In an earlier article we concluded that muscles must be worked to failure if an adequate hypertrophic response is to occur. Whether this involves one or more sets is irrelevant as in either scenario the muscles must be worked to failure and beyond. This causes significant microscopic damage to the muscle tissues and it is during the period of recovery that protein synthesis undertakes the repair process that results in bigger muscle fibers. But how long does this process take and when is it safe to expose those same muscles to further intensive exercise? Scientific studies suggest that muscle fiber degradation takes approximately five to seven days to repair and recover. Any further exposure of the affected muscle to intensive activity will interfere with the recovery process and actually prevent it from achieving maximum growth. However, using the muscle to assist in exercising other body parts or even taking part in low intensity aerobic exercise will not prevent recovery. It follows therefore that each muscle group should be trained intensively only once each week in order to allow full recovery. This can be achieved by incorportating a split training regime that allows you to work out several times each week but still exercise each muscle group intensively only once every seven days.