Older Athletes Have Anabolic Resistance
Amino acids, which are building blocks of proteins, can be essential, non-essential or conditional. Non-essential and conditional amino acids are made in your system. Essential amino acids are found in meat, dairy, eggs, poultry and seafood provide all nine essential amino acids and are known as complete proteins. The Branched Chain Amino Acids (BCAAs) consist of the amino acids, leucine, isoleucine, and valine. The amino acid L-Leucine has shown promise to date, and it is associated with enhanced post-meal consumption protein synthesis. As one gets older, there is blunted muscle growth, and coincidentally there has been documentation of “anabolic resistance.” It has been demonstrated that ingestion of 40 grams essential amino acids (equivalent to ~100 g high-quality protein) lacked the capacity to stimulate muscle protein synthesis rates in the elderly, as opposed to the young. The age-related loss of muscle protein must be attributed to an imbalance between muscle protein synthesis and breakdown rates, resulting in a negative muscle protein balance and, over time, a decline in skeletal muscle mass. This means giving an older adult a dose of protein does not result in the same increases in protein synthesis as a younger adult.
Recent work seems to suggest that the elderly show a blunted muscle protein synthetic response to amino acid administration. It is probable that this is mediated through a mechanism involving leucine. Leucine results in an increase in muscle protein synthesis and can reverse the age-related blunted response of muscle protein synthesis. Studies in humans have shown that muscle protein synthesis in the elderly is superior when increasing the leucine content in a standard mixture of essential amino acids (EAAs). Long-term supplementation studies examining the effectiveness of leucine and essential amino acids enriched with leucine for prevention of either age-related sarcopenia. Researchers wanted to compare the efficacy of EAAs supplemented with different amounts of leucine on muscle mass and physical performance in elderly men and women.
Subjects received one of the following daily:
1. Standard EAA mixture (20% leucine)
2. Modified EAA mixture (40% leucine)
3. Isocaloric placebo (lactose).
The subjects were instructed not to change their physical activity level. At the end of the study, the mixture that contained 40 percent leucine resulted in a statistically significant increase in lean tissue mass compared with that of the placebo group. Supplementation with the mixture that contained 20 percent leucine had no effect on lean tissue mass. The Leucine, 40% group, resulted in an increase in lean muscle mass of 1.1%. Although the standard EAA Group (20% leucine) received as much protein and EAAs as those receiving the modified EAA (40% leucine) supplement, the changes in lean muscle mass were small, suggesting that the percentage concentration of AAs in the 20% supplement was not optimised for muscle growth. Concentrations of isoleucine and valine were significantly decreased at the end of the intervention with the added leucine, which is in agreement with other studies. This suggests that a person may want to take a BCAA supplement with the added isoleucine and valine to prevent amino acid imbalance.
Athletes have Blunted Anabolic Responses
Researchers wanted to compare the muscle protein synthesis rates of masters and younger triathletes over three consecutive days of intense endurance training. Recovery of cycling performance, following muscle-damaging running, was also compared between groups. Participants then completed a 30 min downhill run; three 20 km cycling time trials were completed 10, 24 and 48 h following the run. Diet was controlled throughout the study. At the end of the study, over the three days, masters triathletes showed a significantly lower muscle protein synthesis rates compared to the younger. There was also a trend for masters triathletes to produce a slower cycle time trial (-3.0%, d=0.46) compared to younger triathletes at ten hours post-run, in comparison to baseline. The present data show lower muscle protein synthesis rates in well-trained masters triathletes over three days of training, and this likely contributes to poorer muscle protein repair and remodeling. Furthermore, acute recovery of cycle time trial performance tended to be poorer in the masters triathletes. Older athletes can benefit from taking a high quality BCAA powder rich in leucine to help increase muscle protein synthesis and support lean muscle mass.
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