In general, the rule of thumb has always been that you need to let muscles recover for at least 48 hours before you can do another round of resistance training with the same muscle group. This recovery time primarily allows the muscle to restore all of its short-term fuel sources that are stored within the muscle. While these aren’t the only fuel sources that the muscle has, the ‘in-muscle’ fuel sources are often critical when doing short, heavy training like resistance training.
