Blood flow restriction increases metabolic stress but decreases muscle activation during high‐load resistance exercise

Abstract

Introduction: We investigated differences in metabolic stress (lactate) and muscle activation (electromyography; EMG) when high-load resistance exercise (HL) is compared with a condition in which blood flow restriction (BFR) is applied during the exercise or during the rest interval. Methods: Twelve participants performed HL with BFR during the intervals (BFR-I), during the set (BFR-S), and without BFR. Each condition consisted of 3 sets of 8 repetitions with knee extension at 70% of 1-repetition maximum. Lactate and root mean square (RMS) from the surface EMG of the vastus lateralis were calculated. Results: Lactate increased in all protocols but was higher with BFR-I than with BFR-S and HL. RMS decreased under all conditions, with a larger effect size in BFR-I (1.47) than in BFR-S (0.66) and HL (0.59). Discussion: BFR-I increases lactate, possibly as a result of reduced restoration of ATP. Muscle activation seems to be impacted by mechanical stress but may be reduced by metabolic stress. Muscle Nerve 57: 107-111, 2018The American College of Sports Medicine recommends that participants perform resistance exercise with a load of at least 70% of their 1-repetition maximum (1RM) to stimulate substantial gains in muscle mass and strength.1 However, over the past decade, several studies have found that low-load resistance exercise (e.g., 20%-40% of 1RM) in combination with blood flow restriction (BFR) results in muscle mass gain similar to that obtained with traditional high-load resistance exercise (HL; $70% 1RM). 2-7The benefits of low-load resistance exercise combined with BFR are thought to be driven by acute metabolic stress, whereas HL is driven predominantly by mechanical factors.8 It is conceivable that the combination of high levels of both mechanical and metabolic stress could work together to augment muscle growth. Therefore, it seems reasonable to speculate on the importance of keeping both mechanical and metabolic stress elevated.Given that restricting blood flow increases metabolic stress during low-load resistance training 9,10 and that muscle contraction against high loads restricts blood flow while performing the set, [11][12][13] one possible strategy to increase metabolic stress is to restrict blood flow during rest intervals. However, maintenance of BFR after completion of exercise does not offer benefits to muscle growth, 14 suggesting that metabolites, per se, do not appear to have anabolic properties in the absence of mechanical stress.Taken together, these results suggest that maintenance of BFR only during the rest intervals may offer a novel strategy for potentially augmenting the effects of high-load contractions in resistance exercise by increasing both metabolic stress and muscle activation. Therefore, this study compares metabolic stress (by blood lactate) and muscle activation (by electromyography-root mean square [EMG-RMS] amplitude) during HL under 3 conditions: blood flow restricted during the sets (BFR-S), blood flow restricted during the rest intervals (BFR-I), and witho...

The effects of acute blood flow restriction on climbing-specific tests

“…Still, the present study only compared maximal isometric and dynamic strength with and without BFR and demonstrated no harms or benefits. The isometric and dynamic strength results in the present study were supported by previous studies, which also reported no acute effects of BFR on strength tests (Fatela et al, 2016;Teixeira et al, 2018).…”

“…One might speculate that specific finger and forearms adaptions after years of climbing, could reduce the peripheral fatigue. For example, previous studies not including climbers have demonstrated increased peripheral fatigue with BFR (Schoenfeld, 2013;Teixeira et al, 2018). In addition, the present study examined relatively small muscles in contrast to previous studies examining the legs (MacDougall et al, 1992).…”

“…The aim of the study was, therefore, to compare the acute effects of BFR in climbing specific grip tests (maximal isometric grip strength), power (dynamic pull-up test) and intermittent finger endurance test among climbers. We hypothesized reduced performance in the intermittent endurance test with BFR, but similar results with and without BFR in the strength tests (isometric and dynamic) due to short period of maximal effort (Fatela et al, 2016;Teixeira et al, 2018).…”

The Cardiovascular and Perceptual Response to Very Low Load Blood Flow Restricted Exercise

“…Blood flow restriction was applied by placing a 5 cm wide nylon cuff (SC5, Hokanson, Bellevue, WA) to the proximal portion of the exercising limb and inflating it to either 40 or 80 % of pre-exercise arterial occlusion. These particular pressures were investigated as they are often used in the blood flow restriction research [4,7,14,27] and both have been shown to elicit muscle adaptation [8,15]. After inflation the participants performed four sets of elbow flexion with one of three experimental loads (10, 15, or 30 % of 1RM).…”

Pre-competition and recovery strategies in elite sport: the use of vascular occlusion and ischemic preconditioning

“…Further studies have started to investigate the effect of higher intensity exercise with occlusion immediately prior to performance. Teixeira et al (2017) applied vascular occlusion during the rest period between sets, whilst exercising and compared this to knee-extension exercise performed at 70% 1RM without any vascular occlusion. The results infer vascular occlusion applied during the rest intervals increased lactate to a greater extent, possibly due to reduced restoration of ATP, however, EMG of the vastus laterallis indicate a decreased activation in all conditions.…”