The precise role of age-related muscle anabolic resistance in the progression of sarcopenia and functional decline in older individuals is unclear. The present aim was to assess whether the muscle protein synthesis (MPS) response to acute exercise (endurance or resistance) and/or amino acid-based nutrition is attenuated in older compared with young individuals. A systematic review was conducted on studies that directly examined the influence of age on the MPS response to exercise and/or amino acid-based nutrition. Each study arm was synthesized and reported as providing sufficient or insufficient "evidence of age-related muscle anabolic resistance". Subsequently, three models were established to compare age-related differences in the MPS response to 1) exercise alone, 2) amino acid-based nutrition alone, or 3) the combination of exercise and amino acid-based nutrition. Following exercise alone, 8 of the 17 study arms provided sufficient evidence of age-related muscle anabolic resistance, while in response to amino acid-based nutrition alone, 8 of the 21 study arms provided sufficient evidence of age-related muscle anabolic resistance. When exercise and amino acid-based nutrition were combined, only 2 of the 10 study arms provided sufficient evidence of age-related muscle anabolic resistance. Our results highlight that optimization of exercise and amino acid-based nutrition is sufficient to induce a comparable MPS response between young and older individuals. However, the exercise volume completed and/or the amino acid/protein dose and leucine content must exceed a certain threshold to stimulate equivalent MPS rates in young and older adults, below which age-related muscle anabolic resistance may become apparent.

Despite advancing age, this review suggests that chronic exercise training preserves physical function, muscular strength and body fat levels similar to that of young, healthy individuals in an exercise mode-specific manner.

Regular physical activity (PA) promotes musculoskeletal health in older adults. However, the majority of older individuals do not meet current PA guidelines and are also highly sedentary. Emerging evidence indicates that large amounts of sedentary time accelerate the loss of skeletal muscle mass (i.e., sarcopenia) and physical function with advancing age. However, current PA recommendations for sedentary time are non-specific (i.e., keep sedentary time to a minimum). Research indicates that physical inactivity and large amounts of sedentary time accelerate sarcopenic muscle loss by inducing skeletal muscle 'anabolic resistance'. These findings suggest a critical interaction between engaging in 'sufficient' levels of PA, minimising sedentary time, and consuming 'adequate' nutrition to promote optimal musculoskeletal health in older adults. However, current PA recommendations do not take into account the important role that nutrition plays in ensuring older adults can maximise the benefits from the PA in which they engage. The aim of this narrative review is: (1) to briefly summarise the evidence used to inform current public health recommendations for PA and sedentary time in older adults; and (2) to discuss the presence of 'anabolic resistance' in older adults, highlighting the importance of regular PA and minimising sedentary behaviour. It is imperative that the synergy between PA, minimising sedentary behaviour and adequate nutrition is integrated into future PA guidelines to promote optimal musculoskeletal health and metabolic responses in the growing ageing population.