Multistage, ultra-endurance events in hot, humid conditions necessitate thermal adaptation, often achieved through short term heat acclimation (STHA), to improve performance by reducing thermoregulatory strain and perceptions of heat stress. This study investigated the physiological, perceptual and immunological responses to STHA prior to the Marathon des Sables. Eight athletes (age 42 ± 4 years and body mass 81.9 ± 15.0 kg) completed 4 days of controlled hyperthermia STHA (60 min·day, 45°C and 30% relative humidity). Pre, during and post sessions, physiological and perceptual measures were recorded. Immunological measures were recorded pre-post sessions 1 and 4. STHA improved thermal comfort (P = 0.02), sensation (P = 0.03) and perceived exertion (P = 0.04). A dissociated relationship between perceptual fatigue and T was evident after STHA, with reductions in perceived Physical (P = 0.04) and General (P = 0.04) fatigue. Exercising T and HR did not change (P > 0.05) however, sweat rate increased 14% (P = 0.02). No changes were found in white blood cell counts or content (P > 0.05). Four days of STHA facilitates effective perceptual adaptations, without compromising immune status prior to an ultra-endurance race in heat stress. A greater physiological strain is required to confer optimal physiological adaptations.

When completing exercise that equates to activities of daily living, elderly people could have a decreased perceptual awareness of the environment even though physiological markers of thermal strain are elevated. Consequently, the elderly could be less likely to implement behavioural thermoregulation interventions (i.e. seek shade and/or remove excess layers) due to a decreased awareness of an increasingly thermally challenging environment.

Objectives: To investigate the efficacy of heat acclimation (HA) in the young (Y EX ) and elderly (E EX ) following exercise-HA, and the elderly utilising post-exercise hot water immersion HA (E HWI ). Design: Cross-sectional study. Method: Twenty-six participants (Y EX : n = 11 aged 22 ± 2 years, E EX: n = 8 aged 68 ± 3 years, E HWI : n = 7 aged 73 ± 3 years) completed two pre-/post-tests, separated by five intervention days. Y EX and E EX exercised in hot conditions to raise rectal temperature (T rec ) ≥38.5°C within 60 min, with this increase maintained for a further 60 min. E HWI completed 30 min of cycling in temperate conditions, then 30 min of HWI (40°C), followed by 30 min seated blanket wrap. Pre-and post-testing comprised 30 min rest, followed by 30 min of cycling exercise (3.5 W•kg −1 Ḣ prod), and a six-minute walk test (6MWT), all in 35°C, 50% RH. Results: The HA protocols did not elicit different mean heart rate (HR), T rec , and duration T rec ≥ 38.5°C (p > 0.05) between Y EX , E EX , and E HWI groups. Resting T rec , peak skin temperature, systolic and mean arterial pressure, perceived exertion and thermal sensation decreased, and 6MWT distance increased pre-to post-HA (p < 0.05), with no difference between groups. Y EX also demonstrated a reduction in resting HR (p < 0.05). No change was observed in peak T rec or HR, vascular conductance, sweat rate, or thermal comfort in any group (p > 0.05). Conclusions: Irrespective of age or intervention, HA induced thermoregulatory, perceptual and exercise performance improvements. Both exercise-HA (E EX ), and post-exercise HWI (E HWI ) are considered viable interventions to prepare the elderly for heat stress.

Introduction: the aim of this study was to assess the validity of a novel wearable sweat rate monitor against an array of sweat analysis techniques which determine sudomotor function when exercising moderately under heat stress. Construct validity was determined utilising a 5-day short-term heat acclimation (STHA) intervention. Methods: Nineteen healthy individuals (age: 41 ± 23 years, body mass: 74.0 ± 12.2 kg, height: 174.9 ± 6.9 cm) [male; n = 15, female; n = 4] completed nine trials over a three-week period, in a controlled chamber set to 35°C, 50% relative humidity for all sessions. The pre and post-trials were separated by five consecutive controlled hyperthermia HA sessions. Sweat analysis was compared from pre and post-trial, whereby whole body sweat rate (WBSR) was assessed via pre and post nude body mass. Local sweat rate (LSR) was determined via technical absorbent patches (TA) (weighed pre and post) and a novel wearable KuduSmart® (SMART) monitor which was placed on the left arm during the 30-minutes of exercise. Tegaderm patches, used to measure sweat sodium chloride conductivity (SC), and TA patches were placed on the back, chest and forearm for the 30-minutes cycling. Results: Sudomotor function significantly adapted via STHA (p < 0.05); demonstrated by a WBSR increase of 24%, LSR increase via the TA method (back: 26%, chest: 45% and arm: 48%) and LSR increase by the SMART monitor (35%). Finally, SC decreased (back: -21%, chest: -25% and arm: -24%, p < 0.05). Conclusion: All sweat techniques were sensitive to sudomotor function adaptation following STHA, reinforcing their validity. The real time data given by the wearable KuduSmart® monitor provides coaches and athletes instant comparable sudomotor function feedback to traditional routinely used sweat analysis techniques.

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