Acta physiol. scand. 1975. 95. 201-202 From the Department of Physiology, Gymnastik- och idrottshogskolan, Stockholm, Sweden
The Effects of Hypothermia on Submaximal and Maximal Work Performance BY MERVYN DAVIES,~ BJORNEKBLOM, ULFBERCHand INGE-LISKANSTRUP-JENSEN
Key words: Hypothermia, exercise, heart rate, atropine,
/3 blockade, aerobic power output
It is well known that hypothermia affects physical performance (Keatinge 1969) and may result in death if exposure is severe (Pugh 1964). It has also been shown that swimming in cold water ( + 18°C) results in an increased metabolic rate at a given speed and a decreased heart rate at a given oxygen uptake (Nielsen 1973, Nadel et al. 1974, Holm& and Bergh 1974). Similar results have been obtained during submaximal bicycle exercise (Nadel et al. 1974), but to our knowledge no attempts have been made to explain this HR response t o hypothermia. We also intended to study the effect of hypothermia on the response to maximal exercise under standardized laboratory conditions. In the present study we made 5 normal healthy male subjects hypothermic by allowing them to swim at a speed of 0.55 m/s (Vo2about 50% of Vo, max) for 30 min (until rectal temperature of approximately 35°C was reached) in a swimming flume ( h t r a n d and Englesson 1972) containing water at 18°C. Immediately after the end of the swim the response t o submaximal and maximal exercise on an arm and leg bicycle ergometer under standardized laboratory conditions with and without atropine (2 mg i.v.) was measured and the data collected were compared to results obtained during normal cycling. In addition one subject was also studied after /3-blockade with propranolol (10 mg i.v.1. The results show that following hypothermia VE and V0, at a given submaximal work load of 100 W increased (p
The Effects of Hypothermia on Submaximal and Maximal Work Performance BY MERVYN DAVIES,~ BJORNEKBLOM, ULFBERCHand INGE-LISKANSTRUP-JENSEN
Key words: Hypothermia, exercise, heart rate, atropine,
/3 blockade, aerobic power output
It is well known that hypothermia affects physical performance (Keatinge 1969) and may result in death if exposure is severe (Pugh 1964). It has also been shown that swimming in cold water ( + 18°C) results in an increased metabolic rate at a given speed and a decreased heart rate at a given oxygen uptake (Nielsen 1973, Nadel et al. 1974, Holm& and Bergh 1974). Similar results have been obtained during submaximal bicycle exercise (Nadel et al. 1974), but to our knowledge no attempts have been made to explain this HR response t o hypothermia. We also intended to study the effect of hypothermia on the response to maximal exercise under standardized laboratory conditions. In the present study we made 5 normal healthy male subjects hypothermic by allowing them to swim at a speed of 0.55 m/s (Vo2about 50% of Vo, max) for 30 min (until rectal temperature of approximately 35°C was reached) in a swimming flume ( h t r a n d and Englesson 1972) containing water at 18°C. Immediately after the end of the swim the response t o submaximal and maximal exercise on an arm and leg bicycle ergometer under standardized laboratory conditions with and without atropine (2 mg i.v.) was measured and the data collected were compared to results obtained during normal cycling. In addition one subject was also studied after /3-blockade with propranolol (10 mg i.v.1. The results show that following hypothermia VE and V0, at a given submaximal work load of 100 W increased (p
