The Long Ride with Greg Pallone
I was 35 when I co-founded my firm. I was training hard, cycling competitively every week at the Thursday Night UBC Crits, and felt, in most of the ways that matter, that I was close to my best. I didn’t know it then, but the research now suggests that, at 35, I was about as good as I was ever going to get. Not in a dramatic sense. More like a long, gradual slope that begins in the mid-thirties and continues, at an increasing rate, throughout the rest of your life.
A study published in late 2025 in the Journal of Cachexia, Sarcopenia and Muscle — one of the most comprehensive longitudinal fitness studies ever conducted — put a precise number to it. The researchers found that peak physical performance occurs around age 35. After that, the long downhill slide begins.
The study is worth understanding in some detail because the findings are more nuanced and more useful than the headline suggests. The slope is real. But so is the evidence that what you do about it makes an enormous difference in where you end up by the time you reach your 60s.
And there is much you can do about it.
The Swedish Physical Activity and Fitness Study, known as SPAF, was conducted at the Karolinska Institutet in Stockholm over 47 years. That alone makes it unusual. Most of what we know about aging and physical performance comes from cross-sectional research: studies comparing different age groups at a single point in time. You take a group of 30-year-olds and a group of 60-year-olds, measure their fitness, and conclude what happens between those ages.
The problem is that you’re not actually watching the same group of people age. You’re comparing different generations with distinct life experiences, habits, and health histories.
SPAF did something far more rigorous. It followed 427 randomly selected Swedish men and women, all born in 1958, from age 16 to 63, measuring aerobic capacity, muscular strength, muscle power, and endurance at regular intervals over nearly five decades. The same people. The same measurements. Repeated over almost half a century.
The result is one of the clearest pictures ever assembled of what happens to a human body across the arc of adult life.
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The headline finding is uncomfortable if you’re reading this in your sixties: aerobic capacity and muscular endurance peaked between ages 26 and 36, then declined throughout the rest of the study period. Muscle power — the explosive combination of speed and strength that determines whether you can catch yourself when you stumble or react quickly enough to avoid a fall- peaked even earlier.
Men reached their maximum jumping ability at 27. Women at 19. Let that sink in.
After the peak, the rate of decline in aerobic capacity began at 0.3 to 0.6 percent per year and accelerated to 2.0 to 2.5 percent annually as participants entered their fifties and sixties. That acceleration is worth noting: the slope steepens measurably while we age.
What felt like a gentle incline in your forties becomes noticeably steeper in your sixties — not because you’ve done anything wrong, but because of biology.
None of this decline, the researchers noted, was affected by how much people trained. The decline occurred regardless of training volume. Peak performance occurred around age 35 for everyone in the study, whether active or not.
That sounds bleak, but the study has a second finding that changes the whole picture.
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An Important Finding: It’s Never Too Late
The most important number in the entire study, for anyone reading this in their sixties or seventies, is this: participants who became physically active in adulthood — those who started exercising later rather than earlier — improved their physical capacity by 5 to 10 percent.
The study documenting the inevitable decline also shows that late starters gain ground. Not as much as those who were active their whole lives, but meaningfully, measurably more than those who didn’t start.
The lead researcher, Maria Westerståhl, put it into context: “It is never too late to start moving. Our study shows that physical activity can slow the decline in performance, even if it cannot completely stop it.”
There is also a finding in the SPAF data that I find both sobering and clarifying. The variance in physical capacity between individuals increased dramatically with age. The spread in relative aerobic capacity increased 25-fold from adolescence to age 63. Jump height variance increased nearly fivefold. Muscular endurance variance tripled.
While everyone experiences decline, the range of outcomes widens dramatically with age. At 16, most people in the study were roughly similar in physical capacity. By 63, some participants were significantly more capable than others — by a margin that would have been difficult to predict at the start.
The researchers concluded that lifestyle choices are the primary driver of the widening gap. The decline is universal. The rate and pace of decline are not.
I returned to competitive cycling seriously in my late forties, after recovering from a serious illness at 45 that forced me to reckon with what my body was then capable of. I didn’t know about the SPAF research then, but I was, without knowing it, doing exactly what the study’s late starters did: returning to serious physical activity after a period of reduced engagement and gaining ground as a result.
At 69, I am not the cyclist I was at 35. But the SPAF study confirms this is not a failure of will or discipline. It’s biology, documented in hundreds of people over nearly five decades. The peak is 35, and the slope is real.
The study also confirms that where I sit on that slope — and where you sit on yours — is not fixed. The 25-fold variance in aerobic capacity at age 63 means two people the same age can have dramatically different physical lives. The research argues that the difference largely reflects their physical training. More importantly, what they continue to do.
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The SPAF findings, read carefully, point to a few specific conclusions worth incorporating into your thinking about training.
The decline is real — train for it, not against it.
Trying to train the way you did at 35 is not a strategy. You have biologically changed. What worked then, high intensity, fast recovery, and volume as the primary lever, needs recalibration for a body that now requires more recovery time, more deliberate stimulus, and greater attention to movement quality rather than just quantity.
Adapting is not conceding. It is the intelligent response to accurate information.
Aerobic capacity is the priority.
The SPAF data show that aerobic decline accelerates in the fifties and sixties. This metric is also most strongly linked to all-cause mortality and cognitive health. Zone 2 training, sustained, conversational-pace aerobic work that builds a cardiovascular base, is your most important long-term investment.
It slows the slope. It does not reverse it, but meaningful slowing is meaningful.
Power work deserves deliberate attention.
Power, the ability to move quickly and forcefully, peaks earlier and declines faster than strength or endurance. It is also the quality most directly linked to fall prevention and to responding to unexpected demands. Most older adults are not training for power at all. Five minutes of explosive movement after your warm-up, such as a jump, a medicine ball throw, or a fast bodyweight squat, is enough to provide the stimulus. Low volume, high intention.
Starting late is still starting.
If you are in your sixties or seventies and reading this after a period of relative inactivity, the SPAF finding that late starters improved by 5 to 10 percent is the number that matters most. The window has not closed. The biology still responds. The slope is already in motion, but how steep it becomes from here is largely within your control.
The gap between people widens — be on the right side of it.
The 25-fold increase in aerobic variance between adolescence and age 63 is perhaps the study’s most striking finding. It shows that the difference between active and inactive adults grows, not shrinks, with age. At 63, the most active and least active participants are extraordinarily far apart in physical capacity — far more so than at 16. Each year of consistent training compounds the advantage on the right side of that gap.
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The SPAF study will continue. The participants are currently in their late sixties, and the researchers plan to measure them again at age 68. The data from that wave — a group of several hundred people whose physical lives have been tracked since adolescence and who are now entering the age range most relevant to The Long Ride readership — will be worth watching.
For now, the study gives us something genuinely rare: not a snapshot, but a feature film. Nearly five decades of consistent measurements of the same bodies show us what actually happens, rather than what we extrapolate from cross-sectional comparisons.
The picture it produces is honest. Decline begins earlier than most people assume, continues longer than most people plan for, and accelerates in ways that catch people off guard.
It also shows, with equal clarity, that the body continues to respond to what you ask of it. Later than you’d like. More slowly than at 25. Yet it still responds.
As always, consult your physician or a qualified trainer before changing your exercise programme, especially if you are returning to activity after a period of inactivity or managing existing health conditions.
Next, on The Long Ride: Your body at 60.
Research & sources referenced in this piece
Westerståhl, M., Jörnåker, G., Jansson, E., Aasa, U., Ingre, M., Pourhamidi, K., Ulfhake, B. & Gustafsson, T. (2025). Rise and Fall of Physical Capacity in a General Population: A 47-Year Longitudinal Study. Journal of Cachexia, Sarcopenia and Muscle, 16(6). DOI: 10.1002/jcsm.70134
Karolinska Institutet press release (2025, December 16). Long-term study reveals physical ability peaks at age 35. news.ki.se
ScienceDaily (2026, January 18). A 47-year study reveals when fitness and strength start to fade. sciencedaily.com
The peak-at-35 narrative is compelling but needs the nuance that biological age and chronological age are different trajectories. Some people are biologically older at 35 than others are at 55. The decline story is mostly about accumulated neglect rather than an inevitable clock. The more interesting question is not when you peaked but what your trajectory looks like from here. A 50-year-old who has been strength training for five years is in a different position than a 30-year-old who has been sedentary for a decade. Current choices compound in both directions.