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.
Key words
body temperature - counter-movement jump - assessment - monitoring
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Correspondence
Kristie-Lee Taylor
Australian Institute of Sport
Physiology
PO Box 176
2616 Belconnen
Australia
Phone: +61/2621/47 890
Fax: +61/2621/41 904
Email: kristie.taylor@ausport.gov.au
