Muscle Health Before Sarcopenia: A Primary Care Approach to Preserving Strength, Function, and Healthy Longevity From Midlife.

Sarcopenia is traditionally framed as a geriatric condition characterized by age-related loss of muscle mass and strength. However, muscle mass, strength, power, and quality follow distinct age-related trajectories, with deterioration in several functional dimensions becoming detectable during midlife and, in some cases, preceding substantial changes in muscle quantity. A predominant focus on established sarcopenia may therefore overlook earlier opportunities to preserve muscle health. This narrative review examines the life-course trajectory of muscle health from midlife, evaluates evidence-based strategies for preserving muscle function, and considers practical opportunities for early identification in primary care. Resistance training is supported by substantial evidence for improving muscle strength, mass, power, and physical function, including evidence of benefit during midlife. Adequate dietary protein intake complements exercise-induced adaptations and may help preserve lean tissue, particularly during intentional weight loss, whereas routine vitamin D supplementation has not demonstrated comparable benefits for muscle outcomes in otherwise healthy adults. Current evidence remains insufficient to support universal muscle-health screening in asymptomatic middle-aged adults. Targeted, opportunistic case-finding may provide a pragmatic alternative in primary care, particularly for individuals with relevant comorbidities, functional concerns, nutritional risk, or periods of physical disuse. Brief assessment may incorporate objective measures such as handgrip strength and the Five Times Sit-to-Stand Test, whereas the relatively low sensitivity of SARC-F (Strength, Assistance with walking, Rise from a chair, Climb stairs, and Falls) may limit its utility for detecting subtle functional decline. Muscle-health deterioration is not confined to old age, and midlife represents a clinically relevant window for preserving strength, function, and muscular reserve. Current evidence supports resistance exercise, adequate nutrition, and physical activity as modifiable determinants of muscle health; however, prospective studies are needed to determine whether systematic midlife assessment and early intervention reduce future sarcopenia, disability, or loss of independence and improve long-term healthspan.