Abstract (eng)
At present, supplementation with proteins and amino acids is a highly controversial issue and plays a major role in the field of resistance training. Here, the focus is primarily on the amino acid leucine, which is one of the BCAAs (branched-chain amino acids). The essential amino acid favors the stimulation of muscle protein synthesis, because the quality of added proteins has a beneficial effect on the buildup of muscle mass. In addition, the quantity is crucial, especially with regard to an adequate intake of older persons. Because the continuous loss of muscle mass (sarcopenia) in old age can lead to limitations of body functions and frailty. As part of this systematic review and meta-analysis of intervention trials, a possible anabolic effect of protein supplementation in combination with strength training was investigated. In the review, 23 studies with a minimum duration of six weeks were included and 18 studies included the quantitative analysis. The statistical analyses were performed using Review Manager 5.3, and a qualitative evaluation of the studies was also carried out. In addition, sensitivity analyses on the subgroups: age, study length and training condition were evaluated. This systematic review and meta-analyses showed that protein supplementation in combination with resistance training has no anabolic effect on the anthropometric parameters (body weight, lean body mass, fat mass, and fat mass in %). However, there were significant improvements in the parameters for measuring muscle strength, muscle type-specific cross-sectional area, and functional performance.