Slowing Muscle Protein Breakdown
A popular misconception about building lean body mass is all you to do is stimulate the pathways that turn on muscle protein synthesis. This is only half the issue. Your lean body mass is a dynamic process. At all times, we are building new muscle protein (anabolism) and simultaneously breaking it down (catabolism). The key is net protein balance. When protein synthesis is greater than protein breakdown, we have a net positive balance and we increase lean body mass. When protein breakdown exceeds protein synthesis we have a negative protein balance and we decrease lean body mass. Normally we are at balance neither increasing or decreasing lean body mass. However the goal of most endurance athletes is to increase lean body mass. Understanding the factors that cause protein breakdown help us better achieve this goal.

Moderate to intense exercise increases protein breakdown primarily due to two factors. One cortisol and the second, reactive oxygen species better known as free radicals. Exercise increases both. Cortisol levels rise during exercise. One reason is the stress of physical exercise. For example dehydration cause a increase in cortisol levels. Cortisol levels also rise as your body seeks ways to provide working muscles the fuel for energy. During moderate to intense exercise, 30 minutes or more, up  to 20% of your muscle’s energy can be derived from protein.

The second factor which increases protein degradation is reactive oxygen species. During aerobic exercise, there is an increase in reactive oxygen species. Reactive oxygen species activate specific enzyme pathways which increase muscle protein breakdown.

Fortunately there are a number of  mechanisms to slow protein degradation. One of the most important is the hormone insulin. One reason insulin is such a powerful anabolic agent for building lean body mass, is its delivers dual effects. Insulin stimulates protein synthesis through multiple mechanisms. It turns on the switch mTOR which actives protein synthesis and it helps transport amino acids into the cell where they can be assembled into protein. However one of the most overlooked actions of insulin is that is slows protein degradation. The net result is an increase in lean body mass.

Since cortisol and reactive oxygen species are elevated after exercise recovery nutrition plays an important role. A carbohydrate/protein/electrolyte sports drink that contains antioxidants can slow muscle breakdown through a number of mechanisms including:
  • Electrolytes help re-hydrate thereby reducing cortisol levels
  • Carbohydrate stimulates insulin which increases protein synthesis, reduces  cortisol and slows protein breakdown
  • Protein provides the raw material for the rebuilding and repair of muscle protein
  • Antioxidants reduce reactive oxygen species and slow protein degradation
  • For all of the above reasons a recovery drink such as Endurox R4 should be an essential part of your post exercise regimen.