The threshold ambient temperature for the use of pre-cooling to improve cycling time trial performance

Purpose. Cycling time trial performance can be compromised by moderate to high ambient temperatures. It has become commonplace to implement pre-cooling prior to competition to alleviate this performance decline. However, little is known about the ambient temperature threshold above which pre-cooling becomes an effective strategy for enhancing endurance performance. It was the aim of this study to investigate the effect of pre-cooling in different environmental temperatures on time trial performance. Methods. Trained cyclists completed two time trials with (COLD) and without (CON) pre-cooling using an ice-vest and sleeves ensemble in ambient temperatures of 24˚C, 27˚C and 35˚C. Results. Time trial performance faster following COLD in both 35˚C (6.2%) and 27˚C (2.6%; both P<0.05) but not 24˚C (1.2%). Magnitude based inferential statistics indicate that COLD was very likely beneficial to performance in 35˚C and likely beneficial in 27˚C and possibly beneficial in 24°C. Mean power was 2.4%, 2.5% and 5.6% higher following COLD and considered to be likely beneficial in 24°C and very likely beneficial in 27˚C and 35˚C. COLD reduced mean skin temperature throughout the warm-up and into the time trial in all ambient temperatures (P<0.05). Sweat loss was lower following COLD in 24˚C and 27˚C but not 35˚C. There was no effect of COLD on gastrointestinal temperature at any point. Conclusions. Pre-cooling with an ice-vest and sleeves is likely to have a positive effect on time trial performance at temperatures above 24˚C, with a clear relationship between ambient temperature and the magnitude of effect of pre-cooling