Hand and Forearm Cooling Alters Perceptual Comfort but Not Self-Paced Cycling Performance in the Heat.

PURPOSE: We tested the effectiveness of hand and forearm per-cooling on self-paced cycling performance in the heat. We hypothesized that continuous, localized cooling would attenuate thermal strain and improve thermal perception, thereby enhancing performance. METHODS: Ten trained cyclists (7 males and 3 females; 34 [12] y, 174.4 [8.2] cm, 75.5 [10.6] kg, 55.3 [10.7] mL·kg-1·min-1) completed 3 randomized 20-km cycling time trials in the heat (35 °C, 50% relative humidity) while immersing their forearms and hands in a circulating water bath at 10 °C, 20 °C, or 32 °C (control) throughout. RESULTS: Whole-body thermal comfort was significantly reduced in the 10 °C and 20 °C trials compared with the 32 °C trial (both P ≤ .005). However, time to completion did not improve with either 10 °C (36.6 [2.1] min) or 20 °C (36.8 [2.2] min) compared with control (37.0 [1.9] min, P = .476), nor did power output (10 °C: 202 [39] W, 20 °C: 201 [42] W, 32 °C: 202 [37] W; P = .988) or pacing strategy. Physiological strain was also not different across conditions for both mean heart rate (P = .535) and rectal temperature change (10 °C: +1.3 [0.7] °C, 20 °C: +1.3 [0.5] °C, 32 °C: +1.5 [0.4] °C; P = .153). CONCLUSION: Despite perceptual benefits, passive water immersion of the extremities did not improve time-trial performance and appears insufficient to lower the physiological strain experienced during a self-paced 20-km time trial in the heat.