Abstract
The aim of this study was to evaluate the acute and adaptive effects of passive extreme heat (100 ± 3 °C) exposition in combination with a strength training protocol on maximal isometric handgrip strength. Fifty-four untrained male university students participated in this investigation. Twenty-nine formed the control group (NG) and 25 the heat-exposed group (HG). All the participants performed a 3-week isotonic handgrip strength training program twice a week with a training volume of 10 series of 10 repetitions with 45-s rest between series, per session. All the subjects only trained their right hand, leaving their left hand untrained. HG performed the same training protocol in hot (100 ± 3 °C) conditions in a dry sauna. Maximal isometric handgrip strength was evaluated each training day before and after the session. NG participants did not experience any modifications in either hand by the end of the study while HG increased maximal strength values in both hands (p < 0.05), decreased the difference between hands (p < 0.05), and recorded higher values than the controls in the trained (p < 0.05) and untrained (p < 0.01) hands after the intervention period. These changes were not accompanied by any modification in body composition in either group. The performance of a unilateral isotonic handgrip strength program in hot conditions during the three weeks induced an increase in maximal isometric handgrip strength in both hands without modifications to bodyweight or absolute body composition.
Highlights
In the context of sport performance, heat stress has been traditionally considered a critical issue by physicians and athletes, especially in endurance disciplines [1]
The exposure of humans to heat by using saunas or thermal chambers has been used for several decades as a strategy to increase heat tolerance as well as to decrease its negative side effects on human physical performance [2]
The Normothermia Group (NG) did not experience any change during the intervention, the heat-exposed group (HG) experienced a decrease in body lean mass percentage (p < 0.05; R = 0.21) and body water percentage (p < 0.05; R = 0.33) at the end of the study in comparison to the respective initial values
Summary
In the context of sport performance, heat stress has been traditionally considered a critical issue by physicians and athletes, especially in endurance disciplines [1]. By itself, develops interesting physiological responses beyond these endurance effects and information has emerged over the last few years on the positive effect of muscle temperature on its mechanical and metabolic properties [3]. New ergogenic properties have recently been attributed to heat in the context of high-intensity physical performance [4] as well as in muscle anabolism [5]. A recent review suggests that heat stress seems favorable for short-term, maximal performance [6]. High-intensity physical exercises generally lead to dramatic demands on the nervous and metabolic systems [7,8], as well as to high amounts of muscle damage; as occurs in the
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