Age‐related differences in the neuromuscular performance of fatigue‐provoking exercise under severe whole‐body hyperthermia conditions.

Purpose: The purpose of this study was to determine if aging would lead to greater decline in neuromuscular function during a fatiguing task under severe whole‐body hyperthermia conditions. Methods: Twelve young (aged 19–21 years) and 11 older (aged 65–80 years) males were enrolled in the study, which comprised a randomized control trial under a thermoneutral condition at an ambient temperature of 23°C (CON) and an experimental trial with passive lower body heating in 43°C water (HWI‐43°C). Changes in neuromuscular function and fatigability, and physical performance‐influencing factors such as psychological, thermoregulatory, neuroendocrine, and immune responses to whole‐body hyperthermia were measured. Results: A slower increase in rectal temperature, and a lower heart rate, thermal sensation, and sweating rate were observed in older males than young males in response to HWI‐43°C trial (p < 0.05). Nevertheless, prolactin increased more in response to hyperthermia in young males, while interleukin‐6 and cortisol levels increased more in older males (p < 0.05). Peripheral dopamine levels decreased in older males and increased in young males in response to hyperthermia (p < 0.05). Surprisingly, older males demonstrated greater neuromuscular fatigability resistance and faster maximal voluntary contraction (MVC) torque recovery after a 2‐min sustained isometric MVC task under thermoneutral and severe hyperthermic conditions (p < 0.05). Conclusion: Neuromuscular performance during fatigue‐provoking sustained isometric exercise under severe whole‐body hyperthermia conditions appears to decline in both age groups, but a lower relative decline in torque production for older males may relate to lower psychological and thermophysiological strain along with a diminished dopamine response and prolactin release. [ABSTRACT FROM AUTHOR]