Protein and Exercise

Protein requirements have been the subject of many studies in the sports and scientific world for many years. There has also been vast amounts of inconclusive evidence that either support or refute recommended daily averages (RDA's) as set out by the various food councils and health governing bodies.

There are a multitude of recommendations on the average amount of protein that an individual requires to remain in a positive protein balance. Until recently many nutritionists believed that sportspeople did not require more protein than those who led a more sedentary lifestyle.
It is generally recommended that we need to consume 0.75g of protein per kg of bodyweight for the average adult regardless of your lifestyle, however recent studies have shown that various levels of exercise intensity place different protein requirements on the human body. For years bodybuilders, weightlifters, strength athletes and their coaches have insisted that their protein requirement must be higher than average to gain strength and increase muscle mass and this would now appear to be a valid case.

The Protein content of skeletal muscle represents 65% of the body's total protein and can be dramatically increased through applied resistance training.

Studies on two groups of males at a research institute in San Francisco gave healthy men 2.8g of protein/ kg of bodyweight (BW) and 1.45g of protein / kg of BW and trained them to exhaustion for 40 days.
The group on 2.8g / kg gained 3.3kg (7lbs) of lean mass and those on 1.45g / kg gained 1.2kg of lean mass. The studies proved that by increasing protein intake gains in lean mass are possible than with a lesser amount of protein. It is also important to emphasise that the amount of training that was undertaken to achieve these gains was quite considerable and by just increasing your protein intake will not see you developing huge gains in lean body mass.

Further studies simulating the Tour De France found athletes who cycled 5 hours per day required 1.8g of protein / kg of bodyweight to remain in a positive Protein (Nitrogen) balance. The type of exercise or the reason behind the exercise can play a vital role in determining the amount of protein that you will require. The truth is that any moderate form of running or resistance type weigh training causes tissue damage that will need an increase in protein to repair that tissue. So if you partake in moderate to strenuous levels of exercise you will need more protein than an individual who does nothing at all.

Amino Acids provide the major substance for the synthesis of new tissue, which is referred to as 'Anabolism' or Anabolic State'. It is this state that those individuals wishing to gain muscle are trying to achieve.

'Catabolism' is the opposite of Anabolism and is the degradation of protein from muscle into its amino acid form for energy. It is very rare that his state will ever occur in a sedentary individual. It is quite common however to see overtrained individuals start to lose muscle mass due to insufficient energy in the form of carbohydrates or insufficient protein to maintain muscle tone.
You are most likely to find yourself in a catabolic state in endurance type events that last longer than 2 hours. (See Fuel Utilisation) When protein is broken down or catabolised to its amino acid form protein supplies the same amount of energy as carbohydrate (4 Kcals / g) at the expense of muscle loss.

It is therefore true to say that under certain conditions protein demand by the body increases with exercise duration and type.

Regular moderate endurance exercise increases the body's protein needs from the recommended 0.75g / kg of bodyweight to approximately 1.45g / kg of bodyweight.

Further Reading : -

The relationship between Protein and exercise
Calculation of Protein intake depending on exercise levels
Protein supplementation

A more technical view on Proteins and Amino acids