High Reps vs Heavy Weights: What Should Runners Actually Do?
If running involves thousands of repetitions, surely your strength training should involve lots of repetitions too?
It sounds logical. But it leaves out an important question: what are you trying to improve?
Building muscle, improving maximal strength and developing muscular endurance are related, but they aren't the same thing. The rep range that suits one goal won't necessarily be the best choice for another.
For most runners, I don't think this needs to be an either-or debate. My preference is usually a combination of heavier strength work, moderate reps and some higher-rep work where appropriate. And here's why.
Can high reps build muscle?
Yes. You don't have to lift heavy weights to build muscle.
Research comparing lighter and heavier loads shows that muscle growth can occur across a wide range of repetitions, provided the sets are sufficiently challenging. [1]
That last part matters. Twenty calf raises that you could comfortably turn into forty are a different stimulus from twenty where the final few are difficult.
With lighter weights, you generally need to get closer to the point where you can't complete another repetition to make the set effective for muscle growth. That can mean longer sets and a fair bit of discomfort.
So choosing light weights doesn't automatically mean an easier session. It also means avoiding heavy weights isn't a reliable way to avoid building muscle.
Strength is a different story
If your main goal is to improve maximal strength, heavier loads generally have the edge. Reviews comparing different training approaches support this, even when muscle growth is similar. [1,2]
For runners, there's also evidence that heavy strength training can improve running economy: the energy required to run at a given speed. That doesn't guarantee a faster race, but it gives us a good reason to include heavier work in a running programme. [3]
Heavy is relative to you: a weighted single-leg calf raise might be heavy for one runner, while another needs a loaded machine to provide a similar challenge.
For someone who is ready for it, around 3-6 repetitions can be a useful range for heavier strength work. That isn't an instruction to start testing your maximum. Build familiarity with the exercise and progress the load over time.
What about the soleus?
The soleus, one of the muscles in your calf, comes up a lot in this discussion because it contains a high proportion of slow-twitch muscle fibres. That has led to the suggestion that it might respond particularly well to higher-repetition training.
It's an interesting idea, but muscle fibre type alone doesn't tell us the best rep range.
In a small study of untrained young men, eight weeks of calf training with 20 to 30 reps produced similar muscle growth to training with 6 to 10 reps, including in the soleus. [4]
That study doesn't settle every question about calf training in runners. It does mean we should be cautious about saying the soleus needs high reps because it's mostly slow-twitch.
I still see a place for higher-rep calf work. I just wouldn't use it as a reason to leave heavier calf loading out of the programme.
How I would put this into a programme
I like each exercise to have a clear purpose. The following ranges are practical starting points, with plenty of overlap between them.
Goal | A useful starting point | What I am looking for |
Maximal strength | 3 to 6 reps | A challenging load with controlled technique. |
Muscle growth | 6 to 15 reps | Challenging sets that can be progressed. Growth can also occur outside this range. |
Local muscular endurance | 15 to 25 reps or more | Repeated effort with a load that still challenges the target muscle. |
For example, I might use heavier split squats, moderate-rep leg extensions, and a combination of heavier and higher-rep calf raises across the week.
For a runner rebuilding muscle after injury, moderate reps may get more attention. For someone whose main limitation is strength, I might place more emphasis on heavier work. If equipment is limited, higher reps can help make a lighter load more challenging.
You don't need every rep range in every session. Choose the mix that addresses what you need.
How hard should the sets be?
Writing “3 sets of 10” only tells you part of the story. The weight and how many repetitions you could still complete matter too.
A practical starting point for many exercises is finishing with around two good repetitions left in reserve. In other words, you could do another two if you had to, without changing your technique.
That isn't a rule for every exercise or every runner. Very light loads used for muscle growth may need to be taken closer to your limit. Someone learning an exercise or returning from injury may need a more conservative starting point.
I don't want runners assuming every set needs to end with a failed repetition. There needs to be enough challenge to stimulate improvement, while leaving room for the rest of the training week.
The gym session has to fit your running
A programme can look sensible on paper and still be too much alongside your running.
If you're consistently sore for your key sessions, I'd review the strength dose. That might mean fewer sets, a smaller progression or changing where the session sits in the week. Automatically swapping heavy weights for lots of light reps may not solve the problem.
My preference is to start with an amount you can recover from, repeat it consistently and progress from there. Keep a record of your weights and reps so you can see whether you're improving.
What should runners actually do?
Use the rep range that suits the purpose of the exercise.
For most runners, my starting point would be heavier work for force production, moderate reps when building muscle is useful, and higher-rep work where it addresses a particular need.
Then look at the response. Are you getting stronger? Are you tolerating the sessions? Can you still complete your important runs well?
You don't need to find one perfect rep range. You need a programme that challenges you, progresses over time and fits with your running.
Want to hear more?
Kate Baldwin and I discuss strength training for runners in Episode 14 of The Rehab Runway, including what actually matters when putting a programme together.
If you'd like help working out what your strength training needs to focus on, book an appointment with the team at Health & High Performance.
References
Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. Journal of Strength and Conditioning Research. 2017;31(12):3508-3523
Currier BS, Mcleod JC, Banfield L, et al. Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis. British Journal of Sports Medicine. 2023;57(18):1211-1220
Llanos-Lagos C, Ramirez-Campillo R, Moran J, Saez de Villarreal E. Effect of strength training programs in middle- and long-distance runners’ economy at different running speeds: a systematic review with meta-analysis. Sports Medicine. 2024;54:895-932
Schoenfeld BJ, Vigotsky AD, Grgic J, et al. Do the anatomical and physiological properties of a muscle determine its adaptive response to different loading protocols? Physiological Reports. 2020;8(9):e14427
