title: Effects of heat acclimation on time perception.
abstract: Cognitive performance is impaired during prolonged exercise in hot environment compared to temperate conditions. These effects are related to both peripheral markers of heats stress and alterations in CNS functioning. Repeated-exposure to heat stress results in physiological adaptations, and therefore improvement in exercise capacity and cognitive functioning are observed. The objective of the current study was to clarify the factors contributing to time perception under heat stress and examine the effect of heat acclimation. 20 young healthy male subjects completed three exercise tests on a treadmill: H1 (at 60% VO(2)peak until exhaustion at 42°C), N (at 22°C; duration equal to H1) and H2 (walk until exhaustion at 42°C) following a 10-day heat acclimation program. Core temperature (T(C)) and heart rate (HR), ratings of perceived fatigue and exertion were obtained continuously during the exercise, and blood samples of hormones were taken before, during and after the exercise test for estimating the prolactin, growth hormone and cortisol response to acute exercise-heat stress. Interval production task was performed before, during and after the exercise test. Lower rate of rise in core temperature, heart rate, hormone response and subjective ratings indicated that the subjects had successfully acclimated. Before heat acclimation, significant distortions in produced intervals occurred after 60 minutes of exercise relative to pre-trial coefficients, indicating speeded temporal processing. However, this effect was absent after in acclimated subjects. Blood prolactin concentration predicted temporal performance in both conditions. Heat acclimation slows down the increase in physiological measures, and improvement in temporal processing is also evident. The results are explained within the internal clock model in terms of the pacemaker-accumulator functioning.
authors.affiliation: Institute of Psychology, University of Tartu, Estonia; Doctoral School of Behavioural, Social and Health Sciences, University of Tartu, Estonia. Electronic address: maria.tamm@ut.ee.
authors.forename: Maria
authors.initials: M
authors.lastname: Tamm
authors.affiliation: Institute of Psychology, University of Tartu, Estonia; Doctoral School of Behavioural, Social and Health Sciences, University of Tartu, Estonia.
authors.forename: Ainika
authors.initials: A
authors.lastname: Jakobson
authors.affiliation: Institute of Psychology, University of Tartu, Estonia; Doctoral School of Behavioural, Social and Health Sciences, University of Tartu, Estonia.
authors.forename: Merle
authors.initials: M
authors.lastname: Havik
authors.affiliation: Laboratory of Exercise Physiology, University of Tartu, Estonia.
authors.forename: Saima
authors.initials: S
authors.lastname: Timpmann
authors.affiliation: Laboratory of Exercise Physiology, University of Tartu, Estonia.
authors.forename: Andres
authors.initials: A
authors.lastname: Burk
authors.affiliation: Laboratory of Exercise Physiology, University of Tartu, Estonia; Doctoral School of Behavioural, Social and Health Sciences, University of Tartu, Estonia.
authors.forename: Vahur
authors.initials: V
authors.lastname: Ööpik
authors.affiliation: Institute of Psychology, University of Tartu, Estonia; Doctoral School of Behavioural, Social and Health Sciences, University of Tartu, Estonia; Estonian Academy of Sciences.
authors.forename: Jüri
authors.initials: J
authors.lastname: Allik
authors.affiliation: Institute of Psychology, University of Tartu, Estonia.
authors.forename: Kairi
authors.initials: K
authors.lastname: Kreegipuu
mesh_terms: D000222:Adaptation, Physiological; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D001831:Body Temperature; D005080:Exercise Test; D005221:Fatigue; D013006:Growth Hormone / Q000097:blood; D006339:Heart Rate / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology; D011388:Prolactin / Q000097:blood; D011601:Psychophysics; D012044:Regression Analysis; D013997:Time Factors; D013998:Time Perception / Q000502:physiology*; D055815:Young Adult
chemical_list: D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D013006:Growth Hormone; D006854:Hydrocortisone
keywords: Core temperature; Heart rate; Heat acclimation; Internal clock; Interval production; Prolactin; Time perception