Identifying Chronotype for the Preservation of Muscle Mass, Quality and Strength.

Chronotype, an individual's preferred timing of sleep and activity within a 24 h cycle, significantly influences metabolic health, muscle function, and body composition. This review explores the interplay between circadian rhythms, hormonal fluctuations, and behavioral patterns-such as nutrition timing, physical activity and sleep quality-and their impact on muscle mass, strength, and quality. Evening chronotypes (ETs) are consistently associated with poorer sleep, irregular eating habits, reduced physical activity, and increased risk of obesity, sarcopenia and metabolic disorders compared to morning types (MTs). At the molecular level, disruptions in circadian clock gene expression (e.g., BMAL1, PER2, CRY1) affect protein synthesis, insulin sensitivity, and energy metabolism, contributing to muscle degradation and impaired recovery. The review highlights critical components-targeting chrono-nutrition, sleep quality, and exercise timing-to align lifestyle behaviors with circadian biology, thereby preserving muscle health and improving overall metabolic outcomes.