Fascicles & Speed A fascicle is simply a bundle of muscle fibers,...
Fred Duncan@Fred__Duncan
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Sep 09, 2025
~1 min read
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Fascicles & Speed
A fascicle is simply a bundle of muscle fibers, but the length of those fascicles plays a big role in performance.
Longer fascicles mean more sarcomeres in series -> faster shortening velocity -> better ability to produce force at high velocities.
A fascicle is simply a bundle of muscle fibers, but the length of those fascicles plays a big role in performance.
Longer fascicles mean more sarcomeres in series -> faster shortening velocity -> better ability to produce force at high velocities.
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That’s why we care about them in sprinting and explosive sport.
We can influence fascicle length with…
✅ Sprinting itself
✅ Eccentrics (RDLs, flywheel work)
✅ Isometrics to support tendon/muscle interaction
I go into this much deeper in The Art &
We can influence fascicle length with…
✅ Sprinting itself
✅ Eccentrics (RDLs, flywheel work)
✅ Isometrics to support tendon/muscle interaction
I go into this much deeper in The Art &
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Science of Sport Preparation, where I cover structural adaptations like fascicle length, tendon remodeling, architectural gear ratio, eccentrics, and isometrics in detail. This also features a 10-week offseason program.
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I also touch on these in Speed Kills, but that book is the true blueprint for speed, how to program sprint work, rest intervals, resisted runs, volumes, and put everything together for athletes.
