There is no such thing as gaining lean muscle from doing nothing.
When you sleep, you rest and your body recovers from the day's activities.
When you have an intense workout, you capitalize on in by resting.
It is a well-known fact that the muscle you get from doing weights stays on the more you rest afterward.
The concept of how much to sleep and when to sleep as part of a regimented workout is an often misunderstood and unfortunately not discussed as much in lean muscle circles as much as supplements and exercise routines.
The fact is, if you just kept on training every day in the week without letting your body rest, not only is it bad for your mental and physical health, but you can severely impact on your potential to gain lean muscle every time you work out.
Typical symptoms of someone who has not had enough rest after a work out are apathy (feeling indifferent towards everything), working out for a shorter amount of time and still feeling exhausted and feeling tired before you've even started a workout.
We all have an integrated warning alarm within us.
It's called our gut instinct.
If you pick up the weights and you REALLY don't feel like doing them, don't.
Trusting your own feelings could protect your chances for gaining more lean muscle in the future.
To most effectively gain lean muscle while your sleeping, you should warm up before a workout, maybe run a lap of the gym or the neighborhood, do the workout, make sure you've pushed yourself, warm down and then rest.
When you sleep, make sure you sleep enough so that the effects of the previous day's workout is negligible.