Adenosine Triphosphate (ATP) is a vital molecule that stores and provides energy for a wide range of cellular functions. ATP paired with Adenosine Diphosphate (ADP) plays a crucial role in muscle function as it directly powers muscle contraction and relaxation. In order for a muscle to contract, Calcium ions need to bind to Troponin (TnC) which results in displacing Tropomyosin and exposes the Myosin binding sites on the Actin filament. The head of each Myosin unit is bound to ADP and a phosphate group from a previous contraction. The phosphate group gets released when the myosin head binds to the actin filaments. The two filaments glide past each other, releasing ADP and thus contracting the muscle. To relax the muscle, ATP comes in and binds to the myosin head, releasing it from actin. This allows the muscle to reset and Myosin ATPase hydrolyzes ATP back to ADP and a phosphate group that primes the myosin head into a high energy state in preparation for the next contraction. This cross bridge cycle can be repeated numerous times but is heavily dependent on the amount of ATP.
Creatine is stored as phosphocreatine in skeletal muscles and it can serve as a small energy reservoir for ATP. Phosphocreatine donates a phosphate group to ADP, helping it convert back to ATP. This reaction is catalyzed by the enzyme creatine kinase and occurs very quickly, making the phosphocreatine system an immediate source of ATP, especially during short bursts of high-intensity muscle activity. With more ATP, it allows the body to undergo more contraction cycles which would result in a higher Vmax of myosin ATPase. A higher Vmax allows for rapid cross bridge cycling and more powerful contractions. This greatly benefits fast twitch type 2b muscle fibers.
Our bodies naturally synthesize creatine via the liver, pancreas and kidneys. However, it only produces roughly 1 gram of creatine. We also can get creatine from eating beef, pork and fish. Creatine supplementation increases the amount of phosphocreatine stored in muscles, allowing for greater ATP regeneration during intense exercise. This means muscles can sustain high-intensity contractions for longer periods before fatigue sets in.
Overall, creatine supports ATP regeneration during high-intensity exercise, allowing for improved performance, greater training volume, and enhanced recovery. This leads to better muscle gains and overall strength increases, making it a popular and effective supplement for building muscle mass.
Guimarães-Ferreira L. Role of the phosphocreatine system on energetic homeostasis in skeletal and cardiac muscles. Einstein (Sao Paulo). 2014 Jan-Mar;12(1):126-31. doi: 10.1590/s1679-45082014rb2741. PMID: 24728259; PMCID: PMC4898252.
I have used creatine supplements for physical activity, but I didn't understand exactly how it worked in the body. I thought it was fascinating that we actually store and generate creatine in the body, and that it's critical in supplying skeletal muscles with ATP during high intensity activity. I have always noticed that I'm less sore after a workout if I took creatine, and I was curious if there is a physiological explanation for this. A source I found said there may not be a direct relationship between creatine usage and muscle repair (Mckinnon, 2012).
ReplyDeleteMcKinnon, N. B., Graham, M. T., & Tiidus, P. M. (2012). Effect of creatine supplementation on muscle damage and repair following eccentrically-induced damage to the elbow flexor muscles. Journal of sports science & medicine, 11(4), 653–659.
I liked your correlation of muscle and creatine. I thought it was interesting that our body synthesizes creatine on its own without needing the supplement/dietary sources. Although, from your readings, what way do you think is best to increase creatine intake, dietary or supplementally? And, we know that creatine plays a role in muscle contraction, but do you think this also goes for heart contractions? I found an article (Balestrino M. (2021). Role of Creatine in the Heart: Health and Disease. Nutrients, 13(4), 1215. https://doi-org.dml.regis.edu/10.3390/nu13041215) that states creatine plays a major role in heart contraction and energy metabolism. Do you think it would be a good idea to recommend to consume high levels of creatine to someone who could be at risk of cardiac arrest?
ReplyDeleteYour post provides a clear and detailed explanation of how ATP functions in muscle contraction. The way you describe the cross-bridge cycle and the role of creatine in supporting ATP production really highlights the physiological mechanisms behind muscle performance. It’s fascinating to see how the phosphocreatine system serves as a rapid energy reservoir allowing for more powerful contractions and prolonged high-intensity activity. Creatine supplementation clearly has significant benefits in terms of improving performance and delaying fatigue during intense workouts, but I’m curious about its long-term effects, particularly on muscle recovery and any risks. Have you come across any studies that explore the potential for overtraining or muscle strain due to sustained high-intensity activity from supplementation? Here is an article that I found really interesting regarding this:
ReplyDeleteGuilherme, Berriel et al., 2020. Stress and recovery perception, creatine kinase levels, and performance parameters of male volleyball athletes in a preseason for a championship. Sports medicine - open, 6(1), 26. https://doi-org.dml.regis.edu/10.1186/s40798-020-00255-w