**7. Conclusions**

Interestingly the beneficial effects of BCAA mixtures supplementation has been reported also following moderate resistance training and endurance training both in rodents [188] and humans [189-191]. In these conditions the effect of supplementation seems to mainly reflected on a reduced rate of perceived exertion (RPE) [189] and reduced proteolysis as demonstrated by reduced phenyalanine release from the muscle [192], whereas no beneficial effects have been found in terms of changes in exercise performance [189]. In particular in the study by Greer and coworkers nine untrained male subjects where supplemented with a BCAA enriched beverage, an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo beverage. The subjects performed three 90-minute cycling bouts at 55% VO2 peak followed by 15-minute time trials and ingested a total of 200 kcal via the CHO or BCAA beverage before and at 60 minutes of exercise or the placebo beverage on the same time course. A greater distance was traveled during the CHO trial than the BCAA and placebo trial. On the contrary the RPE was reduced during the BCAA trial as compared with the placebo trial. This study clearly demonstrated that CHO supplementation improved performance compared with BCAA and PLAC beverage. Thus BCAA supplementation did not influence aerobic perform‐ ance but attenuated RPE [189]. Accordingly BCAA supplementation (0.8% BCAA in a 3.5% carbohydrate solution; 2,500 mL/day for four days) effectively reduced the muscle soreness and fatigue sensation when supplementation was carried out during an intensive endurance training programme in male and female, and the perceived changes could be attributed to the attenuation of muscle damage as demonstrated by decreased LDH, CK and granulocyte

Importantly a minority of works contradict the general findings from other research on the benefits of BCAA on resistance exercise muscle damage. In particular conflicting results have been reported by Stock et al. [193] showing that in a mixed sex group of trained participants there were no differences in damage indices of resistance exercise (6 sets of squats to fatigue using 75% of the 1 repetition maximum) between a carbohydrate versus a carbohydrate/ leucine supplement. The subjects enrolled consumed the carbohydrate beverage 30 minutes before and immediately after exercise with or without the addition of 22.5 mg kg-1 of leucine. Results showed that the addition of leucine did not significantly decrease CK and LDH activity or DOMS evaluated at different time points following exercise thus suggesting that adding leucine to carbohydrate beverages did not affect acute muscle recovery from exercise. Con‐ sidering that in the study by Stock and coworkers the amino acid supplement consisted of leucine alone (and not of a mixture of BCAA), one can speculate that a methodological bias

may account for the observed different outcome of this study compared to others.

In conclusion the overall effect of resistance exercise on circulating BCAA suggests that exercise induced muscle damage is followed by an increase of skeletal muscle BCAA uptake from the serum being used as energy source and/or participate in translation initiation signaling pathway involved in muscle remodeling. Functionally this appears to have some consequence in muscle pain. A similar effect on the rate of perceived exertion has been found following BCAA supplementation before and during endurance exercise, when muscle remodeling is reasonably much less than in resistance exercise. The mechanisms beyond the

elastase levels, and inflammation [190, 191].

76 Muscle Injuries in Sport Medicine

The skeletal muscle is placed under considerable stress during high repetitive eccentric, or lengthening, contractions.

Several studies have used a variety of nutritional supplementation strategies including macronutrients and micronutrients, with variations in dosage, timing and duration of supplementation, finalized to minimize exercise induced muscle injury. Although there is proper rationale and some evidence showing the efficacy of certain supplements such as creatine and essential amino acids, there is little evidence to support a role for others including the antioxidants. Indeed, antioxidant supplementation may interfere with the cellular signal‐ ling paths thereby unfavorably affecting muscle function, performance, and recovery from injury.
