The purpose of this study was to compare peak (VO 2 peak) and maximal (VO 2 max) oxygen uptake, physical performance, and lactate accumulation [la-] in warm versus cold environments. The influence of inhaled air temperature and different warm up modes on these variables as well as arterial oxygen saturation (SaO 2%) and pulmonary function were also studied. Two studies were performed. In study A, 10 males performed maximal exercise tests on a bicycle at +20°C and -12°C. In study B, 8 elite cross-country skiers performed maximal cross-country skiing tests at +13.7°C. Different warm up modes (continuous and intermittent) and different temperatures of the inhaled air (-8°C and +13°C) were used. In study A, we found significantly higher VO 2 peak, peak carbon dioxide (VCO 2 peak), peak ventilation (V E peak) and respiratory exchange ratio (RER) in +20°C compared to -12°C. In study B, we found significantly lower SaO 2% at the end compared to the beginning of the maximal performance test. Time to exhaustion (T ex) was significantly longer using intermittent warm up irrespectively of inhaled air temperature. In conclusion, we found that VO 2 max was affected by different environmental temperatures but not by different temperatures of the inhaled air and that intermittent warm up increased T ex without affecting VO 2 max.