Bolzplatz - An der Bastion - Deutz

This graphic is from my book Force & Expression.

One important distinction, the forces shown here are estimated internal muscle forces, not external ground reaction forces.

Internal forces within the muscle tendon system can be several x BW and shouldn’t be confused with the amount of force the athlete is applying to the ground.

The glute max contributes heavily to hip ext, but peak force isn’t the whole story. In sprinting, it works with the hamstrings and other muscles to control the pelvis/ hip and contribute to the direction and transfer of force.

The hamstrings experience extremely high forces during sprinting because of their role across both the hip and knee. During stance, their fascicles can behave relatively isometrically while the muscle tendon system transmits force, and during late swing they experience particularly high loading as the limb prepares for ground contact.

The iliopsoas and other hip flexors dont just simply “lift the knee.” They contribute to rapid thigh recovery and repositioning of the limb for the next ground contact.

The soleus also handles enormous internal forces at high speeds. Its fascicles can behave relatively isometrically during portions of stance while the Achilles tendon undergoes substantial stretch and recoil, allowing the muscle tendon unit to contribute to force production and elastic energy storage and return.

You can find images and information like this throughout my best selling Speed Kills program and in Force and Expression.

I’m also almost done with the follow-up programming to Speed Kills, where I’ll break down what I’ve changed, why I’ve changed it, and how my programming has continued to evolve.

Tomorrow I’m also releasing a new four-week Strength x Speed block. It’ll only be available for one month.

Link in bio.

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