A 47-year Karolinska Institutet study tracking 427 Swedes reveals physical fitness and muscle endurance peak between ages 26 and 36, declining around age 35 even among active adults. By age 63, performance decreases 30 to 48 percent. Though exercise cannot halt biological aging, taking up physical activity in adulthood improves capacity by 5 to 10 percent and preserves cardiovascular health, including lower arterial stiffness at age 63.
Trajectory of age-related physical decline
- ▪Overall rates of age-related physical decline were similar between men and women across the 47-year study cohort.
- ▪By age 63, average physical performance across measured metrics fell by roughly 30 to 48 percent from peak levels.
- ▪Aerobic fitness and muscular endurance reached their peak levels between ages 26 and 36 before physical performance began declining in the mid-30s.
- ▪A 47-year Swedish study found that physical fitness, muscular endurance, and physical performance generally begin declining around age 35, even among active individuals.
Design of the longitudinal study
- ▪The Swedish Physical Activity and Fitness study, conducted by Karolinska Institutet researchers, tracked 427 randomly selected men and women born in 1958 from age 16 through age 63.
- ▪The Karolinska Institutet research team repeatedly evaluated the same individuals over 47 years across aerobic fitness, muscular endurance, and explosive muscle power.
Biological mechanisms behind physical decline
- ▪Biological factors contributing to physical performance decline after age 35 include alterations in muscle cell function, nervous system signaling, and reduced mitochondrial energy production.
- ▪Progressive loss of muscle mass and cellular responsiveness with age contributes to sarcopenia, impairing the capacity to perform daily physical activities.
Impact of physical activity on performance
- ▪Regular physical exercise does not entirely stop biological physical decline, but active individuals maintain higher baseline endurance, mobility, and muscle power throughout adulthood.
- ▪Participants in the Karolinska Institutet study who became physically active during adulthood achieved physical capacity improvements of approximately 5 to 10 percent.
Aerobic fitness and cardiovascular health
- ▪A 2026 Scientific Reports follow-up study found higher aerobic fitness at ages 34 and 52 correlated with reduced arterial stiffness at age 63, remaining statistically significant after controlling for obesity, smoking, and blood pressure.
- ▪Greater arterial stiffness, which occurs when blood vessels become less flexible, is associated with an increased cardiovascular risk.
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