Longitudinal Muscle Strength Changes in Older Adults: Influence of Muscle Mass, Physical Activity, and Health

TLDR

Muscle mass changes influence strength decline, yet strength can worsen even when muscle mass is maintained or increases, highlighting the need to investigate other cellular, neural, or metabolic contributors. The study followed 120 adults (46–78 y) over ~9.7 years, repeatedly measuring isokinetic knee and elbow strength, muscle mass, physical activity, and health. Strength declined at ~14–16% per decade for knee extensors/flexors, with women showing slower elbow decline; older adults had steeper declines, men's leg strength fell ~60% faster than cross‑sectional estimates, and leg strength changes correlated with muscle mass changes and inversely with medication use, while physical activity decline was not directly linked to strength loss.

Abstract

The longitudinal changes in isokinetic strength of knee and elbow extensors and flexors, muscle mass, physical activity, and health were examined in 120 subjects initially 46 to 78 years old. Sixty-eight women and 52 men were reexamined after 9.7 ± 1.1 years. The rates of decline in isokinetic strength averaged 14% per decade for knee extensors and 16% per decade for knee flexors in men and women. Women demonstrated slower rates of decline in elbow extensors and flexors (2% per decade) than men (12% per decade). Older subjects demonstrated a greater rate of decline in strength. In men, longitudinal rates of decline of leg muscle strength were ∼60% greater than estimates from a cross-sectional analysis in the same population. The change in leg strength was directly related to the change in muscle mass in both men and women, and it was inversely related to the change in medication use in men. Physical activity declined yet was not directly associated with strength changes. Although muscle mass changes influenced the magnitude of the strength changes over time, strength declines in spite of muscle mass maintenance or even gain emphasize the need to explore the contribution of other cellular, neural, or metabolic mediators of strength changes.