A recent study investigated whether high or moderate protein intake would affect recovery and performance during strength training.
There are three macronutrients that make up the total calories found in all the food we consume: proteins, fats, and carbohydrates. For active individuals, particularly those training for strength or muscle building, protein has been identified as a key player in improved performance, muscle size, and recovery. Although science is confident in the importance of regular, adequate protein intake, an exact threshold amount or upper limit has not been identified. It is also still up for debate whether the timing of when you consume protein is more significant or if total protein consumption, irrespective of timing, is more important.
Researchers from Cambridge in the United Kingdom tested the recovery effects of moderate and high protein diets in 14 strength trained individuals. The study was recently published in the Journal of the International Society of Sports Nutrition. The participants included both healthy males and females who have been undergoing strength training for at least 18 months and at least three hours each week. They were also required to meet basic gender strength standards for the squat and bench press. The participants underwent testing before dietary changes, then adhered to either a moderate or high protein diet for 10 days, took a 24-hour break to eat however they liked, and then underwent another 10-day test period under the second condition.
The researchers evaluated the muscle quality of the participants before the study conditions and at the end of each test period. The participants had blood taken before and after they performed squat, bench, and bent over row strength testing. The scientists analysed the blood for markers of muscle damage.
Muscle Recovery Not Significantly Affected by Amount of Protein Intake
The results suggest that there were no profound differences between moderate and high protein intake. Moderate intake was 1.8g/kg of body weight whereas high intake was 2.8g/kg body weight. Markers of muscle damage were consistent across dietary manipulations, and self-reports of muscle soreness did not differ between the two groups suggesting that recovery was not significantly affected by a decrease or increase in protein consumption. Other studies have suggested 1.8g/kg to be sufficient which strengthens other research findings as well.
Squat Reps Significantly Lower in the Moderate Intake Group
Two significant findings did arise in the current study. The number of repetitions of squats was significantly lower in the moderate group versus the high protein group suggesting perhaps significance to only lower body exercises. Additionally, muscle quality was assessed, and the high protein group scored higher suggesting potential long-term strength benefits.
The strengths of this current study are that the individuals were all trained and thus would likely respond to training and diet in a similar manner when compared to untrained individuals. Additionally, the participants were not capped at how many repetitions they were to do but rather were pushed to reach exhaustion to simulate a similar experience for all no matter their abilities. Also, the study included both upper and lower body exercises whereas many previous studies looking at protein have only included heavy lower body workouts. Furthermore, the nutrient timing was a control in this study which potentially alludes to the importance of protein timing over total protein intake.
Some limitations of this study include its exclusion of untrained individuals and endurance athletes for comparison and the inclusion of both male and female participants. Gender may play a role since the type of muscle fibre present may be different and thus individuals of different genders could potentially respond differently to protein intake. Furthermore, testing under similar manipulations and only lower body exercises may be of benefit to determine whether the squat performance was truly dependent on total protein intake.
No Significant Improvements in Performance and Recovery
The take-home message for those who are currently strength training and have performance-based strength goals (i.e. powerlifting) is that protein is an absolute necessity in order to optimize performance; however, high protein consumption at 2.8g/kg of body weight did not show significant short-term improvements in overall performance and recovery. Individuals will likely perform and recover adequately with a moderate protein intake of 1.8g/kg of body weight even when well trained. Certain results suggest that prolonged high protein intake may have long-term effects on performance and muscle quality, but further research needs to be done to determine whether this is indeed a valid conclusion.
Written by Elena Popadic
Reference: Roberts, J., Zinchenko, A., Suckling, C., Smith, L., Johnstone, J., & Henselmans, M. (2017). The short-term effect of high versus moderate protein intake on recovery after strength training in resistance-trained individuals. Journal Of The International Society Of Sports Nutrition, 14(1). http://dx.doi.org/10.1186/s12970-017-0201-z