Effects of Resistance Training with Heat Stress on Muscle Mass, Strength and Performance

Abstract: Background: Recent research has demonstrated the presence of heat being an effective stimulus for increasing skeletal muscle and strength. The exposure of increased environmental temperature combined with resistance training has been shown to amplify muscle adaptation for hypertrophy and strength. However, research into the potential effects of using heat stress combined with resistance training to increase performance criteria, such as speed and agility, are minimal. Utilizing a hot environment coupled with an intense exercise regime has been considered as a potential aid for sport preparation given the evidence that heat stress has on promoting hypertrophy and strength. The desired result is to enhance athletic performance. Aim: The aim of this study was to examine if (a) performing resistance training in a hot environment for 10 weeks induces greater increases in muscle mass and (b) whether this combination improves performance in speed, agility and strength compared to resistance training in a standard temperate environment. Methods: 17 healthy male adults, who have undergone a consistent regime of resistance training in the six months leading up to the study, were distributed at random into two groups; (1) Intervention group (Heat n=8) training in 40°C and (2) control group (Con, n=9) training in 23°C. Each group would follow a 10-week resistance exercise protocol. To monitor time-course adaptations, lean body mass, speed, agility and strength were measured at baseline, week 5 and week 10. Results: Over the selected training period, there was no statistically significant difference observed between the two groups or time x group interaction, over the 10-week exercise duration with respect to lean body mass, speed, agility or strength. Conclusion: Compared to the resistance training regime in the standard temperature condition of 23°C (group two), training results suggest heat stress in the hot environment at 40°C (group one) had no effective stimulus in amplifying hypertrophic adaptations in skeletal muscle nor in increasing performance in speed, agility or strength. Certain hypothetical factors were implicated for heat stress being ineffective such as potential counter-productive aspects from heat exposure or flawed methodology.