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Protein Intake Vs. Training Split​

How much protein do you need after training to trigger the most muscle protein synthesis? And does your workout split matter? Here's the science.​

The Study: Researchers wanted to figure out how much protein we need after weight training to maximize muscle protein synthesis (MPS). Previous studies say 20 to 25 grams after lifting is all you need, so they wanted to compare this to 40 grams. They also wanted to see if protein needs in this context differed for less or more muscular guys, based on lean body mass.

As a refresher, MPS is how your body builds new muscle proteins by repairing and replacing damaged ones. MPS occurs when there's a net increase in muscle protein – more protein is being synthesized than degraded.

The researchers gathered up 30 weight-lifting men and divided them based on their lean body mass. All the participants did full-body workouts, but some drank a 20-gram protein shake afterward and some drank a 40-gram shake (whey protein isolate). This was a crossover design, so everyone switched groups later and did it again.

MPS was measured with the infusion of (13)C6-phenylalanine tracer and muscle biopsies. Ouch.

What Happened?​

Here's what they found:

• Consuming 40 grams of protein post-workout was better than 20 grams. Forty grams resulted in a 20% greater stimulation of muscle protein synthesis over the five-hour post-workout period.
• The participants with less lean body mass also did better with 40 grams. In other words, the size of the lifter didn't matter much: 40 grams was better than 20 grams post-workout.

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Why Your Training Split Matters​

Two previous studies said that all you need is 20-something grams to stimulate muscle protein synthesis. Consuming more didn't make a difference.

Were those studies wrong? Not necessarily. Here's where it gets interesting (as if you weren't already riveted). The older studies didn't use full-body workouts; they used lower-body-only workouts, stimulating fewer overall muscles.

Those previous studies also used a different amount of training volume: 12 and 16 sets respectively versus 20 sets in this study.

In short, using more muscles in a workout requires more post-workout protein to maximize MPS. The researchers concluded:

"Nutritive blood flow increases following resistance exercise facilitating the delivery of amino acids to the working muscle. Resistance exercise increases amino acid transport and uptake into the muscle. Therefore, the greater the amount of muscle activated the greater the overall amount of amino acids taken up by muscle after exercise."

How to Use This Info​

If you're using a body part split, 20-25 grams of protein after training may be all you need to trigger the most muscle protein synthesis, though if you use a very high volume of work (lots of exercises, sets, and reps), you may need a bit more.

If you like full-body workouts, shoot for at least 40 grams of protein after training.

It's still a good idea to spread your protein intake evenly throughout the day. Total daily protein intake seems to make the biggest difference, and the "consume about 1 gram per pound of body weight" rule still holds true for most people. (Very overweight folks should shoot for 1 gram per pound of ideal body weight.)

However, based on this study, it seems wise to time some of that protein intake after training, at least 40 grams if you do full-body or high-volume workouts that hit a lot of different muscles.