The Training Principle

Suppose you do a weight workout on Monday. Afterward, you could not do it again, correct? This means that you have fatigued your body by doing more work than it is used to. To compensate for the overload, your body has to get stronger, faster or gain endurance and it does.

It takes 48 hours (Wednesday) for your body to recover from Monday's workout, and more to overcompensate (Thursday +).

For any weight exercise you do on Monday, you should repeat on Thursday or later.

Example:
If you can lift 100lbs, 5 times on a Monday, by Wednesday you can again lift 100lbs 5 times, but then by thursday you could lift 103lbs, 5 times.