title: Warm-up affects diurnal variation in power output.
abstract: The purpose of this study was to examine whether time of day variations in power output can be accounted for by the diurnal fluctuations existent in body temperature. 8 recreationally trained males (29.8±5.2 yrs; 178.3±5.2 cm; 80.3±6.5 kg) were assessed on 4 occasions following a: (a) control warm-up at 8.00 am; (b) control warm-up at 4.00 pm; (c) extended warm-up at 8.00 am; and, (d) extended warm-up at 4.00 pm. The control warm-up consisted of dynamic exercises and practice jumps. The extended warm-up incorporated a 20 min general warm-up on a stationary bike prior to completion of the control warm-up, resulting in a whole body temperature increase of 0.3±0.2°C. Kinetic and kinematic variables were measured using a linear optical encoder attached to a barbell during 6 loaded counter-movement jumps. Results were 2-6% higher in the afternoon control condition than morning control condition. No substantial performance differences were observed between the extended morning condition and afternoon control condition where body temperatures were similar. Results indicate that diurnal variation in whole body temperature may explain diurnal performance differences in explosive power output and associated variables. It is suggested that warm-up protocols designed to increase body temperature are beneficial in reducing diurnal differences in jump performance.
authors.affiliation: Department of Physiology, Australian Institute of Sport, Canberra, Australia. kristie.taylor@ausport.gov.au
authors.forename: K
authors.initials: K
authors.lastname: Taylor
authors.forename: J B
authors.initials: JB
authors.lastname: Cronin
authors.forename: N
authors.initials: N
authors.lastname: Gill
authors.forename: D W
authors.initials: DW
authors.lastname: Chapman
authors.forename: J M
authors.initials: JM
authors.lastname: Sheppard
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001696:Biomechanical Phenomena; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D018592:Cross-Over Studies; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007866:Leg / Q000502:physiology; D008297:Male; D008991:Monitoring, Physiologic; D018482:Muscle, Skeletal / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors