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May 7, 2024

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Effects of Creatine Supplementation on Muscle Strength, Power, and Aerobic Capacity Introduction When it comes to athletic performance, athletes are always looking for an advantage over their opponent. One common method that athletes utilize for increasing performance are supplements such as creatine. Creatine has been proven to increase muscular strength and power in addition to improved performance of high intensity, short duration activity. Improvements in muscular activity caused by creatine supplementation are due to an increase in phosphocreatine levels in the muscle and an increased rate of phosphocreatine resynthesis during rest periods. Creatine is essential in activating the phosphagen, or ATP-PC, system. Phosphocreatine, also known as creatine phosphate, is a high energy phosphate molecule essential to the phosphagen system (Haff & Triplett, 2016). Increased levels of creatine phosphate in the body signal the phosphagen system to generate more ATP. ATP produced by the phosphagen system is typically replenished within 2 to 3 minutes (Haff & Triplett, 2016). The phosphagen system is the first bioenergetic pathway to be activated in the onset of physical activity and is primarily responsible for energy in activity lasting 6 to 30 seconds (Haff & Triplett, 2016). Creatine Supplementation in Resistance Training Creatine is one of the most popular supplements in resistance training, and therefore has become a highly tested supplement in research studies. In response to heavy resistance training, creatine supplementation enhanced muscle creatine levels, fat-free mass, muscle hypertrophy, and physical performance. In studies which separated subjects into creatine or placebo groups, muscle creatine was significantly higher in the group who ingested creatine (Volek et al., 1999). Increase in lean mass is seen after creatine supplementation combined with resistance training.
Even lean mass in older women increased significantly with creatine supplementation and training (Guluano et al., 2014). This is a significant finding considering the elderly population, especially women, experience age-related decrease in muscle mass and strength. Increased fat- free mass in the creatine group can be attributed to increased muscle hypertrophy (Voltek et al., 1999). Subjects supplemented with creatine saw a 29 to 35% increase of all muscle fiber cross- sectional area, more than double that of the placebo group (Voltek et al., 1999). This muscle fiber hypertrophy can be a result of enhanced protein synthesis, either through protein metabolism or enhancement of training intensity (Volek et al., 1999). Previous literature has found that muscle hypertrophy produced by creatine ingestion may be caused by satellite cell proliferation, and increased secretion of insulin-like growth factor (Van Beneden et al., 2004). Subjects who ingested creatine also exhibited increased 1-RM strength in the bench press and squat (Volek et al., 1999). Another study determined that 1-RM leg press was significantly greater when creatine supplementation and training were combined (Guluano et al., 2014). Muscle fiber hypertrophy and adaptation to training is a significant reason for this increased maximum strength. Greater maximal strength may have also been caused by higher creatine stores (Volek et al., 1999). Higher creatine stores indicates that ATP can be resynthesized through the phosphagen system at a faster rate. Creatine Supplementation in High-Intensity Exercise Because of its impact on the phosphagen system, creatine is extremely useful in short- duration, high-intensity exercise. Studies have found that performance of high intensity exercise following creatine supplementation was improved and work output was increased. This improvement in performance and work output can be attributed to higher initial creatine phosphate content available and increased creatine phosphate resynthesis during recovery
(Balsom et al., 1993). In another study, creatine supplementation significantly improved peak power of bench press and jump squat (Volek et al., 1997). Increase in power in all 5 sets could be attributed to lower repetitions and a longer rest time to allow the phosphagen system to resynthesize ATP (Volek et al., 1997). Creatine supplementation can sustain high intensity exercise because muscle creatine concentration is maintained (Haff & Triplett, 2016). Creatine Supplementation in Aerobic Exercise Most research involving creatine includes subjects participating in a resistance or power training program. In a study observing the effects of creatine on oxygen uptake during aerobic exercise such as cycling, it was found that creatine decreased oxygen uptake and increased the oxygen deficit (Nemezio et al., 2015). Creatine also increased the anaerobic energy contribution to the cycling trial (Nemezio et al., 2015). Another study examining the effects of creatine on cycling also observed a significant decrease in oxygen uptake after creatine ingestion (Balsom et al., 1993). Increase in total muscular creatine content leads to an increase in metabolic capacitance. This increased creatine content slows VO2 kinetics during the beginning of exercise, therefore creating a delayed VO2 response (Nemezio et al., 2015). In fact, as the length of exercise increases, the effects of creatine are diminished (Haff & Triplett, 2016). ATP produced by the phosphagen system is rapidly used, which means that creatine cannot supply energy for longer duration activities (Nemezio et al., 2015). Time to complete the cycling trial was not improved after creatine consumption; this could be due to the reduced oxygen uptake (Nemezio et al., 2015). Creatine also caused an increase in body mass, which may be an unwanted result for aerobic athletes (Nemezio et al., 2015). Therefore, creatine is not found to enhance aerobic or endurance exercise.
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