The effect of acute low-load resistance exercise with the addition of blood flow occlusion on muscle function in children and adults
Background: Resistance training recommendations to increase muscular strength suggest using high loads. However, some individuals cannot withstand high mechanical stress. Thus, in adults, low-load training is used with blood flow occlusion (BFO), to mimic strength increases from high-load training. Due to differing physiological responses to exercise, children may respond differently to BFO than adults. This study compares the effect of low-load exercise with BFO on maximal voluntary contraction (MVC) and electromyographical (EMG) activity in children and adults. Methods: 16 men (24.4±2.5y) and 14 boys (10.7±2.0y) performed two experimental conditions: (1) occlusion and (2) control. During the occlusion condition, a blood pressure cuff on the upper arm was inflated above systolic pressure during 25 wrist flexions at 35% MVC. Participants then performed an MVC and rated their perceived exertion (RPE). The control condition was the same as the occlusion condition but without the use of BFO. EMG signal was recorded from the flexor carpi radialis (FCR). Results: Men displayed a 16.9±7.1% increase in FCR EMG amplitude across the occlusion (p=0.005) but not the control condition (p=0.919). The boys did not show a change in EMG amplitude between time points (p=0.576) or conditions (p=0.549). Across both age groups, EMG mean power frequency was influenced by a condition-x-time interaction, with a larger decrease across the occlusion (-20.1±9.6%; p<0.001) than the control condition (-5.6±9.7%; p=0.002). Furthermore, across both age groups, MVC torque decreased more following the occlusion (-18.7±12.8%; p<0.001) than the control condition (-6.7±12.5%; p<0.001). Discussion: Based on our findings, a partial explanation for increases in EMG amplitude in the men but not the boys may be that the men recruited more of their higher-threshold motor units than the boys. However, not all measures were consistent in showing child-adult differences, as BFO caused similar decreases in MPF for both groups. Thus, while adults use low-loads with BFO to simulate high-load training, it remains unclear whether this form of training would be as effective for children.