Physiological and perceptual responses to exercising in restrictive heat loss attire with use of an upper-body sauna suit in temperate and hot conditions

The aim of this experiment was to quantify physiological and perceptual responses to exercise with and without restrictive heat loss attire in hot and temperate conditions. 

Ten moderately-trained individuals (mass; 69.44±7.50 kg, body fat; 19.7±7.6%) cycled for 30-mins (15-mins at 2 W.kg⁻¹ then 15-mins at 1 W.kg⁻¹) under four experimental conditions; temperate (TEMP, 22°C/45%), hot (HOT, 45°C/20%) and, temperate (TEMP_SUIT, 22°C/45%) and hot (HOT_SUIT, 45°C/20%) whilst wearing an upper-body “sauna suit”. Core temperature changes were higher (P<0.05) in TEMP_SUIT (+1.7±0.4°C.hr⁻¹), HOT (+1.9±0.5°C.hr⁻¹) and HOT_SUIT (+2.3±0.5°C.hr⁻¹) than TEMP (+1.3±0.3°C.hr⁻¹). Skin temperature was higher (P<0.05) in HOT (36.53±0.93°C) and HOT_SUIT (37.68±0.68°C) than TEMP (33.50±1.77°C) and TEMP_SUIT (33.41±0.70°C). Sweat rate was greater (P<0.05) in TEMP_SUIT (0.89±0.24 L.hr⁻¹), HOT (1.14±0.48 L.hr⁻¹) and HOT_SUIT (1.51±0.52 L.hr⁻¹) than TEMP (0.56±0.27 L.hr⁻¹). Peak heart rate was higher (P<0.05) in TEMP_SUIT (155±23 b.min⁻¹), HOT (163±18 b.min⁻¹) and HOT_SUIT (171±18 b.min⁻¹) than TEMP (151±20 b.min⁻¹). Thermal sensation and perceived exertion were greater (P<0.05) in TEMP_SUIT (5.8±0.5 and 14±1), HOT (6.4±0.5 and 15±1) and HOT_SUIT (7.1±0.5 and 16±1) than TEMP (5.3±0.5 and 14±1). 

Exercising in an upper-body sauna suit within temperate conditions induces a greater physiological strain and evokes larger sweat losses compared to exercising in the same conditions, without restricting heat loss. In hot conditions, wearing a sauna suit increases physiological and perceptual strain further, which may accelerate the stimuli for heat adaptation and improve HA efficiency.