Changes in nocturnal-skin temperature and sleep parameters following endurance training sessions in female long-distance runners

The present study investigated nocturnal skin temperature and sleep parameters after endurance training sessions in female long-distance runners. Eleven female long-distance runners were monitored for 7 consecutive days. Proximal skin temperature was measured every 5 min using a button-type thermometer (Hal-Share, SUN·WISE Co., Ltd., Osaka, Japan) attached to the groin area. Sleep parameters, including sleep efficiency, total sleep time, sleep latency, and wake time after sleep onset (WASO), were assessed using actigraphy (wGT3X-BT, ActiGraph LLC, Pensacola, FL, USA). Data were compared between two conditions: a day involving strenuous endurance training (Training Day; a total of 130 min comprising high-intensity running from 10:00-10:40 A.M., and jogging from 5:00-5:30 A.M. and 3:30-4:30 P.M.) and a day without training (Rest Day). Skin temperature during sleep was significantly higher on the Training Day compared with the Rest Day at 10 and 20 min after bedtime (p < 0.05), but significantly lower 60 min after bedtime (p < 0.05). Between 90 and 130 min after bedtime, skin temperature was significantly elevated compared with the value at sleep onset (p < 0.05). Total sleep time was significantly longer on the Training Day than on the Rest Day (447.6 ± 60.5 min vs. 360.2 ± 45.3 min; p < 0.05); sleep efficiency, sleep latency, and WASO showed no significant differences between the conditions. In conclusion, multiple endurance training sessions (three sessions per day) altered nocturnal skin temperature patterns during the initial 130 min of sleep and increased total sleep time in female long-distance runners.