Effects of dietary protein level on the energy metabolism of rats during exercise

The experiments were designed to study the effects of exercise of various intensities in albino rats fed diets containing 8 per cent or 20 per cent casein. Male rats about 7 weeks old were divided into exercise groups and control (non-exercise) groups. The exercise groups were forced to run 57 km or 76 km in total during a 28-day period. The oxygen uptake of rats was measured in order to study the influence of exercise on energy metabolism of rats and the effects of training. Body weight and food intake were also measured. 1. In all exercise groups the total amount of food intake and body weight gain during the exercise period were smaller than those of the control groups, regardless of the protein levels of the diets. but while the rats were kept at rest after the exercise period, the food intake and body weight of these groups increased and approached those of the control groups. 2. No difference in resting metabolism was observed both in the 8 per cent and 20 per cent casein groups. At lower speeds up to 1.5 km/hr the 8 per cent casein group indicated lower oxygen requirement during the exercise but at speeds higher than 2.0 km/hr the oxygen requirement was definitely higher than that of the 20 per cent casein group. The estimated optimum speed for rats weighing 300 g on the average is somewhere between 1.5 and 2.0 km/hr is calculated on the basis of oxygen requirement for running 100 m. 3. The obvious effects of training on oxygen uptake were seen in the 20 per cent casein group after four weeks' training, although no effect was found in the 8 per cent casein group.