Let's start with a refresher on why protein is a vital nutrient, and especially critical for the triathlete.
First, protein is a key regulator of the body and its many essential functions. It plays major roles in hormone and enzyme production, blood clotting, fluid balance and tissue repair, just to name a few.
In fact, nearly 20% of your body mass is protein (via lean tissue), and every cell in your body contains it.
Thus it's no surprise that protein consumption is a key part of adequate nutrition, and while sedentary folks need a healthy supply of it, endurance athletes require substantially more than the average Joe ... a lot more, in fact.
Well, for starters, intense and long-duration exercise (i.e. training or competition) place a great protein demand on your body, both in terms of the energy required to fuel the exercise, but also during the subsequent recovery period.
During endurance training characterized by large energy deficits - such as IRONMAN training, for example - large demands on certain amino acids (the building blocks of protein) require protein to contribute as much as 15% of total energy output.
Also, the intensity and duration of this training causes "microtrauma" (physical separation and breakdown) to muscle fibers, a process called catabolism, which must be repaired during recovery in order to produce positive training outcomes.
By consuming sufficient quality protein at key times before and after training or competition, you can ensure the steady supply of critical amino acids to working muscles in order to support repetitive and optimal muscle contraction, as well as the repair and growth of muscle tissue during your subsequent recovery period.
Now, a quick word on what constitutes "critical amino acids."
Amino acids, the so-called "building blocks" of protein, are responsible for protein's benefits. When protein is digested, it is broken down into these constituent amino acids, which then enter the bloodstream through your small intestine.
Then the magic happens ... the extent of which is predicated by the amino acid profile of the formerly ingested protein.
It has long been understood that the branched-chain amino acids ("BCAAs") leucine, isoleucine, and valine are crucial to protein synthesis, and thus the ability of protein to support muscle contraction, repair damaged tissue and support training adaptations.
More recently, research is not only affirming this understanding of BCAAs, but adding to their long list of benefits.
Leucine, in particular, is believed to be the key amino acid responsible for virtually all of protein's affect on stimulating protein synthesis. It does this by activating a biochemical sequence of events referred to as the "mTor pathway."
The biochemistry is beyond our scope, but it's enough to say that proteins high in leucine concentration, and BCAAs more generally, are extremely important to endurance athletes.
BCAAs confer the following additional benefits to athletes: