Physical Recovery
Physical recovery is one aspect of the training effect. Training depletes your energy stores. To perform work, your muscles undergo a chemical reaction. A molecule, or nucleotide, called adenosine triphosphate (ATP) is split leaving behind adenosine diphosphate (ADP). Some of the ADP can be paired with creatine to recreate another ATP molecule. More energy, however, is taken from stores of carbohydrates in the muscle cell called glycogen. Special proteins, called branched-chain amino acids, are also used. Muscle tissue is damaged, a condition referred to as microtrauma, and amino acids are released into the bloodstream. Some amino acids leak into surrounding tissue. One particular amino acid, hydroxyproline, may cause inflammation and could be a contributing factor to delayed onset muscle soreness (DOMS) or the soreness you get a few days after an intense training session.
Full recovery depends on several factors. Your body must replenish its ATP, indirectly through the restoration of creatine and glycogen reserves. It must also repair the damaged muscle tissue. The overcompensation principles states that if the training is followed by adequate recovery, most likely your body will overcompensate and build more muscle tissue than previously existed (hypertrophy).
These processes all happen at different rates. Some tissue may repair within hours, while intense workouts involving extremely large muscle groups have been shown to take several days to fully recover. Creatine replenishment can happen within days and may be accelerated through intake of creatine supplements. Because creatine occurs naturally in flesh meats, vegetarians may benefit more from creatine supplementation than those who incorporate animal proteins in their diet. Glycogen replenishment can occur within hours of the workout provided adequate carbohydrate is supplied. This is why post-workout shakes are popular because it is believed they can accelerate recovery from the workout.
As a general rule of thumb, expect several days to recover from intense workouts involving massive muscles (such as leg muscles, chest muscles, and back muscles). Some of these muscles may take a full week to recover. On the other hand, muscles that are involved with daily movement and posture such as arm, wrist, calf, abdominal, and lower back muscles may recover with 24 hours of the workout session.
Neurological Recovery
Physical recovery is not the only factor involved. Every training session taxes your central nervous system (CNS) to a certain extent. The CNS recovers by increasing efficiency and coordination. Improved efficiency with coordinating muscular contractions results in strength gains - this is why you can improve strength without gaining muscle mass. In addition, coordination and spatial awareness can be improved. This causes your actions to become more efficient, conserves energy, and can also improve strength and agility.
The central nervous system can become fatigued by too much stimulus. While physical recovery may be isolated to the muscles involved in the workout, neurological recovery is more universal. A heavy leg workout followed by a heavy upper body workout may tax different muscle groups, but both workouts will impact the central nervous system.

Jeremy Likness, Health Coach



