You need to rest your muscles for 24 hours after training those specific muscles. (gymjunkies.com)
This is due to increased muscle tone (or resting muscle activity) that full - term babies have the first month of life. (candokiddo.com)
The reason for that is our body builds muscle when we are at rest not when we workout, so if you are not resting your muscles will break down and NOT grow. (lovingfit.com)