First, muscle growth is best between 4 and 6 p.m. Why? This is because the ratio of testosterone to cortisol is the highest during this period, which is conducive to the body's muscle synthesis.
According to the scientists, cortisol decreases by 92% between 6 and 23. Studies have also shown that cortisol is lowest between 18 and 24 hours a day.
The peak of testosterone is at 8 am, but some studies have found that the increase in testosterone caused by resistance training can also be observed in the evening.
We've said that while testosterone levels represent muscle growth, cortisol does the opposite, affecting muscle synthesis and even breaking it down. That is, when you exercise in the afternoon, your cortisol levels are at their lowest, increasing the ratio of testosterone to cortisol. This means your muscle synthesis rate is accelerating and muscle growth is at its highest!