Abstract
BackgroundThe purpose of this study was to clarify whether there is a synergistic effect on muscular strength and hypertrophy when low-intensity resistance training is performed after heat stress.MethodsThirty healthy young male volunteers were randomly allocated to either the low-intensity resistance training with heat stress group or the control group. The control group performed low-intensity resistance training alone. In the low-intensity resistance training with heat stress group, a hot pack was applied to cover the muscle belly of the triceps brachii for 20 min before the training. The duration of the intervention was 6 weeks. In both groups, the training resistance was 30% of the one repetition maximum, applied in three sets with eight repetitions each and 60-s intervals. The one repetition maximum of elbow extension and muscle thickness of triceps brachii were measured before and after 6 weeks of low intensity resistance training.ResultsThere was no significant change in the one-repetition maximum and muscle thickness in the control group, whereas there was a significant increase in the muscle strength and thickness in the low-intensity resistance training with heat stress group.ConclusionThe combination of heat stress and low-intensity resistance training was an effective method for increasing muscle strength and volume.Trial registrationUniversity Hospital Medical Information Network Clinical Trials Registry (UMIN000036167; March 11, 2019).
Highlights
The purpose of this study was to clarify whether there is a synergistic effect on muscular strength and hypertrophy when low-intensity resistance training is performed after heat stress
We aimed to investigate the effect of lowintensity resistance training performed after heat stress, which was applied in a manner that is realistic in clinical settings, on muscle mass and strength
No significant differences were found between these group in terms of 1RM before intervention using unpaired t-test (p = 0.873)
Summary
The purpose of this study was to clarify whether there is a synergistic effect on muscular strength and hypertrophy when low-intensity resistance training is performed after heat stress. High-intensity resistance training with at least 60– 80% of one-repetition maximum (1RM) is recommended to increase muscle mass [1, 2]. Studies have reported that low-intensity resistance training with blood flow restriction training or slow movements and tonic force generation induced a significant increase in muscle mass [6, 7]. It has to be considered that the training intensity and the total work (training intensity × repetitions) performed is important to increase muscle mass. No significant difference has been found in the increase in muscle mass between low-intensity, high-repetition resistance training, and high-intensity resistance training when the total work was the same [8,9,10]. It is necessary to develop a more effective low-intensity resistance training method for this scenario
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