Physical function decreases with aging leading to a wide spectrum of negative outcomes, such as mobility disability, falls, social isolation, reduced quality of life, dependency and institutionalization. The age-related loss of physical performance typically results from multiple clinical and subclinical conditions. The clinical picture of frailty (especially when assessed using instruments focused on the physical function domain) shows remarkable overlap with that of sarcopenia (“a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes such as physical disability, poor quality of life and death”). In this paper, the conceptualisation of sarcopenia as the biological substrate of physical frailty is illustrated. It is also elaborated that sarcopenia may be envisioned as the pathophysiologic pathway through which the negative health-related outcomes of physical frailty develop.