Twenty-five athletes were selected to receive three kinds of loads (endurance, strength and sprint training) at the same training time, as well as to receive the same kind of load at different time (morning, am. pm), then the tricarboxylic acid (TCA) cycle products, free fatty acids (FFA), urea nitrogen, creatinine and free amino acids contents in their serum were measured. The results showed that at the same training time, different loads led to different physiological effects, while the same kind of exercise training resulted in more protein catabolism in p.m. than in the morning or a.m. Endurance or training in the morning had considerable influence on the levels of TCA cycle products and FFA components. Training in p. m. may be favourable to improving the quality of the sports of speed and strength.