What you train at 45 shapes what you can still do at 75

Jerome Fleg, a US government cardiologist who spent years retesting the same people on a treadmill as they aged, summed up what he found in one sentence: “If I start higher, I'm going to end higher.”¹

The surprise in his data was the regular exercisers. They didn't lose fitness more slowly than anyone else. People at every activity level declined at about the same rate, and that rate climbed from a few percent a decade in their 20s and 30s to more than 20% a decade from their 70s.² The active people stayed ahead the whole way because they started higher. Fleg admitted the team was “a little disappointed” that exercise didn't change the rate.¹

For you, that's good news. If the slope is roughly the same for everyone, your height on it is the part you control. Here's how to raise it, then why it buys you so much.

What to train at 45

Most of the things that slip first at 75 come down to strength and balance: a low chair, the floor, a heavy bag, a wet step. Each one maps to a movement you can practise at home, in normal clothes, with a dining chair, the bottom stair and a couple of dumbbells or full shopping bags.

A starting dose. Twice a week, pick five of the strength moves. Do 2 sets of 8 to 12 of each, with a weight where the last two reps are hard but still tidy. That's about half an hour. When both sets reach 12 good reps, make it a little harder: a few pounds more, a slower lowering, a lower chair or a higher step. If you've never lifted anything, starting to lift at 50 with zero gym background walks you through the first weeks.

Balance doesn't need a session of its own. Do a minute on each foot most days, while the kettle boils or you brush your teeth, and take the hand away from the counter once that feels easy. How to train balance back has the next steps.

How strong is strong enough? Picture lifting a 20 lb (9 kg) carry-on into an overhead bin with both hands when you're 75. Pressing two dumbbells overhead is the same push, so it makes a fair test. On the rough path our backcasting guide sketches for someone who doesn't train, a 45-year-old keeps about two-thirds of their strength by 75 and about half by 85 (our arithmetic). So pressing two dumbbells of about 15 lb (6 to 7 kg) each today only just covers the bag at 75. Two of 20 lb (9 kg) each, about 40 lb (18 kg) in total, leaves room to spare at 75 and still just covers it at 85. If that sounds a long way off, good: it's a target for the next year or two, not for week one. The guide shows how to turn your own tasks into targets like this.

Lift with some effort, and some speed. In people in their 70s, leg strength faded about three times faster than leg muscle shrank,³ so keeping muscle isn't the whole job. Strength is the goal, which is why the last reps of each set should feel hard. And power, the ability to push hard and fast, fell away faster with age than plain strength.⁴ So do some reps briskly: stand up from the chair quickly, take the stairs at a lively pace. Power is what gets you up a high curb or catches you when you trip, and it fades faster than strength.

Then the stamina. The World Health Organization and the CDC ask every adult for about 150 minutes of moderate aerobic activity a week, or 75 of harder effort, on top of two strength days.⁵ Brisk walking, cycling, swimming, anything that gets you breathing harder but still able to talk. Most of it can be easy. A longevity training week shows how the strength and the cardio fit together.

For women, the late 40s and early 50s add one more reason. Bone loss is fastest from about a year before the last period to two years after it,⁶ and bone responds to lifting with real load plus a little impact. Menopause and muscle has the numbers and a routine built for it.

And keep it going. The exercisers in the treadmill study stayed ahead for as long as they were followed. Starting partway through still counts: in a Swedish group followed from 16 to 63, people who became active as adults raised their scores on aerobic, strength and jumping tests.⁷

If you have heart, lung or metabolic disease, get chest pain or unusual breathlessness when you exert yourself, or haven't exercised in years and plan to work hard, check with your doctor before you start.

If you'd rather not learn these moves alone, this is what our coaches do, one on one and live over video. Your coach watches every rep for form, keeps an eye on your heart rate from an Apple Watch or a strap to decide when to push and when to rest, and moves you on to the heavier weight or the higher step when you're ready. Sessions run 45 to 90 minutes, most people settle at about an hour, and the first 14 days are free, then $299 a month.

Why 45, and not 35 or 60

It isn't a magic number, but it isn't random either. In about 20,000 adults tested again and again at a Dallas clinic between 1974 and 2006, fitness declined slowly until about 45, then faster.⁸ Grip strength shows a similar shape: fairly steady from your 30s to about midlife, then falling.⁹

So 45 is roughly where the gentle stretch ends. The slide has started, and you still have about three decades to build ahead of it. What shifts along the way is covered in training in your 40s and training in your 50s.

Where everyday life starts to get hard

Every ordinary task needs a certain amount of strength and fitness: getting off a low sofa without pushing on your knees, a flight of stairs without stopping halfway. Above that amount, losing a bit makes no visible difference. Among older adults, the stronger ones walked no faster for their extra strength; in the weaker ones, every bit counted.¹⁰

That's why decline seems to arrive all at once. For years you lose capacity you weren't using, and nothing changes. Then you reach the zone where it all counts, and one bad winter can take away a task you'd always taken for granted.

The strength side of this has been checked in the same people, decades apart. In Honolulu, healthy men whose grip was in the weakest third at 45 to 68 had more than twice the risk of needing help with self-care 25 years later, and nearly three times the odds of walking very slowly, under about a mile an hour (1.6 km/h), compared with the strongest third. The researchers' conclusion: good strength in midlife may protect against disability in old age “by providing a greater safety margin above the threshold of disability.”¹¹

Stamina has a rough number for that zone. It's measured as VO2 max, how much oxygen your body can use flat out, per kilo of body weight. Somewhere around 18 to 20 is where everyday tasks start to get hard, and it's a zone rather than a cliff edge.¹²

How many years a higher start buys

Here's that margin with real numbers. Take two 45-year-olds, one with a VO2 max of 30 and one with 35. Both lose fitness at the average rates seen at that Dallas clinic.

Our arithmetic, using average decline rates from the Aerobics Center Longitudinal Study (Jackson and colleagues, 2009), extended past 80 at 20% a decade. Fleg's study saw steeper drops in the 70s, so real crossings may come sooner. An illustration, not a forecast for you.

Look at 75 first, since that's the age in the title. Both people are still above the band. The difference is margin: the one who started at 35 sits about 6 points above the top of it, the one who started at 30 about 2. A bad flu, a fall or a few weeks laid up hits both of them, but only one has room to absorb it. Follow the lines on and the lower one slips below 18 around 87, the higher one around 94. Same rate of decline, roughly seven extra years.

That high line exists in real people. Men in their early 80s who had cross-country skied all their lives had a VO2 max of about 38, the level of untrained men some 40 years younger.¹³ You don't need six decades on skis to bank a useful margin, though.

The same arithmetic across a range of starting points:

Which row are you in? In a US registry of lab treadmill tests on adults without known heart or lung disease, the middle woman in her 40s scored about 27, between the 25 and 30 rows, and a quarter of women scored below about 22. The middle man scored about 38, between the 35 and 40 rows, and a quarter of men scored below about 32.¹⁴ So on these averages, a typical man's stamina holds into his late 90s, and his thinner margin is more likely strength, power and balance, which the yearly check below covers. A watch estimate gives a rough idea of where you sit. Without one or a lab test you can't place yourself precisely, only watch the direction from year to year.

Now the last column. An extra 3.5 points pushes the crossing about 5 to 9 years later, most for the lowest starts. That gain is realistic: in trials of sedentary people averaging 60 or older, regular cardio raised VO2 max by about that much. The biggest gains came from programmes lasting more than 20 weeks at a steady, moderate effort, around 60 to 70% of each person's maximum.¹⁵ There's more on how in can you raise VO2 max at 50.

These are averages from healthy clinic volunteers, extended past 80 by us, so treat the ages as an illustration. The gaps between the rows are the point. For why this one number tracks health so closely, see why VO2 max predicts how long you will live.

Check your own reserve once a year

You don't need a lab. A chair, a clock, a staircase and a notebook will do. Pick a date you'll remember, like your birthday.

The direction matters more than any single score. A chair-rise time creeping up by a second a year tells you more than one good result. And the floor test isn't a party trick: in adults aged 51 to 80, people who scored 8 or more had the lowest risk of dying, and each extra point went with about 21% better survival over the following years.¹⁹

Already 60 or 70? It still pays

The model works the same way from later starting points. A 65-year-old at 24 slips below 18 in the early 80s on these averages. Add 3.5 points and that moves to around 88 to 90.

Strength responds late in life too. In a small, well-known trial, frail nursing-home residents around 90 nearly tripled their leg strength in eight weeks.²⁰ Pooled trials in older people show the same thing on a bigger scale: clearly stronger, and an easier time getting up out of a chair.²¹

What does change is how much muscle you add: older people gain a bit less from the same training.²² That's the real sense in which earlier is cheaper. It doesn't make later pointless. There are full guides to training in your 60s and training in your 70s, and to what the frailty studies show about muscle at 80.

What this can't promise

Almost all of this comes from studies that follow people over time. They show that fitter, stronger people tend to do better later. They can't prove that training at 45 is the cause. The groups were mostly healthy volunteers, often mostly white or one ethnic group, often mostly men. Illness, injury and luck bend everyone's curve, and nobody's line is as smooth as the one in the chart.

Common questions

Is it all in your genes?

Genes set a lot of your starting point, and people drift further apart as they age. But in the 20,000-person study behind the chart, being active, not smoking and carrying less weight went with higher fitness at every age. Your genes pick the range. Your habits pick where you sit in it.

If I only have time for one, cardio or weights?

You'll get further with a little of both than a lot of one, because they guard different things. Strength keeps you getting up, lifting and climbing. Aerobic fitness keeps a long walk or a hill from leaving you wiped out. If you truly must pick, pick the one you'll still be doing in five years.

I'm 45 and have never exercised. Is it too late to build anything?

No, and you have the most room to climb. If five moves sounds like a lot, start with three from the table, twice a week, and add the others over the next month. Walk a bit more on the days in between.

Sources

1. Associated Press, 2005. Exercise does an elderly body good, study finds. NBC News. ↩ ↩²

2. Fleg JL, Morrell CH, Bos AG, et al., 2005. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation. ↩

3. Goodpaster BH, Park SW, Harris TB, et al., 2006. The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study. Journals of Gerontology Series A. Leg strength fell 2.6 to 4.1% a year against about 1% for leg lean mass, over three years. ↩

4. Skelton DA, Greig CA, Davies JM, Young A, 1994. Strength, power and related functional ability of healthy people aged 65-89 years. Age and Ageing. A comparison across ages: leg power about 3.5% lower per year of age, strength 1 to 2%; the difference was clear in men, not significant in women. ↩

5. Bull FC, Al-Ansari SS, Biddle S, et al., 2020. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British Journal of Sports Medicine. See also the CDC's guidelines for adults. ↩

6. Greendale GA, Sowers M, Han W, et al., 2012. Bone mineral density loss in relation to the final menstrual period in a multiethnic cohort: results from the Study of Women's Health Across the Nation (SWAN). Journal of Bone and Mineral Research. ↩

7. Westerståhl M, Jörnåker G, Jansson E, et al., 2025. Rise and fall of physical capacity in a general population: a 47-year longitudinal study. Journal of Cachexia, Sarcopenia and Muscle. Becoming active went with about 6 to 7% higher aerobic capacity, 11% more on a bench-press endurance test and 4% on a vertical jump. ↩

8. Jackson AS, Sui X, Hébert JR, Church TS, Blair SN, 2009. Role of lifestyle and aging on the longitudinal change in cardiorespiratory fitness. Archives of Internal Medicine. ↩

9. Dodds RM, Syddall HE, Cooper R, et al., 2014. Grip strength across the life course: normative data from twelve British studies. PLoS One. ↩

10. Buchner DM, Larson EB, Wagner EH, et al., 1996. Evidence for a non-linear relationship between leg strength and gait speed. Age and Ageing. Adults aged 60 to 96. ↩

11. Rantanen T, Guralnik JM, Foley D, et al., 1999. Midlife hand grip strength as a predictor of old age disability. JAMA. The Honolulu Heart Program: 6,089 Japanese-American men measured 1965 to 1970; 3,218 survivors retested 25 years later. ↩

12. Cress ME, Meyer M, 2003. Maximal voluntary and functional performance levels needed for independence in adults aged 65 to 97 years. Physical Therapy. Below about 20 mL/kg/min, people aged 65 to 97 were the ones reporting trouble with daily tasks. The 18 figure is the US Social Security Administration's disability criterion, cited by Jackson and colleagues (2009) as a threshold for independent living. Marsh AP and colleagues, 2006, the InCHIANTI study, found the links between leg strength, power and walking curved, with no clear cut-off. ↩

13. Trappe S, Hayes E, Galpin A, et al., 2013. New records in aerobic power among octogenarian lifelong endurance athletes. Journal of Applied Physiology. Nine skiers against six healthy untrained men the same age, who averaged about 21. ↩

14. Kaminsky LA, Arena R, Myers J, 2015. Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the Fitness Registry and the Importance of Exercise National Database. Mayo Clinic Proceedings. Table 3, ages 40 to 49. ↩

15. Huang G, Gibson CA, Tran ZV, Osness WH, 2005. Controlled endurance exercise training and VO2max changes in older adults: a meta-analysis. Preventive Cardiology. ↩

16. Grgic J, Schoenfeld BJ, Maier AB, Pedisic Z, 2026. Reference values for the five-times-sit-to-stand test: a pooled analysis including 45,470 participants from 14 countries. GeroScience. Ages 50 to 54: median 10 seconds for women and 9 for men; 80th percentile 7 seconds for both. ↩

17. Cruz-Jentoft AJ, Bahat G, Bauer J, et al., 2019. Sarcopenia: revised European consensus on definition and diagnosis. Age and Ageing. ↩

18. Araujo CG, de Souza e Silva CG, Laukkanen JA, et al., 2022. Successful 10-second one-legged stance performance predicts survival in middle-aged and older individuals. British Journal of Sports Medicine. 1,702 adults, median follow-up 7 years; adjusted for age, sex, BMI and illness. ↩

19. Brito LB, Ricardo DR, Araújo DS, et al., 2014. Ability to sit and rise from the floor as a predictor of all-cause mortality. European Journal of Preventive Cardiology. About 2,000 adults, followed for a median of 6.3 years. ↩

20. Fiatarone MA, Marks EC, Ryan ND, et al., 1990. High-intensity strength training in nonagenarians: effects on skeletal muscle. JAMA. Ten residents, average age 90; the nine who finished gained 174%. ↩

21. Liu CJ, Latham NK, 2009. Progressive resistance strength training for improving physical function in older adults. Cochrane Database of Systematic Reviews. 121 trials. ↩

22. Peterson MD, Sen A, Gordon PM, 2011. Influence of resistance exercise on lean body mass in aging adults: a meta-analysis. Medicine and Science in Sports and Exercise. ↩