The Truth About Strength Training for Runners: Why High Reps and Low Load Won't Cut It
If you've been told that runners should only do high reps with light weights to avoid "getting bulky" or "slowing down," it's time to rethink that advice.
This myth has been circulating in the running community for years. Unfortunately, it's holding a lot of runners back from getting stronger, faster, and more resilient. The truth? Heavy strength training is not only safe for runners, but it's also essential.
Let's break down where this misconception came from, what the research actually says, and why lifting heavier weights might be the missing piece in your training.
Where Did the "High Reps, Low Load" Myth Come From?
The idea that runners should stick to high reps and light weights comes from a few places:
1. Fear of getting bulky
Many runners worry that lifting heavy weights will add muscle mass and slow them down. This concern is especially common among distance runners who've been told that lighter is always better.
2. The endurance mindset
Running is an endurance sport, so it makes intuitive sense that strength training should mirror that. This means lots of reps, lighter loads, and staying in the "endurance zone." Right? Not so much, and I’ll explain why in the coming sections.
3. Misconceptions about muscle fiber types
There's a belief that runners primarily use slow-twitch muscle fibers, so training should focus on muscular endurance rather than strength or power.
While these concerns sound logical on the surface, the research tells a very different story.
What Does the Research Actually Say?
Multiple studies have looked at the effects of heavy strength training on runners, and the results are clear: heavier loads improve running performance and running economy. Plus, these gains are possible without adding bulk or slowing you down.
Heavy Strength Training Improves Running Economy
One of the most important findings is that heavy strength training improves running economy. This is the amount of oxygen you need to maintain a given pace. Essentially, the more economical you are, the less energy you burn at any given speed.
A systematic review by Blagrove et al. (2018) found that runners who included heavy strength training (using loads of 70-90% of their one-rep max) saw significant improvements in running economy within just 4 weeks.
These improvements translated to better performance in middle- and long-distance events. That said, the researchers recommend a combination of heavy resistance training, explosive movements, and plyometrics performed 2-3 times per week for maximum benefit.
Want to learn more about how plyometric training benefits runners? Check out how jump training improves bone strength.
Tendon Health and Injury Prevention
Heavy loading is also crucial for tendon health. Tendons respond best to high loads, not high repetitions. A 2024 systematic review and meta-analysis by Llanos-Lagos et al. examined the effects of different strength training methods on running economy in middle- and long-distance runners.
While the study primarily focused on running economy, it reinforces that heavy resistance training (loads ≥ 80% of one-rep max) creates important adaptations in how your muscles and nervous system work together. As a result, your mechanical efficiency will improve. This includes making your tendons stiffer and stronger, which is an important outcome for runners.
You Won't Get Bulky
Here's the reality: gaining significant muscle mass is hard, and it definitely doesn’t happen overnight. It requires eating more calories, adding more protein to your diet, progressive overload, and consistent training over months or years, amongst other things. Runners who strength train 2-3 times per week while maintaining high running volume are not going to accidentally bulk up.
In fact, research consistently shows that runners who incorporate heavy strength training into their routines improve performance without increases in body mass (Blagrove et al., 2018). Your body adapts to the demands you place on it, and when you're running high mileage, it's not going to prioritize building unnecessary muscle.
Power and Rate of Force Development
Heavy strength training also improves your ability to generate force quickly. In other words, this refers to how fast you can "turn on" your muscles when you need them. This matters in the later stages of a race when you're fatigued, when you need to push up a hill, or when you're sprinting to the finish.
The same 2024 systematic review by Llanos-Lagos et al. found that heavy resistance training improved running performance. This was specifically because it improved how quickly runners could produce force, not just how much force they could produce overall. This ability to generate force rapidly translates directly to more powerful, efficient strides, especially when it counts most.
High reps with light weights don't create these same adaptations in how your nervous system recruits muscle fibers or how quickly your muscles respond.
So What Should Runners Actually Do?
If high reps and low loads aren't the answer, what is? I’ll explain exactly what runners should do below.
Lift Heavy (Relative to Your Ability)
Heavy shouldn’t be synonymous with scary. Heavy will look different for everyone, depending on where you’re starting from. This means you don’t necessarily need fancy gym equipment, especially if you’re just starting out. Some kettlebells and dumbbells will do the trick, especially if you’re doing the right kind of exercises.
For most runners, this means working in the 8-12 rep range with a weight that feels challenging by the last few reps. You should be able to complete the set with good form, but the final reps should require real effort. You should have maybe 1-2 reps left in the tank (reps in reserve).
Some essential exercises to focus on:
Squats (back squat, goblet squat, split squat)
Deadlifts (conventional, Romanian, single-leg)
Lunges and step-ups
Hip thrusts and bridges
Single-leg exercises for stability and strength imbalances
Not sure where to start? Read my guide on 5 tips for strength training as a runner for a complete beginner-friendly approach.
Use Progressive Overload
Progressive overload means gradually increasing the challenge over time. This could be adding weight, increasing reps, or changing up the tempo. This is how you continue to see improvements rather than plateauing.
Start with a weight you can lift with good form, then gradually increase the load or reps every few weeks as you get stronger. If you’re unsure when to progress, use the 2-for-2 rule. If you can perform 2 more reps than your target in your last 2 sets for 2 consecutive workouts, it’s time to increase your weights.
For example, if your goal is 10 reps, and you hit 12 reps on your last two sets in two workouts in a row, you’re ready to go heavier!
If you're wondering whether you're doing enough to build strength as a runner, this guide I linked will help.
Train 2-3 Times Per Week
You don't need to strength train every day; in fact, that would lead to overtraining. Research shows that 2-3 strength sessions per week are enough to see significant improvements in running performance and economy. Plus, each session can be as short as 20-30 minutes if you're focused and efficient.
What’s most important is consistency. Sporadic heavy lifting won't give you the adaptations you're looking for, but regular, progressive training will.
When Should You Use High Reps and Light Loads?
To be clear, high reps and lighter loads aren't useless, but they just shouldn't be the foundation of your strength training as a runner.
High-rep work can be useful for:
Injury rehab or return-to-training: Building back load tolerance and confidence after an injury.
Muscular endurance work: Supplementing heavy strength training during certain phases.
Accessory work: Adding volume after your main lifts.
However, if your goal is to get stronger, more powerful, and more resilient as a runner, you need to lift heavy.
The Recap
The myth that runners should only do high reps with light weights is outdated and not supported by research. Heavy strength training improves running economy and performance, builds resilient tendons, and increases power and force production. This all happens without making you bulky or slowing you down.
If you've been avoiding heavier weights because you thought they weren't for runners, it's time to reconsider. Start with basic movements, progressive overload, and 2-3 sessions per week. Your running will thank you.
Happy running,
April :)
References:
Blagrove, R. C., Howatson, G., & Hayes, P. R. (2018). Effects of Strength Training on the Physiological Determinants of Middle- and Long-Distance Running Performance: A Systematic Review. Sports Medicine, 48(5), 1117–1149. https://doi.org/10.1007/s40279-017-0835-7
Geantă, V. A., & Ardelean, V. P. (2022). Improving muscle size with Weider's principle of progressive overload in non-performance athletes. Timisoara Physical Education and Rehabilitation Journal, 14(27), 52–56. https://doi.org/10.2478/tperj-2021-0011
Llanos-Lagos, C., Ramirez-Campillo, R., Moran, J., & Sáez de Villarreal, E. (2024). Effect of Strength Training Programs in Middle- and Long-Distance Runners' Economy at Different Running Speeds: A Systematic Review with Meta-analysis. Sports Medicine, 54(4), 895–932. https://doi.org/10.1007/s40279-023-01978-y
