title: The effects of cranial cooling during recovery on subsequent uncompensable heat stress tolerance.
abstract: 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.
authors.affiliation: a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Wallace
authors.affiliation: a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.
authors.forename: Anaïs T
authors.initials: AT
authors.lastname: Masbou
authors.affiliation: b Work Physiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G-2H9, Canada.
authors.forename: Stewart R
authors.initials: SR
authors.lastname: Petersen
authors.affiliation: a Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada.
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Cheung
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology; D003020:Clothing; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D061388:Firefighters; D018882:Heat Stress Disorders / Q000503:physiopathology / Q000517:prevention & control*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D012146:Rest / Q000502:physiology; D012886:Skull
keywords: cooling strategy; exertional heat illness; firefighting; lutte contre l’incendie; malaise thermique de l’effort; occupational physiology; perception thermique; physiologie du travail; stratégie de refroidissement; thermal perception