Eight weeks supplementation with 40 grams of whey-based protein in shake format by manufacturer Fresenius Kabi combined with an endurance and resistance training exercise regime significantly improved leg muscle strength compared to placebo.
“Individuals combining low-volume endurance and resistance training in the same session may benefit from targeted protein supplementation, particularly to maximize leg muscle strength improvements,” wrote researchers from Friedrich-Alexander University Erlangen-Nürnberg in Germany.
Endurance and resistance training
Both aerobic and resistance training are recommended for improved overall fitness and health, however, research has found that concurrent training—especially when both modalities are performed in the same session—can cause physiological stress and potentially interfere with muscle strength and hypertrophy gains due to competing adaptations. Simultaneous endurance and resistance training may also result in a reduced capacity to develop muscle strength, as compared to resistance-only training.
Nutrition strategies are often employed to mitigate the negative effects of training, and protein is a popular choice for its evidenced ability to aid muscle repair and growth, but data is mostly limited to athletes and trained or physically active individuals.
Study details
To fill that knowledge gap, 44 untrained, healthy men and women between the ages of 21 and 33 were recruited and assigned to perform two sessions per week of low-volume high-intensity interval training followed by five machine-based resistance training exercises. Half the participants received 40 g of whey-based protein and the other an isocaloric placebo after each session.
Maximal oxygen consumption (VO2max) and overall fitness scores (computed from volunteers’ VO2max and one-repetition maximum scores, 1-RM) significantly increased in both groups.
In addition, muscular strength also improved regardless of supplementation, but the protein group experienced significantly greater gains in leg muscle strength, said the researchers.
The researchers noted that although other fitness improvements between the protein and placebo groups were not statistically significant, the findings highlight the potential clinical relevance of even small strength gains.
“Our results indicate that adaptations to low-volume concurrent training, particularly leg muscle strength, can be improved with targeted post-exercise protein supplementation in untrained healthy individuals,” they wrote.
The researchers hypothesized that the increased muscle protein synthesis response from protein supplementation had offset the catabolic effects of endurance training, promoting muscle hypertrophy. They added that protein intake after exercise stimulates the synthesis of muscle protein by providing essential amino acids, which activate the mechanistic target of the rapamycin (mTOR) pathway that is "crucial for initiating the translation process necessary for muscle repair and growth."
However, they noted that the study was limited by the absence of biochemical markers, such as mTOR.
“The inclusion of such markers would have allowed for a more comprehensive understanding of the molecular mechanisms driving the observed physiological changes,” they wrote. “Future research should integrate biochemical analyses to provide deeper insight into the anabolic signaling pathways and their contribution to muscle strength and adaptation in response to exercise interventions.”
Journal: Nutrients
“Protein Supplementation Increases Adaptations to Low-Volume, Intra-Session Concurrent Training in Untrained Healthy Adults: A Double-Blind, Placebo-Controlled, Randomized Trial”
doi: 10.3390/nu16162713
Authors: Reljic, D. et al.