2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
124
PSYCHOLOGICAL TRAINING TO IMPROVE EXERCISE
PERFORMANCE IN THE HEAT
Martin Barwood, Avijit Datta, Richard Thelwell & Michael Tipton
Department of Sport & Exercise Science, Institute of Biomedical &Biomolecular
Sciences, University of Portsmouth, UK
Contact person: martin.barwood@port.ac.uk
INTRODUCTION
Fatigue occurs earlier at the same work rate in hot compared to cool conditions. This
has been attributed to either, a critical deep body temperatures being reached
(Gonzalez-Alonso et al. 1999), anticipatory changes in pacing strategy due to
uncompensible heat storage (Tucker et al. 2006), or alterations in central
neurotransmitter substances, such as serotonin (Davis & Bailey, 1997) and
interleukin-6 (IL-6; Robson et al. 2004). Premature fatigue is often acknowledged to
include the reduction in the ‘drive’ or motivation to continue exercising (Nybo &
Nielsen, 2001). This psychological component is rarely investigated, and has yet to be
quantified. One means of examining the extent of the psychological component to
tolerate hyperthermia and exertion in the heat is to attempt to alter this factor. Sports
psychology research studies demonstrate that psychological skills training (PST) can
facilitate the suppression of sensations elicited during high intensity exercise in
trained individuals (Thelwell & Greenlees, 2003) and those sensations arising from
strong thermal stimuli (e.g. on immersion to cold-water; Barwood et al. 2006).
This study examined the impact of PST on exercise performance in the heat (30°C,
40%RH). The hypothesis was (H1) that a PST package would significantly increase
distance covered during 90-minutes of treadmill running and enable subjects to
tolerate high deep body temperatures.
METHODS
Subjects, Design & Protocol: Ethical approval was provided by the local ethics
committee. Eighteen male subjects provided written informed consent to take part in
the study (mean [SD]; N = 18; Age: 26 [5] years; height: 1.75 [0.05] m; mass: 71.13
[6.27]kg; Body Fat: 15.06 [2.63]%). Pre-experimental measures included an
assessment of VO2max (mL.kg -1 .min -1 ). The study employed a test re-test
experimental design, with each subject attempting to run as far as they could on a
treadmill in 90 minutes on three occasions in 30°C, 40% RH, air velocity 2.5m.s -1 .
Following R2 the subjects were matched and allocated to two separate groups
according to the difference in distance run between R1 and R2. Between R2 and R3 the
Control Group (CG, N=8) undertook normal daily activity, whilst the Psychological
Skills Group (PSG, N=10) received PST. Each run was separated by > 4 days and
took place at the same time of day within subject. Subjects wore shorts, socks and
running shoes.
Temperature measurements included deep body temperature (aural thermistor; Tau)
and skin temperature (Tsk) at 4 body sites: chest, arm, thigh and calf. 20mL of whole
blood was drawn prior to and following the end of exercise for the measurement of
prolactin (an index of serotonergic activity) and interleukin-6. Each subject had
control of the treadmill speed but received no feedback of distance, speed or time until
after R3. RPE and exercise intensity (Douglas bag;VO2; mL.kg -1 .min -1 ) were
measured during each run. During R1 subjects were allowed to drink tap water ad