Abstract:
This study examined the interactions between the reproductive status and the
thermoregulatory responses during exercise in the cold in girls involved in competitive
sports. Four girls with established menstrual cycles comprised the eumenorrheic
menarcheal group (EM) and 5 non-menstruating girls comprised the pre-menarcheal
group (PM). During the first visit maximal oxygen consumption, height, weight and
percent body fat (%BF) were measured. The second visit involved: a determination of
metabolic rate in thermoneutrality (21°C) involving 10-min rest and 20-min cycling (30%
of VCL max), and a cold stress test (5°C, 40% humidity, <0.3 m/s air velocity) involving
20-min rest and 40-min cycling (30% of VCL max.). Subjects in the EM group were
tested twice in the chamber during the follicular and luteal phases. Pre-menarcheal
subjects were found to have significantly (p<0.05) lower core temperatures during the
final stages of cold exposure. Overall, body fat was not significantly correlated with core
temperature in the cold, however there was a significant surface-to-mass ratio difference
between the groups. While in the follicular phase, EM girls had a higher core temperature
during cold exposure. Therefore, reproductive hormonal status seems to be an important
factor in terms of cold tolerance in females during adolescence.
