using an acute intervention (11 in the lower body and 4 in the upper body), and 11 were performed with a chronic intervention (8 in the lower body, 1 in the upper body, and 2 in both the upper and the lower body). Three pBFR techniques could be identified: (a) based on the perceptual response (perceived pressure technique), (b) based on the overlap of the cuff (absolute and relative overlap technique), and (c) based on the cuffs' maximal tensile strength (maximal cuff elasticity technique). In conclusion, the perceived pressure technique is simple, valid for the first application, and can be used independently of the cuffs' material properties, but is less reliable within a person over time. The absolute and relative overlap technique as well as the maximal cuff elasticity technique might be applied more reliably due to markings, but require a cuff with constant material properties over time.

Time to Save Time: Beneficial Effects of Blood Flow Restriction Training and the Need to Quantify the Time Potentially Saved by Its Application During Musculoskeletal Rehabilitation

The main goal of musculoskeletal rehabilitation is to achieve the pre-injury and/or pre-surgery physical function level with a low risk of re-injury. Blood flow restriction (BFR) training is a promising alternative to conventional therapy approaches during musculoskeletal rehabilitation because various studies support its beneficial effects on muscle mass, strength, aerobic capacity, and pain perception. In this perspective article, we used an evidence-based progressive model of a rehabilitative program that integrated BFR in 4 rehabilitation phases: (1) passive BFR, (2) BFR combined with aerobic training, (3) BFR combined with low-load resistance training, and (4) BFR combined with low-load resistance training and traditional high-load resistance training. Considering the current research, we propose that a BFR-assisted rehabilitation has the potential to shorten the time course of therapy to reach the stage where the patient is able to tolerate resistance training with high loads. The information and arguments presented are intended to stimulate future research, which compares the time to achieve rehabilitative milestones and their physiological bases in each stage of the musculoskeletal rehabilitation process. This requires the quantification of BFR training-induced adaptations (eg, muscle mass, strength, capillary-to-muscle-area ratio, hypoalgesia, molecular changes) and the associated changes in performance with a high measurement frequency (≤1 week) to test our hypothesis. This information will help to quantify the time saved by BFR-assisted musculoskeletal rehabilitation. This is of particular importance for patients, because the potentially accelerated recovery of physical functioning would allow them to return to their work and/or social life earlier. Furthermore, other stakeholders in the health care system (eg, physicians, nurses, physical therapists, insurance companies) might benefit from that with regard to work and financial burden.

Blood Flow Restriction Training Can Improve Peak Torque Strength in Chronic Atrophic Postoperative Quadriceps and Hamstrings Muscles

PURPOSE

To report a prospective study of patients who underwent blood flow restriction training (BFRT) for marked quadriceps or hamstring muscle deficits after failure to respond to traditional rehabilitation after knee surgery.

METHODS

The BFRT protocol consisted of 4 low resistance exercises (30% of 1 repetition maximum): leg press, knee extension, mini-squats, and hamstring curls with 60% to 80% limb arterial occlusion pressure. Knee peak isometric muscle torque (60° flexion) was measured on an isokinetic dynamometer.

RESULTS

Twenty-seven patients (18 females, 9 males; mean age, 40.1 years) with severe quadriceps and/or hamstrings deficits were enrolled from April 2017 to January 2020. They had undergone a mean of 5.3 ± 3.5 months of outpatient therapy and 22 ± 10 supervised therapy visits and did not respond to traditional rehabilitation. Prior surgery included anterior cruciate ligament reconstruction, partial or total knee replacements, meniscus repairs, and others. All patients completed 9 BFRT sessions, and 14 patients completed 18 sessions. The mean quadriceps and hamstrings torque deficits before BFRT were 43% ± 16% and 38% ± 14%, respectively. After 9 BFRT sessions, statistically significant improvements were found in muscle peak torque deficits for the quadriceps (P = .003) and hamstring (P = .02), with continued improvements after 18 sessions (P = .004 and P = .002, respectively). After 18 BFRT sessions, the peak quadriceps and hamstring peak torques increased > 20% in 86% and 76% of the patients, respectively. The failure rate of achieving this improvement in peak quadriceps and hamstring torque after 18 BFRT sessions was 14% and 24%, respectively.

CONCLUSIONS

BFRT produced statistically significant improvements in peak quadriceps and hamstring torque measurements after 9 and 18 sessions in a majority of patients with severe quadriceps and hamstring strength deficits that had failed to respond to many months of standard and monitored postoperative rehabilitation.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

The effect of muscle blood flow restriction on hemodynamics, cerebral oxygenation and activation at rest

This study tested the hypothesis that muscle blood flow restriction reduces muscle and cerebral oxygenation, at rest. In 26 healthy males, aged 33±2 yrs, physiological variables were continuously recorded during a 10-min period in two experimental conditions: a) with muscle blood flow restriction through thigh cuffs application inflated at 120 mmHg (With Cuffs, WC) and b) without restriction (No Cuffs, NC). Muscle and cerebral oxygenation were reduced by muscle blood flow restriction as suggested by the increase in both muscle and cerebral deoxygenated hemoglobin (Δ[HHb]; p<0.01) and the decrease of muscle and cerebral oxygenation index (Δ[HbDiff]; p<0.01). Hemodynamic responses were not affected by such muscle blood flow restriction, whereas baroreflex sensitivity was reduced (p=0.009). The perception of leg discomfort was higher (p<0.001) in the WC than in the NC condition. This study suggests that thigh cuffs application inflated at 120 mmHg is an effective method to reduce muscle oxygenation at rest. These changes at the muscular level seem to be sensed by the central nervous system, evoking alterations in cerebral oxygenation and baroreflex sensitivity. Novelty bullets: • Thigh cuffs application inflated at 120 mmHg effectively reduces muscle oxygenation at rest. • Limiting muscle oxygenation appears to reduce cerebral oxygenation, and baroreflex sensitivity, at rest. • Even in healthy subjects, limiting muscle oxygenation, at rest, affects neural integration.

Effects of Blood Flow Restriction Exercise and Possible Applications in Type 2 Diabetes

Blood flow restriction resistance training (BFRT) employs partial vascular occlusion of exercising muscles via inflation cuffs. Compared with high-load resistance training, mechanical load is markedly reduced with BFRT, but induces similar gains in muscle mass and strength. BFRT is thus an effective training strategy for people with physical limitations. Recent research indicates that BFRT has beneficial effects on glucose and mitochondrial metabolism. BFRT may therefore qualify as a valuable exercise alternative for individuals with type 2 diabetes (T2D), a disorder characterized by impaired glucose metabolism, musculoskeletal decline, and exacerbated progression of sarcopenia. This review covers the effects of BFRT in healthy populations and in persons with impaired physical fitness, the mechanisms of action of this novel training modality, and possible applications for individuals with T2D.

Effect of blood flow restriction during low-intensity resistance training on bone markers and physical functions in postmenopausal women

BACKGROUND

The aim of this study was to investigate the effects of 12-week low intensity resistance training (RT) with blood flow restriction on bone mineral density (BMD), bone turnover markers (BTM), physical functions, and blood lactate concentration in postmenopausal women with osteoporosis or osteopenia.

METHODS

26 study participants (56 ± 1.8yrs, T-score: -2.5 ± 0.7) were randomly assigned into Moderate to High-Intensity RT (MHIRT, n = 7), BFR combined with Low-Intensity RT (LIBFR, n = 7), Low-Intensity RT (LIRT, n = 6), or Control group (CON, n = 6). Exercise group performed leg press, leg extension, biceps curl, and triceps extension 3 times a week for 12 weeks. Training intensity were set at 60% of 1-repetition maximum (1-RM) for MHIRT, and at 30% of 1-RM for LIBFR and LIRT, and reset every 4 weeks for increasing intensity.

RESULTS

Lower, and upper limb 1-RM only increased in MHIRT (65%, p < 0.001), and LIBFR (40%, p < 0.05), while LIRT only showed increment on lower limb 1-RM (28%, p < 0.05). All exercise groups demonstrated significant increment on blood lactate concentration after training session (p < 0.001). However, LIBFR showed 2.7 folds higher increment than LIRT (p < 0.001). Although no changes were observed in MHIRT, LIBFR, and LIRT, CON showed significant decrease in BMD (p < 0.05). While, LIRT showed no responses on BTM, LIBFR significantly increased bone formation markers (P1NP) about 7.05 ng/ml (p < 0.05). Lastly, balance improvement was only found in MHIRT, and LIBFR (p < 0.05).

CONCLUSION

12-week LIBFR can be implied as a safe, and effective method to improve muscle strength, P1NP, and balance similar to MHIRT in postmenopausal women with osteoporosis or osteopenia.

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.

Limb occlusion pressure for blood flow restricted exercise: Variability and relations with participant characteristics

OBJECTIVE

Assess lower-extremity blood flow restricted exercise (BFR) limb occlusion pressure (LOP) variability and identify related intrinsic characteristics using a portable Delphi BFR system.

DESIGN

Repeated measures.

SETTING

Laboratory.

PARTICIPANTS

Forty-two healthy males (n = 25) and females (n = 17) (25.8 ± 5.2 y, 1.76 ±0 .09 m, 78.9 ± 14.9 kg) completed two visits. Brachial artery blood pressure, thigh circumferences (TC), and LOP were measured supine.

MAIN OUTCOME MEASURES

Linear mixed-effects models (LMM) and generalizability theory were used to evaluate LOP between legs and days, determine intrinsic characteristic relations, and assess random variance components.

RESULTS

LOP was not different between legs (p = .730) or days (p = .916; grand mean = 183.7 mmHg [178.4, 189.1]). LOP varied significantly between participants (p = .011, standard error = 47.3 mmHg). 47% of LOP variance was between participants, 18% and 6% was within participants between days and legs, respectively, and 28% was associated with random error. The relative error variance was 14.4 mmHg. Pulse pressure (PP) (p = .005) and TC (p = .040) were positively associated with LOP. A LMM including PP and TC predicted LOP with a mean absolute difference of 11.1 mmHg [9.7, 12.6] compared to measured LOP.

CONCLUSIONS

The relative error variance suggests that clinicians should measure LOP consistently for each patient to ensure BFR safety and effectiveness.

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.

THE VALIDITY AND RELIABILITY OF THE HANDHELD OXIMETER TO DETERMINE LIMB OCCLUSION PRESSURE FOR BLOOD FLOW RESTRICTION EXERCISE IN THE LOWER EXTREMITY

Background

The limb occlusion pressure (LOP) is determined to calculate the relative LOP. The different levels of relative LOP (percentage of LOP) influence the treatment effect and perceived discomfort during low-load blood flow restriction (BFR) strength training. Thus, determining the LOP is of the utmost importance when using BFR in clinical practice.

Purpose

The objective of this study was to investigate the concurrent validity and intra-rater (test-retest), intra-day reliability of an inexpensive, portable, easy-to-use handheld (HH) oximeter compared to a high-resolution Doppler ultrasound scanner in detecting LOP in the lower extremity.

Study design

Cross-sectional validity and reliability study.

Methods

Two raters who were blinded from each other simultaneously assessed 50 healthy participants (mean age of 25.8 years). A 20 cm-wide thigh cuff with an attached sphygmomanometer was inflated until the raters independently registered the LOP with the HH oximeter and the Doppler ultrasound scanner. The test session was repeated once after a five-minute time interval.

Results

The HH oximeter recorded a non-significantly higher LOP than the Doppler ultrasound scanner, with a mean difference of 6.3 mmHg in the test session (95% limits of agreement (LoA): -16.2 to 28.8, p = 0.13) and 5.4 mmHg in the retest session (95% LoA: -13.3 to 24.0, p = 0.10). The intra-rater reliability for both devices was moderate (ICC = 0.72-0.79). The measured LOP was significantly lower (p < 0.005) in the retest session than in the test session for both the HH oximeter (mean difference: -5.7 mmHg) and the Doppler ultrasound scanner (mean difference: -4.8 mmHg).

Conclusions

The HH oximeter is a valid and reliable measuring device for determining the LOP in the lower extremity in healthy adults. The authors recommend performing at least two LOP measurements with a one-minute rest interval.

Level of Evidence

2, Validity and reliability study.

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

INTRODUCTION

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

METHODS

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

ETHICAL APPROVAL

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

TRIAL REGISTRATION NUMBER

NCT04081493.

Ischemic Therapy in Musculoskeletal Medicine

BACKGROUND

The competitive environment of athletics has promoted the exploration of any technology application that may offer an edge with performance and recovery from injury. Ischemic therapy is one such technology that has rapidly been incorporated into training rooms and physical therapy clinics worldwide. This therapy modality is reported to increase an athlete's ability to improve muscle mass, strength, and endurance.

PURPOSE

To provide the sports medicine physician with an understanding of the current state of ischemic therapy technology, including treatment specifications, known physiological effects, hypothesized mechanisms, biochemical effects, athletic applications, medical applications, animal models, and future research recommendations.

STUDY DESIGN

Literature review.

METHODS

A computer-based search of the PubMed database was used to perform a comprehensive literature review on musculoskeletal ischemic therapy.

RESULTS

The current research on ischemic therapy is largely composed of case series with varying equipment, methods, and therapy specifications. The publication of case series has value in identifying this technology for future research, but the results of these studies should not be justification for application to athletes without validation of safety and effectiveness.

CONCLUSION

To date, ischemic therapy remains unvalidated, and the mechanism by which it improves muscle performance is not clear.

The blood flow restriction training effect in knee osteoarthritis people: a systematic review and meta-analysis

Objective:

To synthesize evidence on the effects of blood flow restriction (BFR) comparing with high (HLT) and low load (LLT), and on the influence of different forms of application in individuals with knee osteoarthritis.

Data sources:

The CENTRAL, PEDro, PubMed and BVS, which include Lilacs, Medline and SciELO, until April 2020.

Review methods:

A systematic review and meta-analysis of randomized trials used the PRISMA guidelines, whose main keywords were: Therapeutic Occlusion, Resistance Training, and Knee Osteoarthritie, blood flow restriction and Kaatsu training. Method quality was evaluated with the PEDro scale. When studies demonstrated homogeneity on outcome measures, the mean differences or standardized mean differences with 95% confidence interval were calculated and pooled in a meta-analysis for pooled synthesis.

Results:

Five articles were eligible in this review with moderate to low risk bias. Our results, showed no difference between BFR and HLT in knee strength (SMD = 0.00, 95% CI, –0.54 to 0.54, P = 1.00), function (SMD = −0.20, 95% CI, –0.45 to 0.06, P = 0.13), pain and volume. But, when compared BFR and LLT, the descriptive analysis demonstrated significant results in favor BFR to muscle strength (71.4% of measurement) and volume (MD = 1.66, 95% CI, 0.93 to 2.38, P < 0.00001), but not in pain or function.

Conclusion:

BFR can be used as a strategy in the rehabilitation of osteoarthritis due to gains in strength and volume with low mechanical stress. However, its application must be safe and individualized, since they can attenuate the stimuli offered by BFR.

The Safety of Blood Flow Restriction Training as a Therapeutic Intervention for Patients With Musculoskeletal Disorders: A Systematic Review

BACKGROUND

The effectiveness of blood flow restriction training (BFRT) as compared with other forms of training, such as resistance training, has been evaluated in the literature in clinical and nonclinical populations. However, the safety of this intervention has been summarized only in healthy populations and not in clinical populations with musculoskeletal disorders.

PURPOSE

To evaluate the safety and adverse events associated with BFRT in patients with musculoskeletal disorders.

STUDY DESIGN

Systematic review.

METHODS

A literature search was conducted with 3 online databases (MEDLINE, CINAHL, and Embase). Eligibility criteria for selecting studies were as follows: (1) BFRT was used as a clinical intervention, (2) study participants had a disorder of the musculoskeletal system, (3) authors addressed adverse events, (4) studies were published in English, and (5) the intervention was performed with human participants.

RESULTS

Nineteen studies met eligibility criteria, with a pooled sample size of 322. Diagnoses included various knee-related disorders, inclusion body myositis, polymyositis or dermatomyositis, thoracic outlet syndrome, Achilles tendon rupture, and bony fractures. Nine studies reported no adverse events, while 3 reported rare adverse events, including an upper extremity deep vein thrombosis and rhabdomyolysis. Three case studies reported common adverse events, including acute muscle pain and acute muscle fatigue. In the randomized controlled trials, individuals exposed to BFRT were not more likely to have an adverse event than individuals exposed to exercise alone. Of the 19 studies, the adverse events were as follows: overall, 14 of 322; rare overall, 3 of 322; rare BFRT, 3 of 168; rare control, 0 of 154; any adverse BFRT, 10 of 168; any adverse control, 4 of 154. A majority of studies were excluded because they did not address safety.

CONCLUSION

BFRT appears to be a safe strengthening approach for knee-related musculoskeletal disorders, but further research is needed to make definitive conclusions and to evaluate the safety in other musculoskeletal conditions. Improved definitions of adverse events related to BFRT are needed to include clear criteria for differentiating among common, uncommon, and rare adverse events. Finally, further research is needed to effectively screen who might be at risk for rare adverse events.

Determining the Arterial Occlusion Pressure for Blood Flow Restriction: Pulse Oximeter as a New Method Compared With a Handheld Doppler

Lima-Soares, F, Pessoa, KA, Torres Cabido, CE, Lauver, J, Cholewa, J, Rossi, FE, and Zanchi, NE. Determining the arterial occlusion pressure for blood flow restriction: pulse oximeter as a new method compared with a handheld Doppler. J Strength Cond Res XX(X): 000-000, 2020-In laboratorial and clinical settings, the use of Doppler ultrasound equipment has been considered the gold standard method to determine arterial occlusion pressure (AOP). However, the use of Doppler equipment is inherently limited to the technical expertise needed to perform AOP measurements. To overcome the technical difficulties of the use of Doppler equipment use in the determination of AOP, a simpler and less subjective methodology would be helpful for blood flow restriction (BFR) practitioners. In this regard, portable pulse oximetry has been largely used in clinical practice for measuring systolic pressures, as well as loss or recovery of pulse, with results similar to those observed with the use of Doppler equipment. For such purposes, the AOP from young male and female subjects was evaluated after different body positions (standing, seated, and supine positions). Loss of capillary blood flow or AOP was readily determined by simple visual inspection for the pulse oximeter and loss of sound for the Doppler equipment. The results presented herein strongly suggest the use of the portable pulse oximetry equipment as reliable, when compared with the handheld Doppler (seated K = 0.962, standing K = 0.845, and supine K = 0.963 and seated rs = 0.980, standing rs = 0.958, and supine rs = 0.955). Because AOP measurement by pulse oximetry is relatively easier to perform and financially more accessible than handheld Doppler equipment, BFR practitioners may benefit from this new methodology to measure AOP, thus determining individualized restriction pressures.

The addition of blood flow restriction to resistance exercise in individuals with knee pain: a systematic review and meta-analysis

BACKGROUND

Blood flow restriction (BFR) is an effective clinical intervention used to increase strength in healthy individuals. However, its effects on pain and function in individuals with knee pain are unknown.

OBJECTIVE

To determine the effectiveness of adding BFR to resistance exercise for pain relief and improvement of function in patients with knee pain.

METHODS

Systematic review with meta-analysis of randomized clinical trials. Medline, Central, Embase, PEDro, Lilacs, CINAHL, SPORTDiscus, and Web of Science databases were searched from inception to May 2019. Randomized clinical trials that compared resistance exercise with or without BFR to treat knee pain and function in individuals older than 18 years of age with knee pain were included.

RESULTS

Eight randomized clinical trials met the eligibility criteria and for the quantitative synthesis, five studies were included. The pooled standardized mean difference (SMD) estimate showed that resistance exercises with BFR was not more effective than resistance exercises for reducing pain (SMD: -0.37cm, 95% CI=-0.93, 0.19) and improving knee function (SMD=-0.23 points, 95% CI=-0.71, 0.26) in patients with knee pain.

CONCLUSION

In the short term, there is low quality of evidence that resistance exercise with BFR does not provide significant differences in pain relief and knee function compared to resistance exercises in patients with knee pain. PROSPERO registration number: CRD42018102839.

Acute Muscular Responses to Practical Low-Load Blood Flow Restriction Exercise Versus Traditional Low-Load Blood Flow Restriction and High-/Low-Load Exercise

CONTEXT

Blood flow restriction (BFR) increases muscle size and strength when combined with low loads, but various methods are used to produce this stimulus. It is unclear how using elastic knee wraps can impact acute muscular responses compared with using nylon cuffs, where the pressure can be standardized.

OBJECTIVE

Investigate how elastic knee wraps compare with nylon cuffs and high-load (HL)/low-load (LL) resistance exercise.

DESIGN

A randomized cross-over experimental design using 6 conditions combined with unilateral knee extension.

SETTING

Human Performance Laboratory.

PARTICIPANTS

A total of 9 healthy participants (males = 7 and females = 2) and had an average age of 22 (4) years.

INTERVENTION

LL (30% of 1-repetition maximum [1-RM]), HL (70% 1-RM), BFR at 40% of arterial occlusion pressure (BFR-LOW), BFR at 80% of arterial occlusion pressure (BFR-HIGH), elastic knee wraps stretched by 2 in (PRACTICAL-LOW), and elastic knee wraps stretched to a new length equivalent to 85% of thigh circumference (PRACTICAL-HIGH). BFR and practical conditions used 30% 1-RM.

MAIN OUTCOME MEASURES

Muscle thickness, maximum voluntary isometric contraction, and electromyography amplitude. Bayesian statistics evaluated differences in changes between conditions using the Bayes factor (BF10), and median and 95% credible intervals were reported from the posterior distribution.

RESULTS

Total repetitions completed were greater for BFR-LOW versus PRACTICAL-HIGH (BF10 = 3.2, 48.6 vs 44 repetitions) and greater for PRACTICAL-LOW versus BFR-HIGH (BF10 = 717, 51.8 vs 36.3 repetitions). Greater decreases in changes in maximum voluntary isometric contraction were found in PRACTICAL-HIGH versus HL (BF10 = 1035, ∼103 N) and LL (BF10 = 45, ∼66 N). No differences in changes in muscle thickness were found between LL versus PRACTICAL-LOW/PRACTICAL-HIGH conditions (BF10 = 0.32). Greater changes in electromyography amplitude were also found for BFR-LOW versus PRACTICAL-HIGH condition (BF10 = 6.13, ∼12%), but no differences were noted between the other BFR conditions.

CONCLUSIONS

Overall, elastic knee wraps produce a more fatiguing stimulus than LL or HL conditions and might be used as an alternative to pneumatic cuffs that are traditionally used for BFR exercise.

Neuromuscular effects of dorsiflexor training with and without blood flow restriction

Blood flow restriction training (BFRT) has been proposed for elderly and clinical populations with weakness. Before being used in these populations it is important to understand the neurological effects of, and subject perceptions to, BFRT. Seventeen healthy subjects were recruited and performed 2 experimental sessions, BFRT and training without blood flow restriction (TR-only), on separate days. Four sets of concentric/eccentric dorsiflexion contractions against theraband resistance were performed. Surface electromyography of the tibialis anterior was recorded during exercise and for the electrophysiological measures. At baseline, immediately-post, 10-min-post and 20-min-post exercise, motor evoked potentials (MEPs) from single pulse transcranial magnetic stimulation (TMS), paired-pulse TMS with interstimulus intervals of 2-ms (SICI) and 15-ms (ICF), and the M-max amplitude were recorded in the resting TA. Following training, subjects provided a numerical rating of the levels of pain, discomfort, fatigue, focus and difficulty during training. Muscle activation was higher in the last 20 contractions during BFRT compared to TR. There was no difference (time × condition interaction) between BFRT and TR for single-pulse MEP, SICI, ICF or M-max amplitude. There was a significant main effect of timepoint for single-pulse MEP and M-max amplitudes with both significantly reduced for 20-min-post exercise. No reductions were observed for SICI and ICF amplitudes. Taken together, BFRT and TR-only were only different during exercise and both regimes induced similar significant reductions in M-Max and MEP-amplitude post-training. Due to the lack of changes in SICI and ICF, it is unlikely that changes occurred in cortical sites related to these pathways. The increased surface electromyography activity in the last 20 contractions, indicate that the training regimes are different and that BFRT possibly induces more fatigue than TR. As such, BFRT could be used as an adjunct to conventional training. However, as subjects perceived BFRT as more painful, difficult and uncomfortable than TR-only, people should be selected carefully to undertake BFRT.

Progression of Blood Flow Restricted Resistance Training in Older Adults at Risk of Mobility Limitations

Blood flow restriction (BFR) resistance training leads to increased muscle mass and strength but the progression leading to adaptations may be different as strength gains are often to a lesser magnitude than high-load (HL) training. The impact of training loads and repetitions on older adults’ muscle mass and strength following BFR or HL training was evaluated. Twenty-one older adults (67–90 years) classified as being at risk of mobility limitations were randomly assigned to HL (n = 11) or BFR (n = 10) knee extension (KE) and flexion (KF) training twice per week for 12 weeks. Strength was measured with 10-repetition maximum (10-RM) tests and isometric contractions. Cross-sectional area (CSA) of the quadriceps and hamstrings was measured. HL and BFR interventions increased 10-RM KF and isometric strength (P < 0.05) and hamstrings CSA increased an average of 4.8 ± 5.9% after HL and BFR training (time main effect P < 0.01). There were no differences between the training groups (time x group interactions P > 0.05). The rate of progression of KF training load and repetitions was comparable (time × group interactions of each variable P > 0.05). The groups averaged an increase of 0.50 ± 25 kg⋅week^-1 and 1.8 ± 0.1.7 repetitions⋅week^-1 of training (time main effects P < 0.05). The HL training group experienced greater improvements in KE 10-RM strength than the BFR group (60.7 ± 36.0% vs. 35.3 ± 25.5%; P = 0.03). In both groups, isometric KE strength increased 17.3 ± 18.5% (P = 0.001) and there were no differences between groups (P = 0.24). Quadriceps CSA increased (time main effect P < 0.01) and to similar magnitudes (time x group interaction P = 0.62) following HL (6.5 ± 3.1%) and BFR training (7.8 ± 8.2%). The HL group experienced accelerated progression of load when compared to BFR (0.90 ± 0.60 kg⋅week^-1 vs. 30 ± 0.21 kg⋅week^-1; P = 0.006) but was not different when expressed in relative terms. BFR training progressed at a rate of 3.6 ± 1.3 repetitions⋅week^-1 while the HL group progressed at 2.2 ± 0.43 repetitions⋅week^-1 (P = 0.003). HL training led to greater increases in KE 10-RM and it may be attributed to the greater load and/or faster rate of progression of the load throughout the 12-week training period and the specificity of the testing modality. Incorporating systematic load progression throughout BFR training periods should be employed to lead to maximal strength gains.

Effects of Blood Flow Restriction and Exercise Intensity on Aerobic, Anaerobic, and Muscle Strength Adaptations in Physically Active Collegiate Women

The purpose of this study was to compare the effects of different combinations of blood flow restriction (BFR) pressure and exercise intensity on aerobic, anaerobic, and muscle strength adaptations in physically active collegiate women. Thirty-two women (age 22.8 ± 2.9 years; body mass index 22.3 ± 2.7 kg/m²) were randomly assigned into four experimental training groups: (a) increasing BFR pressure with constant exercise intensity (IP-CE), (b) constant partial BFR pressure with increasing exercise intensity (CP_p-IE), (c) constant complete BFR pressure with increasing exercise intensity (CP_C-IE), and (d) increasing BFR pressure with increasing exercise intensity (IP-IE). The participants completed 12 training sessions comprised of repeated bouts of 2 min running on a treadmill with BFR interspersed by 1-min recovery without BFR. Participants completed a series of tests to assess muscle strength, aerobic, and anaerobic performances. Muscle strength, anaerobic power, and aerobic parameters including maximum oxygen consumption (VO₂max), time to fatigue (TTF), velocity at VO₂max (vVO₂max), and running economy (RE) improved in all groups (p ≤ 0.01). The CP_C-IE group outscored the other groups in muscle strength, RE, and TTF (p < 0.05). In summary, participants with complete occlusion experienced the greatest improvements in muscle strength, aerobic, and anaerobic parameters possibly due to increased oxygen deficiency and higher metabolic stress.

The impact of cuff width and biological sex on cuff preference and the perceived discomfort to blood-flow-restricted arm exercise

OBJECTIVE

To investigate the influence of cuff width, sex, and applied pressure on the perceived discomfort associated with blood flow restriction at rest and following exercise.

APPROACH

Experiment 1 (n  =  96) consisted of four sets of biceps exercise to failure with a narrow and wide cuff inflated to the same relative pressure. Experiment 2 (n  =  87) compared two wide cuffs, one of which was inflated to a relative pressure obtained from a narrow cuff. Experiment 3 (n  =  50) compared the discomfort of wide and narrow cuffs at rest. Effects are presented as median δ (95% credible interval).

MAIN RESULTS

There was no sex effect for any variable of interest. In Experiment 1, the narrow cuff resulted in less discomfort than the wide cuff (39.3 versus 42.5; median δ  -0.388 (-0.670, -0.109)). Participants also rated the narrow cuff as more preferable. Experiment 2 found that a wide cuff inflated to a narrow cuffs pressure resulted in greater discomfort than a wide cuff (44 versus 40.9; median δ: 0.420 (0.118, 0.716)). Experiment 3 found no difference between cuff widths.

SIGNIFICANCE

Blood flow restricted exercise with a narrow cuff results in less discomfort than a wider cuff inflated to the same relative pressure. This effect is not observed at rest and suggests that the wide cuff produces a differential environment compared to a narrow cuff when combined with exercise. Additionally, applying a pressure meant for a narrow cuff to a wide cuff augments the applied pressure and subsequent discomfort to blood flow restricted exercise.

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.

The influence of biological sex and cuff width on muscle swelling, echo intensity, and the fatigue response to blood flow restricted exercise

The purpose was to determine if the muscle swelling, echo intensity, and fatigue responses to blood flow restriction differs based on cuff width (Experiment 1), applied pressure (Experiment 2), and sex. Ultrasound of muscle was taken before and after exercise. In Experiment 1 (n = 96), men swelled more than women and more with a narrow cuff than a wide cuff (0.60 cm vs. 0.52 cm). Expressed as a percentage change, there were no longer differences between cuffs (Narrow: 15% vs. Wide: 14%) or sex (Men: 14% vs. Women: 15%). Echo intensity remained unchanged. Women required more repetitions to reach task failure in sets 2, 3, and 4. In Experiment 2 (n = 87), men swelled more than women (Men: 0.46 cm vs. Women: 0.31 cm). Expressed as a percentage change, there were no differences. Echo intensity decreased in both conditions and to a greater extent with a higher applied pressure. If the acute muscle swelling response is important for initiating long term adaptation, then our results indicate that neither cuff width, sex, nor applied pressure will differentially impact the adaptation observed via this mechanism. Changes in echo intensity were inconsistent and the utility of this measurement may need to be reconsidered.

Strengthening the Brain-Is Resistance Training with Blood Flow Restriction an Effective Strategy for Cognitive Improvement?

Aging is accompanied by a decrease in physical capabilities (e.g., strength loss) and cognitive decline. The observed bidirectional relationship between physical activity and brain health suggests that physical activities could be beneficial to maintain and improve brain functioning (e.g., cognitive performance). However, the exercise type (e.g., resistance training, endurance training) and their exercise variables (e.g., load, duration, frequency) for an effective physical activity that optimally enhance cognitive performance are still unknown. There is growing evidence that resistance training induces substantial brain changes which contribute to improved cognitive functions. A relative new method in the field of resistance training is blood flow restriction training (BFR). While resistance training with BFR is widely studied in the context of muscular performance, this training strategy also induces an activation of signaling pathways associated with neuroplasticity and cognitive functions. Based on this, it seems reasonable to hypothesize that resistance training with BFR is a promising new strategy to boost the effectiveness of resistance training interventions regarding cognitive performance. To support our hypothesis, we provide rationales of possible adaptation processes induced by resistance training with BFR. Furthermore, we outline recommendations for future studies planning to investigate the effects of resistance training with BFR on cognition.