The effects of cranial cooling during recovery on subsequent uncompensable heat stress tolerance

• Published in: Applied physiology, nutrition, and metabolism nutrition, and metabolism, 2015-08, Vol.40 (8), p.811-816
• Main Authors: Wallace, Phillip J, Masbou, Anaïs T, Petersen, Stewart R, Cheung, Stephen S
• Format: Article
• Language: English
• Subjects: Adult; Body Temperature - physiology; Cold Temperature; Cooling; cooling strategy; Effects; Exercise; Exercise - physiology; Exercise Test; exertional heat illness; Fire extinction; Firefighters; firefighting; Head; Health aspects; Heat; Heat stress disorders; Heat Stress Disorders - physiopathology; Heat Stress Disorders - prevention & control; Hot Temperature; Humans; lutte contre l’incendie; malaise thermique de l’effort; Male; Occupational health and safety; occupational physiology; perception thermique; Physiological aspects; Physiological research; physiologie du travail; Physiology; Rest - physiology; Skull; stratégie de refroidissement; thermal perception
• ISSN: 1715-5312; 1715-5320
• DOI: 10.1139/apnm-2015-0067

This study compared cranial (CC) with passive (CON) cooling during recovery on tolerance to subsequent exercise while wearing firefighting protective ensemble and self-contained breathing apparatus in a hot-humid environment. Eleven males (mean ± SD; age, 30.9 ± 9.2 years; peak oxygen consumption, 49.5 ± 5.1 mL·kg −1 ·min −1 ) performed 2 × 20 min treadmill walks (5.6 km·h −1 , 4% incline) in 35 °C and 60% relative humidity. During a 20-min recovery (rest), participants sat and removed gloves, helmets, and flash hoods but otherwise remained encapsulated. A close-fitting liquid-perfused hood pumped 13 °C water at ∼500 mL·min −1 through the head and neck (CC) or no cooling hood was worn (CON). During rest, neck temperature was lower in CC compared with CON from 4 min (CC: 35.73 ± 3.28 °C, CON: 37.66 ± 1.35 °C, p = 0.025) until the end (CC: 33.06 ± 4.70 °C, CON: 36.85 ± 1.63 °C, p = 0.014). Rectal temperature rose in both CC (0.11 ± 0.19 °C) and CON (0.26 ± 0.15 °C) during rest, with nonsignificant interaction between conditions (p = 0.076). Perceived thermal stress was lower (p = 0.006) from 5 min of CC (median: 3 (quartile 1: 3, quartile 3: 4)) until the end of rest compared with CON (median: 4 (quartile 1: 4, quartile 3: 4)). However, there were no significant differences (p = 0.906) in tolerance times during the second exercise between CC (16.55 ± 1.14 min) and CON (16.60 ± 1.31 min), nor were there any difference in rectal temperature at the start (CC: 38.30 ± 0.40 °C, CON: 38.40 ± 0.16 °C, p = 0.496) or at the end (CC: 38.82 ± 0.23 °C, CON: 39.07 ± 0.22 °C, p = 0.173). With high ambient heat and encapsulation, cranial and neck cooling during recovery decreases physiological strain and perceived thermal stress, but is ineffective in improving subsequent uncompensable heat stress tolerance.