Recovery and Rebuilding Physiology

As a general rule, one should not exercise the same muscle group two days in a row, and usually not more than three times in a week; otherwise the body eventually becomes fatigued and reaches an overtrained state (definition of "Recovery").

The physiology of rebuilding: when a muscle is stressed beyond its normal demands, a certain amount of time is required for the tissues to recover and make positive physiological adaptations. The contractile force of a muscle decreases during a training session due to the stress imposed on it, but increases to a slightly higher strength level during a recovery period of sufficient duration.

Two failure modes:

• If the time between workouts is too short, the muscle cannot rebuild to a higher level before being stressed again; the cumulative effect is chronically fatigued muscles that actually decrease in strength.
• If the non-training period is too long, the muscle gradually returns to its original level of contractile force.

Because the length of the rest interval depends on the intensity of the work interval, more hours are required for rebuilding after a hard workout than after an easy one; each person must experimentally determine their optimal recovery period. Following exercise, repair and building processes synthesize proteins so the muscle achieves a slightly greater level of strength and size — generally about 48 hours are required to complete this recovery (48 to 72 hours between workouts for the same muscle group).

• Don't train the same muscle group two days in a row; usually ≤3 times/week — else overtraining.
• Contractile force drops during a session, then rises to a slightly higher level with adequate recovery.
• Too little rest → chronic fatigue and strength loss.
• Too much rest → strength returns toward original level.
• Harder workouts need longer recovery; recovery is individual.
• Generally ~48 hours to complete repair/protein synthesis (48–72 h between workouts per muscle group).

• muscle-atrophy — strength loss from inadequate recovery / lay-off.
• muscle-soreness — soreness during the recovery window.
• rebuilding-time — the training principle this physiology supports.
• frequency — 48–72 h between workouts per muscle group.