Years, and What's in Them.
Ask people what they want from the decades ahead, and the answer is rarely a number. One wants to keep his Saturday morning tennis game. Another wants to keep travelling on her own, lift her own bag into the overhead bin and not think twice about the stairs at the other end. A third wants to get down on the floor with his grandchildren, and back up again without reaching for a hand.
None of them mentioned living to a hundred. Each described a life rather than a lifespan, and that distinction sits at the centre of how Ascent approaches longevity. It is worth unpacking, because the word longevity has come to mean very different things.
Three ways to measure a life
Lifespan is the simplest measure: the number of years from birth to death. Extending it was one of medicine's great achievements of the last century, and the progress has been remarkable. This is where modern medical care shines: increasing the number of birthdays a person celebrates.
Healthspan speaks to a harder question: how many of those years are lived free of serious disease and disability. Around the world, the gap between the two now runs close to a decade. For many people, the added years of life have arrived at the end of their healthspan as years spent managing illness rather than living freely.
Peakspan is a newer idea, and it changes the picture again. Researchers define it as the stretch of life during which a person holds at least 90 percent of their best-ever performance in a particular domain, such as aerobic capacity, strength or memory. Because most of those systems peak in the twenties or early thirties, most people reach their forties or fifties well inside their healthspan and already outside their peakspan.
The value of that idea is less as a target than as a signal. Few people will hold 90 percent of their twenty-five-year-old aerobic capacity at sixty, and that is not the point. What peakspan tries to shine light on is that physiologic decline begins long before diagnosis. A person can pass every blood test and still be steadily losing the strength, fitness and balance that determine what they will be able to do at seventy-five. Waiting for a disease to appear before taking physical capacity seriously means waiting too long.
Physiologic reserve: your back-up plan
The idea that ties these three life measures together is physiologic reserve: the distance between the most your body can do and what a given day asks of it.
At thirty, that distance is large. Climbing four flights of stairs, carrying shopping up a hill or running for a bus uses a fraction of what is available. With age, the ceiling comes down. Aerobic capacity declines by roughly ten percent per decade through adulthood on average, and the decline speeds up in later life. Strength follows a similar path. The demands of daily life, meanwhile, stay exactly where they were. The stairs do not get shorter, and the suitcase does not get lighter.
Physiologic reserve is easy to overlook because ordinary days rarely test it. Walking to the car or cooking dinner does not require anything close to your maximum, so a shrinking margin can go unnoticed for years. It reveals itself under stress: a hospital stay, a surgery, a bad bout of flu, a fall, a major injury, a significant life change.
The effect of that stress can be striking. In one well-known study, healthy adults in their sixties and seventies spent ten days on bed rest. In that short time they lost about a kilogram of leg muscle, roughly fifteen percent of their leg strength and more than a tenth of their aerobic capacity.
A person with a large reserve absorbs a loss like that and recovers. A person already close to the edge can drop below the level needed to climb stairs, rise from a low chair or walk comfortably outside, and may not come all the way back. While reserve can decline slowly, those thresholds do not behave the same. Crossing one is often the difference between living independently and needing help.
Reserve is not only protection against the bad days. It is also what makes the good ones possible: saying yes to the hike on holiday, the extra set on the court, the grandchild who wants to be carried the rest of the way home. Reserve is the part of your capacity that gives you options.
This brings us to two key points: 1. Reserve is built before it is needed, which means the best time to build it is while nothing is wrong. And 2: reserve can be measured. Aerobic capacity, strength, balance and body composition can be tested, tracked and compared over time. That turns a vague sense of slowing down into a clear picture of where your margin is thinnest and whether it is growing or shrinking.
Enjoy ageing, don’t simply survive it
Much of the language around longevity treats ageing as an enemy to defeat. That framing misses what most people actually want. Ageing is the privilege of having more time; the real question is what that time holds.
Surviving ageing means reaching an older age. Enjoying it means arriving there with the capacity to keep doing what gives your life meaning: travelling, playing, working, looking after the people who depend on you and being present for the moments you care about. The difference between the two is rarely a single event. It is the accumulation of years of gradual change in strength, fitness and resilience, most of which can be measured and much of which responds to the right work done at the right time.
That is the version of longevity Ascent is built around. It is not about chasing a younger version of yourself, adding years at any cost, or spending tens of hours a week on some new “miracle longevity protocol”. It means protecting the capacity that lets you live the years you have. That involves measuring it honestly, knowing where your reserve is strongest and where it is thinnest, ranking the priorities that matter most for the life you want, and adjusting the plan as your body and circumstances change.
Nobody can stop the clock. The real work is making sure that at sixty-five, or even eighty-five, the things you love are still within reach.
Dr. Steven Murray
Founder and Clinical Director, Ascent