Can creatine supplements enhance muscle recovery?

Creatine has become a popular nutritional supplement among athletes, often taken as supplement by people who want to gain muscle mass, but there is increasingly evidence that it may also help in recovering from exercise induced muscle damage. My previous article suggested there may be a beneficial effect of creatine supplements on inflammation and muscle soreness following prolonged running.

Now a study from Victoria University, Australia has set out to examine the effects of creatine supplementation on the recovery of muscle proteins and force after eccentrically induced muscle damage.

Eccentric contractions are used to decelerate a body part or object, such as when you lower an object gently rather than just letting it drop. Damage caused by eccentric exercise is known to lead to a reduction in muscle force, increased muscle soreness and impaired muscle function.

During the study 14 untrained male subjects consumed either creatine and carbohydrate (Cr-CHO) or only carbohydrate (CHO) for five days before a resistance exercise session. The Cr-CHO group consumed a daily supplement of creatine (0.3 g per kg of body weight) and glucose (1.2 g per kg of body weight); The CHO group took glucose only.

The workout consisted of three exercises: 1) leg press; 2) leg extension and 3) leg curl. For each exercise their concentric 1-RM (repetition maximum) was determined. This is the maximum weight that a single repetition could be performed of a muscle shortening exercise, such as a curl. The resistance exercise session involved 4 sets of 10 eccentric only repetitions at 120% of their maximum concentric 1-RM, lowering the weight by themselves through the entire range of motion over 4 seconds.

Every day for 14 days whilst recovering from the exercises the Cr-CHO group took 0.1 g per kg of body weight of creatine and 0.4 g per kg of body weight of glucose, again the CHO group took glucose only.

The study found isokinetic strength, (where the muscle contracts and shortens at a constant speed), was 10% greater during recovery in the Cr-CHO group compared to the placebo group of CHO alone.

During isometric knee extension (where the muscle length stays the same even though it contracts), it was also found that the creatine supplemented groups had significantly greater strength (21%) during recovery from exercise induced muscle damage.

The paper’s author Matthew Cooke concluded that there is a significant improvement in the rate of recovery of knee extensor muscle function after creatine supplementation following injury. Blood creatine kinase (CK) activity was significantly lower by an average of 84% after 48hrs recovery in the creatine supplement group and peaked at 96hrs. Levels had returned to baseline by 7 days in both groups.

Blood CK levels can be raised from damage of the muscle tissue as a result of intense training, but also due to a number of other factors:

• Age – levels decline slightly with age
• Gender – at rest CK levels are lower in females than males.
• Race – black men usually have higher values than Caucasians.
• Climate – standard exercise in cold weather induces higher blood CK levels than the same exercise in warm weather.
• Muscle mass and physical activity – at rest CK levels in athletes are higher than in sedentary subjects, this may be due to persistent training which keeps the CK levels elevated.

However, if trained and untrained subjects do the same exercise the CK levels will still be lower in athletes than the untrained. This study published in the Journal of International Society Sports Nutrition did involve untrained subjects which may have resulted in the very high CK levels initially following the exercise.

The major finding of this study was the significantly higher muscle strength after creatine supplementation during recovery from a muscle damaging exercise session; this may be due in part to a faster muscle growth during the recovery period. The study did not report if the subjects gained weight before or after the exercise session as is often reported with taking creatine supplements.

It is not known how creatine may act to increase recovery although it may be that the reduced leakage of creatine kinase from the muscle is an indication of less initial damage to the muscle.  There appears to be a large number of studies supporting the use of creatine supplements whether to increase muscle mass or aiding recovery to allow further training. Maybe now scientists need to discover just how creatine supplements work so they can advise athletes on the ideal duration and concentration to use to aid recovery, optimise weight gain and avoid side effects.

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