Myoelectric Activity and Fatigue in Low-Load Resistance Exercise With Different Pressure of Blood Flow Restriction: A Systematic Review and Meta-Analysis.

Victor Sabino De Queiros,Dihogo Gama De Matos,Michal Wilk,Gabriel Rodrigues Neto,Jefferson Da Silva Novaes,Robert Trybulski,Breno Guilherme De Araújo Tinoco Cabral,Piotr Makar,João Guilherme Vieira,Paulo Moreira Silva Dantas,Ingrid Martins De França,Wouber Hérickson De Brito Vieira,Isis Kelly Dos Santos

doi:10.3389/fphys.2021.786752

Abstract

Background: Low-load resistance exercise (LL-RE) with blood flow restriction (BFR) promotes increased metabolic response and fatigue, as well as more pronounced myoelectric activity than traditional LL-RE. Some studies have shown that the relative pressure applied during exercise may have an effect on these variables, but existing evidence is contradictory.Purpose: The aim of this study was to systematically review and pool the available evidence on the differences in neuromuscular and metabolic responses at LL-RE with different pressure of BFR.Methods: The systematic review and meta-analysis was reported according to PRISMA items. Searches were performed in the following databases: CINAHL, PubMed, Scopus, SPORTDiscus and Web of Science, until June 15, 2021. Randomized or non-randomized experimental studies that analyzed LL-RE, associated with at least two relative BFR pressures [arterial occlusion pressure (AOP)%], on myoelectric activity, fatigue, or metabolic responses were included. Random-effects meta-analyses were performed for MVC torque (fatigue measure) and myoelectric activity. The quality of evidence was assessed using the PEDro scale.Results: Ten studies were included, all of moderate to high methodological quality. For MVC torque, there were no differences in the comparisons between exercise with 40–50% vs. 80–90% AOP. When analyzing the meta-analysis data, the results indicated differences in comparisons in exercise with 15–20% 1 repetition maximum (1RM), with higher restriction pressure evoking greater MVC torque decline (4 interventions, 73 participants; MD = −5.05 Nm [95%CI = −8.09; −2.01], p = 0.001, I2 = 0%). For myoelectric activity, meta-analyses indicated a difference between exercise with 40% vs. 60% AOP (3 interventions, 38 participants; SMD = 0.47 [95%CI = 0.02; 0.93], p = 0.04, I2 = 0%), with higher pressure of restriction causing greater myoelectric activity. This result was not identified in the comparisons between 40% vs. 80% AOP. In analysis of studies that adopted pre-defined repetition schemes, differences were found (4 interventions, 52 participants; SMD = 0.58 [95%CI = 0.11; 1.05], p = 0.02, I2 = 27%).Conclusion: The BFR pressure applied during the LL-RE may affect the magnitude of muscle fatigue and excitability when loads between 15 and 20% of 1RM and predefined repetition protocols (not failure) are prescribed, respectively.Systematic Review Registration: [http://www.crd.york.ac.uk/prospero], identifier [CRD42021229345].

Highlights

Blood flow restriction (BFR) is a commonly used technique by physical therapists and trainers aiming at physical rehabilitation and neuromuscular adaptations (Nakajima et al, 2006; Patterson and Brandner, 2018; de Queiros et al, 2021)
When analyzing the meta-analysis data, the results indicated differences in comparisons in exercise with 15–20% 1 repetition maximum (1RM), with higher restriction pressure evoking greater maximum voluntary contraction (MVC) torque decline (4 interventions, 73 participants; MD = −5.05 Nm [95% confidence interval (95%CI) = −8.09; −2.01], p = 0.001, I2 = 0%)
Meta-analyses indicated a difference between exercise with 40% vs. 60% arterial occlusion pressure (AOP) (3 interventions, 38 participants; standardized mean difference (SMD) = 0.47 [95%CI = 0.02; 0.93], p = 0.04, I2 = 0%), with higher pressure of restriction causing greater myoelectric activity

Summary

Introduction

Blood flow restriction (BFR) is a commonly used technique by physical therapists and trainers aiming at physical rehabilitation and neuromuscular adaptations (Nakajima et al, 2006; Patterson and Brandner, 2018; de Queiros et al, 2021) This is certainly justified by the fact that some evidence indicates that lowload {20–40% of 1 repetition maximum [1RM] (Lopez et al, 2021)} resistance training with arterial BFR and venous occlusion artificially induced can promote gains in muscle strength and hypertrophy more pronounced than low-load resistance training without BFR (NO-BFR) (Loenneke et al, 2012) and, in some cases, similar to NO-BFR high-load resistance training (Takarada et al, 2000a; Laurentino et al, 2012).

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