Muscle activation during low-intensity muscle contractions with restricted blood flow

Abstract

We examined muscle activation during low-intensity muscle contractions with a moderate restriction of blood flow and complete occlusion of blood flow. Unilateral elbow flexion muscle contractions (20% of 1-RM) were performed in Experiment 1 (30 contractions), Experiment 2 (3 sets x 10 contractions), and Experiment 3 (30 repetitive contractions followed by 3 sets x 15 contractions) with moderate restriction, complete occlusion of blood flow or unrestricted blood flow (control). Electromyography (EMG) was recorded from surface electrodes placed on the biceps brachii muscle and the integrated EMG (iEMG) and mean power frequency (MPF) obtained. During Experiments 1 and 2, muscle activation was progressively increased in complete occlusion and moderate restriction of blood flow to levels greater than in the control. The decline in maximal voluntary isometric contraction (MVC) following the bout of contractions was greater with complete occlusion (39-48%) than moderate restriction of blood flow (16-19%); control MVC did not change. In Experiment 3, changes in MVC, iEMG, and MPF were greater with moderate restriction of blood flow than in the control but comparable with complete occlusion of blood flow where less total work was performed. In conclusion, moderate restriction of blood flow results in similar neural manifestations in muscle as complete occlusion of blood flow but without the apparent contractile/metabolic impairment observed with complete occlusion. Thus, low-intensity muscle contractions, with moderate restriction of blood flow, leads to more intense activation of the muscle relative to the external load.

Skeletal muscle size and strength are increased following walk training with restricted leg muscle blood flow: implications for training duration and frequency

“…Further, the average reported score for intensity and discomfort (including pain) for all participants was 11-14 on a scale of 6-20, using the Borg RPE Scale (Borg, 1982). These scores are significantly lower than those reported in previous KAATSU resistance training studies (Takarada et al, 2002;Yasuda et al, 2009) and in HIT studies, which reported intense muscle fatigue and discomfort (Campos et al, 2002;Hurley et al, 1984 [Borg RPE scores were reported as 18 1]). This contrast makes KAATSU-walk training ideal for elderly or frail individuals.…”

Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development

“…Importantly, this accumulation of metabolites may increase muscle cell swelling [25], intramuscular anabolic/anti-catabolic signalling [9,26,27], and muscle fibre recruitment [4,28], which are all thought to be beneficial for muscular adaptation [23]. Furthermore, evidence suggests that the hypoxic environment created during BFR may increase the activation and proliferation of myogenic stem cells, enhancing the hypertrophic response [29].…”

Physiological stimuli necessary for muscle hypertrophy

“…Metabolic stress results from the accumulation of metabolic by-products such as H + and Pi 18) . It has been hypothesized that the development of metabolic stress triggers secondary reactions including the recruitment of additional motor units to compensate for the force loss 19) , elevation of systemic hormones 20) , greater acute muscle cell swelling 21) and production of reactive oxygen species (ROS) 22) . These mechanisms may increase the rate of muscle protein synthesis through activation of anabolic and/or prevention of catabolic signaling pathways, leading to hypertrophy [23][24][25][26] as well as the proliferation of satellite cells 27) .…”