Why does flexibility decline in men after 40 — and does it actually matter for health?

A 2024 longitudinal study of 3,000 middle-aged adults found men in the bottom quartile of body flexibility had a 4.6-fold higher all-cause mortality risk over 11 years after controlling for cardiovascular fitness, BMI, and age, likely because arterial stiffness and musculoskeletal stiffness share common biological mechanisms: collagen cross-linking, advanced glycation end-products, reduced proteoglycan hydration, and diminished fibroblast activity that all progress together with aging and chronic cortisol elevation (Araújo et al., Eur J Prev Cardiol, 2024).

Flexibility in men declines after 40 due to reduced collagen hydration (proteoglycans that hold water in connective tissue decline), increased collagen cross-linking from AGE accumulation, reduced fibroblast activity (testosterone supports fibroblast collagen remodeling), and the accumulated musculotendinous shortening from years of sustained postures (desk work, driving, sleeping) without offsetting movement. The clinical significance is not primarily about touching your toes, it is that the same biological processes limiting your hip range of motion are limiting your arterial compliance.

Honesty Scale: Promising (2) for the flexibility-mortality association (the Araújo 2024 data is compelling but newer and pending replication). Solid (1) for the shared biological mechanisms between musculoskeletal and arterial stiffness.

What to do: Include flexibility assessment at your annual medical check. The Sit-and-Reach test and the Body Flexibility Index (a combination of trunk and shoulder flexibility) are quick, cost-free clinical assessments. If your flexibility places you in the bottom quartile for age, this warrants attention as a cardiovascular-adjacent health signal.

For the full picture, read The Flexibility/Mobility Deep Dive