I recently read an article from CTS (Carmichael Training Systems) about strength training, and honestly, it was so good I had to bring it here.

For those who don’t know them, CTS is a company founded by Chris Carmichael, one of the most recognized endurance coaches in the world. They coach everyone from Tour de France cyclists to triathletes and ultrarunners, and what they publish is usually grounded in both science and years of real-world experience with high-performance athletes.

The article is titled:
“Muscular Endurance for Ultrarunners: Why High-Rep Strength Training Doesn’t Work”,
and it basically breaks a very common myth:

👉 That doing gym circuits with high repetitions and low weight helps you improve endurance.

Let me tell you upfront: not only does it not work the way many people think, it can actually be a waste of time if your goal is to run stronger, more efficiently, and for longer.

🧠 The “more reps = more endurance” myth

The idea of doing lots of light reps comes from a logical—but incomplete—assumption:

“If my sport is endurance, then I should train muscular endurance in the gym.”

The problem is that high-rep muscular endurance in the gym does not transfer to the kind of endurance you need while running.

CTS explains it clearly: when you run, what limits your performance is not how many times you can lift a 10 kg dumbbell, but how long you can apply force efficiently while your neuromuscular system is under fatigue.

That’s the key: running economy.

The CTS article references three studies I reviewed closely. Here’s the most important part:

1.- Balsalobre-Fernández et al. (2016)

This meta-analysis compiled multiple studies on runners and concluded that strength training with heavy loads (70–90% of 1RM) improves running economy—meaning how much energy you use at a given pace.

Simple: you can run at the same pace using less oxygen.

That means your body becomes more efficient, not necessarily bigger or more “muscular.”

👉 The authors explain that this type of training improves tendon stiffness and the ability to apply force quickly—exactly what makes you more elastic and efficient when running.

2.- Millet et al. (2011)

This study examined what happens to your body after an extreme mountain ultramarathon.

The results were brutal: up to a 40% drop in muscle strength after the race, along with significant neuromuscular alterations.

What this shows us is that fatigue isn’t just muscular—it’s also neurological.

That’s why heavy, controlled strength training helps so much: it teaches your neuromuscular system to maintain coordination and muscle activation under fatigue.

👉 In simple terms, you’re not just strengthening muscle—you’re strengthening the brain-to-muscle connection.

3. Schoenfeld et al. (2021)

This group reviewed what’s known as the repetition continuum:

• Low reps with heavy weight → strength

• Moderate reps with moderate load → hypertrophy

• High reps with low load → local muscular endurance

The key takeaway: while all ranges can produce adaptations, high reps with low weight are not the best path to improve strength or power.

The nervous system adapts much better when you lift heavy, with good technique and low reps.

⚡ So… why don’t light circuits work for us?

Because we already train endurance when we run.

What we’re missing is not more “endurance,” but more usable strength to sustain that endurance efficiently and without breaking down.

When you do high-rep, low-load circuits, you mainly train slow-twitch fibers, but you don’t stimulate the fast-twitch fibers or the neuromuscular adaptations that actually make you a better runner.

And just to be clear: this is not about becoming a weightlifter.
It’s about teaching your body to produce more force with less relative effort.

🏋️ This made me reflect on how we train strength at The Journey 100

At The Journey 100, strength training is not an accessory—it’s a strategic part of endurance training. We recommend it to every athlete, regardless of level or goal.

We apply strength training in a periodized way, aligned with your season and your goals, so each phase has a clear purpose without interfering with your running:

• Base phase → build general strength and technical control

• Pre-competition → increase power and efficiency

• In-season → maintain strength without compromising volume or running quality

All of this without taking away from your main sport: you train strength to run better, not to lift heavier for the sake of it or for aesthetics.

That’s why we use big, functional movements (squats, deadlifts, hip thrusts, presses, etc.) with progressions adapted to each athlete.

🚀 In summary

👉 High-repetition circuits do not improve a runner’s specific endurance
👉 Heavy-load, low-repetition strength training improves running economy, power, and neuromuscular endurance

👉 The key is integrating it intelligently into your plan—not as an extra, but as part of the process

And if you want to do it the right way, with planning and guidance, I invite you to train with us at The Journey 100.

We don’t guess—we teach you how to use strength as a tool to become a better endurance athlete, without losing sight of what you love most: running.

If you want to read the CTS article:
“Muscular Endurance for Ultrarunners: Why High-Rep Strength Training Doesn’t Work.”

Leer este artículo en Español: ¿Por qué el entrenamiento de fuerza con altas repeticiones no funciona? Revisando el artículo de CTS