Assessing the Impact of "Super-whey" vs. Isonitrogenous Whey on Muscle Protein Synthesis at Rest and in Response to Acute Resistance Exercise Across the Lifespan

Skeletal muscle accounts for approximately 45-55% of total body mass in healthy adults and plays a pivotal role in whole-body metabolic health, locomotion and physical independence. Undesirable loss of skeletal muscle mass (atrophy) is, however, a common feature of many diseases and scenarios including ageing, bed rest/immobilisation, cancer and physical inactivity. Despite the exact mechanisms causing muscle atrophy being not yet fully understood, "anabolic resistance" (reduced muscle building in response to protein feeding and exercise) is thought to be key, especially for age-related skeletal muscle losses (known as sarcopenia). As such, the search for optimal strategies (e.g., exercise and/ or nutritional interventions) to combat this anabolic blunting remains a hot-topic in scientific research. Leucine, an essential and branched chain amino acid (EAA/BCAA), is thought to be the most potent AA for stimulating muscle protein synthesis (MPS; the muscle building process). Although, as a stand-alone supplement, leucine is unlikely to provoke a robust and prolonged state of MPS, low doses of leucine-enriched mixed-EAAs can elicit similar increases in MPS as compared to a large dose of whey protein. As reduced appetite and increased satiety (feeling fuller) are common with advancing age, supplementation of a low-dose protein (i.e., leucine-enriched) that can adequately stimulate MPS may contribute to muscle health maintenance in older adults and reduce satiation following a meal. This study aims to examine whether a novel whey protein with greater leucine content ("super-whey") has superior muscle building properties compared to a regular whey protein, at rest and after a single bout of exercise, in both young and older adults