The short answer
- Recreational running is associated with less hip and knee arthritis than not running. The joints are not the reason people stop.
- The declines that track age in runners are at the ankle. Hip and knee measures did not correlate with age at all in a study of 110 runners aged 18 to 60.
- Strength training improved running economy across 24 studies without changing body composition, and roughly halved overuse injuries in a separate meta-analysis.
- Under-fuelling and under-sleeping lower the ceiling everything else runs into, quietly, over months.
- Most people who stop running stop because of an injury cycle they never got on top of, not because of age.
Almost everything written for runners is about the next twelve weeks. This is about the next twenty years, which is a different question with different answers.
The thing that is not the problem
Start by removing the worry most people carry.
People who did not run had roughly three times the arthritis rate of people who ran recreationally. Our article on running and arthritis goes through the caveats, including the four-year study showing that people over 50 who already had knee arthritis did not get worse.
So the joints are not why people stop. What stops people is an injury cycle they never got on top of, and eventually they decide they are too old for this.
The one thing that does change
Ageing in running turns out to be an ankle story. Not a general fading.
Which is unusually good news, because the calf is trainable at any age and almost nobody trains it properly. If you do one thing differently after reading this page, make it heavy calf work twice a week, and test yourself occasionally so you know where you stand.
The thing with the best evidence
Faster at the same effort, and substantially less likely to get hurt. There is nothing else on the list with that combination.
The reason people do not do it is that the payoff is invisible on any given week and only shows up over years. Which is exactly the timescale this article is about.
The two quiet ones
These do not feel like training, and they set the ceiling everything else runs into.
Eating enough. Chronically taking in less than your training costs produces a syndrome across bone, hormones, immune function and mood, in men as well as women, and it usually builds accidentally when training rises and eating does not follow5. It is the mechanism behind a lot of repeated bone injuries in runners who are doing everything else right. Our article on under-fuelling covers it.
Sleeping enough. Habitually under seven hours raises susceptibility to respiratory infection, which across a training block means lost fortnights rather than slower sessions6. The expert consensus declined to give a target number and recommended working out your own, which our sleep article explains.
What to actually keep doing
Change things slowly enough that your tissues get a vote. Most injuries live in the gap between how fast a plan changes and how fast a tendon does, which is the argument in why runners get injured.
Keep some easy running genuinely easy. A week where nothing is hard and nothing is easy is the most common way to accumulate fatigue without accumulating fitness.
Finish rehab. Previous injury is one of the most consistent predictors of the next one, and stopping when the pain stops is why.
Rotate your shoes. Runners using more than one pair had a lower injury rate in a cohort study, and it costs nothing to act on. Our shoes article has the detail and the caveats.
Take a proper break once a year. Not because the research demands it, but because the people still running at sixty tend to be the ones who were not training hard for fifty-two weeks a year at forty.
When to ask for help
The last one is what most of our work actually is, and it is the least likely thing for someone to ask for.