A comparison of alternative ways of reaching the window of anabolic potential


With traditional dietary intake unable to realise the full potential of muscle protein synthesis, alternative strategies must be considered by serious athletes to maximise recovery and strength gains following competition and training.

One option available to athletes is consuming protein before exercise.  Here, studies have shown mixed results.  Some studies showed that consumption of protein before exercise resulted in higher levels of MPS than when the same nutrients were eaten post exercise [56].  However other studies showed the opposite effect [32] [57].  One study found that ingesting protein during exercise was also beneficial [58].

The mixed results seen in these studies could well be explained by amino acid availability declining quickly [59].  Protein ingested too early will have little benefit as amino acids do not remain circulating in the blood indefinitely, whilst those ingested too late will miss the window of maximum anabolic potential.  The complexities of timing the digestion of a protein requiring digestion to result in the presence of free amino acids in the blood during the window of maximum anabolic potential is very complicated.

Compounding the pre-eating regimen conundrum is the fact that it can result in unwanted reactions such as increased nausea and decreased performance in training and competition [60].

A second option currently available to athletes is the consumption of branched-chain amino acids immediately after exercise to stimulate muscle growth.  There are three such amino acids, leucine, isoleucine and valine and these are claimed by some to stimulate MPS.

Of the three branched-chain amino acids, it is only leucine which provides maximum stimulation for MPS, with the other branched-chain amino acids being essential for muscle growth only in the same way that all other amino acids are essential.  Leucine stimulates MPS by activating mTOR which, as previously mentioned, kick-starts MPS.  Studies have shown that inadequate leucine results in poor stimulation of MPS whilst leucine alone can initiate it[41] [61-63].

Once MPS has been initiated, all essential amino acids are required for building muscle, and the absence of any will impede muscle production and inhibit recovery.   The presence of all 20 amino acids is desirable as the regenerating muscle tissues requires optimal body conditions and balanced metabolism [64-67].  Absence of non-essential amino acids can impair these functions and reduce the window of anabolic potential [67].  For this reason, branched-chain amino acids alone do not possess the ideal properties for maximising MPS in order to speed recovery and increase strength.  It is possible to conclude that claims made for branched-chain amino acid nutritional products may be somewhat overstated.

A third approach, the direct intravenous injection of amino acids is not appropriate and is not discussed.