Whether you are a gym novice or a bulked-up weightlifter, the ideal amount of protein to consume after exercise remains the same, according to a new study.
The research, published in Physiological Reports, found that existing muscle mass doesn’t affect the amount of protein required, as previously thought — but that the type of exercise undertaken does.
The research also suggested that for whole-body resistance workouts, 40 grams of protein was more effective for rebuilding muscle than 20 grams.
During the study, young male weightlifters were divided into two groups — one for those with a body mass under 65 kilograms and one for those with a body mass higher than 70 kilograms.
The volunteers consumed whey protein after resistance exercise. In one trial participants consumed 20 grams of whey protein and in the second they consumed 40 grams. The researchers measured the ability of muscle to grow at an increased rate with metabolic tracers and muscle biopsies.
They found that consuming 40 grams of protein after exercise was more effective at stimulating muscle growth than consuming 20 grams — but the increase occurred regardless of the size of the participants.
Kevin Tipton, professor of sport, health and exercise science, said: ‘There is a widely held assumption that larger athletes need more protein, with nutrition recommendations often given in direct relation to body mass.
‘In our study, participants completed a bout of whole-body resistance exercise, where earlier studies — on which protein recommendations are based — examined the response to leg-only exercise. This difference suggests the amount of muscle worked in a single session has a bigger impact on the amount of protein needed afterwards, than the amount of muscle in the body.
‘Until now the consensus among leading sports nutritionists, including the American College of Sports Medicine and the British Nutrition Foundation, is that weightlifters do not need more than around 25 grams of protein after exercise to maximally stimulate the muscle’s ability to grow.
‘In order for nutritionists to recommend the correct amount of protein we first need to consider specific demands of the workout, regardless of athletes’ size. This throws commonly held recommendations into question and suggests the amount of protein our muscles need after exercise may be dependent on the type of workout performed.
‘These results are limited to younger trained men so we may see different results with other groups, such as older individuals or females digesting different amounts of protein.’
Convention suggests that protein ingestion should be proportionate to the amount of muscle there is to rebuild and repair. This idea is fuelling a greater consumption of protein-based food supplements.
The paper debated numerous factors involved in the stimulation of muscle growth — pre-existing muscle mass, type of exercise done, time of ingestion of protein and so on.
However, the authors of this paper, which was predominantly funded by GlaxoSmithKline, sought to establish what the appropriate dosage of protein should be according to the exercise done. The study took two groups, of high and low muscle mass, and exposed them to two different protein doses, and two different exercise regimes in a two-group randomised double-blind crossover study. They were given a protein dosage via a whey isolate drink immediately after exercise of 20g or 40g.
The participants were assessed according to their ‘one rep max’ for a variety of exercises before undergoing a phenylalanine infusion trial with concurrent blood sampling. After the infusion, the participants then underwent an exercise regime. Immediately after exercise, a skeletal muscle biopsy was taken, and then the participants took either a 20g or 40g whey protein drink. The drinks were enriched with a phenylalanine tracer. Subsequent blood sampling and muscle biopsy was taken at 180 and 300 minutes.
In the second trial the alternative dosage of protein was used and muscle samples taken from the alternate leg. The phenylalanine recorded in the subsequent muscle biopsies would serve as a surrogate marker for muscle protein synthesis (ie, muscle growth).
The paper showed results at odds with prior studies — that a widely accepted protein dosage of 20-25g post exercise would be sufficient to stimulate the maximum possible amount of muscular growth.
However, this study found that an increase to 40g of protein after exercise showed greater myofibrillar muscle growth (that is, a greater increase in the size and number of individual muscle fibres), but that there seemed not to be a relationship with lean muscle mass and protein synthesis.
The theory is that the amount of muscle stimulation and activation is what matters, and that there is a difference between split exercise work and whole body exercise work (eg, leg presses in isolation versus a general workout involving upper and lower body). The last suggestion is that 20g of protein intake does not maximally stimulate muscle growth in all circumstances.
Conclusion: ingesting 25g of protein for split exercise, or 40g for whole body exercise, is sufficient for muscle growth.