How long should you workout for building muscle

In order to have the best androgens to cortisol ratio, avoid working out for long duration.

This concept was further endorsed Bulgarian Olympic lifting coach extraordinaire Ivan Abadjiev. After spending over 30 years coaching Olympians, I am more and more convinced, that if, after warm-up is completed, you can train longer than one hour, you are making friends…
More simply, training 2 times one hour per day, provides more results than a single two hour workout, in terms of muscle building. One of the reason that shorter workouts may work better is the testosterone to cortisol ratio.
We know now that cortisol production is linked to how much adaptation will be forced. Yet, you need to recover. Keeping your androgens in check with the catabolic hormonal response is one of the keys to rapid gains.

However if you want to gain strength you should train in long hours, throughout the day, with long rest period between each set, as someone call this method "greasing the groove"