Blood Flow Restriction Resistance Exercise Improves Muscle Strength and Hemodynamics, but Not Vascular Function in Coronary Artery Disease Patients: A Pilot Randomized Controlled Trial

Mechanisms of blood flow restriction training for knee pain: a mini review

Knee pain, affecting an estimated 654 million people worldwide, so blood flow restriction training (BFRT) is catching the spotlight as an effective intervention. Evidence continues to demonstrate the effectiveness of BFRT in managing knee pain. However, the mechanism by which BFRT alleviates knee pain remains unclear, thereby limiting its application in clinical pain management. This study aims to elucidate the underlying mechanisms of BFRT to better understand its efficacy in treating knee pain. This review will discuss the influence of muscle hypertrophy, endogenous opioid system, endocannabinoids, inflammation regulation, and conditional pain regulation on BFRT treatment of knee pain. Current studies on BFRT have limitations, such as small sample sizes, relatively low-quality evidence, and lack of mechanistic studies. Therefore, further research on BFRT is needed, particularly high-quality and large-sized randomized controlled trials.

Role of Resistance Exercise in Cardiology

Resistance exercise is a form of exercise that increases muscular strength and endurance by exercising a muscle or muscle group against external resistance. Resistance exercises have an important potential in preventing cardiac diseases, increasing treatment efficiency, and improving quality of life. In spite of the fact that the vast majority of cardiology research to date has focused on aerobic exercise, an increasing number of studies on resistance exercise have been published in the past few years. Although resistance exercise was combined with aerobic exercise in most of these studies, its isolated efficacy was also examined. In conditions such as coronary artery disease, peripheral artery disease, heart failure, arrhythmias, and cardiac rehabilitation, resistance exercise (RE) is regarded as a potentially beneficial approach. In addition to interventional and medical treatments, resistance exercise can also be considered as a cost-effective and sustainable method. The effects of resistance exercise on a variety of cardiovascular conditions were investigated in this evaluation of the literature.

Effects of blood flow restriction training on muscle fitness and cardiovascular risk of obese college students

Purpose: The aim of this study was to investigate the effect of blood flow restriction (BFR) combined with low-intensity resistance training (RT) on cardiovascular risk factors in obese individuals. Methods: Twenty-six male obese college students were recruited and randomly assigned to a control group (CON, n = 8), a low-intensity RT group (RT, n = 9), and a combined BFR training and low-intensity RT group (BFRT, n = 9). Results: The subjects in BFRT group showed significant reductions in body fat percentage and waist-to-hip ratio and a significant increase in lean mass and muscle mass; the peak torque, peak power, and endurance ratio of knee extensors and elbow flexors were significantly upregulated; the root mean square (RMS) for the medial femoral muscle, lateral femoral muscle and biceps significantly increased; the diastolic blood pressure (DBP) showed a significant decrease. The BFRT group also showed significant up-regulations in RMS of the difference between the adjacent R-R intervals (RMSSD), high-frequency power (HF) of parasympathetic modulatory capacity, the standard deviation of R-R intervals (SDNN) of overall heart rate variability (HRV) changes and low-frequency power (LF) of predominantly sympathetic activity. In addition, glycated hemoglobin (HbA1C), insulin resistance index (HOMA-IR) and fasting blood glucose (FBG) were all significantly downregulated in BFRT group. In parallel, low-density lipoprotein (LDL-C) significantly reduced while high-density lipoprotein (HDL-C) significantly increased in BFRT group. Conclusion: BFR combined with low-intensity RT training effectively improved body composition index, increased muscle mass, improved neuromuscular activation, enhanced muscle strength and endurance, which in turn improved abnormal glucolipid metabolism and enhanced cardiac autonomic regulation.

Effects of Blood Flow Restriction Resistance Training on Autonomic and Endothelial Function in Persons with Parkinson's Disease

Background

Autonomic dysfunction precedes endothelial dysfunction in Parkinson's disease (PD) and causes blood pressure and circulation abnormalities that are highly disruptive to one's quality of life. While exercise interventions have proven helpful for motor symptoms of PD, improving associated non-motor symptoms is limited. Low-intensity resistance training with blood flow restriction (LIRT-BFR) improves autonomic dysfunction in non-PD patients and high-intensity resistance training (HIRT) is recommended for motor symptom improvements for people with PD (PwPD).

Objective

To determine the effects of LIRT-BFR and HIRT on homocysteine and autonomic and endothelial function in PwPD and to determine the hemodynamic loads during LIRT-BFR and HIRT in PwPD using a novel exercise protocol.

Methods

Thirty-eight PwPD were assigned LIRT-BFR, HIRT or to a control (CNTRL) group. The LIRT-BFR and HIRT groups exercised three days per week for four weeks. The LIRT-BFR protocol used 60% limb occlusion pressure (LOP) and performed three sets of 20 repetitions at 20% of the one-repetition maximum (1RM). The HIRT group performed three sets of eight repetitions at 80% 1RM. The CNTRL group was asked to continue their normal daily routines.

Results

LIRT-BFR significantly improved orthostatic hypotension (p = 0.026), homocysteine levels (p < 0.001), peripheral circulation (p = 0.003), supine blood pressure (p = 0.028) and heart rate variability (p = 0.041); LIRT-BFR improved homocysteine levels (p < 0.018), peripheral circulation (p = 0.005), supine blood pressure (p = 0.007) and heart rate variability (p = 0.047) more than HIRT; and hemodynamic loads for LIRT-BFR and HIRT were similar.

Conclusions

LIRT-BFR may be more effective than HIRT for autonomic and endothelial function improvements in PwPD and hemodynamic loads may be lessened in LIRT-BFR protocols using single-joint exercises with intermittent blood flow restriction. Further research is needed to determine if non-motor symptoms improve over time and if results are sustainable.

Changes in Arterial Stiffness in Response to Blood Flow Restriction Resistance Training: A Narrative Review

Arterial stiffness naturally increases with age and is a known predictor of cardiovascular morbimortality. Blood flow restriction (BFR) training involves decreasing muscle blood flow by applying a strap or a pneumatic cuff during exercise. BFR induces muscle hypertrophy even at low intensities, making it an appealing option for older, untrained individuals. However, BFR use in patients with cardiovascular comorbidities is limited by the increased pressor and chronotropic response observed in hypertensive elderly patients. Furthermore, the impact of BFR on vascular function remains unclear. We conducted a comprehensive literature review according to PRISMA guidelines, summarizing available data on the acute and long-term consequences of BFR training on vascular function. Although evidence is still scarce, it seems that BFR has a mild or neutral long-term impact on arterial stiffness. However, current research shows that BFR can cause an abrupt, albeit transient, increase in PWV and central blood pressure. BFR and, preferably, lower-body BFR, should be prescribed with caution in older populations, especially in hypertensive patients who have an exacerbated muscle metaboreflex pressor response. Longer follow-up studies are required to assess the chronic effect of BFR training on arterial stiffness, especially in elderly patients who are usually unable to tolerate high-intensity resistance exercises.

Low-intensity resistance exercise with blood flow restriction for patients with claudication: A randomized controlled feasibility trial

BACKGROUND

Claudication is a common and debilitating symptom of peripheral artery disease, resulting in poor exercise performance and quality of life (QoL). Supervised exercise programs are an effective rehabilitation for patients with claudication, but they are poorly adhered to, in part due to the high pain and effort associated with walking, aerobic, and resistance exercise. Low-intensity resistance exercise with blood flow restriction (BFR) represents an alternative exercise method for individuals who are intolerant to high-intensity protocols. The aim of this study was to evaluate the feasibility of a supervised BFR program in patients with claudication.

METHODS

Thirty patients with stable claudication completed an 8-week supervised exercise program and were randomized to either BFR (n = 15) or a control of matched exercise without BFR (control; n = 15). Feasibility, safety, and efficacy were assessed.

RESULTS

All success criteria of the feasibility trial were met. Exercise adherence was high (BFR = 78.3%, control = 83.8%), loss to follow up was 10%, and there were no adverse events. Clinical improvement in walking was achieved in 86% of patients in the BFR group but in only 46% of patients in the control group. Time to claudication pain during walking increased by 35% for BFR but was unchanged for the control. QoL for the BFR group showed improved mobility, ability to do usual activities, pain, depression, and overall health at follow up.

CONCLUSION

A supervised blood flow restriction program is feasible in patients with claudication and has the potential to increase exercise performance, reduce pain, and improve QoL. (Clinicaltrials.gov Identifier: NCT04890275).

Blood flow restriction as a potential therapy to restore physical function following COVID-19 infection

Accumulating evidence indicates that some COVID-19 survivors display reduced muscle mass, muscle strength, and aerobic capacity, which contribute to impairments in physical function that can persist for months after the acute phase of illness. Accordingly, strategies to restore muscle mass, muscle strength, and aerobic capacity following infection are critical to mitigate the long-term consequences of COVID-19. Blood flow restriction (BFR), which involves the application of mechanical compression to the limbs, presents a promising therapy that could be utilized throughout different phases of COVID-19 illness. Specifically, we hypothesize that: 1) use of passive BFR modalities can mitigate losses of muscle mass and muscle strength that occur during acute infection and 2) exercise with BFR can serve as an effective alternative to high-intensity exercise without BFR for regaining muscle mass, muscle strength, and aerobic capacity during convalescence. The various applications of BFR may also serve as a targeted therapy to address the underlying pathophysiology of COVID-19 and provide benefits to the musculoskeletal system as well as other organ systems affected by the disease. Consequently, we present a theoretical framework with which BFR could be implemented throughout the progression from acute illness to outpatient rehabilitation with the goal of improving short- and long-term outcomes in COVID-19 survivors. We envision that this paper will encourage discussion and consideration among researchers and clinicians of the potential therapeutic benefits of BFR to treat not only COVID-19 but similar pathologies and cases of acute critical illness.

Effects of 4-Week Low-Load Resistance Training with Blood Flow Restriction on Muscle Strength and Left Ventricular Function in Young Swimmers: A Pilot Randomized Trial

Low-load resistance training combined with blood flow restriction (BFR) is known to result in muscle hypertrophy and strength similar to that observed with higher loads. However, the effects of resistance training with BFR on cardiac structure and cardiac function remain largely unknown. Therefore, the purpose of this randomized study was to compare the effects of conventional high-load resistance training (HL-RT) with the effects of low-load resistance training with BFR (LL-BFR) on muscle strength and left ventricular function. Sixteen young swimmers (mean ± standard deviation: age = 19.7 ± 1.6 years, body mass = 78.9 ± 9.7 kg, body height = 180.8 ± 5.8 cm) were randomly allocated to a conventional HL-RT group (n = 8) or a LL-BFR group (n = 8) with a pressure band (200 mmHg) placed on both thighs of participants for 4 weeks (3 days•week-1). Outcome measures were taken at baseline and after 4 weeks of training, and included body composition, one-repetition maximum (1RM) back squat, and echocardiography measures. The 1RM back squat significantly improved (partial eta squared (Ƞ2) = 0.365; p = 0.013) in HL-RT (mean difference (Δ) = 6.6 kg; [95% confidence interval (CI) -7.09 to 20.27]) and LL-BFR groups (Δ = 14.7 kg; [95% CI 3.39 to 26.10]), with no main effect of group or group × time interaction (p > 0.05). Interventricular septum end-systolic thickness showed a slight but statistically significant increase in LL-BFR and HL-RT groups (Ƞ2 = 0.253; p = 0.047), yet there was no main effect of group or group × time interaction (p > 0.05). There were no statistically significant changes (p > 0.05) in other cardiac structure or function parameters (e.g., left ventricular (LV) mass, LV cardiac output, LV ejection fraction, LV stroke volume) after the training programs. Results suggest that 4 weeks of HL-RT and LL-BFR improve muscle strength similarly with limited effects on left ventricular function in young swimmers.

The effectiveness of blood flow restriction training in cardiovascular disease patients: A scoping review

Therapeutic exercise is integral to the comprehensive rehabilitation of patients with cardiovascular disease and, as such, is recommended by the American Heart Association as a valuable and effective treatment method for such patients. The type of exercise applied to these patients is aerobic and resistance exercise with mild intensities and loads to avoid overloading the cardiovascular system. Blood flow restriction exercise is a novel exercise modality in clinical settings that has in many studies a similar effect on muscle hypertrophy, strength, and cardiovascular response to training at a 70% strength level without blood flow restriction. Since this exercise mode does not require high-intensity loads, it can be a safe method for improving muscle strength, cardiovascular endurance, and functionality in cardiovascular patients. Given that, the objective of this review is to assess and summarize existing evidence for the use of blood flow restriction in cardiovascular patients. A scoping review of existing clinical trials was conducted. Eleven studies were examined that suggested the use of blood flow restrictions in cardiovascular patients to achieve improvements in muscle strength, functionality, and cardiovascular parameters such as blood pressure decrease.

Impact of Blood-Flow-Restricted Training on Arterial Functions and Angiogenesis-A Systematic Review with Meta-Analysis

Despite growing evidence of the significant influence of blood-flow-restricted (BFR) training on different body functions, its impact on the vascular system, especially the arteries, is controversial. Therefore, the objective of our study was to analyze how BFR exercise, compared to other types of exercise without the restriction of blood flow, influences arterial functions and angiogenesis in adults. Studies comparing the effect of BFR versus non-BFR training on arterial parameters were divided into three categories: endothelial function, angiogenesis, and other vasculature functions. The search was based on Cochrane Library, PubMed®, and Embase, and 38 studies were included. The meta-analysis revealed a more significant improvement in flow-mediated dilatation (FMD) (p = 0.002) and the production of the primary angiogenesis biomarker vascular endothelial growth factor (VEGF) (p = 0.009) after BFR compared to non-BFR training (p = 0.002). The analysis of the pulse wave velocity, ankle-brachial index, systolic blood pressure, and heart rate did not show significant differences in changes between BFR and non-BFR training. The other parameters examined did not have sufficient data to be included in the meta-analysis. The results obtained present trends that suggest significant impacts of BFR training on endothelial functions and angiogenesis. There is still a lack of multicenter randomized clinical trials including many participants, and such studies are necessary to confirm the advantage of BFR over non-BFR activity.

Myofiber hypertrophy adaptations following 6 weeks of low-load resistance training with blood flow restriction in untrained males and females

The effects of low-load resistance training with blood flow restriction (BFR) on hypertrophy of type I/II myofibers remains unclear, especially in females. The purpose of the present study is to examine changes in type I/II myofiber cross-sectional area (fCSA) and muscle CSA (mCSA) of the vastus lateralis (VL) from before (Pre) to after (Post) 6 wk of high-load resistance training (HL; n = 15, 8 females) and low-load resistance training with BFR (n = 16, 8 females). Mixed-effects models were used to analyze fCSA with group (HL, BFR), sex (M, F), fiber type (I, II), and time (Pre, Post) included as factors. mCSA increased from pre- to posttraining (P < 0.001, d = 0.91) and was greater in males compared with females (P < 0.001, d = 2.26). Type II fCSA increased pre- to post-HL (P < 0.05, d = 0.46) and was greater in males compared with females (P < 0.05, d = 0.78). There were no significant increases in fCSA pre- to post-BFR for either fiber type or sex. Cohen's d, however, revealed moderate effect sizes in type I and II fCSA for males (d = 0.59 and 0.67), although this did not hold true for females (d = 0.29 and 0.34). Conversely, the increase in type II fCSA was greater for females than for males after HL. In conclusion, low-load resistance training with BFR may not promote myofiber hypertrophy to the level of HL resistance training, and similar responses were generally observed for males and females. In contrast, comparable effect sizes for mCSA and 1-repetition maximum (1RM) between groups suggest that BFR could play a role in a resistance training program.NEW & NOTEWORTHY This is the first study, to our knowledge, to examine myofiber hypertrophy from low-load resistance training with blood flow restriction (BFR) in females. Although this type of training did not result in myofiber hypertrophy, there were comparable increases in muscle cross-sectional area compared with high-load resistance training. These findings possibly highlight that males and females respond in a similar manner to high-load resistance training and low-load resistance training with BFR.

Insulin resistance, lipids and body composition in patients with coronary artery disease after combined aerobic training and resistance training: a randomised, controlled trial

BACKGROUND

The effect of resistance training (RT) in cardiac rehabilitation (CR) on insulin resistance remains elusive. We examined whether the addition of high-load (HL) or low loads (LL) RT has any effect on the levels of insulin resistance and lipids versus aerobic training (AT) alone in patients with coronary artery disease (CAD).

METHODS

Seventy-nine CAD patients were randomised to HL-RT [70-80% of one repetition maximum (1-RM)] and AT, LL-RT (35-40% of 1-RM) and AT or AT (50-80% of maximal power output), and 59 patients [75% males, 15% diabetics, age: 61 (8) years, left ventricular ejection fraction: 53 (9) %] completed the study. Plasma levels of glucose, insulin, blood lipids [total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL)] cholesterol and body composition were measured at baseline and post-training (36 training sessions).

RESULTS

Training intervention had only time effect on lean mass (p = 0.002), total and LDL cholesterol levels (both p < 0.001), and no effects on levels of glucose and insulin resistance (homeostatic assessment 2-insulin resistance). Total and LDL cholesterols levels decreased following AT [mean difference (95% confidence interval); total cholesterol: - 0.4 mmol/l (- 0.7 mmol/l, - 0.1 mmol/l), p = 0.013; LDL: - 0.4 mmol/l (- 0.7 mmol/l, - 0.1 mmol/l), p = 0.006] and HL-RT [total cholesterol: - 0.5 mmol/l (- 0.8 mmol/l, - 0.2 mmol/l), p = 0.002; LDL: - 0.5 mol/l (- 0.7 mmol/l, - 0.2 mmol/l), p = 0.002]. No associations were observed between post-training change in body composition and post-training change in blood biomarkers.

CONCLUSIONS

RT when combined with AT had no additional effect beyond AT alone on fasting glucose metabolism, blood lipids and body composition in patients with CAD. Trial registration number NCT04638764.

Application and progress of blood flow restriction training in improving muscle mass and strength in the elderly

As an emerging training method, blood flow restriction training has been proved to promote the growth of muscle mass and strength. In recent years, it has been gradually applied in different populations. However, there are few studies on how blood flow restriction training affects muscle mass and strength in the elderly. The relevant literature is compiled and summarized in this study. Through the comparison of blood flow restriction training with traditional training methods and its application in the elderly, it shows that blood flow restriction training can effectively increase muscle mass and strength, prevent muscle atrophy, improve cardiopulmonary function, facilitate injury and postoperative rehabilitation, and intervene in related degenerative diseases as a training method suitable for the elderly,. The main mechanism of blood flow restriction training promoting muscle mass and strength growth is metabolic stress response, including muscle fiber recruitment, protein synthesis signal pathway activation, hormone secretion, etc., and is also related to cell swelling caused by pressure. At present, although the application of blood flow restriction training in the elderly population is increasing, there is a lack of personalized programs. In the future, more research on the dose effect and safety of blood flow restriction training is needed to develop more accurate personalized training programs.

Stimulation of the Vascular Endothelium and Angiogenesis by Blood-Flow-Restricted Exercise

Blood-flow-restricted exercise (BFRE) has been gaining constantly increasing interest in rehabilitation, but its influence on endothelial functions has not been well studied yet. Our aim is to examine the influence of low-resistance BFRE on endothelial functions and angiogenesis. This prospective cross-over study involved 35 young healthy adults. They conducted a 21-min low-resistant exercise with blood flow restricted by pressure cuffs placed on arms and tights. They also did the same training but without blood flow restriction. Endothelial parameters and angiogenesis biomarkers were evaluated before and up to 20 min after exercise. Both types of exercise increased Flow-Mediated Dilatation (FMD) but elevation after BFRE was more significant compared to the controls. The stiffness index decreased only after BFRE, while the reflection index decreased significantly after both types of exercise but was higher after BFRE. Platelet endothelial cell adhesion molecule (PECAM-1) and vascular endothelial growth factor receptor 2 (VEGFR-2) concentrations were increased by both exercise types but elevations were higher after BFRE compared to the controls. Only BFRE elevated the mean serum CD34 protein concentration. Based on these results, we can assume that low-resistance BFR exercise stimulates angiogenesis and improves endothelial functions more significantly compared to the same training performed without blood flow restriction.

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

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

Beneficial Role of Blood Flow Restriction Exercise in Heart Disease and Heart Failure Using the Muscle Hypothesis of Chronic Heart Failure and a Growing Literature

Background: Blood flow restriction exercise (BFRE) has become a common method to increase skeletal muscle strength and hypertrophy for individuals with a variety of conditions. A substantial literature of BFRE in older adults exists in which significant gains in strength and functional performance have been observed without report of adverse events. Research examining the effects of BFRE in heart disease (HD) and heart failure (HF) appears to be increasing for which reason the Muscle Hypothesis of Chronic Heart Failure (MHCHF) will be used to fully elucidate the effects BFRE may have in patients with HD and HF highlighted in the MHCHF.

Methods: A comprehensive literature review was performed in PubMed and the Cochrane library through February 2022. Inclusion criteria were: 1) the study was original research conducted in human subjects older than 18 years of age and diagnosed with either HD or HF, 2) study participants performed BFRE, and 3) post-intervention outcome measures of cardiovascular function, physical performance, skeletal muscle function and structure, and/or systemic biomarkers were provided. Exclusion criteria included review articles and articles on viewpoints and opinions of BFRE, book chapters, theses, dissertations, and case study articles.

Results: Seven BFRE studies in HD and two BFRE studies in HF were found of which four of the HD and the two HF studies examined a variety of measures reflected within the MHCHF over a period of 8–24 weeks. No adverse events were reported in any of the studies and significant improvements in skeletal muscle strength, endurance, and work as well as cardiorespiratory performance, mitochondrial function, exercise tolerance, functional performance, immune humoral function, and possibly cardiac performance were observed in one or more of the reviewed studies.

Conclusion: In view of the above systematic review, BFRE has been performed safely with no report of adverse event in patients with a variety of different types of HD and in patients with HF. The components of the MHCHF that can be potentially improved with BFRE include left ventricular dysfunction, inflammatory markers, inactivity, a catabolic state, skeletal and possibly respiratory muscle myopathy, dyspnea and fatigue, ANS activity, and peripheral blood flow. Furthermore, investigation of feasibility, acceptability, adherence, adverse effects, and symptoms during and after BFRE is needed since very few studies have examined these important issues comprehensively in patients with HD and HF.

Greater Neuromuscular Fatigue Following Low Load Blood Flow Restriction than Non Blood Flow Restriction Resistance Exercise Among Recreationally Active Men

PURPOSE

The purpose of this study was to examine the acute effects of low-load blood flow restriction (LLBFR) and low-load non-BFR (LL) on neuromuscular function following a bout of standardized, fatiguing leg extension muscle actions.

METHODS

Fourteen men (mean age ± SD = 23±4 yrs) volunteered to participate in this investigation and randomly performed LLBFR and LL on separate days. Resistance exercise consisted of 75 isotonic, unilateral leg extension muscle actions performed at 30% of one-repetition maximum. Prior to (pretest) and after (posttest) performing each bout of exercise, strength and neural assessments were determined.

RESULTS

There was no pretest to posttest differences between LLBFR and LL for maximal voluntary isometric contraction (MVIC) torque or V-wave/M-wave responses (muscle compound action potentials assessed during a superimposed MVIC muscle action) which exhibited decreases (collapsed across condition) of 41.2% and 26.2%, respectively. There were pretest to posttest decreases in peak twitch torque (36.0%) and sEMG (29.5%) for LLBFR but not LL, and larger decreases in voluntary activation for LLBFR (11.3%) than LL (4.5%).

CONCLUSIONS

These findings suggested that LLBFR elicited greater fatigue-induced decreases in several indices of neuromuscular function relative to LL. Despite this, both LLBFR and LL resulted in similar decrements in performance as assessed by maximal strength.

Effects of Low-Load Blood Flow Restriction Training on Hemodynamic Responses and Vascular Function in Older Adults: A Meta-Analysis

Background: The combination of low-load (LL) training with blood flow restriction (BFR) has recently been shown to trigger a series of hemodynamic responses and promote vascular function in various populations. To date, however, evidence is sparse as to how this training regimen influences hemodynamic response and vascular function in older adults. Objective: To systematically evaluate the effects of LL-BFR training on hemodynamic response and vascular function in older adults. Methods: A PRISMA-compliant systematic review and meta-analysis were conducted. The systematic literature research was performed in the following electronic databases from their inception to 30 February 2022: PubMed, Web of Science, Scopus, EBSCO host, the Cochrane Library and CNKI. Subsequently, a meta-analysis with inverse variance weighting was conducted. Results: A total of 1437 articles were screened, and 12 randomized controlled trials with a total 378 subjects were included in the meta-analysis. The meta-analysis results showed that LL-BFR training caused a significant acute increase in heart rate (WMD: 4.02, 95% CI: 0.93, 7.10, p < 0.05), systolic blood pressure (WMD: 5.05, 95% CI: 0.63, 9.48, p < 0.05) and diastolic blood pressure (WMD: 4.87, 95% CI: 1.37, 8.37, p < 0.01). The acute hemodynamic response induced by LL-BFR training is similar to that elicited by high-load (HL) training. Training volume, cuff pressure and width were identified as significant moderators in our subgroup and meta-regression analyses. After 30 min of training, resting systolic blood pressure significantly decreased (WMD: −6.595, 95% CI: −8.88, −3.31, p < 0.01) in the LL-BFR training group, but resting hemodynamic indexes exhibited no significant differences compared with common LL and HL training; long-term LL-BFR training resulted in significant improvements in flow-mediated vasodilation (FMD) (WMD: 1.30, 95% CI: 0.50, 2.10, p < 0.01), cardio ankle vascular index (CAVI) (WMD: 0.55, 95% CI: 0.11, 0.99, p < 0.05) and ankle brachial index (ABI) (WMD: 0.03, 95% CI: 0.00, 0.06, p < 0.05) in older adults. Conclusion: This systematic review and meta-analysis reveals that LL-BFR training will cause an acute hemodynamic response in older adults, which can return to normal levels 30 min after training, and systolic blood pressure significantly decreased. Furthermore, the beneficial effect of LL-BFR training on vascular function is to improve FMD, CAVI and ABI of older adults. However, due to the influence of the quality of the included studies and the sample size, more high-quality studies are needed to confirm such issues as BFR pressure and training risk.

Cardiac Rehabilitation Improves Endothelial Function in Coronary Artery Disease Patients

Exercise-based cardiac rehabilitation may be an effective non-pharmacological intervention for improving endothelial function in coronary artery disease patients. Therefore, this systematic review with meta-analysis aimed to (a) estimate the training-induced effect on endothelial and vascular smooth muscle function, assessed by flow-mediated dilation and nitroglycerin-mediated dilation, respectively, in coronary artery disease patients; and to (b) study the influence of potential trial-level variables (i. e. study and intervention characteristics) on the training-induced effect on endothelial and vascular smooth muscle function. Electronic searches were performed in Pubmed, Scopus, and Embase up to February 2021. Random-effects models of standardised mean change were estimated. Heterogeneity analyses were performed by using the Chi ² test and I ² index. Our results showed that exercise-based cardiac rehabilitation significantly enhanced flow-mediated dilation (1.04 [95% confidence interval=0.76 to 1.31]) but did not significantly change nitroglycerin-mediated dilation (0.05 [95% confidence interval=-0.03 to 0.13]). Heterogeneity testing reached statistical significance (p<.001) with high inconsistency for flow-mediated dilation (I ² =92%). Nevertheless, none of the analysed variables influenced the training-induced effect on flow-mediated dilation. Exercise-based cardiac rehabilitation seems to be an effective therapeutic strategy for improving endothelial-dependent dilation in coronary artery disease patients, which may aid in the prevention of cardiovascular events.

The Effect of a Single Bout of Resistance Exercise with Blood Flow Restriction on Arterial Stiffness in Older People with Slow Gait Speed: A Pilot Randomized Study

Purpose: Low-intensity resistance exercise with moderate blood-flow restriction (LIRE-BFR) is a new trending form of exercises worldwide. The purpose of this study was to compare the acute effect of a single bout of traditional resistance exercise (TRE) and LIRE-BFR on arterial stiffness in older people with slow gait speeds. Methods: This was a randomized, controlled clinical study. Seventeen older adults (3 men; 14 women; 82 ± 5 years old) completed a session of TRE (n = 7) or LIRE-BFR (n = 10). At baseline and after 60 min post-exercise, participants were subject to blood pressure measurement, heart rate measurements and a determination of arterial stiffness parameters. Results: There was no significant difference between the TRE and LIRE-BFR group at baseline. Pulse-wave velocity increased in both groups (p < 0.05) post-exercise with no between-group differences. Both exercise modalities did not produce any adverse events. The increase in systolic blood pressure, pulse pressure, augmentation pressure and pulse wave velocity (all p > 0.05) were similar after both TRE and LIRE-BFR. Conclusion: TRE and LIRE-BFR had similar responses regarding hemodynamic parameters and pulse-wave velocity in older people with slow gait speed. Long-term studies should assess the cardiovascular risk and safety of LIRE-BFR training in this population.

A Useful Blood Flow Restriction Training Risk Stratification for Exercise and Rehabilitation

Blood flow restriction training (BFRT) is a modality with growing interest in the last decade and has been recognized as a critical tool in rehabilitation medicine, athletic and clinical populations. Besides its potential for positive benefits, BFRT has the capability to induce adverse responses. BFRT may evoke increased blood pressure, abnormal cardiovascular responses and impact vascular health. Furthermore, some important concerns with the use of BFRT exists for individuals with established cardiovascular disease (e.g., hypertension, diabetes mellitus, and chronic kidney disease patients). In addition, considering the potential risks of thrombosis promoted by BFRT in medically compromised populations, BFRT use warrants caution for patients that already display impaired blood coagulability, loss of antithrombotic mechanisms in the vessel wall, and stasis caused by immobility (e.g., COVID-19 patients, diabetes mellitus, hypertension, chronic kidney disease, cardiovascular disease, orthopedic post-surgery, anabolic steroid and ergogenic substance users, rheumatoid arthritis, and pregnant/postpartum women). To avoid untoward outcomes and ensure that BFRT is properly used, efficacy endpoints such as a questionnaire for risk stratification involving a review of the patient's medical history, signs, and symptoms indicative of underlying pathology is strongly advised. Here we present a model for BFRT pre-participation screening to theoretically reduce risk by excluding people with comorbidities or medically complex histories that could unnecessarily heighten intra- and/or post-exercise occurrence of adverse events. We propose this risk stratification tool as a framework to allow clinicians to use their knowledge, skills and expertise to assess and manage any risks related to the delivery of an appropriate BFRT exercise program. The questionnaires for risk stratification are adapted to guide clinicians for the referral, assessment, and suggestion of other modalities/approaches if/when necessary. Finally, the risk stratification might serve as a guideline for clinical protocols and future randomized controlled trial studies.

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.

Aging-Induced Impairment of Vascular Function: Mitochondrial Redox Contributions and Physiological/Clinical Implications

Significance: The vasculature responds to the respiratory needs of tissue by modulating luminal diameter through smooth muscle constriction or relaxation. Coronary perfusion, diastolic function, and coronary flow reserve are drastically reduced with aging. This loss of blood flow contributes to and exacerbates pathological processes such as angina pectoris, atherosclerosis, and coronary artery and microvascular disease. Recent Advances: Increased attention has recently been given to defining mechanisms behind aging-mediated loss of vascular function and development of therapeutic strategies to restore youthful vascular responsiveness. The ultimate goal aims at providing new avenues for symptom management, reversal of tissue damage, and preventing or delaying of aging-induced vascular damage and dysfunction in the first place. Critical Issues: Our major objective is to describe how aging-associated mitochondrial dysfunction contributes to endothelial and smooth muscle dysfunction via dysregulated reactive oxygen species production, the clinical impact of this phenomenon, and to discuss emerging therapeutic strategies. Pathological changes in regulation of mitochondrial oxidative and nitrosative balance (Section 1) and mitochondrial dynamics of fission/fusion (Section 2) have widespread effects on the mechanisms underlying the ability of the vasculature to relax, leading to hyperconstriction with aging. We will focus on flow-mediated dilation, endothelial hyperpolarizing factors (Sections 3 and 4), and adrenergic receptors (Section 5), as outlined in Figure 1. The clinical implications of these changes on major adverse cardiac events and mortality are described (Section 6). Future Directions: We discuss antioxidative therapeutic strategies currently in development to restore mitochondrial redox homeostasis and subsequently vascular function and evaluate their potential clinical impact (Section 7). Antioxid. Redox Signal. 35, 974-1015.

Feasibility of a high-PRotein Mediterranean-style diet and resistance Exercise in cardiac Rehabilitation patients with sarcopenic obesity (PRiMER): Study protocol for a randomised control trial

BACKGROUND

Cardiac rehabilitation (CR) is an essential component of long-term recovery following a cardiac event. Typical CR may not be optimal for patients presenting with sarcopenic obesity (SO) who present with reduced muscle mass and elevated adipose tissue, and may indicate greater cardiovascular disease (CVD) risk. Resistance exercise and high-protein diets are known to increase muscle mass, while Mediterranean-style diets have been shown to reduce CVD risk. A high-protein Mediterranean-style diet combined with resistance exercise intervention is yet to be trialled in cardiac rehabilitation populations.

OBJECTIVES

Primary outcome: to determine the feasibility of such an intervention by investigating the perceptions, acceptance and adherence to a resistance exercise protocol and high-protein Mediterranean style diet in a UK cardiac rehabilitation population with SO. Secondary outcome: to trial this protocol ahead of a fully powered clinical study.

METHODS

Eligible cardiac rehabilitation patients will be randomised to one of the following: 1) a control group (standard CR), 2) high-protein Mediterranean-style diet, 3) resistance exercise group, or 4) both high-protein Mediterranean-style diet and resistance exercise group. The pilot study will last 12 weeks. Measures of body composition (dual energy x-ray absorptiometry) grip strength, CVD risk (e.g., fasting triglycerides, glucose, cholesterol) and dietary adherence will be assessed at baseline and after 12 weeks. To compare groups, a mixed model ANOVA (time x intervention) will be performed. Patient participant involvement throughout the development of this project will be used to determine the feasibility of a future, fully powered, randomised control trial. A feasibility questionnaire will help establish the proportion of eligible participants, their willingness to be randomised, response rates, and ethical considerations. Furthermore, focus groups, food tasting and telephone interviews will be conducted to assess the acceptability of recipes and exercise protocols provided.

DISCUSSION

This pilot trial will determine whether a fully powered, multi-centred randomised control trial in CR patients with SO can be implemented. The information received from patient involvement will be invaluable for identifying possible barriers to participation and tailoring interventions to participant needs, helping to increase the likelihood of long-term compliance to health-promoting lifestyle changes.

REGISTRATION

This study is registered at clinicaltrials.gov (NCT04272073), registered on 17/02/2020, https://clinicaltrials.gov/ct2/show/NCT04272073.

DATE AND VERSION

28/12/20 version 3.0.

Resistance training in heart failure patients: a systematic review and meta-analysis

Aerobic training (AT) has been the primary mode of exercise training in cardiac rehabilitation. Historically, the reason for the prescription of AT was that it was speculated that although RT may be beneficial for some clinical outcomes, it may have an adverse effect on ventricular structure and function. However, RT has now made its way into current cardiac rehabilitation guidelines, including those directed towards patients with HF, albeit differences exist across institutions and guidelines. A systematic search of PubMed, EMBASE and Cochrane Trials Register on April 30, 2021, was conducted for exercise-based rehabilitation trials in HF. Randomised and controlled trials that reported on resistance training versus usual care or trials that directly compared RT to an AT intervention were included. Resistance training versus controls improves parameters of lower (SMD 0.76 (95%CI 0.26, 1.25, p = 0.003] and upper extremity muscle strength (SMD 0.85 (95%CI 0.35, 1.35), p = 0.0009], both key parameters of physical function throughout the lifespan. Importantly, RT in isolation, versus control, improves VO2peak [MD: 2.64 ml/kg/min (95%CI 1.67, 3.60), p < 0.00001] and 6MWD [MD: 49.94 m (95%CI 34.59, 65.29), p < 0.00001], without any detrimental effect on left ventricular parameters. Resistance training in HF patients is safe and improves parameters of physical function and quality of life. Where people with HF are unable to, or are not inclined to, partake in aerobic activity, RT alone is appropriate to elicit meaningful benefit.

Effects of exercise training with blood flow restriction on vascular function in adults: a systematic review and meta-analysis

Background

Blood flow restricted exercise (BFRE) improves physical fitness, with theorized positive effects on vascular function. This systematic review and meta-analysis aimed to report (1) the effects of BFRE on vascular function in adults with or without chronic health conditions, and (2) adverse events and adherence reported for BFRE.

Methodology

Five electronic databases were searched by two researchers independently to identify studies reporting vascular outcomes following BFRE in adults with and without chronic conditions. When sufficient data were provided, meta-analysis and exploratory meta-regression were performed.

Results

Twenty-six studies were included in the review (total participants n = 472; n = 41 older adults with chronic conditions). Meta-analysis (k = 9 studies) indicated that compared to exercise without blood flow restriction, resistance training with blood flow restriction resulted in significantly greater effects on endothelial function (SMD 0.76; 95% CI [0.36–1.14]). No significant differences were estimated for changes in vascular structure (SMD −0.24; 95% CI [−1.08 to 0.59]). In exploratory meta-regression analyses, several experimental protocol factors (design, exercise modality, exercised limbs, intervention length and number of sets per exercise) were significantly associated with the effect size for endothelial function outcomes. Adverse events in BFRE studies were rarely reported.

Conclusion

There is limited evidence, predominantly available in healthy young adults, on the effect of BFRE on vascular function. Signals pointing to effect of specific dynamic resistance exercise protocols with blood flow restriction (≥4 weeks with exercises for the upper and lower limbs) on endothelial function warrant further investigation.

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

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

Contralateral training effects of low-intensity blood-flow restricted and high-intensity unilateral resistance training

PURPOSE

Determine whether unilateral low-intensity blood-flow restricted (LIBFR) exercise is as effective as high-intensity (HI) resistance training for improving contralateral muscle strength.

METHODS

Thirty healthy adults (20-30 years) were randomly allocated to the following dynamic plantar-flexion training interventions: HI [75% of one-repetition maximum (1RM), 4 sets, 10 reps] and LIBFR [20% of 1RM, 4 sets, 30 + 15 + 15 + 15 reps]. Evoked V-wave and H-reflex recruitment curves, as well as maximal voluntary contraction (MVC) and panoramic ultrasound assessments of the trained and untrained soleus muscles were obtained pre-training, post-4 weeks of training and post-4 weeks of detraining.

RESULTS

Both interventions failed to increase contralateral MVC and muscle cross-sectional area (CSA). Yet, contralateral rate of torque development (RTD) was enhanced by both regimens (12-26%) and this was accompanied by heightened soleus EMG within the first milliseconds of the rising torque-time curve (14-22%; p < 0.05). These improvements were dissipated after detraining. Contralateral adaptations were not accompanied by changes in V-wave or H-reflex excitability. Conversely, LIBFR and HI elicited a similar magnitude of ipsilateral increase in MVC, RTD and CSA post-training (10-18%). Improvements in V-wave amplitude and soleus EMG were limited to the trained leg assigned to LIBFR training (p < 0.05). While gains in strength and CSA remained preserved post-4 weeks of detraining, this did not occur with RTD.

CONCLUSION

Since gains in RTD were similar between interventions, our findings indicate that both training regimens can be used interchangeably for improving contralateral rapid torque production. Ultimately, this may be beneficial in circumstances of limb immobilization after injury or surgery.

Does Resistance Training with Blood Flow Restriction Affect Blood Pressure and Cardiac Autonomic Modulation in Older Adults?

Resistance training (RT) with blood flow restriction (BFR) appears to accelerate muscle hypertrophy and strength gains in older populations. However, the training-related effects of RT with BFR upon blood pressure (BP) and cardiac autonomic modulation in the elderly remains unclear. The objective of this study is to compare the chronic effects of low-intensity RT performed with soft BFR (BFR) vs. high-intensity (HI) and low-intensity RT (CON) without BFR on BP and heart rate variability (HRV) indices in older adults. Thirty-two physically inactive participants (72 ± 7 yrs) performed RT for upper and lower limbs (50-min sessions, 3 times/week) for 12 weeks, being assigned into three groups: a) BFR; 30% of 1 repetition maximum (RM) with BFR corresponding to 50% of arterial occlusion pressure; b) HI; 70% of 1RM without BFR; c) CON; 30% of 1 RM without BFR. Resting BP and HRV were assessed at rest in the supine position, before and after exercise interventions. Systolic BP (Δ = -7.9 ± 8.0 mmHg; p = 0.002; effect size = 0.62), diastolic BP (Δ = trace length by the duration of the test 5.0 ± 6.0 mmHg; p = 0.007; effect size = 0.67) and mean arterial pressure (Δ = -6.3 ± 6.5 mmHg; p = 0.003/effect size = 0.77) reduced after BFR, remaining unaltered in HI and CON. HRV indices of sympathetic and vagal modulation did not change in all groups (p ≥ 0.07 for all comparisons). 12-wk RT with low intensity and relatively soft BFR substantially reduced BP at rest in older adults vs. traditional RT performed with either low or high intensity. Those reductions were not parallel to changes in autonomic modulation.

Effects of Blood Flow Restriction Training on Muscle Strength and Pain in Patients With Knee Injuries: A Meta-Analysis

BACKGROUND

Due to the pain caused by knee injuries, low-load resistance training with blood flow restriction (L-BFR) may be a potential adjuvant therapeutic tool in the rehabilitation of knee injuries. This review aimed to analyze the effectiveness of L-BFR training modality in knee rehabilitation.

DESIGN

A meta-analysis was conducted to determine the potential impact of blood flow restriction on patients with knee injuries. PubMed, EBSCO, and Web of Science databases were searched for eligible studies from January 2000 until January 2020. The mean differences of the data were analyzed using Revman 5.3 software with a 95% confidence interval.

RESULTS

Nine studies fulfilled the inclusion criteria. These studies involved 179 patients who received L-BFR, 96 patients who underwent high-load resistance training, and another 94 patients who underwent low-load resistance training. The analysis of pooled data showed that patients in both the L-BFR (standardized mean difference, 0.83 [0.53, 1.14], P < 0.01) and high-load resistance training (standardized mean difference, -0.09 [-0.43, 0.24], P = 0.58) groups experienced an increase in muscle strength after the training. In addition, pain score was significantly reduced in the L-BFR group compared with the other two groups (standardized mean difference, -0.61 [-1.19, -0.03], P = 0.04).

CONCLUSIONS

Muscle strength increased after L-BFR and high-load resistance training compared with low-load resistance training. Furthermore, pain score was significantly reduced after L-BFR. Hence, L-BFR is a potential intervention to be applied in rehabilitation of knee injuries.

Acute effects of physical exercise with different levels of blood flow restriction on vascular reactivity and biomarkers of muscle hypertrophy, endothelial function and oxidative stress in young and elderly subjects - A randomized controlled protocol

Background

Gains in muscle mass and strength have been documented in exercise training with blood flow restriction (BFR). However, the impact of retrograde blood flow during BFR training on vascular health remains unclear. The present study designed a protocol to evaluate the acute effects of exercise performed with different levels of BFR on vascular reactivity and biomarkers of endothelial function, oxidative stress, and muscle hypertrophy in young and older individuals.

Methods and study design

Sixty-eight physically inactive eutrophic men [34 young (18–25-yrs old) and 34 elderly (≥65-yrs old)] will be included in the study. Subjects will undergo three experimental protocols: a) control (ExCON) – handgrip exercise with intensity of 30% of the maximum voluntary contraction (MVC); b) blood flow restriction (ExBFR) – handgrip exercise with a resistance of 30% of the MVC with low level of BFR [80% of arterial occlusion pressure at rest (rAOP)]; and c) arterial occlusion pressure (ExAOP) – handgrip exercise with a resistance of 30% of the MVC with high level of BFR (120% of rAOP). Primary outcomes will be: a) vascular reactivity assessed by venous occlusion plethysmography; b) endothelial function (nitric oxide and apoptotic endothelial micro particles; c) oxidative stress (thiobarbituric acid reactive substances). Growth hormone and lactate concentration will be measured as secondary outcomes reflecting the hypertrophic drive and metabolic stress, respectively.

Discussion

The findings of the present study may help to elucidate the age-related impacts of BFR training on the vascular health.

Low-load resistance training with blood flow restriction prevent renal function decline: The role of the redox balance, angiotensin 1-7 and vasopressin✰,✰✰

AIMS

We sought to investigate the effect of resistance training (RT) and low-load RT with moderate blood flow restriction (RT+BFR) on blood pressure, exercise pressor response, redox balance and vasoactive peptides, body composition and muscle strength in patients with stage two of chronic kidney disease (CKD).

METHODS

We conducted a 6-month randomized controlled exercise intervention in 90 male and female hypertensive CKD patients (58±9 years with estimated glomerular filtration rate (eGFR; of 66.1 ± 1.2 mL/kg/1.73m²). Participants were randomized to one of three groups (n = 30/group); control group (CTL), RT, and RT+BFR. RT and RT+BFR performed three weekly training sessions using similar periodization for six months (two-month mesocycles), but of different intensities.

RESULTS

There was similarly effects between RT and RT+BFR in reducing systolic and diastolic blood pressure during daytime and 24hour period (RT: 10.4%; RT+BFR: 10.3% of decrease), fat mass, F₂-isoprostanes, asymmetric dimethylarginine (ADMA) and vasopressin (p<0.05 pre-vs post). Also promoted the increase of angiotensin 1-7, nitric oxide (NO), catalase, Trolox equivalent and muscle strength (p<0.05). Both training models attenuated the decline of estimated glomerular filtration rate (p<0.0001 vs CTL). However, only RT+BFR was associated with lower discomfort during exercise (p<0.0001 pre-vs post). Statistical significance was considered with p < 0.05.

CONCLUSION

These findings suggest low-load RT+BFR as a promising non-pharmacological strategy to control blood pressure, oxidative stress, vasoactive peptides, and consequently, attenuate the decrease of the eGFR.

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 TRAINING ON MUSCULAR PERFORMANCE, PAIN AND VASCULAR FUNCTION

Background

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

Purpose

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

Study Design

Randomized control trial.

Methods

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

Results

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

Conclusion

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

Level of Evidence

Therapy, Level 2.

Insulin resistance is associated with an exaggerated blood pressure response to ischemic rhythmic handgrip exercise in nondiabetic older adults

Patients with type 2 diabetes display an exaggerated pressor response to exercise. However, evidence supporting the association between the magnitude of the pressor response to exercise and insulin resistance-related factors including hemoglobin A1c (HbA1c) or homeostatic model assessment of insulin resistance (HOMA-IR) in nondiabetic subjects has remained sparse and inconclusive. Thus we investigated the relationship between cardiovascular responses to exercise and insulin resistance-related factors in nondiabetic healthy men (n = 23) and women (n = 22) above 60 yr old. We measured heart rate (HR) and blood pressure (BP) responses during: isometric handgrip (IHG) exercise of 30% maximal voluntary contraction, a period of skeletal muscle ischemia (SMI) induced by tourniqueting the arm after IHG, and rhythmic dynamic handgrip (DHG) exercise during SMI. Greater diastolic BP (DBP) responses to DHG with SMI was associated with male sex (r = 0.44, P = 0.02) and higher HbA1c (r = 0.33, P = 0.03), heart-ankle pulse wave velocity (haPWV) (r = 0.45, P < 0.01), and resting systolic BP (SBP) (r = 0.36, P = 0.02). HbA1c persisted as a significant determinant explaining the variance in the DBP response to DHG with SMI in multivariate models despite adjustment for sex, haPWV, and resting SBP. It was also determined that the DBP response to DHG with SMI in a group in which HOMA-IR was abnormal (Δ33 ± 3 mmHg) was significantly higher than that of groups in which HOMA-IR was at intermediate (Δ20 ± 4 mmHg) and normal (Δ23 ± 2 mmHg) levels. These data suggest that even in nondiabetic older adults, insulin resistance is related to an exaggerated pressor response to exercise especially when performed under ischemic conditions.NEW & NOTEWORTHY The diastolic blood pressure response to rhythmic dynamic handgrip exercise under ischemic conditions was demonstrated to be correlated with insulin resistance-related factors in nondiabetic older adults. This finding provides important insight to the prescription of exercise in this particular patient population as the blood pressure response to exercise, especially under ischemic conditions, could be exaggerated to nonsafe levels.

Blood flow restriction exercise stimulates mobilization of hematopoietic stem/progenitor cells and increases the circulating ACE2 levels in healthy adults

Adult CD34⁺ hematopoietic stem/progenitor cells (HSPC) in the systemic circulation are bone marrow-derived and have the propensity of maintaining cardiovascular health. Activation of angiotensin-converting enzyme-2 (ACE2)-angiotensin-(1-7)-Mas receptor pathway, the vascular protective axis of the renin-angiotensin system (RAS), stimulates vasculogenic functions of HSPCs. In a previous study, exposure to hypoxia increased the expressions of ACE2 and Mas, and stimulated ACE2 shedding. The current study tested if blood flow restriction exercise (BFR)-induced regional hypoxia recapitulates the in vitro observations in healthy adults. Hypoxia was induced by 80% limb occlusion pressure (LOP) via inflation cuff. Muscle oxygen saturation was determined using near-infrared spectroscopy. Peripheral blood was collected 30 min after quiet sitting (control) or after BFR. Lin^-CD45^lowCD34⁺ HSPCs were enumerated by flow cytometry, and ACE and ACE2 activities were determined in plasma and cell lysates and supernatants. Regional hypoxia resulted in muscle oxygen saturation of 17.5% compared with 49.7% in the control condition (P < 0.0001, n = 9). Circulating HSPCs were increased following BFR (834.8 ± 62.1/mL) compared with control (365 ± 59, P < 0.001, n = 7), which was associated with increased stromal-derived factor 1α and vascular endothelial growth factor receptor levels by four- and threefold, respectively (P < 0.001). ACE2 activity was increased in the whole cell lysates of HSPCs, resulting in an ACE2-to-ACE ratio of 11.7 ± 0.5 in BFR vs 9.1 ± 0.9 in control (P < 0.05). Cell supernatants have threefold increase in the ACE2-to-ACE ratio following BFR compared with control (P < 0.001). Collectively, these findings provide strong evidence for the upregulation of ACE2 by acute regional hypoxia in vivo. Hypoxic exercise regimens appear to be promising means of enhancing vascular regenerative capacity.NEW & NOTEWORTHY Although many studies have explored the mechanisms of skeletal muscle growth and adaptation with hypoxia exercise interventions, less attention has been given to the potential for vascular adaptation and regenerative capacity. This study shows for the first time an acute upregulation of the angiotensin-converting enzyme 2 and increase in CD34⁺ vasculogenic cells following an acute bout of blood flow restriction with low-intensity exercise. These rapid changes collectively promote skeletal muscle angiogenesis. Therefore, this study supports the potential of hypoxic exercise interventions with low intensity for vascular and muscle health.

A focused review of myokines as a potential contributor to muscle hypertrophy from resistance-based exercise

PURPOSE

Resistance exercise induces muscle growth and is an important treatment for age-related losses in muscle mass and strength. Myokines are hypothesized as a signal conveying physiological information to skeletal muscle, possibly to "fine-tune" other regulatory pathways. While myokines are released from skeletal muscle following contraction, their role in increasing muscle mass and strength in response to resistance exercise or training is not established. Recent research identified both local and systemic release of myokines after an acute bout of resistance exercise. However, it is not known whether myokines with putative anabolic function are mechanistically involved in producing muscle hypertrophy after resistance exercise. Further, nitric oxide (NO), an important mediator of muscle stem cell activation, upregulates the expression of certain myokine genes in skeletal muscle.

METHOD

In the systemic context of complex hypertrophic signaling, this review: (1) summarizes literature on several well-recognized, representative myokines with anabolic potential; (2) explores the potential mechanistic role of myokines in skeletal muscle hypertrophy; and (3) identifies future research required to advance our understanding of myokine anabolism specifically in skeletal muscle.

RESULT

This review establishes a link between myokines and NO production, and emphasizes the importance of considering systemic release of potential anabolic myokines during resistance exercise as complementary to other signals that promote hypertrophy.

CONCLUSION

Investigating adaptations to resistance exercise in aging opens a novel avenue of interdisciplinary research into myokines and NO metabolites during resistance exercise, with the longer-term goal to improve muscle health in daily living, aging, and rehabilitation.

Blood flow restriction impairs the inflammatory adaptations of strength training in overweight men: a clinical randomized trial

The aim of this study was to evaluate the impact of high-intensity strength training (ST) or low-intensity strength training with blood flow restriction (ST-BFR) on monocyte subsets, the expression of C-C chemokine receptor 5 (CCR5), and CD16 on monocytes, and tumor necrosis factor alpha (TNF-α) production of overweight men. Thirty overweight men were randomly assigned to conventional ST or ST-BFR. Both groups performed exercises of knee extension and biceps curl with equal volume (3 sessions/week) over 8 weeks, and the peripheral frequency of monocytes (CD14+CD16-, classical monocytes; CD14+CD16+, intermediate monocytes; CD14-CD16+, nonclassical monocytes), the mean fluorescence intensity (MFI) of CCR5 and CD16 on CD14+ monocytes; and the production of TNF-α by lipopolysaccharide (LPS)-stimulated cells were quantified. Eight weeks of ST increased the frequency of CD14+CD16- monocytes (p = 0.04) and reduced the percentage of CD14-CD16+ (p = 0.02) and the production of TNF-α by LPS-stimulated cells (p = 0.03). The MFI of CD16 on CD14+ monocytes decreased after the ST intervention (p = 0.02). No difference in monocyte subsets, CCR5 or CD16 expression, and TNF-α production were identified after ST-BFR intervention (p > 0.05). The adoption of ST promotes anti-inflammatory effects on monocyte subsets of overweight men, but this effect was lost when BFR was adopted. Novelty High-intensity strength training reduces the production of TNF-α and the peripheral frequency of CD16+ monocytes in overweight men. Blood flow restriction method blunts the strength training adaptations on monocyte subsets and pro-inflammatory TNF-α production in overweight men.

Clinical safety of blood flow-restricted training? A comprehensive review of altered muscle metaboreflex in cardiovascular disease during ischemic exercise

Blood flow restriction training (BFRT) is an increasingly widespread method of exercise that involves imposed restriction of blood flow to the exercising muscle. Blood flow restriction is achieved by inflating a pneumatic pressure cuff (or a tourniquet) positioned proximal to the exercising muscle before, and during, the bout of exercise (i.e., ischemic exercise). Low-intensity BFRT with resistance training promotes comparable increases in muscle mass and strength observed during high-intensity exercise without blood flow restriction. BFRT has expanded into the clinical research setting as a potential therapeutic approach to treat functionally impaired individuals, such as the elderly, and patients with orthopedic and cardiovascular disease/conditions. However, questions regarding the safety of BFRT must be fully examined and addressed before the implementation of this exercise methodology in the clinical setting. In this respect, there is a general concern that BFRT may generate abnormal reflex-mediated cardiovascular responses. Indeed, the muscle metaboreflex is an ischemia-induced, sympathoexcitatory pressor reflex originating in skeletal muscle, and the present review synthesizes evidence that BFRT may elicit abnormal cardiovascular responses resulting from increased metaboreflex activation. Importantly, abnormal cardiovascular responses are more clearly evidenced in populations with increased cardiovascular risk (e.g., elderly and individuals with cardiovascular disease). The evidence provided in the present review draws into question the cardiovascular safety of BFRT, which clearly needs to be further investigated in future studies. This information will be paramount for the consideration of BFRT exercise implementation in clinical populations.

Strength training with blood flow restriction - a novel therapeutic approach for older adults with sarcopenia? A case report

Introduction

A 91-year-old sedentary man presenting exhaustion, lower-limb weakness, hypertension, and history of multiple falls was diagnosed with sarcopenia – appendicular skeletal muscle mass index (ASM) of 7.10 kg/m².

Purpose

To investigate the effects of strength training performed with low intensity in isolation (LI) or with blood flow restriction (LI-BFR) on strength, muscle mass, IGF-1, endothelial function, microcirculation, inflammatory biomarkers, and oxidative stress.

Methods

In the first 3 months, LI was performed with intensity corresponding to 30% of 1 repetition maximum, followed by 1 month of inactivity, and another 3 months of LI-BFR (similar load than LI concomitant to BFR equivalent to 50% of resting systolic blood pressure).

Results

LI-BFR, but not LI improved muscle mass, ASM, handgrip strength, isokinetic peak torque, IL-6, and IGF-1. Endothelial function, red blood cell velocity, and concentrations of C-reactive protein, and soluble intercellular adhesion molecules-1 improved after both LI and LI-BFR. Endothelin-1 and oxidative stress increased after LI-BFR, and lowered after LI.

Conclusion

LI-BFR, but not LI improved strength, muscle mass, IGF-1, endothelial function, and selected inflammatory markers in a nonagenarian sarcopenic patient. These results are promising and suggest that LI-BFR should be considered as an alternative to prevent muscle loss and improve functional fitness in frail older populations.