Muscle disuse leads to muscle atrophy (decreased muscle volume) with reduced muscle strength, reduced muscle energy reserves, and a lower maximum power.
The most common form of atrophy is the result of immobilization, for example when a broken leg or arm is immobilized in a cast for some time, or if an athlete has to stop training and competing due to an injury.
Legs or arms that have become wasted clearly show the atrophied muscle. Increased mechanical loading of the muscle either by muscle rehabilitation training or by resumption of a normal level of physical activity reverses the muscle atrophy with time. Creatine's important role in energy metabolism in muscles raised the issue of whether creatine supplementation can reduce the effects on the muscle during immobilization, and whether creatine supplementation can speed up recovery.
In 2001, the effects of creatine supplementation during muscle disuse and subsequent training were studied in a double-blind placebo-controlled trial. The right leg of 22 healthy young volunteers was immobilized in a cast for 2 weeks after which the subjects participated in a 10-week rehabilitation program (intensive strength training). During immobilization, muscle phosphocreatine concentrations decreased by 15% in the placebo group and returned to baseline within the first 3 weeks of rehabilitation.
In contrast, creatine supplementation prevented the decrease in phosphocreatine and offset the decline in muscle protein during immobilization and resulted in an increase of 12% for phosphocreatine after the first three weeks of rehabilitation. Muscle strength, measured as the maximum isometric knee-extension strength, decreased in both groups to the same degree during immobilization, but muscle strength increased at a significantly faster rate in the creatine group during rehabilitation. Muscle strength at the end of rehabilitation compared to the baseline was significantly higher in the creatine group compared to the placebo group.
It can be concluded that oral creatine administration reduces the biochemical and structural deterioration of skeletal muscles during immobilization. Clinical trials have shown that creatine supplementation in combination with appropriate training program markedly decreases the recovery time after muscular atrophy due to injury.