How Long to Rest
To get the most of every workout and to prevent injury it is essential to rest after a strength-training workout. During rest, muscles rebuild and repair themselves. You may be wondering how much time your body needs to rest and repair. An adequate time to rest each muscle group is 48-72 hours between workouts.
Lighter exercises and cardio can be done every day, but when you tear and repair new muscle, you must give it time to heal, thereby making them stronger.