Does strength training make you a better runner? Or does it actually make you heavier and slower? Many runners and triathletes are unsure about this. I had the same question. This winter I’m competing in Hyrox events, where running and strength are inseparably linked. That’s why I headed back into the weight room.

In this article, I share my personal experience—supported by training data and running tests—about what ten weeks of serious strength training did to my running.

Rediscovering strength training

The deadlift and the squat—how did those work again? That’s what I wondered when I stepped into the gym ten weeks ago for the first time in twenty years. During Hyrox Rotterdam (March 2025), I thought I could post a top time without strength training. I was wrong. After 67 minutes, I crossed the finish line completely exhausted—far from my sub-60 minute goal.

The conclusion was clear. If I want to be faster at Hyrox Amsterdam (January 2026), I’ll have to start lifting weights again. And I wasn’t exactly looking forward to that.

The first strength session was an immediate reality check. After box jumps, deadlifts, squats, and pull-ups, I moved on to sandbag lunges. After 40 reps, cramps hit both left and right. Training over. I limped out of the gym—but with a grin on my face. Because despite everything: I was really enjoying it again! The second session already went a lot better.

Ten weeks later: massive progress

What perhaps surprised us the most was how quickly strength training delivers results. While progress in running often takes months, I saw myself getting stronger week by week. The numbers after ten weeks:

• Box jumps: 45 cm → 64 cm

• Deadlift: 50 → 100 kg

• Squats: 60 → 100 kg

That kind of progress builds confidence. But the key question for runners, of course, is: does strength training make you a better runner?

What does strength training do to my running feel?

What surprised me most was how I feel during my runs. In the build-up to Hyrox Rotterdam, I did two specific Hyrox exercises: every week a set of 100 sandbag lunges and 100 wall balls. They hit so hard that for the rest of the week I struggled with stiff hamstrings and glutes while running. It didn’t feel good at all. Especially during short intervals, faster than 3:20/km, it felt like a constant battle.

Since I started doing maximal-strength sessions, that feeling has completely disappeared. In fact, I now run those short intervals smoothly at sub-3:20/km. And that feels great.

Fewer running kilometers: worse running?

Strength training takes time—and that time comes at the expense of running mileage. Where I previously ran 80–120 kilometers per week, I’m now between 50 and 70. Yet running feels surprisingly good. The interval sessions are even faster than last year. That inevitably raised a question.

Ten weeks later: massive progress

What surprised me the most is how quickly strength training delivers results. Where progress with running often takes months, I saw myself getting stronger week by week. The numbers after ten weeks:

• Box jump: 45 cm → 64 cm
• Deadlift: 50 → 100 kg
• Squat: 60 → 100 kg

That kind of progress builds confidence. The key question for runners, of course, is: does strength training make you a better runner?

What does strength training do to my running form?

I was amazed by how I feel during running workouts. In preparation for Hyrox Rotterdam I did two specific Hyrox exercises. Every week a set of 100 sandbag lunges and 100 wall balls. They hit so hard that, for the rest of the week, I was plagued by stiff hamstrings and glutes while running. That didn’t feel good. Especially during short intervals, faster than 3:20/km, it was all pulling and grinding.

Since I started doing maximal-strength sessions, that feeling is completely gone. Even more so: I now run those short intervals smoothly at sub-3:20/km. And that feels great.

Fewer running kilometers: worse running?

Strength training takes time. And that time comes at the expense of running mileage. Where I previously ran 80–120 kilometers per week, I’m now between 50 and 70. Still, running feels surprisingly good. The interval sessions are even faster than last year. That inevitably raised a question: how good is my running?

The big question: what is my real running level now?

Does strength training make you a better runner? Feeling is important, but to measure is to know. That’s why I treated myself to an exercise test, including respiratory gas analysis and lactate measurement. I expected to see a drop compared to the test I did 1.5 years ago in the build-up to the Rotterdam Marathon (2:38). Back then, my running level was at its peak.

The test of 27-11-2025 followed ten weeks of strength training. The earlier test of 29-02-2024 was done during the running-specific marathon preparation for Rotterdam.

Results: VO₂Max up despite fewer kilometers

To my surprise, the key maximal values had improved:

• VO₂max (relative): 66 → 70 ml/min/kg
• VO₂max (absolute): 5256 → 5618 ml/min
• Maximal heart rate: 165 → 170

The speeds at the aerobic (15.6 → 15.4 km/h) and anaerobic threshold (17.4 → 17.1 km/h) were slightly lower. This was mainly due to a lower maximal lactate value. With a few anaerobic stimuli, that can be quickly brought back up.

An important detail: at all speeds, lactate values were lower in the post–strength-training test. You can see that below.

Why strength training can improve your running performance

1. From an exercise physiology perspective: lower relative load

By increasing maximal strength, you need to produce relatively less power at a given running speed. This allows more slow-twitch muscle fibers to be recruited, resulting in lower lactate production. (Opinions on this differ—fortunately, we don’t know everything yet 😉)

2. Biomechanical explanation: better running efficiency

A second explanation is improved running efficiency. Research by Baldwin et al. (2021) shows that increased muscle–tendon stiffness as a result of strength training can make running more efficient.

Extra benefit for masters: strength training and testosterone

Strength training also has a positive effect on testosterone levels. Testosterone peaks around the age of 30 and then declines by an average of 0.8–1.2% per year.

That’s a nice side benefit for “older youngsters”.

What can you take from this as a runner or triathlete?

These data are based on a single person (N = 1), so nuance remains important. Still, a few cautious conclusions:

• Maximal strength training does not make you a worse runner—often quite the opposite
• Not everyone responds the same. For some athletes, heavy strength training can have a temporary negative effect
• Especially after the age of 40, strength training is strongly recommended
• The winter period is ideal for making this a focus, with maintenance during spring and summer
• Keep it simple (the KISS principle): squat, deadlift, leg press, optionally bench press, pull-ups, and rows. In the article by Baldwin and colleagues (2021) you’ll find a well-supported set of exercises
• Haven’t mastered the technique yet? Learn it properly first. It will pay off many times over

Want to know more about strength training and running?

Would you like to know how to smartly combine strength training with running or triathlon? Send me an email at bertflier@3in1sports.com or drop by at my test facility in Utrecht for a cup of coffee. The weights are waiting for you 😉