The short answer
- Up to about 7 m/s, the calf muscles are the main contributors to the vertical force that holds you up while you run.
- In 566 adults tested on a 10 degree incline, men managed a median of 24 single-leg heel raises and women 21.
- Repeat the test a week later and your own score can move by up to six repetitions either way. Anything smaller than that is noise.
- The comparison that tells you most is left against right, on the same day, in the same way.
- If one side is clearly behind, that is the side to train, whether or not it is the side that hurts.
Runners train hips. Hips get all the attention, all the glute bridges, all the resistance bands. Meanwhile the muscle doing most of the actual work sits below the knee and gets four sets of calf raises in a bad week.
Why the calf carries it
7 m/s is about 2:23 per kilometre. Faster than almost anyone reading this runs, outside of a short sprint.
So for essentially all of your running, the calf is the engine. It holds you up, it pushes you along, and when it cannot do enough of that the work has to go somewhere else.
The ageing research points the same way. In 110 runners aged 18 to 60, the declines that tracked age were at the ankle, while hip and knee measures did not correlate with age at all2.
The test
Stand on one leg. Fingertips on a wall for balance, not for support. Rise onto the ball of your foot as high as you can, lower under control, repeat. Keep going until you cannot get to full height any more.
Count as you go, then do the other side.
That last detail is the one to hold on to, and it is the reason most people misread their own test.
Your score can move by six repetitions from one week to the next without anything about your calf having changed. So if you get 18 today and 22 next month, you have learnt nothing. You need a bigger change than that, or a different comparison.
The comparison that works
Left against right, on the same day.
You are your own control group. Same body, same technique, same amount of sleep, same everything except the leg. A difference between sides is far more informative than either number on its own, and it is not affected by which protocol you used.
A gap of a few repetitions is nothing. A gap of eight or ten, repeatedly, is a finding.
What to do with the answer
Heavy calf raises, both legs at first if a single leg is too much, progressing to single leg with weight in a backpack or held in one hand. Full range, all the way up, all the way down under control. Two sessions a week.
Do them with the knee straight and again with the knee bent, because those load the two calf muscles differently. Our calf pain article explains why the knee angle changes which one is working.
Progress by adding weight rather than by adding repetitions once you can do about 25 with good height. Thirty slow repetitions with body weight is endurance work, and it stops building strength somewhere around there.
Once heavy work is established, add something fast: skipping, pogo hops, short ground contacts. Strength training across the studies in Blagrove's review improved running economy, and the reviews describe a mixture of heavy and explosive work rather than one or the other4.
How long before the number moves
Longer than you want. Give it eight weeks before retesting, and expect the first visible change to be that the weak side catches up rather than that both sides go higher.
Calf endurance improves fairly quickly. Tendon adaptation, which is what you actually need for running, is slower and runs on months.
When to get it looked at
Not being able to do one repetition at all is a different conversation from being weak, and it should be looked at rather than trained around.