De-bunking the Fear of Bulk

Why Runners Should Lift Heavy Weights.
Strength training is a HOT TOPIC for distance runners, and while some athletes are interested in building muscle mass, fear of unnecessary “bulk” or “hypertrophy” is a common worry, too.

Full Disclosure:

We never want athletes to start a brand-new strength program with heavy lifting. Even bodyweight strength and consistent multi-planar movement will enhance performance. And if we can simply work on a trajectory leaning in that direction, we are confident the athlete will benefit.

The evidence is clear. Regular strength work performed 2x per week is essential for runners of all skill levels. The benefits range from injury prevention to improved fatigue resistance. And let’s be honest, who doesn’t want to feel less tired at the end of their 5K, half marathon, or marathon?!

Achieving excess muscle mass is much more complicated than once believed.
Heavy lifting, once associated with bulking up, increases running “ground force production.” A solid weightlifting program can impact the force being placed with each stride. That force moves the athlete forward with less effort. That’s a beautiful thing, right?

Our stance? Runners should strength train regularly and progress to lifting heavier weights with fewer repetitions. The timeline depends on the individual, but the progression is critical.
Once general strength is established, lifting for strength gains is a powerful next step.
Lifting for strength, by definition, means heavier weights (≥ 85% 1-RM), fewer repetitions (≤ 6), and 90-second – 5-minute rest intervals between. The rest is crucial.

Conversely, lifting lighter weights for more reps leads to muscular endurance gains (for example, 15 repetitions of crunches, 2 – 3 sets). Most of the time, endurance athletes get muscular endurance gains through their endurance activities. Hills, high volumes of running, and long runs are a few examples of how we can gain muscular endurance through running.

Now, let’s break down the common fear of “bulking”:

Will muscular size increase from regular heavy lifting?

More than likely.

Will muscular size increase excessively if a distance runner begins lifting heavier weights?

Highly unlikely.


Runners are prioritizing running over lifting.

Long durations of low-intensity running leads to increased muscular and cardiovascular endurance. Lifting weights 2 – 3x per week with a running program will make *excessive hypertrophy hard to come by.

*If the athlete wants that, nutrition will play a role. We won’t go there in this post, though.

Exercise science is always evolving. Here is what we can take away from the most current research:

  • The running motion places a repetitive load of up to 3x bodyweight on each leg (130 lb. athlete = up to 390 lbs.)
  • Fewer exercises, repetitions, and sets with heavier weight loads recruit muscle fibers that generate higher amounts of force.
  • Higher ground force production = faster, more efficient running.

Simply put, anyone who wants to run without injury and to the best of their ability should strength train. Progressive overload is key.

Happy lifting!

References and Further Reading:

American College of Sports Medicine (2018). ACSM’s Guidelines for Exercise Testing and Prescription 10thed.).

Baechle, T.R. & Earle, R.W. (2008). Essentials of Strength Training and Conditioning (3rd ed.). Champaign, Ill.: Human Kinetics

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