Cardiorespiratory fitness mediates cortisol and lactate responses to winter and summer marches

Background: The extent to which homeostatically regulated physiological processes (including cardiorespiratory fitness expressed as VO2max) are involved in response physical stressors (which include acclimatization and marching) has not been studied,, we intended make this assessment based on measured cortisol levels blood lactate subjects exposed summer winter marching.
 Methods: Two groups of young men with poor (PCF; n=9) better condition (GCF; n=21), corresponding the VO2max threshold 40mL O2/kg/min, marched 15 km at an average speed 6-7 km/h, (5˚C) (32˚C). Blood sampling was performed morning hours (10 am) before immediately after march. At same time, participants' pulses had yet settled, analyses were using routine methods.
 Results: Basal significantly elevated 5°C PCF group. After marching, decreased substantially both 5°C. post-marching only 32°C GCF group.
 Conclusions: Cold is more stressful body than heat activity reduces cold-related stress, regardless fitness. Individuals poorer susceptible cold or stress. Only individuals (associated lower levels) higher baseline marching 32 °C, confirming that their energy metabolism dependent they less stressed under these conditions.