## 5 The Roles of Creatine, Caffeine, Phosphate, Beta-Alanine and Carnitine  
### Creatine  
Creatine supplementation is probably the most efficient way to improve strength and sports performance, promote exercise adaptation and recovery and prevent injury and neurodegenerative disease incidence, with its efficacy supported by dozens of studies. About 95% of creatine is found in skeletal muscle, playing a key role in anaerobic ergogenesis as part of the phosphagen system. In an omnivorous diet, about half of creatine is provided by the diet, and the rest is synthetized from glycine, methionine and arginine. Numerous scientific studies have proven that supplementation with this organic compound effectively increases the concentration of creatine found in muscle cells, which explains the improvement in sports performance in high-intensity exercise and leads to better training adaptation. In addition, creatine may have a beneficial effect on post-workout regeneration, thermoregulation, prevention of sports injuries, neuroprotection of the spinal cord, rehabilitation, improvement of the health of people suffering from neurodegenerative diseases, diabetes, osteoarthritis or old age and the associated loss of lean body mass. The rate of synthesis may vary indirectly proportionally to exogen intake [48]. There are several recommended protocols regarding creatine supplementation. The most common protocol includes a loading phase of 20 g of creatine divided into four meals during the day for 1 week, followed by a maintenance dose of 3-5g/day. Undoubtedly, the advantage of such a procedure is the rapid increase in creatine concentration in the muscles of about 20%, but the same effects are also obtained by supplementation with a lower dose (even 3 g/d) but for a much longer period, e.g., four weeks. The optimal solution is to take creatine in small portions with meals rich in carbohydrates, especially during the so-called loading phase, because creatine from a single dose of more than 5 grams will not be effectively absorbed by the muscle cells [61; 62; 63]. Producers of dietary supplements offer a number of different forms of creatine on the market, which are often even in one product (the so-called creatine stack).  
Most fears regarding side effects such as kidney damage, hair loss, dehydration, fat mass increase, concerns about use in the young or elderly population, musculoskeletal injuries and muscle cramps have been infirmed in multiple studies, and creatine use is considered safe and efficient by the scientific community [48; 49]. In combat sports, the main targeted advantage of creatine use is the increase in muscle mass, resulting in increased explosive power via the phosphagen system. Several studies have validated the theory, finding the applicability of creatine in most combat sports. A study performed by [PERSON] et al. demonstrated the positive effect of creatine in judo training, with an increase in VO2 max and a decrease in time to generate peak power [146]. Anaerobic performance and peak power enhancement were also observed in takewondo athletes supplemented with creatine and bicarbonate [147]. In elite wrestlers, a significant increase in average and peak power was noted after creatine supplementation [148]. Along with anaerobic power, a slight increase in fat mass was obtained after creatine supplementation in takewondo practitioners [149]. An increase in fat mass caused by creatine was extensively researched in other studies, which failed to validate this theory [49].  
Creatinine can be a useful and safe product for all combat sports participants who want to improve important parameters of their performance, such as maximum anaerobic power.