Recently, I have been reviewing my running biomechanics notes (I can never stop learning)....
And I wanted to share some tid-bits of information with all of you!

When I was first learning about kinetics and kinematics, I was overwhelmed, but also amazed at what happens at each major joint and muscle group when we run!

Don’t Underestimate the Force of Your Muscles

Did you know that every stride you take while running sends up to 2–3 times your body weight through your body due to the ground reaction forces (this is the force coming back up from the ground on a body, as a reaction to the force the body exerts on the ground).

And your muscles? They’re not just along for the ride, they’re working hard to manage those forces, stabilize your posture and joints, and propel you forward. Some major muscle groups generate 6–8 times your body weight in force!

The Muscles Doing the Work (and How Much Force They Handle)

Here’s what the research tells us about peak muscle forces during running:

• Soleus: 6–8x body weight throughout most of the stance phase
• Gastroc: 2–4x body weight also throughout most of the stance phase
• Quads: 4–6x body weight during impact absorption
• Hamstrings: 2–9x body weight, especially late swing and push-off
• Glute Max: 1.5–3x body weight, increasing with speed or incline
• Hip Flexors: 2–3x body weight, initiating swing phase

Speed Changes Everything

As your pace increases, where the work happens in your body shifts:

• At slower paces, you rely heavily on your calves and ankles, especially the soleus, to absorb and return energy.
• As you run faster, more of the workload shifts upward, into your hamstrings and glutes, which become the prime movers during push-off and propulsion.
• Sprinting? The hip extensors (glute max + hamstrings) dominate, and calf force decreases slightly in comparison.

This is why sprinters tend to have powerful glutes and hamstrings and why marathoners need durable, fatigue-resistant calves.

Why Strength Training Matters

Runners often focus on endurance, but strength gives you the foundation to:

• Absorb impact safely
• Produce force efficiently
• Maintain good mechanics under fatigue
• Run faster with less risk of injury

And no, strength training won’t make you bulky. It’ll make you better.

Want to Train Smarter? Here’s How:

• Lift heavy (3–6 rep range) for your glutes, quads, hamstrings, and calves.
• Don’t skip calf training
• Include single-leg work because running is a single-leg sport.
• Progress to plyometrics to prepare your body for the fast, elastic forces of running.

Where does the magic happen in long-distance running?​
The plantar flexors, your gastrocnemius and soleus. They are the primary movers in propelling us forward.

That is why it is so important to make sure you are doing your calf work properly!

Calf Raise Form Cues

• Press through your big toe
• Use full range of motion
• Control the tempo—no bouncing
• Train both bent-knee (soleus focus) and straight-knee (gastroc focus)
• Work up to 20–25 solid single-leg reps before adding weight

I often see runners moving too quickly through their reps, losing control on the descent, and rolling away from the big toe.

​See my latest reel for these examples!
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​Want Help Building a Plan?

I create strength programs built for runners, from beginners to those chasing PRs or running pain-free again. Whether you want to get faster, feel stronger, or reduce your injury risk, I’ve got you.

Send me a message to learn more!

Thank you for reading,

Adria