Blog · Running & strength

Why circuit training will not make your marathon faster

By Remko Opdam · 6 July 2026 · 4 min read

In short

Circuit training tires you out, but it does not build the strength a runner needs.
Getting stronger needs enough load, progression in weight or repetitions, and attention to technique. Three things a circuit lacks.
Targeted strength training improves running economy and helps prevent injuries.

Many runners I speak to are willing to do something about their strength but dislike the gym. They already get plenty of cardio, counting repetitions bores them, so they pick something bearable: a circuit. Moving nicely, no fuss, done.

I understand the choice. But if your goal is a half or a full marathon, and you want to run it without picking up injury after injury, a circuit will not get you there. Here is why.

Moving is not the same as getting stronger

A circuit makes you sweat, your heart rate climbs, you do a bit of everything. It feels like a good session, and as general movement it is fine. But it does not build the foundation a runner benefits from.

To genuinely get stronger your body needs three things, and those are precisely what a circuit lacks:

Enough load. In a circuit the weight stays light and the pace stays high. Your muscles get no reason to become stronger, only to become tired.
Progression. Getting stronger asks you to do a little heavier or a little more every few weeks. In a circuit you do roughly the same thing every time.
Technique. In a squat or a deadlift, execution decides whether you get stronger or overload something. In a busy circuit nobody is really watching that.

A runner is not helped by getting even more tired. They are already tired from running. What a runner needs is a stronger chassis that can take the running.

What getting stronger gives a runner

When your legs, hips and trunk are stronger, you run more efficiently. You cover the same distance with less effort, your form holds up longer, and you are far better protected against the classic running injuries in the knee, hamstring and Achilles tendon. That is not a side issue when you are building towards a marathon, it is the difference between enjoying it and suffering.

And the good news is that it does not take five sessions a week. Two targeted strength sessions alongside your running plan are enough for most people to lay the foundation.

"But strength training is boring"

I hear that often, and I understand it. If strength training means endlessly counting repetitions on a machine, then yes, it is boring.

It does not have to be that way. You do not need twenty exercises, you need a handful of good movements you build up step by step. The interesting part is the progress: last month you struggled through your long run, this month the same distance feels lighter. That is the reward, not the counting.

More importantly: the strength training is not the goal. The goal is running that marathon and still enjoying it. Strength is the means, not the homework.

What you can do with this yourself

Put strength alongside your running, not instead of it. Keep running as you are used to, and add two short strength sessions a week. You do not have to choose between them.
Pick a few basic movements and get better at them. A squat, a hip hinge such as a deadlift in a safe form, a lunge and some trunk stability cover most of it. Add weight calmly, technique first.
Measure your progress by your running, not by the scales. Does your usual route feel lighter? Do you recover faster after a long run? Those are the signals that it is working.

And if you have an injury that keeps coming back, or you cannot find any consistency, have someone look at it with you. Not to take over your running, but to get the foundation underneath it right so you can carry on doing what you love.

Frequently asked questions

Does strength training really help you run faster?

Yes. Targeted strength training can improve running economy, particularly in middle and long distance runners. A systematic review with meta-analysis of strength programmes in this group found that heavy strength training, plyometric training and combinations of the two can improve running economy, with the largest effect from heavy loading at higher running speeds. That is a different mechanism from circuit training, where the weight stays light and the pace stays high: your muscles mostly get tired rather than stronger. For a lasting effect you need progression, something heavier or more explosive every few weeks, combined with attention to technique in movements like the squat or the deadlift. At Infinite Health we build this up carefully alongside your running plan. Think of two targeted strength sessions a week of 30 to 45 minutes, with squats, deadlifts and a few plyometric movements, matched to your current mileage.
Source: systematic review on strength training & running economy (PMC) →

Is circuit training a good substitute for strength training as a runner?

No. Circuit training is usually not a good substitute for targeted strength work if you are serious about running. Circuits make you sweat and raise your heart rate, but they miss the three ingredients muscles need to get stronger: enough load, gradual progression in weight or repetitions, and attention to technique. In a circuit the weight stays light and little changes from week to week, so you mainly get tired without getting stronger. For a runner who wants to stay injury free and run more efficiently, two or three targeted strength sessions a week alongside the running itself are more effective than a circuit. After 40 this counts double, because recovery is slower and you need fewer training stimuli to progress, but they have to be the right ones, aimed at strength and power rather than piling on more fatigue.

How much strength work fits alongside a running plan?

For most runners twice a week is the point where the effect is clear without your running suffering. More important than the number is the placement: do not put a heavy strength session right before your key running day, but on the day after an easy run, or at least six hours apart if it has to be the same day. Heavy and short works better here than light and long. With high loads and few repetitions you mainly train the nervous system, and that costs less recovery than a long set at moderate weight. In a busy running week one good strength session beats two half ones that only make you tired. And in the weeks around a race you keep the volume low but do not stop altogether, because that is how you lose what you built.