Very-low-load resistance exercise in the upper body with and without blood flow restriction: cardiovascular outcomes

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.

Acute effects of resistance exercise with blood flow restriction on cardiovascular response: a meta-analysis

Aim: To compare the acute effects of low-load resistance training associated with blood flow restriction (LLRT-BFR) with low-load resistance training (LLRT) and high-load resistance training (HLRT) on cardiovascular outcomes in healthy individuals. Methods: This review was registered and the studies were selected using seven databases. Randomized controlled clinical trials were included that evaluated LLRT-BFR compared with LLRT and HLRT in young individuals for the cardiovascular outcomes. Results: 19 studies were included. In the comparison of LLRT-BFR with HLRT, there were significant differences for cardiac output and heart rate - with reduced values and in favor of LLRT-BFR. Conclusion: There are no greater acute effects of the addition of blood flow restriction, with the exception of the reduction in cardiac output and heart rate for LLRT-BFR compared with HLRT.

Blood flow restriction training on resting blood pressure and heart rate: a meta-analysis of the available literature

The purpose of this meta-analysis was to examine the effects of blood flow restriction training on resting blood pressure and heart rate. A meta-analysis was completed in May 2020 including all previously published papers on blood flow restriction and was analyzed using a random effects model. To be included, studies needed to implement a blood flow restriction protocol compared to the same exercise protocol without restriction. A total of four studies met the inclusion criteria for quantitative analysis including four effect sizes for resting systolic blood pressure, four effect sizes for resting diastolic blood pressure, and three effect sizes for resting heart rate. There was evidence of a difference [mean difference (95 CI)] in resting systolic blood pressure between training with and without blood flow restriction [4.2 (0.3, 8.0) mmHg, p = 0.031]. No significant differences were observed when comparing resting diastolic blood pressure [1.2 (-1, 3.5) mmHg p = 0.274] and resting heart rate [-0.2 (-4.7, 4.1) bpm, p = 0.902] between chronic exercise with and without blood flow restriction. These results indicate that training with blood flow restriction may elicit an increase in resting systolic blood pressure. However, lack of data addressing this topic makes any conclusion speculative. Based on the results of the present study along with the overall lack of long-term data, it is suggested that future research on this topic is warranted. Recommendations include making changes in resting blood pressure a primary outcome and increasing the sample size of the interventions.

The Evolution of Blood Flow Restricted Exercise

The use of blood flow restricted (BFR) exercise has become an accepted alternative approach to improve skeletal muscle mass and function and improve cardiovascular function in individuals that are not able to or do not wish to use traditional exercise protocols that rely on heavy loads and high training volumes. BFR exercise involves the reduction of blood flow to working skeletal muscle by applying a flexible cuff to the most proximal portions of a person’s arms or legs that results in decreased arterial flow to the exercising muscle and occluded venous return back to the central circulation. Safety concerns, especially related to the cardiovascular system, have not been consistently reported with a few exceptions; however, most researchers agree that BFR exercise can be a relatively safe technique for most people that are free from serious cardiovascular disease, as well as those with coronary artery disease, and also for people suffering from chronic conditions, such as multiple sclerosis, Parkinson’s, and osteoarthritis. Potential mechanisms to explain the benefits of BFR exercise are still mostly speculative and may require more invasive studies or the use of animal models to fully explore mechanisms of adaptation. The setting of absolute resistive pressures has evolved, from being based on an individual’s systolic blood pressure to a relative measure that is based on various percentages of the pressures needed to totally occlude blood flow in the exercising limb. However, since several other issues remain unresolved, such as the actual external loads used in combination with BFR, the type of cuff used to induce the blood flow restriction, and whether the restriction is continuous or intermittent, this paper will attempt to address these additional concerns.

The Effect of Increasing Blood Flow Restriction Pressure When the Contractions Are Already Occlusive

CONTEXT

Blood flow restricted exercise involves the use of external pressure to enhance fatigue and augment exercise adaptations. The mechanisms by which blood flow restricted exercise limits muscular endurance are not well understood.

OBJECTIVE

To determine how increasing blood flow restriction pressure impacts local muscular endurance, discomfort, and force steadiness when the contractions are already occlusive.

DESIGN

Within-participant, repeated-measures crossover design.

SETTING

University laboratory.

PATIENTS

A total of 22 individuals (13 males and 9 females).

INTERVENTION

Individuals performed a contraction at 30% of maximal isometric elbow flexion force for as long as possible. One arm completed the contraction with 100% of arterial occlusion pressure applied, while the other arm had 150% of arterial occlusion pressure applied. At the end of the protocol, individuals were asked to rate their perceived discomfort.

MAIN OUTCOME MEASURES

Time to task failure, discomfort, and force steadiness.

RESULTS

Individuals had a longer time to task failure when performing the 100% arterial occlusion condition compared with the 150% arterial occlusion pressure condition (time to task failure = 82.4 vs 70.8 s; Bayes factors = 5.77). There were no differences in discomfort between the 100% and 150% conditions (median discomfort = 5.5 vs 6; Bayes factors = 0.375) nor were there differences in force steadiness (SD of force output 3.16 vs 3.31 N; Bayes factors = 0.282).

CONCLUSION

The results of the present study suggest that, even when contractions are already occlusive, increasing the restriction pressure reduces local muscle endurance but does not impact discomfort or force steadiness. This provides an indication that mechanisms other than the direct alteration of blood flow are contributing to the increased fatigue with added restrictive pressure. Future studies are needed to examine neural mechanisms that may explain this finding.

The Systemic Effects of Blood Flow Restriction Training: A Systematic Review

BACKGROUND

Blood flow restriction (BFR) training has been reported to have significant benefits on local skeletal muscle including increasing local muscle mass, strength, and endurance while exercising with lower resistance. As a result, patients unable to perform traditional resistance training may benefit from this technique. However, it is unclear what effects BFR may have on other body systems, such as the cardiovascular and pulmonary systems. It is important to explore the systemic effects of BFR training to ensure it is safe for use in physical therapy.

PURPOSE

The purpose of this study was to systematically review the systemic effects of blood flow restriction training when combined with exercise intervention.

STUDY DESIGN

Systematic review.

METHODS

Three literature searches were performed: June 2019, September 2019, and January 2020; using MedLine, ScienceDirect, PubMed, Cochrane Reviews and CINAHL Complete. Inclusion criteria included: at least one outcome measure addressing a cardiovascular, endocrinological, systemic or proximal musculoskeletal, or psychosocial outcome, use of clinically available blood flow restriction equipment, use of either resistance or aerobic training in combination with BFR, and use of quantitative measures. Exclusion criteria for articles included only measuring local or distal musculoskeletal changes due to BFR training, examining only passive BFR or ischemic preconditioning, articles not originating from a scholarly peer-reviewed journal, CEBM level of evidence less than two, or PEDro score less than four. Articles included in this review were analyzed with the CEBM levels of evidence hierarchy and PEDro scale.

RESULTS

Thirty-five articles were included in the review. PEDro scores ranged between 4 and 8, and had CEBM levels of evidence of 1 and 2. Common systems studied included cardiovascular, musculoskeletal, endocrine, and psychosocial. This review found positive or neutral effects of blood flow restriction training on cardiovascular, endocrinological, musculoskeletal, and psychosocial outcomes.

CONCLUSIONS

Although BFR prescription parameters and exercise interventions varied, the majority of included articles reported BFR training to produce favorable or non-detrimental effects to the cardiovascular, endocrine, and musculoskeletal systems. This review also found mixed effects on psychosocial outcomes when using BFR. Additionally, this review found no detrimental outcomes directly attributed to blood flow restriction training on the test subjects or outcomes tested. Thus, BFR training may be an effective intervention for patient populations that are unable to perform traditional exercise training with positive effects other than traditional distal muscle hypertrophy and strength and without significant drawbacks to the individual.

LEVEL OF EVIDENCE

1b.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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

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

The Effect of Blood Flow Restriction Therapy on Recovery After Experimentally Induced Muscle Weakness and Pain

Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res XX(X): 000-000, 2020-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

Knee extension with blood flow restriction: Impact of cuff pressure on hemodynamics

INTRODUCTION

Blood flow restriction (BFR) exercise has emerged as a method of increasing muscle size and strength with low intensity resistance training. While the cuff pressures used during BFR are typically a percentage of resting arterial occlusion pressure (AOP), the impact these cuff pressures have on blood flow during lower body exercise is unknown.

PURPOSE

To determine how various cuff pressures impact blood flow and tissue perfusion during exercise.

METHODS

Eleven healthy male participants completed four sets of knee extension (30 reps per set at 30% max torque) with 0%, 60%, 80%, and 100% of arterial occlusion pressure (AOP) was applied to the proximal portion of the thigh. Femoral artery blood flow, tissue oxygenation, and central hemodynamics were continuously recorded before, during, and after exercise. Electromyography (EMG) amplitude was recorded from the vastus lateralis during exercise.

RESULTS

Blood flow increased during exercise compared to rest across all cuff pressures (p < 0.001), however compared to 0%, the absolute blood flow was reduced by 34 ± 17%, 45 ± 22%, and 72 ± 19% for 60, 80, and 100% AOP, respectively. Furthermore, each cuff pressure resulted in similar relative changes in blood flow before, during, and after exercise. During exercise, tissue saturation index (TSI) decreased as cuff pressure increased (p ≤ 0.005) with the exception of 80 to 100% AOP. Deoxyhemoglobin increased (p ≤ 0.001) with cuff pressure.

CONCLUSION

Our data indicate that while BFR knee extension elicits an absolute hyperemic response at cuff pressures up to 100% resting AOP, the relative reductions in blood flow are consistent across rest, exercise and recovery.

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.

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.