Most people in their 30s and 40s assume their physical edge holds steady. Train consistently, eat well, sleep enough, and the body keeps up. A 47-year study from Karolinska Institutet tells a different story. Researchers followed 427 Swedish adults from age 16 to 63 with repeated objective testing. Aerobic capacity and muscular endurance peaked between 26 and 36, then slipped year after year. By age 63, total decline ranged from 30 to 48 percent.
Sources: Westerståhl et al. 2025 (J Cachexia Sarcopenia Muscle). WHO 2020 Physical Activity Guidelines.
Where the peak sits
The Swedish Physical Activity and Fitness study (SPAF) measured the same people repeatedly across nearly five decades. Maximal aerobic capacity, a marker of cardiorespiratory fitness, and bench press endurance both peaked at ages 26 to 36 in men and women. Sargent jump power peaked earlier: age 27 in men and age 19 in women. The paper appeared in the Journal of Cachexia, Sarcopenia and Muscle in December 2025.
The decline curve across four decades
After the peak, fitness drops at 0.3 to 0.6 percent per year. The number sounds small. It compounds. By the late 50s and early 60s, the rate accelerates to 2.0 to 2.5 percent per year. The chart below traces the loss across the four decades the Swedish cohort was measured.
Source: Westerståhl M et al. Rise and Fall of Physical Capacity in a General Population. J Cachexia Sarcopenia Muscle. 2025, vol 16, issue 6. PMID 41243424.
What separated the people who held on
Two factors stood out. Higher leisure-time physical activity at age 16 was linked to better adult performance across every measure. Adults who started exercising later in life still added 5 to 10 percent to their physical capacity. Lead author Maria Westerståhl summarised the finding plainly: physical activity slows performance loss but does not stop it.
The takeaway is direct. You will lose capacity over time. The size of the loss is partly your decision.
The minimum dose for protection
The World Health Organization sets the floor at 150 to 300 minutes of moderate aerobic activity per week, or 75 to 150 minutes of vigorous activity. On top of those, two or more sessions of muscle-strengthening work per week. The 2020 update dropped the old rule about 10-minute bouts. Short bursts now count toward the total, including stair climbs, brisk walks between meetings, and short cycling commutes.
For a London adult with a desk job, a working week looks like this:
- Three brisk 35 to 40 minute walks across the week (cycle commute, lunch loops, stairs).
- Two strength sessions covering legs, back, push, pull, and a loaded carry (35 to 45 minutes each).
- Daily light movement broken across the day (standing meetings, a 10-minute walk after the largest meal).
Why strength matters more after 35
Aerobic loss is real. Muscle and power loss hits harder after the mid 30s. The Swedish data showed jumping power peaked years before aerobic capacity, with men topping out at 27 and women at 19. Power loss tracks closely with falls, mobility limits, and reduced independence in later life. Two strength sessions per week, anchored on compound lifts (squat, hinge, press, row, loaded carry), defend this trajectory better than cardio alone.
Five things to do this week
- Audit your training. Count strength sessions completed in the last four weeks.
- Add one compound lift to every session: squat, deadlift, row, press, or loaded carry.
- Hit 30 to 40 minutes of moderate aerobic work on four days this week.
- Take a 10-minute walk after your largest meal each day.
- Track a single performance number quarterly: bench reps, vertical jump, or time over 5 km. Treat it as an early warning, not a vanity score.
The bottom line
A 47-year dataset from Sweden gives a precise answer to a simple question. Physical capacity peaks near 35 and falls at a quickening rate. The reassuring finding sits inside the same study. Adults who started training later still added 5 to 10 percent. The tools are well established: structured strength work, regular aerobic activity, and consistent daily movement.
A structured plan tailored to your age, current fitness, and schedule changes the trajectory of the next decade. Book a personal training and nutrition consultation at www.dushyantatomar.com. Every plan is built around evidence, not trends.
Dushyanta Tomar, MSc Applied Sports and Exercise Physiology, CIMSPA Accredited Personal Trainer.
Sources
- Westerståhl M, Jörnåker G, Jansson E, Aasa U, Ingre M, Pourhamidi K, Ulfhake B, Gustafsson T. Rise and Fall of Physical Capacity in a General Population: A 47-Year Longitudinal Study. J Cachexia Sarcopenia Muscle. 2025, vol 16, issue 6. doi 10.1002/jcsm.70134. PMID 41243424. pubmed.ncbi.nlm.nih.gov/41243424
- Karolinska Institutet. Long-term study reveals physical ability peaks at age 35. Press release, 16 December 2025. news.ki.se
- Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020, vol 54, issue 24, pages 1451 to 1462. PMID 33239350. pubmed.ncbi.nlm.nih.gov/33239350