The media have hyped a number of anecdotal reports about creatine supposedly causing a range of harmful side effects. A large focus of these anecdotal reports has been an increased risk of soft tissue injury as a result of creatine supplementation. However, no formal research has indicated that creatine supplementation may increase the risk of muscle tears or tendon strains.
Creatine in theory . . .
The theoretical argument put forth regarding the risk of muscle tears and strains from creatine supplementation is as follows. Previous research shows that an increase in strength produces an increase in musculotendon stiffness [1]. The musculotendon is where the tendon merges into muscle before attaching to bone. We know from the research that creatine increases the contractile force of muscle, fluid retention within the muscle cell, and accelerates contractile protein growth [2]. Due to these effects, some “experts” have suggested that creatine supplementation may alter the contractile and elastic properties of skeletal muscle.
Recently, a group of Australian researchers undertook the difficult task of directly assessing the impact of creatine supplementation on the elasticity of muscle and determined whether creatine may increase the risk of muscle strain by increasing muscle-tendon stiffness[4].
The series elastic component (SEC) in muscle provides the link between the muscular system and the skeletal system. The stiffness of this SEC component determines numerous performance and injury-related indices [3]. However, before you go worrying about weight training causing “stiff” or “inelastic” muscles”, remember that a relatively stiff musculotendinous unit is essential for the transfer of maximal force. It is a highly desired, tremendous benefit of resistance training that does not impair muscle function.
The research . . .
In this study, it was hypothesized that the rapid strength gains, fluid retention, and accelerated muscle fiber growth that are evident after creatine supplementation might cause an increase in musculotendinous stiffness and predispose the athlete to an increased risk of injury.
The Australian researchers conducted a unique and well-designed study that attempted to quantify any alterations to muscular strength after creatine supplementation, as well as quantifying any alterations to the SEC of the muscle after creatine supplementation. An examination of these 2 variables would provide an insight into any potential soft tissue risks that may be associated with creatine supplementation.
In a randomized, placebo-controlled, double-blind design twenty men were allocated to a control group or an experimental group and were examined for musculotendinous stiffness and force production of the triceps surae muscle. The triceps surae is a muscle in the lower leg. This muscle was examined because of its important involvement during running and jumping movements as well as the relative ease of isolation of this muscle group [4]. Jumping performance was also assessed by a series of field tests before and after creatine ingestion (20 grams per day for 7 days followed by 10 grams a day for 21 days).
Isometric force and rate of force development and musculotendinous stiffness of the triceps surae were assessed before, during, and after creatine treatment using a simple but cleverly designed instrumented seated calf raise machine. Muscles work pretty much like springs. So when weight is loaded on to the seated calf press, oscillations within the muscle can be measured to reveal the elastic properties of the muscle-tendon unit and to determine “muscle stiffness”.
Therefore, as you can see, the researchers examined the effects of creatine from a mechanistic point of view as well as using dynamic, athletic assessments that are applicable to people in real-world settings.
The findings . . .
From a performance standpoint, the results showed that while creatine use did not enhance isolated muscle force production, it did significantly improve the men’s performance in the jump height tests.
Regarding musculotendinous stiffness, no significant differences between the creatine or the placebo group were witnessed at any assessment load. In fact, musculotendinous stiffness at the highest assessment load exhibited a 13% decrease after creatine supplementation! The bottom line from the 
results was that creatine supplementation definitely had no adverse effect on muscle-tendon stiffness.
This was the first study to directly assess any possible effect of creatine supplementation on muscle stiffness. It revealed that creatine supplementation enhanced jump performance with no adverse effect on muscle function. The researchers concluded that any media report suggesting that creatine supplementation may cause muscular strain or injury is definitely not supported by this study or any other scientific literature. To date, there is absolutely no evidence that indicates creatine may increase the risk of soft tissue injury.
References:
1. Poussen, M., J. Van Hoeke, and F. Goubel. Changes in elastic characteristics of human muscle induced by eccentric exercise. J. Biomech. 23:343–348. 1990.
2. Francaux, M., and J.R. Poortmans. Effects of training and creatine supplement on muscle strength and body mass. Eur. J. Appl. Physiol. 80:165–168. 1999.
3. Wilson, G.J., G.A. Wood, and B.C. Elliot. Optimal stiffness of the series elastic component in a stretch shorten cycle activity. J. Appl. Physiol. 70:825–833. 1991.
4. Watsford, M.L., A.J. Murphy, W.L. Spinks, and A.D. Walshe. Creatine supplementation and its effect on musculotendinous stiffness and performance. The Journal of Strength and Conditioning Research. 17 (1); 26–33, 2003.
