The Necessity of Rapid Hyperacidaemia

 

The potential for maximum MPS and therefore the greatest recovery and strength gains, declines quickly after competition and training.  There is a necessity to get amino acids into the muscles as quickly as possible in order to see maximum gains.

It is now unequivocal that immediate post-exercise amino acid provision is an effective nutrition-based strategy to enhance MPS above the rates observed with exercise or competition alone [25] [34] [36].  The importance of early post-exercise protein ingestion relates to the fact that exercise-mediated increases in rates of MPS are greatest immediately after exercise (~100–150% above basal rates) [22] [23].

With success defined by slender margins in today’s professional and high-level amateur sport, much effort and research has centred on achieving the rapid hyperacidaemia in the blood that will allow for the maximum MPS to occur.  This is physiologically difficult to achieve.  As a result, most studies report on experiments in which there are no replacement amino acids in the bloodstream within the first 30 minutes after exercise, the period of maximum potential [22] [24] [37].  This has been, simply, impossible using the protein sources available.

Consumption of protein represents the most easily accessible method for getting free amino acids into the bloodstream.  Individuals typically acquire their protein through consumption of either high protein foodstuffs such as meat, poultry, fish and eggs, or via liquid consumption of protein sources such as milk, whey, casein and soy [37-43].

Turning these raw protein sources into the bioavailable amino acids craved by the muscles requires several time-consuming stages of digestion before they can be absorbed into the body via the jejunum, a part of the small intestine, [44] as discussed below.

To be absorbed, amino acids must cross from the digestive system into the blood stream via microscopic hair-like structures called villi which line the jejunum.  Each villus has a good blood supply and serves to maximise the surface area of the intestine to allow for maximum absorption.  The villi thus play a vital role in getting amino acids into the bloodstream quickly, with the limiting factor being the size of the molecules that can be absorbed and released.

The physical size of the villi and the structure of cells makes it impossible for large proteins to be absorbed directly and, for that reason, all protein sources need to be reduced from large and complex to being just a few amino acids in length by the digestive system, a process known as proteolysis.

Proteolysis uses a variety of specially secreted digestive enzymes, each capable of breaking specific links between amino acids.  For example, trypsin, one of the digestive enzymes involved, specifically breaks apart the links between polar amino acids.  Long chains of amino acids can require many interactions with digestive enzymes before they are broken down to bioavailable single amino acids.