The regulation of skeletal muscle mass and function by nutrition and exercise is of fundamental interest in both athletic performance and healthy aging paradigms. The amino acid leucine has received much interest in recent years due its potential anabolic properties in athletes, and has been described as a pharmaconutrient for the preservation of skeletal muscle health in older adults. While it is well accepted that elevating plasma leucinemia is a potent stimulator of muscle protein synthesis (MPS), less is understood about how supplementation and dietary strategies can be manipulated to create a plasma aminoacidemia most optimal for MPS. Furthermore, the role of leucine-rich interventions on recovery from exercise induced muscle damage in young athletes, and longer term changes in muscle mass and function when administered over time in older adults, is inconclusive to date, and warrants further investigation. Consequently, the aim of this thesis is to contribute to our current understanding of these areas. Chapter 4 describes the habitual protein intake, distribution and dietary patterns in young and older adults in Ireland. Chapters 5 and 6 describe the plasma leucine kinetics after ingestion of microencapsulated leucine and free leucine, alone and in combination with a low leucine-containing meal in young, healthy males. Chapter 7 demonstrates that leucine supplementation in the 14 hour recovery period after intense resistance exercise exhibits no beneficial effect on markers of muscle damage and recovery of muscle function. Chapter 8 describes a dietary intervention targeting three leucine-rich meals per day can increase protein intake and improve protein distribution in older adults. Finally, chapter 9 establishes that the same dietary intervention in combination with concurrent aerobic and resistance exercise training is an effective strategy to augment increases in lean body mass and lower limb strength in older adults over 12 weeks compared to training alone.