Exercise heat acclimation and post-exercise hot water immersion improve resting and exercise responses to heat stress in the elderly.

Abstract

OBJECTIVES\nTo investigate the efficacy of heat acclimation (HA) in the young (YEX) and elderly (EEX) following exercise-HA, and the elderly utilising post-exercise hot water immersion HA (EHWI).\n\n\nDESIGN\nCross-sectional study.\n\n\nMETHOD\nTwenty-six participants (YEX: n\u202f=\u202f11 aged 22\u202f±\u202f2\u202fyears, EEX:n\u202f=\u202f8 aged 68\u202f±\u202f3\u202fyears, EHWI: n\u202f=\u202f7 aged 73\u202f±\u202f3\u202fyears) completed two pre-/post-tests, separated by five intervention days. YEX and EEX exercised in hot conditions to raise rectal temperature (Trec) ≥38.5\u202f°C within 60\u202fmin, with this increase maintained for a further 60\u202fmin. EHWI completed 30\u202fmin of cycling in temperate conditions, then 30\u202fmin of HWI (40\u202f°C), followed by 30\u202fmin seated blanket wrap. Pre- and post-testing comprised 30\u202fmin rest, followed by 30\u202fmin of cycling exercise (3.5\u202fW·kg-1 Ḣprod), and a six-minute walk test (6MWT), all in 35\u202f°C, 50% RH.\n\n\nRESULTS\nThe HA protocols did not elicit different mean heart rate (HR), Trec, and duration Trec\u202f≥\u202f38.5\u202f°C (p\u202f>\u202f0.05) between YEX, EEX, and EHWI groups. Resting Trec, peak skin temperature, systolic and mean arterial pressure, perceived exertion and thermal sensation decreased, and 6MWT distance increased pre- to post-HA (p\u202f<\u202f0.05), with no difference between groups. YEX also demonstrated a reduction in resting HR (p\u202f<\u202f0.05). No change was observed in peak Trec or HR, vascular conductance, sweat rate, or thermal comfort in any group (p\u202f>\u202f0.05).\n\n\nCONCLUSIONS\nIrrespective of age or intervention, HA induced thermoregulatory, perceptual and exercise performance improvements. Both exercise-HA (EEX), and post-exercise HWI (EHWI) are considered viable interventions to prepare the elderly for heat stress.