The effects of dietary manipulation on blood acid-base status and the performance of high intensity exercise

Abstract

The effect of a pattern of exercise and dietary modification, which is normally used to alter muscle glycogen content, upon the acid-base status of the blood and the ability to perform high intensity exercise was studied. Eleven healthy male subjects cycled to exhaustion on an electrically braked cycle ergometer at a workload equivalent to 100% of their maximal oxygen uptake (VO2max) on three separate occasions. The first exercise test took place after a normal diet (46.2 +/- 6.7% carbohydrate (CHO)), and was followed by prolonged exercise to exhaustion to deplete muscle glycogen stores. The second test was performed after three days of a low carbohydrate diet (10.1 +/- 6.8% CHO) and subsequently after three days of a high CHO diet (65.5 +/- 9.8% CHO) the final test took place. Acid-base status and selected metabolites were measured on arterialised venous blood at rest prior to exercise and during the post-exercise period. Exercise time to exhaustion was longer after the normal (p less than 0.05) and high (p less than 0.05). CHO dietary phases compared with the low CHO phase. Resting pre-exercise pH was higher after the high CHO diet (p less than 0.05) compared with the low CHO diet. Pre-exercise bicarbonate, PCO2 and base excess measurements were higher after the high CHO treatment compared with both the normal (p less than 0.01, p less than 0.05, p less than 0.01 respectively) and low CHO phases (p less than 0.001, p less than 0.01, p less than 0.001 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)