Karolinska Institute Study Reveals Physical Endurance and Muscle Strength Decline Begins at Age 35

How Aging Affects Physical Endurance

According to НВ — Техно: A comprehensive 47-year study conducted by researchers at Sweden's Karolinska Institute has shown that both physical endurance and muscle strength start to decrease around the age of 35. The research tracked 427 men and women born in 1958, assessing their physical fitness from adolescence (age 16) through to 63 years old. Findings indicated that aerobic capacity and muscular endurance peak between ages 26 and 36, with measurements at age 63 showing a 30-48% decline compared to peak levels.

Engaging in regular physical activity during adulthood can improve these metrics by 5-10%. Furthermore, staying active during teenage years positively impacts the maintenance of endurance and muscle strength later in life. The study's next phase will evaluate participants at age 68, offering deeper insights into how physical abilities evolve with age.

Validation Through Additional Research

Published in 2026 in Scientific Reports, one investigation confirmed a link between higher aerobic fitness at ages 34 and 52 and reduced arterial stiffness by age 63. Another 2026 study in GeroScience followed 82 older adults who regularly cycled; over nine years, their peak aerobic fitness declined by 19.7%, yet they remained in the top 10% for their age group.

Research featured in The American Journal of Medicine, involving 49 men aged 60-82, demonstrated that combining strength training with aerobic exercise over four years increased muscle strength in both upper and lower body regions. This combination also enhanced overall endurance.

Maria Westerstol, a lead researcher, emphasized: 'It’s never too late to start moving. Our findings highlight that physical activity can slow down the decline in physical capabilities, even if it cannot completely halt it.'

These studies underline the critical role of consistent physical activity throughout life, especially in older adulthood when declines become more pronounced. The research opens avenues for designing targeted exercise programs aimed at preserving strength and endurance, ultimately improving quality of life. Future investigations are expected to identify optimal strategies for sustaining physical fitness across different age groups, contributing valuable knowledge to health care and aging prevention efforts.

As individuals reach their 40s, maintaining bone health becomes increasingly vital. Engaging in activities such as brisk walking and jogging has been shown to significantly strengthen bones during this stage of life. To learn more about how these exercises can benefit your skeletal health, check out this article on effective exercises for bone strength after 40.