🟠 Moderate Evidence
- Three Distinct Peaks, Not One Universal Decline
- The Steeper Decline in Leg Power: What Remains Unknown
- Physical Activity in Adulthood Reverses the Expected Decline
- Frequently asked questions
- Why do women’s leg power peak so much earlier than men’s (19 vs. 27)?
- If I’m 50 and have not exercised regularly, can I still gain fitness?
- Why do master athletes at age 63 retain over 80% of peak aerobic capacity while sedentary adults retain only 65%?
- Looking Ahead: Implications for Ageing and Fitness Policy
Peak athletic performance follows markedly different timelines across three distinct physiological systems in men and women, according to a 47-year longitudinal study from Sweden’s Karolinska Institute. Women’s explosive leg power peaks at age 19, whereas men’s bench press strength does not reach its maximum until age 36—a 17-year divergence that challenges the widespread narrative that “fitness peaks at 35” as a universal benchmark.
Key takeaways
- Women’s leg power peaks at 19; men’s at 27—the most explosive, short-lived athletic capacity
- Aerobic fitness peaks later: women at 31, men at 26—heart-lung capacity per kilogram of body weight
- Upper-body muscular endurance peaks last: women at 34, men at 36
- By age 63, average sedentary adults retain 65% of peak aerobic capacity and endurance, but only 50–60% of peak leg power
- Master athletes who remain active retain over 80% of peak endurance capacity at 63, and do not experience power declines until after age 75
Study at a Glance
| Source | Karolinska Institute longitudinal cohort |
| Study type | Prospective longitudinal cohort study |
| Sample size | N = 427 Swedish adults |
| Population | 48% female; followed at ages 16, 27, 34, 52, and 63 |
| Country | Sweden |
| Duration | 47 years of follow-up |
Peak Athletic Performance by Sex and Fitness System
Age at which three distinct physiological capacities reach maximum in Swedish cohort (N=427), 1977–2024
Source: Karolinska Institute longitudinal cohort, 47-year follow-up | Georgian Medical Journal News
Three Distinct Peaks, Not One Universal Decline
The Karolinska cohort tracked 427 Swedish adults (48% female) at five time points spanning nearly five decades, measuring three separate fitness domains. The research reveals that journalists and fitness media have collapsed six distinct peak ages into a single headline, obscuring sex-specific and system-specific patterns.
According to the Karolinska study findings, explosive leg power—measured by jump performance—peaks earliest and declines most steeply. Women reach maximum jump power at 19; men at 27. This rapid-fire neural and muscular capacity then drops by measurable amounts every year thereafter. By contrast, aerobic fitness (maximal oxygen uptake per kilogram of body weight) peaks 7–12 years later, and upper-body muscular endurance (bench press repetition capacity) peaks last of all, in the early-to-mid 30s for women and mid-30s for men.
This staggered architecture matters because it demonstrates that “age 35” is not a biological ceiling for fitness; rather, it is an arithmetic average obscuring three different curves. For readers of health news at GMJ’s Explainers section, the implication is clear: the widely circulated claim that “fitness peaks at 35” fundamentally misrepresents the underlying data.
The Steeper Decline in Leg Power: What Remains Unknown
Among the three measured systems, leg power shows the steepest age-related decline. By age 63, women retain approximately 50% of their peak jump power, and men retain 60%. In contrast, the same cohort retained 65% of peak aerobic capacity and upper-body endurance. The Karolinska researchers attribute this differential decline to the relative demand patterns in everyday life: walking, stair-climbing, and general movement preserve aerobic and endurance capacity in sedentary older adults, whereas explosive jumping power is rarely elicited outside deliberate athletic training.
What the published data do not yet clarify is whether this gap is inevitable due to neuromuscular ageing biology or whether it reflects training patterns. Clinical Updates from exercise physiology research suggest the latter is likely true, given the next critical finding: master athletes—older adults who remain regularly active—do not experience the same precipitous drop in leg power. Master athletes do not reach the 50–60% retention level until after age 75, indicating that the slope of decline is modifiable through sustained training.
Physical Activity in Adulthood Reverses the Expected Decline
Perhaps the most consequential finding, buried under headlines about “peak age,” is that the Karolinska researchers observed significant performance gains among participants who became physically active in their thirties, forties, and fifties. The effect was observed across all three measured fitness domains—leg power, aerobic capacity, and upper-body endurance—and did not interact with age. In other words, starting exercise later in life yielded measurable gains independent of how old the participant was when they began.
The researchers’ conclusion, documented in the cohort analysis, attributes the sustained performance advantage in master athletes to “continuous physical activity.” This suggests that the age-related decline curve shown in average sedentary populations is not fixed biology but a reflection of activity patterns. For clinical audiences, this distinction is critical: the peak age may be set by developmental and neurological constraints, but the slope after the peak—the rate of decline—is modifiable through behaviour.
By age 63, sedentary adults retain 65% of peak aerobic capacity and upper-body endurance, but only 50–60% of peak leg power. Master athletes retain over 80% of endurance capacity at the same age and do not experience proportional leg power declines until after age 75.
— Karolinska Institute longitudinal cohort analysis, 47-year follow-up
What this means
Frequently asked questions
Why do women’s leg power peak so much earlier than men’s (19 vs. 27)?
The Karolinska study documents the difference but does not fully explain the biological mechanism. Possible contributors include sex differences in neuromuscular maturation timing, hormonal profiles during adolescence, and typical activity patterns in women versus men at ages 16–27. The study demonstrates the pattern but does not isolate causation. Further research comparing training histories and hormonal profiles at these ages would clarify whether the difference is developmental or behavioural.
If I’m 50 and have not exercised regularly, can I still gain fitness?
Yes. The Karolinska study explicitly measured fitness gains in participants who became regularly active in their thirties, forties, and fifties. These gains were observed in all three fitness domains—leg power, aerobic capacity, and upper-body endurance. The magnitude of gain was not quantified in the summary, but the directional finding is clear: age of initiation did not reduce the training effect.
Why do master athletes at age 63 retain over 80% of peak aerobic capacity while sedentary adults retain only 65%?
The Karolinska researchers attribute the difference to sustained physical activity. Master athletes engage in regular training, which preserves aerobic capacity and upper-body endurance. The study suggests that approximately 15 percentage points of the typical age-related decline in aerobic fitness is preventable through continuous training. The mechanisms likely involve maintenance of mitochondrial density, cardiac function, and lean muscle mass.
Looking Ahead: Implications for Ageing and Fitness Policy
The Karolinska 47-year longitudinal study provides unusually robust data on the trajectory of human fitness across the lifespan, with particular value in documenting sex-specific differences and the reversibility of age-related decline through sustained activity. As populations age globally, the finding that decline is partially modifiable—not inevitable—shifts the narrative from acceptance of loss to evidence-based intervention. Future research should quantify the training effect size (how much gain per unit of activity), examine whether earlier initiation of training at age 30 versus 50 produces different long-term trajectories, and clarify the mechanisms underlying sex-specific timing of peaks in explosive power. For Global Health policy, the study strengthens the case for physical activity as a key public health intervention, particularly for older adults in whom sedentary decline is not destiny but rather a reflection of behavioural patterns.
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Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD. Spotted an error? Contact the editorial team.
