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What Runners Don’t Know Will Hurt You

“I use weights for my upper body and run for my lower body.”

“I don’t train legs because I don’t want to get injured.”

“I don’t train legs because I don’t want to get bulky and slow down."

As a trainer in the city of one of the biggest endurance races in the world (Boston Marathon), I’m still shocked when I hear these statements when I meet with prospective clients, and it happens pretty frequently. Each time I hear it, it gets a little harder to not show my frustration about this common misconception, especially since Boston is so educated when it comes to health and fitness. However, I always remember that educating people is part of why I got into this business. So, let’s chat about why resistance training for your legs is important for runners by helping to reduce your likelihood for injury and how it aids in making your run times faster/stronger.

Who cares about resistance exercises and its importance in running?

Phoebe from Friends running obnoxiously

Traditionally, distance running performance was thought to be determined by several characteristics, including maximum oxygen consumption (V̇O2max), lactate threshold (LT), and running economy (energy utilization- running like Phoebe uses more energy and leads to bad mechanics that can lead to issues such as knee valgus that can lead to injury.)

The typical and most common way to see improvements in these areas are primarily achieved through endurance training via running “workouts”. However, it has been shown that anaerobic factors also play an important role in distance running performance. A review in the Journal of Sports Medicine showed that because resistance training is unlikely to elicit an aerobic stimulus of greater than 50% of V̇O2max, it is unlikely that resistance training would improve V̇O2max in trained distance runners. However, it appears that V̇O2max is not compromised (i.e. helps maintain) when resistance training is PROPERLY added to an endurance running program. Additionally, it showed that LT improvements have been observed as a result of resistance training.

Anatomy 101- major muscles and what they do

When looking at running, technically it’s a total body exercise/movement and a great example that everything in the body is connected (kinetic chain). Using the shoulders and arms to swing alternatively, the core/trunk to help stabilize and create various levels of rotation/anti-rotation, and the hips/legs to propel yourself forward. For this article's purposes, let's focus on the lower body, hips/legs when looking at the musculature involved. Even after limiting it to the lower body, there are still too many muscles to review here; you’d be stuck cleaning up the word vomit from this page, so we will filter again to the most well-known contributors.

When running we use: glutes (a trio of muscles), hip flexors (a shotgun term for tissue that flexes the hip, we will look at TFL-Tensor Fasciae Latae), Quads (made of four separate muscles), Hamstrings (another term for a group of three muscles), and calves both anterior and posterior sides. Below is a brief list of each and what it’s primary function is (most of them have multiple functions).

Glutes (#peachemoji)

  • Maximus- Extension of the femur from the flexed position in the hip joint; lateral stabilization of the hip and knee joint; external rotation of the femur

  • Medius- Abduction of the hip and stabilization of the pelvis; extension and external rotation

  • Minimus- Abduction of the hip and stabilization of the pelvis; extension and external rotation

Hip Flexors/ Tensor Fasciae Latae

  • Tenses the fascia lata; abduction, flexion and internal rotation at the hip


  • Vastus Lateralis- Extension of the knee

  • Vastus Medialis- Extension of the knee

  • Vastus Intermedius- Extension of the knee

  • Rectus Femoris- Flexion of the hip joint and extension of the knee


  • Semitendinosus- Extension of the hip joint; stabilization of the pelvis; flexion and internal rotation of the knee joint

  • Semimembranosus- Extension of the hip joint; stabilization of the pelvis; flexion and internal rotation of the knee

  • Biceps femoris- Extension of the hip joint; flexion and external rotation of the knee


  • Posterior (backside)- Gastrocnemius- Plantar flexion of the talocrural (ankle) joint; flexion of the knee

  • Soleus- Plantar flexion of talocrural joint

  • Anterior (front/shin)- Tibialis Anterior- Dorsal flexion of the talocrural joint and inversion

  • Extensor Digitorum Longus- Dorsal flexion of the talocrural joint

Common injuries in runners

If you’re a runner, odds are you’ve probably experienced one of the top seven most common and suckiest (super scientific term) injuries for a runner at some point:

  • runner's knee

  • Achilles tendonitis

  • hamstring strain

  • plantar fasciitis

  • shin splints

  • iliotibial (IT) band syndrome

  • and stress fracture.

All of these can be looked at as either overuse/overtraining injuries (not enough rest for how much work is being done) or doing more than the body is ready to handle (doing too much/inappropriate overloading).

How resistance training helps avoid injuries

When properly implemented into a training program (i.e. allowing for proper rest and recovery), resistance training can help reduce the likelihood of most of the aforementioned injuries.

In the Journal of Strength and Conditioning Research, it has been shown that trained distance runners have improvements of up to 8% in running economy following a period of resistance training as a result of improvements in neuromuscular characteristics, including motor unit recruitment and reduced ground contact time. When looking at the length of time people are participating in endurance events (average of 2 hours for a half marathon and over 4 hours for a full marathon), even seemingly insignificant improvements in running economy can have a large impact on distance running performance and injury frequency.

Another study in the American Journal of Sports Medicine also showed that when studied over a 12-month period, fixing your gait (biomechanics of how you run; Phoebe has a TERRIBLE gait) leads to 62% fewer musculoskeletal injuries in runners. Resistance training has been shown to help increase bone density, aiding in the prevention of bone stress fractures and increasing power output, helping to decrease contact time with the ground. It can also help improve your gait by increasing muscle activation, strength, and aiding in correcting movement patterns, making gait adjustments longer-lasting/more permanent.

How to implement strength into runners workouts

So even if we’ve converted you to the “dark side” of resistance training for runners, now what? If you start implementing Arnold Schwarzenegger’s (yes, I had to copy and paste his name from the internet, thanks Google) Mr. Olympia’s lifting program, you can kiss your running goals goodbye. If you do nothing, you’re effectively crossing your fingers and hoping to get better. What’s that saying... doing the same thing over and over again expecting different results is the definition of…

Not just for running, but all training programs should be based on your:

  • goals

  • fitness experience

  • current/previous injuries/movement imbalances

  • with flexibility based on your progress.

(If you're ever part of a 'coaching' program that doesn't take these factors into account, run the other way.)

There are a ton of ways to set up your program. Your training program should also look different based on where you are in relation to your event (if you have one). Just like your running program, your mileage increases the further into your training you get, and then you “deload” as you get closer to the race. You should have an “off-season” where you can focus a little more on strength and adding a little bit of weight as a lot of runners lose weight and muscle during their training. Possibly add a section where you focus more on power (with plyometrics and explosive lifts) and a section where you focus on function (asymmetrical loading and various planes of motion that create running movements). The bottom line is this: there is always a way to incorporate resistance training.

The only wrong way to do it is to do the same workout with the same weights and set/rep ranges year-round. Yes, it will help you at the beginning of your training, but you’ll quickly stop seeing the benefits after 6-8 weeks if nothing changes. If you’re not sure where to begin or just have specific questions, feel free to hit us up on our Instagram story where we do a weekly “Ask a Trainer.” Or contact us on our website; after all, if you’re reading this, you’re just one or two clicks away from getting the answers you’re looking for.

Happy running!

A man sprinting with the blog title overlaid.
Pin this so you can implement a proper strength training program.

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