Endurance training: maintaining muscle mass

It is widely accepted that during prolonged exercise there is a clear decrease in muscle protein synthesis and an increase in muscle protein breakdown. Maintaining muscle mass is all about the ratio between mps and mpb.  A recent paper by Samuel Impey, et al., on the effect of ingesting leucine-enriched protein around endurance training gave some really interesting results.

Most keen endurance athletes out there will be well aware of ‘carbohydrate cycling’ or ‘training low’ which involves training in a glycogen depleted state for some of your sessions. Training low has been found to exert metabolic stress on muscle fibres leading to a greater increase in mitochondrial synthesis (Hawley, 2014). This in turn leads to a greater oxidation capacity (the ability to breakdown carbohydrates and fats for energy).

Due to the nature of glycogen depletion (low carbohydrates, fasting), muscle protein synthesis can fall in to a deep negative, causing high rates of breakdown.  What Impey’s experiments have found is that this does not have to be the case. Ingestion of a high leucine protein source such as whey protein or a high leucine protein gel, before, during and post exercise can prevent muscle atrophy without disrupting the signalling of glycogen depletion on endurance training (Impey, 2015). 

In short, the catabolic effects of glycogen depleted endurance training can be blunted with the use of a high leucine protein source before, during and post training. This should also be the case for all athletes looking to maintain muscle mass whilst increasing their oxidative capacity (footballers, netballers, soccer players, basketballers etc). 

Impey, Samuel G., et al. “Leucine-enriched protein feeding does not impair exercise-induced free fatty acid availability and lipid oxidation: beneficial implications for training in carbohydrate-restricted states.” Amino acids (2015): 1-10.


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