Effects of brief leg cooling after moderate exercise on cardiorespiratory responses to subsequent exercise in the heat

We investigated the effects of brief leg cooling after moderate exercise on the cardiorespiratory responses to subsequent exercise in the heat. Following 40 min of ergometer cycling [65% peak oxygen uptake (V̇O_2peak)] at 35°C (Ex. 1), seven male subjects [21.9 (1.1) years of age; 170.9 (1.9) cm height; 66.0 (2.0) kg body mass; 46.7 (2.0) ml kg⁻¹ min⁻¹ V̇O_2peak] immersed their legs in 35°C (control condition, CONT) or 20°C (cooling condition, COOL) water for 5 min and then repeated the cycling (as before, but for 10 min) (Ex. 2). Just before Ex. 2, esophageal temperature (T _es) was lower in COOL than in CONT [36.9 (0.2) vs 37.5 (0.1)°C] (P<0.01), as also were both mean skin temperature [33.9 (0.2) vs 35.2 (0.2)°C] (P<0.01), and heart rate (HR) [93.2 (6.0) vs 102.7 (4.9) beats min⁻¹] (P<0.05). During Ex. 2, no differences between CONT and COOL were observed in oxygen uptake, arterial blood pressure, blood lactate concentration, or ratings of perceived exertion; however, T _es, skin temperature, and HR were lower in COOL than in CONT. Further, during the first 5 min of Ex. 2, minute ventilation was significantly lower in COOL than in CONT [50.3 (2.0) vs 53.4 (2.6) l min⁻¹] (P<0.01). These results suggest that brief leg cooling during the recovery period may be effective at reducing thermal and cardiorespiratory strain during subsequent exercise in the heat.