Increasing or maintaining muscle mass is of great importance for populations ranging from athletes to patients and elderly. Resistance exercise and protein ingestion are two of the most potent stimulators of muscle protein synthesis. Both the physical characteristic of proteins (e.g. different digestion rates of whey and casein) and the amino acid composition, affects the potential of a certain protein to stimulate muscle protein synthesis. Given its superior ability to rapidly increase blood leucine concentrations to high levels, whey is often considered the most potent protein source to stimulate muscle protein synthesis. Native whey protein is produced by filtration of unprocessed milk. Consequently, native whey has different characteristics than milk. Of special interest is the higher amounts of the highly anabolic amino acid leucine in native whey.~The higher levels of leucine can be of great interest for elderly individuals as some studies in elderly has shown an anabolic resistance to the effects of protein feeding and strength training. By increasing levels of leucine one might overcome this anabolic resistance in the elderly.~The aim of this double-blinded, randomized, partial cross-over study is to compare the changes in muscle hypertrophy and strength after a 11 (elderly) or 12 (young) week training intervention with daily supplementation of either 2x20g of native whey or milk proteins in young and elderly individuals. In order to explain potential differences between supplements an acute study investigating acute responses in blood amino acid concentrations and intracellular signalling is planned, in a subgroup of participants, before and after the training intervention.~The investigators hypothesize that native whey will induce greater muscle hypertrophy and strength gains than milk.
The aim of this study is to investigate the long term adaptations to 11 (elderly) or 12 (young) weeks of strength training when supplemented with native whey or milk. The investigators hypothesize that native whey will give greater increases in muscle hypertrophy and strength than milk.