A study from Finland showed that daily variations in strength and power cease to exist in people who train in the morning. They examined 27 men who weight trained either in the morning (7 a.m. to 9 a.m.) or in the afternoon (5 p.m. to 7 p.m.).
Initially, all subjects were stronger in the afternoon than in the morning. But these differences disappeared in the morning training group, but not in the evening training group.
This study showed that you should exercise in the morning if you have a morning competition, because morning training will eliminate normal strength differences between early and late times of the day.