Authors submitted their contribution of the article to the editorial board. Accepted for pinting in Journal of Human Kinetics vol. 26/2010 on December 2010. Journal of Human Kinetics volume 26 2010, 57-64 Section II - Exercise Physiology & Sports Medicine DOI: 10.2478v10078-010-0049-7 57 Exercise Physiology & Sports Medicine Effects of Ambient Temperature on Physiological Responses to Incremental Exercise Test by Tyka Aleksander 1 , Wiecha Szczepan 1 , Palka Tomasz 1 , Szygula Zbigniew 2 , Tyka Anna 3 , Cison Tomasz 1 , Physiological variables are regularly analyzed by coaches and sport scientists during an incremental exercise test (IET) until exhaustion. Physiological and biochemical responses of the body are modified upon exercising in the heat as well as results obtained in the IET. Heat changes the validity of these results to be used when prescribing or monitoring training processes and predicting performance in athletes To determine the effect of ambient temperature on physiological responses, twelve physically active men com- pleted IET on the cycle ergometer in three ambient temperatures: 23˚C (T23), 31˚C (T31) and 37˚C (T37). We measured continuously: rectal temperature (Tre) and aural canal temperature (Tac), heart rate (HR), 2 VO & , 2 VCO & , respiratory rate (RR), tidal volume (TV), and minute ventilation (VE). Blood samples for pl LA − were taken before, at the end of each exercise step and 3 minutes after the test ended. The exercise duration (DE) and energy expenditure (EE) to reach the threshold of decompensated metabolic aci- dosis (TDMA) decreased (p<0.05) in T31 (11.27 ± 3.03 minutes; 86.2 ± 24.2 kJ) and T37 (10.72 ± 2.76 minutes; 79.5 ± 21.3 kJ) in comparison to T23 (13.10 ± 2.30 minutes; 108.8 ± 23.9 kJ), with no differences observed in pl LA − , VE, 2 VO & or Tre. We observed an increase (p<0.05) in pl LA − after tests in T31 (11.08 ± 1.89 mmol/L) and T37 (11.94 ± 2.25 mmol/L) in comparison to T23 (10.26 ± 2.30 mmol/L), with no differences observed in 2 VO max, & end Tre, EE and DE to exhaustion. The TDMA occurs faster and at a lower WL, while performing IET in 31˚C and 37˚C. Coaches sport scientists should consider these factors when conducting IET to assess the threshold level and performance of athletes.. Key words: hyperthermia, incremental exercise test, TDMA, lactate, performance. 1 - Academy of Physical Edution in Cracow, Dept. of Physiology and Biochemistry, Institute of Human Physiology, Cracow (Poland) 2 - Academy of Physical Edution in Cracow, Dept. of Sports Medicine, Institute of Human Physiology, Cracow (Poland) 3 - Academy of Physical Edution in Cracow, Dept. of Recreation and Biological Regeneration, Cracow (Poland) Introduction The climate conditions modify the reactions of human body during exercise and affect its perform- ance (Gleeson et al., 2001; Tyka et al., 2007). Intense and long lasting aerobic exercise in warm and humid environment causes heat storage in the body and leads to increase in core temperature. Intense mus- cles work during that activity causes the increase of endogenous heat production, because most of en- ergy produced in the muscles is transformed in heat. To avoid heat storage and maintain core temperature on a constant level, excess heat produced by working muscles must be eliminated by intensified thermo- regulatory mechanisms. The efficiency of that mechanism depends on the ambient temperature and its humidity (Saat et al., 2005). Heat production and elimination could be maintained at room tem- perature. But the situation becomes complicated