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Researchers in the UK compared high versus moderate protein intake on recovery after strength training in resistance-trained individuals. They found that, for recovery, more protein isn’t necessarily better, hinting that there may be a benefit to studying lower protein intake in the future.
“A short term, high protein diet did not improve markers of muscle damage or soreness in comparison to a moderate protein approach,” researchers at Anglia Ruskin University in Cambridge, UK, wrote in their report, published this month in the Journal of the International Society of Sports Nutrition.
The researchers wanted to investigate an age-old question in sports nutrition—what matters most when it comes to protein supplementation for faster post-workout recovery, intake amount of protein or timing of supplementation?
“This critical question emerges from the findings of a multi-level meta-analysis which concluded that the total daily protein intake is the most important dietary variable for adaptations to resistance training and not protein timing around workouts,” they wrote, citing a 2013 study published in the same journal.
Recruiting participants, setting a diet plan
What previous studies on protein for post-workout recovery have not yet done, according to the researchers, is control the total energy intake and protein supplementation timing around a workout.
Thus, among the 14 study participants recruited, each were randomly assigned to a 10-day matched calorie period of either moderate protein intake (at 1.8 g per kilogram body weight per day) or high protein intake (2.9 g per kilogram body weight per day). As a crossover study, the participants then switched to the other diet routine after 10 days.
Participants were also required to follow a set diet of ~40% carbohydrate, 25 or 35% protein, and 25-35% fat. The research team guided the participants to keep food options in line with habitual patterns and portion size.
Requirements to participate in the study included a resistance training background of at least 18 months prior to the start of the study, and having had more than three hours per week of resistance training. Another criteria for selection was how much they can lift for a more uniform sample—at least 55% of body weight for women and 110% of body weight for men for a standardized bench press, for example.
During the 10 day periods, participants maintained their own training routines, but were asked to refrain from strenuous training prior to main testing days.
During these testing days, participants consumed a protein beverage called GoPro Whey Protein, provided by British firm Go Protein Ltd., comprising 0.4 g of whey protein concentrate/isolate mix per body kilogram before and after exercise routines, which consisted of squats, bench presses, and bent-over rows.
Then, residual muscle soreness was measured in the anterior deltoid, main pectoral, medial trapezius, main triceps, upper gluteus, upper and middle rectus femoris, and vastus medialis.
Though there was not much variance between the two protein intake amounts for upper body performance and perceived muscle soreness, the researchers found that, when on the high protein diet, lower body performance was “significantly” better.
The researchers found that performance for bench press and the bent-over row did not vary significantly based on protein intake, “indicating that moderate protein intake may be sufficient for resistance trained individuals,” the researchers argued.
Furthermore, there was no significant difference in perceived muscle soreness between the two diet routines.
“Whilst the findings of this study indicate that a short term moderate protein intake may be sufficient to support markers of recovery in resistance-trained individuals undergoing repeated days of intensive exercise, the potential benefit of lower protein intakes (<1.8 g.kg−1.d−1) cannot be excluded,” they added.
However, squat performance ‘significantly declined’ among participants when they consumed a moderate protein diet, but was well-maintained under a high-protein diet.
“Longer term interventions are therefore warranted to determine whether moderate protein intakes are indeed sufficient during prolonged training periods or when extensive exercise (e.g. training twice daily) is undertaken with resistance-trained individuals.”