This study (Bernard et al (1998), European Journal of Applied Physiology, 77, pp. 133-138) looked at differences between the results of three different anaerobic power tests: a 50m dash, vertical jump and max cycles sprint at three different times of day. A group of 23 men undertook each of the three tests on three separate days at 0900, 1400 and 1800 hours

Results showed that anaerobic power and max running speed were significantly lower in the morning compared with the afternoon, with 5-7 per cent greater power achieved in the afternoon. There were no differences between either afternoon test time.

This suggests that for fitness testing procedures, trainers need to be consistent with the time of day when the tests are performed. In addition, this finding suggests that the best time of day for anaerobic training is in the afternoon or early evening. This is consistent with other research into circadian rhythms which shows heart rate, body temperature and muscular strength are all higher in the afternoon than in the morning.