The Feasibility of Blood Flow Restriction Exercise in Patients With Incomplete Spinal Cord Injury

Mechanisms of muscle repair after peripheral nerve injury by electrical stimulation combined with blood flow restriction training

This review elucidates the impact of electrical stimulation (ES) and blood flow restriction (BFR) training on muscle function. ES induces a transformation in muscle fibers type by rearranging myosin heavy chain isoform patterns. Additionally, it influences muscle protein synthesis and degradation through specific signaling pathways such as protein kinase B/mechanistic target of rapamycin (Akt/mTOR), as well as via autophagy and the ubiquitin-proteasome system, thereby effectively maintaining muscle mass. BFR, on the other hand, restricts muscle blood flow, leading to metabolic products accumulation and localized hypoxia, which not only promotes the recruitment of fast-twitch fibers but also activates the mTOR signaling pathway, enhancing muscle protein synthesis. The combination of ES and BFR synergistically facilitates muscle protein synthesis through the mTOR pathway, thereby accelerating the recovery of muscle function following peripheral nerve injury.

Feasibility and safety of two weeks of blood flow restriction exercise in individuals with spinal cord injury

CONTEXT

Reduced muscle strength and function are common after spinal cord injury (SCI). While low-load blood flow restriction exercise (BFRE) enhances muscle strength in healthy and clinical populations, its safety and feasibility in individuals with SCI remain underexplored.

OBJECTIVES

To investigate the feasibility and safety of low-load BFRE in individuals with incomplete SCI.

STUDY DESIGN

Case series.

SETTING

SCI rehabilitation center.

PARTICIPANTS

Six participants with motor incomplete SCI were enrolled in the study.

INTERVENTION

A two-week BFRE intervention for the lower limbs was conducted twice weekly at 40% total arterial occlusion pressure, using 30-40% of 1-repetition maximum loads.

OUTCOME MEASURES

Feasibility measures, specifically recruitment and eligibility rates and intervention acceptability, were collected. Blood pressure (BP) responses and specific coagulation markers for deep vein thrombosis (DVT) were assessed as safety measures.

RESULTS

Recruitment and eligibility rates were 2.8% and 6.6% for individuals admitted for first-time rehabilitation (subacute SCI) and 8.3% and 13.9% for 4-week readmission rehabilitation stays (chronic SCI), respectively. Intervention acceptability was high, characterized by 95.8% training adherence and low-to-moderate self-reported pain levels. BP responses and changes in C-reactive protein, Fibrinogen, and D-dimer during the intervention remained within clinically acceptable levels.

CONCLUSION

BFRE was feasible in an SCI rehabilitation setting despite a low recruitment rate. BFRE imposed no heightened risk of DVT or severe BP fluctuations in the present case series. Additionally, no severe adverse events occurred, and only mild complaints were reported. More extensive safety considerations warrant larger-scale exploration.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03690700.

Enhancing upper extremity muscle strength in individuals with spinal cord injury using low-intensity blood flow restriction exercise

OBJECTIVES

This study explores the feasibility and effects of low-intensity blood flow restriction exercise on forearm muscle strength and function in individuals with spinal cord injury.

STUDY DESIGN

Pilot randomized clinical trial.

PATIENTS AND METHODS

Ten male and female adult participants with chronic cervical and thoracic spinal cord injury underwent an 8-week low-intensity blood flow restriction exercise programme that targeted forearm muscles. Each participant's contralateral forearm served as the control. Grip strength was the primary outcome measure, and participants also provided qualitative feedback on their experiences.

RESULTS

The study revealed a significant increase in participants' forearm muscle strength on the experimental side engaged in low-intensity blood flow restriction training, with an average strength gain of 7.5 ± 0.36 kg after 16 exercise sessions (Cohen's d = -6.32, 95% CI -8.34, -6.68). In comparison, the control side, following a conventional high- intensity exercise regimen without BFR, showed a more modest strength increase of 4.4 ± 0.67 kg. A mean Patient's Global Impression of Change score of 2.2 reflected overall improvements in participants' daily activities and health status.

CONCLUSION

This study highlights the feasibility and effectiveness of low-intensity blood flow restriction exercise as a safe and promising approach to enhancing forearm muscle strength in individuals with spinal cord injury. The observed positive outcomes, coupled with a high level of participant satisfaction, underscore the potential of this innovative method to significantly improve limb muscle strength, thereby contributing to greater functional independence in this population.

Blood flow restriction combined with resistance training on muscle strength and thickness improvement in young adults: a systematic review, meta-analysis, and meta-regression

BACKGROUND

High-intensity resistance training is known to be the most effective method for enhancing muscle strength and thickness, but it carries potential injury risks. Blood flow restriction (BFR) combined with resistance training has been proposed as a safer alternative method for improving muscle strength and thickness.

METHODS

A meta-analysis was conducted, including 20 studies from five databases that met the inclusion criteria, to assess the efficacy of BFR combined with resistance training compared to traditional resistance training (NOBFR). The analysis focused on changes in muscle strength and thickness. Subgroup analysis and meta-regression were performed to explore the effects of tourniquet width and pressure.

RESULTS

The findings showed that BFR combined with resistance training is comparable to traditional resistance training in enhancing muscle strength [0.11, 95%CI: (-0.08 to 0.29), I 2 = 0%] and muscle thickness [-0.07, 95% CI: (-0.25 to 0.12), I 2 = 0%]. Subgroup analysis indicated no significant differences in muscle strength (P = 0.66) and thickness (P = 0.87) between low-intensity BFR training and other intensity levels. Meta-regression suggested that tourniquet width and pressure might affect intervention outcomes, although the effects were not statistically significant (P > 0.05).

CONCLUSION

BFR combined with resistance training offers a viable alternative to high-intensity resistance training with reduced injury risks. We recommend interventions of 2-3 sessions per week at 20%-40% of 1 RM, using a wider cuff and applying an arterial occlusion pressure of 50%-80% to potentially enhance muscle strength and thickness. It is also recommended to release tourniquet pressure during rest intervals to alleviate discomfort. This protocol effectively improves muscle strength with minimal cardiac workload and reduced risk of adverse events.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023495465], identifier [CRD42023495465].

Concerns about the application of resistance exercise with blood-flow restriction and thrombosis risk in hemodialysis patients

BACKGROUND

Hemodialysis (HD) per se is a risk factor for thrombosis. Considering the growing body of evidence on blood-flow restriction (BFR) exercise in HD patients, identification of possible risk factors related to the prothrombotic agent D-dimer is required for the safety and feasibility of this training model. The aim of the present study was to identify risk factors associated with higher D-dimer levels and to determine the acute effect of resistance exercise (RE) with BFR on this molecule.

METHODS

Two hundred and six HD patients volunteered for this study (all with a glomerular filtration rate of <15 mL/min/1.73 m2). The RE + BFR session consisted of 50% arterial occlusion pressure during 50 min sessions of HD (intradialytic exercise). RE repetitions included concentric and eccentric lifting phases (each lasting 2 s) and were supervised by a strength and conditioning specialist.

RESULTS

Several variables were associated with elevated levels of D-dimer, including higher blood glucose, citrate use, recent cardiovascular events, recent intercurrents, higher inflammatory status, catheter as vascular access, older patients (>70 years old), and HD vintage. Furthermore, RE + BFR significantly increases D-dimer after 4 h. Patients with borderline baseline D-dimer levels (400-490 ng/mL) displayed increased risk of elevating D-dimer over the normal range (≥500 ng/mL).

CONCLUSION

These results identified factors associated with a heightened prothrombotic state and may assist in the screening process for HD patients who wish to undergo RE + BFR. D-dimer and/or other fibrinolysis factors should be assessed at baseline and throughout the protocol as a precautionary measure to maximize safety during RE + BFR.

Safety and efficacy of blood flow restriction exercise in individuals with neurological disorders: A systematic review

OBJECTIVES

This systematic review evaluated the safety and efficacy of blood flow restriction exercise (BFRE) on skeletal muscle size, strength, and functional performance in individuals with neurological disorders (ND).

METHODS

A literature search was performed in PubMed, CINAHL, and Embase. Two researchers independently assessed eligibility and performed data extraction and quality assessments.

ELIGIBILITY CRITERIA

Study populations with ND, BFRE as intervention modality, outcome measures related to safety or efficacy.

RESULTS

Out of 443 studies identified, 16 were deemed eligible for review. Three studies examined the efficacy and safety of BFRE, one study focused on efficacy results, and 12 studies investigated safety. Disease populations included spinal cord injury (SCI), inclusion body myositis (sIBM), multiple sclerosis (MS), Parkinson's disease (PD), and stroke. A moderate-to-high risk of bias was presented in the quality assessment. Five studies reported safety concerns, including acutely elevated pain and rating of perceived exertion levels, severe fatigue, muscle soreness, and cases of autonomic dysreflexia. Two RCTs reported a significant between-group difference in physical function outcomes, and two RCTs reported neuromuscular adaptations.

CONCLUSION

BFRE seems to be a potentially safe and effective training modality in individuals with ND. However, the results should be interpreted cautiously due to limited quality and number of studies, small sample sizes, and a general lack of heterogeneity within and between the examined patient cohorts.

The Acute and Chronic Effects of Resistance and Aerobic Exercise in Hemostatic Balance: A Brief Review

Hemostatic balance refers to the dynamic balance between blood clot formation (coagulation), blood clot dissolution (fibrinolysis), anticoagulation, and innate immunity. Although regular habitual exercise may lower the incidence of cardiovascular diseases (CVD) by improving an individual’s hemostatic profile at rest and during exertion, vigorous exercise may increase the risk of sudden cardiac death and venous thromboembolism (VTE). This literature review aims to investigate the hemostatic system’s acute and chronic adaptive responses to different types of exercise in healthy and patient populations. Compared to athletes, sedentary healthy individuals demonstrate similar post-exercise responses in platelet function and coagulatory and fibrinolytic potential. However, hemostatic adaptations of patients with chronic diseases in regular training is a promising field. Despite the increased risk of thrombotic events during an acute bout of vigorous exercise, regular exposure to high-intensity exercise might desensitize exercise-induced platelet aggregation, moderate coagulatory parameters, and up-regulate fibrinolytic potential via increasing tissue plasminogen activator (tPA) and decreasing plasminogen activator inhibitor (PAI-1) response. Future research might focus on combining different types of exercise, manipulating each training characteristic (frequency, intensity, time, and volume), or investigating the minimal exercise dosage required to maintain hemostatic balance, especially in patients with various health conditions.

Effectiveness of Blood Flow Restriction in Neurological Disorders: A Systematic Review

There is scientific evidence that Blood Flow Restriction (BFR) is beneficial in healthy people, the elderly and patients with musculoskeletal disorders. A systematic review was conducted to evaluate the effectiveness of BFR in patients with neurological disorders. The literature search was conducted up until July 2022 in the following databases: PubMed, Web of Science (WOS), Physiotherapy Evidence Database (PEDro), LILACS, Scopus, Cumulative Index of Nursing and Allied Literature Complete (CINAHL), the Cochrane Library and Scientific Electronic Library Online (SciELO). The PEDro scale was used to analyze the methodological quality of the studies, and the Cochrane Collaboration's tool was employed to evaluate the risk of bias. A total of seven articles were included. BFR seems to be beneficial in neurological disorders. Improvements have been found in sensorimotor function, frequency and step length symmetry, perceived exertion, heart rate and gait speed, walking endurance, fatigue, quality of life, muscles thickness, gluteus density and muscle edema. No improvements were found in lower limb strength or balance. However, results must be taken with caution due to the small number of articles and to the large heterogeneity. More clinical trials are needed. These studies should homogenize the protocols used in larger samples, as well as improve their methodological quality.

Sympathetic Nerve Activity and Blood Pressure Response to Exercise in Peripheral Artery Disease: From Molecular Mechanisms, Human Studies, to Intervention Strategy Development

Sympathetic nerve activity (SNA) regulates the contraction of vascular smooth muscle and leads to a change in arterial blood pressure (BP). It was observed that SNA, vascular contractility, and BP are heightened in patients with peripheral artery disease (PAD) during exercise. The exercise pressor reflex (EPR), a neural mechanism responsible for BP response to activation of muscle afferent nerve, is a determinant of the exaggerated exercise-induced BP rise in PAD. Based on recent results obtained from a series of studies in PAD patients and a rat model of PAD, this review will shed light on SNA-driven BP response and the underlying mechanisms by which receptors and molecular mediators in muscle afferent nerves mediate the abnormalities in autonomic activities of PAD. Intervention strategies, particularly non-pharmacological strategies, improving the deleterious exercise-induced SNA and BP in PAD, and enhancing tolerance and performance during exercise will also be discussed.

Acute effects of electrostimulation and blood flow restriction on muscle thickness and fatigue in the lower body

AbstractNeuromuscular electrical stimulation (NMES) in combination with blood flow restriction (BFR) enhances muscle hypertrophy and force-generating capacity. The present study aimed to investigate the acute effects of BFR and NMES, both in isolation and in combination, on muscle thickness (MT) and fatigue in the lower body of 20 young healthy subjects. Different stimuli were applied for 25 min, defined by the combination of BFR with high- and low-frequency NMES, and also isolated BFR or NMES. Changes in MT were then evaluated by ultrasound of the rectus femoris (RF) and vastus lateralis (VL) muscles at the end of the session (POST) and 15 min later (POST 15'). Lower limb fatigue was evaluated indirectly by strength performance. Results showed that RF MT was higher under the combined protocol (BFR+NMES) or isolated BFR than under NMES - regardless of the frequency - both at POST (p ≤ 0.018) and POST 15' (p ≤ 0.016). No significant changes in MT were observed under isolated NMES or BFR at POST 15' when compared with basal values (p ≥ 0.067). No significant differences were observed for VL MT between conditions (p = 0.322) or for fatigue between conditions (p ≥ 0.258). Our results indicate that a combination of BFR and NMES acutely increases MT in sedentary subjects. Also, although not significantly, BFR conditions had a greater tendency to induce fatigue than isolated NMES.

Clinical use of blood flow restriction in people with neurologic conditions: a cross-sectional survey

[Purpose] There is little evidence for blood flow restriction (BFR), or Kaatsu, training in people with neurologic conditions. This study's purpose was to survey clinicians on BFR use in people with neurologic conditions. [Participants and Methods] One-hundred twelve physical therapists and other healthcare professionals who reported using BFR in the past 5 years completed an anonymous, online survey. [Results] Eighty-nine percent of respondents thought BFR was safe in people with neurologic conditions. Meanwhile, 38% reported BFR use in people with neurologic conditions. The most common intervention used with BFR was resistance training (n=33) and the most commonly reported benefit was improved strength (n=27). The most common side-effect causing treatment to stop was intolerance to pressure (n=6). No side-effects requiring medical attention were reported. In order to support future BFR use in neurologic populations, the most common response was the need for more research (n=63). [Conclusion] Despite the lack of evidence, clinical use of BFR in people with neurologic conditions may be somewhat common. Although this study had a relatively small sample size and collected data retrospectively, the results support the potential clinical feasibility and safety of BFR use in patients with neurologic conditions and suggest that more research is needed.

Overall Safety and Risks Associated with Blood Flow Restriction Therapy: A Literature Review

INTRODUCTION

Blood flow restriction therapy (BFRT) is used in scenarios ranging from muscle building in athletic performance to decreasing recovery time in postoperative orthopedic rehabilitation. The efficacy of BFRT for treating diseases has been increasingly researched; however, there has been less literature focused on establishing the safety of this therapy.

MATERIALS AND METHODS

An extensive literature review pertaining to BFRT and any deleterious events related to its usage was completed by searching multiple databases, including PubMed, EMBASE, and Cochrane Library using the terms "blood flow restriction therapy" or "KAATSU."

RESULTS

Ten case reports, five case series, two national surveys, two questionnaires, six randomized controlled studies, and one systematic review were included. A total of 1,672 individuals reported an adverse event following BFRT use out of 25,813 individuals. Commonly reported adverse events were numbness, dizziness, subcutaneous hemorrhage, and rhabdomyolysis. There were unique adverse effects of this therapy reported in individuals with comorbid conditions, such as hypertension and thoracic outlet syndrome, which included isolated cases of central retinal vein occlusion and Paget-Schroeder syndrome.

CONCLUSION

Blood flow restriction provides tremendous opportunity with a potential for accelerated exercise rehabilitation and injury prevention. This modality could be used in the military setting to help injured active duty personnel expeditiously return to deployable status. Further prospective randomized controlled trials are warranted to further support BFRT safety; however, from this literature review, it can be concluded that BFRT can be utilized safely in the proper patient population when administered by qualified professionals who have undergone the appropriate training.

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.

Association of clinical and laboratory variables with in-hospital incidence of deep vein thrombosis in patients after acute ischemic stroke: A retrospective study

Deep vein thrombosis (DVT) is a serious complication in patients with acute ischemic stroke (AIS). Early prediction of DVT could enable physicians to perform a proper prevention strategy. We analyzed the association of clinical and laboratory variables with DVT to evaluate the risk of DVT in patients after AIS.AIS patients admitted to the Changsha Central Hospital between January 2017 and December 2019 with length of stay in hospital ≥7 days were included. Clinical and laboratory variables for DVT at baseline were collected, and the diagnosis of DVT was confirmed by ultrasonography. Independent factors were developed by Multivariate logistic regression analysis.A total of 101 patients were included in the study. The in-hospital incidence of DVT after AIS was 19.8%(20/101). The average level of D-dimer when DVT detected was significant increased around 4-fold than that on admission (P < .001). Pulmonary infection (odds ratio [OR] = 5.4, 95%CI:1.10-26.65, P = .037)) and increased muscle tone (OR = 0.11, 95%CI:0.02-0.58, P = .010) as independent relevant factors for DVT were confirmed.Pulmonary infection as a risk factor and increased muscle tone as a protective factor for DVT were identified in patients after AIS. The level of D-dimer which increased around 4-fold compared to the initial level could be an indicator for DVT occurrence.

Is there rationale for the cuff pressures prescribed for blood flow restriction exercise? A systematic review

BACKGROUND

Blood flow restriction exercise has increasingly broad applications among healthy and clinical populations. Ensuring the technique is applied in a safe, controlled, and beneficial way for target populations is essential. Individualized cuff pressures are a favored method for achieving this. However, there remains marked inconsistency in how individualized cuff pressures are applied.

OBJECTIVES

To quantify the cuff pressures used in the broader blood flow restriction exercise literature, and determine whether there is clear justification for the choice of pressure prescribed.

METHODS

Studies were included in this review from database searches if they employed an experimental design using original data, involved either acute or chronic exercise using blood flow restriction, and they assessed limb or arterial occlusion pressure to determine an individualized cuff pressure. Methodologies of the studies were evaluated using a bespoke quality assessment tool.

RESULTS

Fifty-one studies met the inclusion criteria. Individualized cuff pressures ranged from 30% to 100% arterial occlusion pressure. Only 7 out of 52 studies attempted to justify the individualized cuff pressure applied during exercise. The mean quality rating for all studies was 11.1 ± 1.2 out of 13.

CONCLUSIONS

The broader blood flow restriction exercise literature uses markedly heterogeneous prescription variables despite using individualized cuff pressures. This is problematic in the absence of any clear justification for the individualized cuff pressures selected. Systematically measuring and reporting all relevant acute responses and training adaptations to the full spectrum of BFR pressures alongside increased clarity around the methodology used during blood flow restriction exercise is paramount.

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.

NIRS-EMG for Clinical Applications: A Systematic Review

In this review, we present an overview of the applications and computed parameters of electromyography (EMG) and near-infrared spectroscopy (NIRS) methods on patients in clinical practice. The eligible studies were those where both techniques were combined in order to assess muscle characteristics from the electrical and hemodynamic points of view. With this aim, a comprehensive screening of the literature based on related keywords in the most-used scientific data bases allowed us to identify 17 papers which met the research criteria. We also present a brief overview of the devices designed specifically for muscular applications with EMG and NIRS sensors (a total of eight papers). A critical analysis of the results of the review suggests that the combined use of EMG and NIRS on muscle has been only partially exploited for assessment and evaluation in clinical practice and, thus, this field shows promises for future developments.