Controlling Protein Intake to Maximize Muscle Growth

meat, a good source of protein following a workout

A recent study shows that an intermediate balance in the timing and distribution of protein ingestion optimizes muscle protein synthesis following a resistance workout. 

The goal of an anaerobic workout is to induce muscle damage. When the muscle repairs the workout-damage, the muscle ends up stronger as a result of muscle protein synthesis. This period of regeneration is called the anabolic phase following a workout because of the protein synthesis. It has long been known that protein intake following exercise enhances muscle protein synthesis in the anabolic phase. Amino acids, the monomers that make up proteins, must be in a positive balance in the muscle to stimulate muscle protein synthesis. A study published in the most recent issue of the Journal of Physiology showed that the schedule of protein intake in the 12 hours post-exercise session has an impact on muscle protein synthesis (Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis, 2013. Areta, et al.). Apparently, an intermediate level of protein ingestion spaced out over the course of 12 hours optimizes muscle protein synthesis following a bout of resistance training.

The experiment utilized 24 male subjects of average weight (70-80 kg or 150-180 lbs) who performed a resistance training protocol. The subjects were then directed onto three different 12 hour, 80 gram protein ingestion schedules. The resistance training protocol was 3 sets of 5 repetitions at 80% of their one-repetition maximum on a bilateral leg extension. The subjects consumed 80 grams of commercial whey protein isolate following the resistance exercise according to the following ingestion schedules. The Bolus group consumed 40 grams of whey protein immediately following the resistance exercise and six hours later.  The Intermediate group consumed 20 grams of whey protein every 3 hours following the resistance exercise. The Pulse group consumed 10 grams of whey protein every hour and a half following the resistance exercise bout. The experimental protocol is depicted in the figure below.

Schematic representation of the experimental protocol. Negative time points indicate before exercise, positive time points indicate after exercise. LBM, lean body mass; REX, resistance exercise.

The researchers took blood samples and muscle biopsies from subjects to measure  muscle protein synthesis, amino acid balance in the blood, insulin levels and muscle signaling sequences. The muscle protein synthesis increased significantly higher in the Intermediate protein ingestion group than either Bolus or Pulse protein ingestion groups. Over the total course of the 12 hours post-resistance exercise the Intermediate group had a significantly higher rate of anabolic phase protein synthesis than either Bolus or Pulse groups. However, the study found that only the first 40 gram protein intake in the Bolus group significantly increased an amino acid uptake protein in the muscle. The figure below shows the degree of muscle protein synthesis as a function of post-workout protein ingestion schedule.

Myofibrillar fractional synthetic rate (FSR) between time points (A) and mean FSR throughout 1–12 h (B) following a bout of leg extension resistance exercise and post-exercise BOLUS, INT or PULSE ingestion protocol during a 12 h recovery period, as described in Fig. 2. Data were analysed using a 2-way ANOVA with Student–Newman–Keuls post hoc analysis. Values are mean ± SD expressed as %· h−1. Different vs. a, Rest; b, 1–4 h; ‡, Bolus and *, Pulse at equivalent time point (P < 0.05).

In summary, the discussed study found that 20 grams of protein taken every three hours following resistance training optimizes muscle protein synthesis in the twelve hours post-exercsie bout. The optimal protein distribution may have to be adjusted for people who are not of average weight. Finding an optimal nutritional strategy to maximize muscle growth following exercise is useful to recreational and competitive athletes as well as elderly patients looking to increase muscle growth following an anaerobic workout. 

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