Abstract
Purpose: We examined the effects of moderate resistance exercise (RE) on serum cortisol, testosterone, extracellular heat shock protein (HSP70), and interleukin (IL)-6 and IL-15 concentrations in untrained males in a hot environment.Methods: Ten untrained young males (26 ± 3 years; 75.8 ± 6 kg; 177.4 ± 5.3 cm) performed two series of full body RE [3 sets of 8 to 10 repetitions, 30–60 s recovery between series with 70% of one maximal repetition (1-RM), with a rest period of 1 to 3 min between exercises] carried out in a random order in both heated (∼35°C) and thermoneutral (22°C) conditions. Serum concentrations of testosterone, cortisol, HSP70, and IL-6 and IL-15 were measured before, at the end, and 1 h after RE sessions. Participants in both groups consumed 4 ml of water/kg body mass every 15 min.Results: There were time-related changes in testosterone, HSP70, and IL-6 (P < 0.001), and cortisol and IL-15 (P < 0.05). Levels of cortisol, HSP70, and IL-6 increased immediately for RE at 35°C, and testosterone and IL-15 levels were decreased. Changes in serum testosterone, HSP70, cortisol, and IL-15 and IL-6 levels were reversed after 1 h. A significant time × condition interaction was observed for IL-15 and HSP70 (P < 0.001), cortisol and IL-6 (P < 0.05), but not for testosterone (P > 0.05).Conclusion: RE in a heated environment may not be appropriate for achieving muscle adaptations due to acute changes of hormonal and inflammatory markers.
Highlights
Healthy humans regulate resting body temperature near ∼37◦C, but environmental perturbations can expand the range of temperature regulation without adverse health consequences (Sonna et al, 2000; Byrne et al, 2006)
We investigated the effects of a single session of moderate resistance exercise (RE) in the heat (35◦C) on serum levels of cortisol, testosterone, heat shock protein (HSP), Interleukin 6 (IL-6), and Interleukin 15 (IL-15) in untrained adult males
Shapiro–Wilk tests indicated a normal distribution of cortisol (p = 0.132), testosterone (p = 0.761), 70 kilodalton heat shock protein (HSP70) (p = 0.711), IL-6 (p = 0.238), and IL-15 concentrations (p = 0.315) in thermoneutral conditions, and for cortisol (p = 0.421), testosterone (p = 0.345), HSP70 (p = 0.125), IL-6 (p = 0.241), and IL-15 concentrations (p = 0.433) in heated conditions
Summary
Healthy humans regulate resting body temperature near ∼37◦C, but environmental perturbations can expand the range of temperature regulation (ranging between ∼35◦C and ∼41◦C) without adverse health consequences (Sonna et al, 2000; Byrne et al, 2006). Exercise under heated environmental conditions can lead to dehydration due to changes in plasma volume caused by sweating and transient fluid movement into and out of the intravascular space (Zouhal et al, 2009). This reduction in plasma volume lowers blood supply to working muscles. Increases in stress and body temperature alter cytokine levels, muscle contractility and force transmission, metabolic rate, substrate partitioning, and anabolic status during exercise (Ferguson et al, 2002; Steinacker et al, 2004; Girard et al, 2015; Vingren et al, 2016; Suzuki, 2019). Increases in anabolic hormone concentrations after an acute bout of resistance exercise (RE) in the trained state promote muscle protein synthesis (Kraemer and Ratamess, 2005)
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