Your body’s response to a session of weight training will vary by a number of factors. Some you have control over. Others you don’t. A study published in The Journal of Sports Medicine and Physical Fitness suggests whole body resistance training in the morning might produce a different hormonal response compared to afternoon or evening training sessions.
On separate occasions, 10 men with weight room experience trained at 7 AM, 1 PM and 5 PM. Workouts consisted of 6 upper and 6 lower body exercises for 3 sets of 10 reps. Blood samples were collected before training, 3 minutes after finishing and 48 hours later. Hormone production increased after all workouts. Testosterone was highest before the morning training session, and only the morning workout decreased cortisol and the increased the testosterone/cortisol ratio for up to 48 hours. This might create a more favorable environment for muscle adaptation.