The Threshold Ambient Temperature for the Use of Precooling 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 precooling prior to competition to alleviate this performance decline. However, little is known about the ambient temperature threshold above which precooling becomes an effective strategy for enhancing endurance performance. The aim of this study was to investigate the effect of precooling in different environmental temperatures on time-trial (TT) performance.

Methods: Trained cyclists completed 2 TTs with (COLD) and without (CON) precooling using an ensemble of  ice vest and sleeves in ambient temperatures of 24°C, 27°C, and 35°C.

Results: TT performance was faster following COLD in both 35°C (6.2%) and 27°C (2.6%; both Ps < .05) but not 24°C (1.2%). Magnitude-based inferential statistics indicate that COLD was very likely beneficial to performance in 35°C, 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 TT in all ambient temperatures (P < .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: Precooling with an ice vest and sleeves is likely to have a positive effect on TT performance at temperatures above 24°C, with a clear relationship between ambient temperature and the magnitude of effect of precooling.