Branched Chain Amino Acids

A study from Sacred Heart University in Fairfield, Connecticut showed that taking branched chain amino acids decreased the amount of muscle damage from exercise in untrained volunteers. Branched chain amino acids are protein building blocks that can be converted easily to sugar by your body. A likely explanation for the advantage shown in this study is that muscles become damaged when they run out of their stored sugar and start to burn protein in the muscles themselves for energy.
Journal reference

However, it makes no sense to spend a lot of money on these expensive protein supplements. You will get the same benefit from any food that contains protein. Eat some cheese, seafood, peanut butter, chicken, nuts or any other convenient source of protein when you exercise for more than an hour.