Carbon dioxide bathing has a long history as an aid to the treatment of peripheral vascular disease, hypertension and heart disease, since it is thought to enhance blood flow to the skin and muscles. Could it therefore be a useful warm-up aid for swimmers? This is the hypothesis a pair of Japanese researchers set out to test with a comparison of the warm-up effects of an artificially carbonated bath with those of a fresh water bath in a group of six healthy male swimmers.

All the subjects underwent similar tests a week apart, once in a fresh-water bath heated to 36πC and again in an artificially carbonated bath at the same temperature, where they stayed for 20 minutes. They then sat quietly for 10 minutes before performing a kicking exercise for four minutes in the swimming pool. After the exercise they sat quietly for two hours.

Venous blood samples taken immediately before and after the bath, and five, 20, 60 and 120 minutes after exercise revealed significant differences between the effects of the two types of bath on four key parameters:

Haematocrit (packed cell volume) at 20 minutes after exercise was significantly higher in the carbonated bath group than the fresh-water group;

White blood cell count and total plasma protein were significantly higher in the carbonated bath group five minutes after exercise;

Total cholesterol was significantly higher in the carbonated bath group five and 20 minutes after exercise.

The researchers also examined the time course of changes in blood lactic acid and found that levels were significantly lower in the carbonated bath group immediately after exercise and five and 20 minutes later.

Heart rate was significantly lower in the carbonated bath group one and two minutes after exercise, while a decrease in measured electrical activity of the M, rectus femoris muscle during swimming suggested more efficient muscle activity after a carbonated bath.

The differences in blood parameters suggest, say the researchers, 'that the intensity of exercise in a swimming pool should be strengthened more after warm-up in an artificially carbonated bath than after warm-up in fresh water'. The differences in heart rates and lactic acid levels showed that the carbonated bath group had greater reserves in both their respiratory and circulatory systems after exercise.

'We concluded from this study,' say the researchers, 'that an artificially carbonated bath would have a good warm-up effect and induce a possibility of improvement on swimming records with a great reserve in the cardiovascular system.'
J Human Ergol, 27 (1,2), 22-29, 1998

Isabel Walker