Creatine Supplementation

The objective I will be relating to is: “know the different energy molecules in the cell and their use in anaerobic and aerobic exercise.” In terms of my project directly I will be addressing how supplementing creatine can increase intramuscular creatine content and boost athletic performance. To start we must understand how creatine interacts with the muscles to synthesize energy. ATP, or adenosine triphosphate, is the energy molecule that drives contractions in skeletal muscle. Naturally, skeletal muscle maintains a very low intracellular ATP concentration as ATP that is consumed is broken down into ADP, or adenosine triphosphate, which is then resynthesized back into ATP. However, the overall reaction involves creatine and is as follows; 

Creatine + ATP ←(Creatine kinase)→ ADP + Phosphocreatine + H(+)

The creatine that is stored intracellularly in muscle tissue is donated a phosphate group from ATP and converted into phosphocreatine, which can then be used to resynthesize ADP into ATP (as you can see the reaction is reversible). This whole reaction is catalyzed by the enzyme creatine kinase, which allows for the forward and reverse reactions to proceed.¹ As we learned in lecture, creatine naturally only provides 15 seconds of energy after which all of the intracellular creatine stores in skeletal muscle are depleted. This is where supplementation comes in. According to a study conducted by Jay Hoffman on the effects of pre-workout supplementation, typical creatine supplementation is conducted with a 20g/day loading dose of creatine monohydrate for a week followed by a 5g/day maintenance dose every subsequent day after.² It was shown that 20g/day (or more specifically 0.3g/kg body weight) optimally saturates the muscle tissue with free creatine after 5 days. This is achieved with four 5g doses per day spaced out with 3 hours in between. After the 5-day loading phase, optimal intracellular creatine levels can be maintained with a 5g/day dose. It must also be noted that glucose enhances creatine uptake into skeletal muscle, which is why creatine supplementation is optimally achieved when dosed simultaneously with a high glycemic carbohydrate solution.¹ Shifting over to exercise, it was shown by Paul Balsom at the Karolinska Institute that during bouts of high-intensity exercise creatine depletion occurs inversely proportional to the duration of the exercise. For example, a 25-second bout of sprint cycling depleted 6mmol/sec of free creatine from skeletal muscle tissue, while a 6-second bout of all-out sprint cycling depleted 15mmol/sec of creatine from skeletal muscle tissue.³ Thus, it can be concluded that the amount of creatine depleted depends on the intensity/demand of the muscles being utilized. Now looking at overall effects on athletic performance, Dr. Racette of the Washinton University School of Medicine in St. Louis analyzed the effects of creatine supplementation across a variety of different exercises/sports over short-term (<10 days) and long-term (4-12 weeks) supplementation periods. Through her study, it was shown that during short-term supplementation, individuals that completed endurance exercises (running) and extreme high-intensity exercises (1 rep max exercises) did not experience any improvement in athletic performance. However, in tests where weight/intensity was held constant, but the repetition range was open-ended, athletes that completed short-term creatine supplementation experienced an improvement in the number of repetitions completed. In the long-term portion of Dr. Dacette’s study, athletes experienced an improvement in repetitions and the amount of weight/intensity they were able to exert.¹ It must be noted that during the long-term study endurance exercises were not evaluated for improvement. As a conclusion to her study, Dr. Racette noted that her study provided significant support for the ergogenic benefit that creatine monohydrate supplementation offered athletes. She concluded that supplementation (acute or long-term) enhanced “lean body mass, muscle strength, power, and maximal exercise performance in specific events among many individuals.”¹ Now looking at side-effects of creatine supplementation, it was shown that excessive creation consumption (in excess of 25g/day for more than 5 days) could lead to muscle cramping and dehydration, especially in endurance exercises as creatine supplementation increases the water held in skeletal muscle, which is not available for the body to utilize.¹ Overall, the conclusion drawn from research on this topic is that a loading phase of creatine is necessary to optimally increase intracellular creatine levels, but in excess of 5 days can lead to adverse effects. It was found that a maintenance dose of 5g/day maintains optimal intracellular creatine levels. Furthermore, creatine supplementation should be paired with a high-glycemic carbohydrate solution for optimal uptake by skeletal muscle to experience the increased performance/ergogenic effects shown to occur during creating supplementation. Finally, long-term creatine supplementation (> 4 weeks) increases the improvement in athletic performance observed by athletes supplementing their workouts with creatine.

1) Racette, S. B. (2003). Creatine supplementation and athletic performance. Journal of Orthopaedic & Sports Physical Therapy, 33(10), 615–621. https://doi.org/10.2519/jospt.2003.33.10.615

2) Department of Health and Exercise Science. (n.d.). Effect of a pre-exercise energy supplement on the acute… : The Journal of Strength & Conditioning Research. LWW. Retrieved November 23, 2021, from https://journals.lww.com/nsca-jscr/Fulltext/2008/05000/Effect_of_a_Pre_Exercise_Energy_Supplement_on_the.32.aspx.

3) Balsom, P. D., Soderlund, K., & Ekblom, B. (1994). (PDF) creatine in humans with special reference to creatine supplementation. ResearchGate. Retrieved November 23, 2021, from https://www.researchgate.net/publication/15382274_Creatine_in_Humans_with_Special_Reference_to_Creatine_Supplementation.