Elasticity, Stiffness, and Context When you watch this clip, you...
Fred Duncan@Fred__Duncan
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Sep 11, 2025
~2 min read
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Elasticity, Stiffness, and Context
When you watch this clip, you see an athlete hitting low hurdle hops with rapid, stiff ground contacts.
Many would call this the ultimate display of “elasticity.” The ground looks like a springboard…minimal deformation, quick return
When you watch this clip, you see an athlete hitting low hurdle hops with rapid, stiff ground contacts.
Many would call this the ultimate display of “elasticity.” The ground looks like a springboard…minimal deformation, quick return
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of energy.
But let’s go deeper. Terms like stiffness and elasticity get used a lot, sometimes too loosely. Stiffness isn’t a universal “good” or “bad.” It’s simply the ability to resist deformation and restore the system to its prior state.
Whether that’s desirable
But let’s go deeper. Terms like stiffness and elasticity get used a lot, sometimes too loosely. Stiffness isn’t a universal “good” or “bad.” It’s simply the ability to resist deformation and restore the system to its prior state.
Whether that’s desirable
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depends on context…the drill, the adaptation we’re chasing and the athlete in front of us.
Take hurdle hops. You can bias them toward stiffness…lower barriers, short contacts, high frequency. Or you can bias them toward yielding…higher barriers, deeper hip/knee flexion,
Take hurdle hops. You can bias them toward stiffness…lower barriers, short contacts, high frequency. Or you can bias them toward yielding…higher barriers, deeper hip/knee flexion,
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longer contacts.
Both are valuable. Both train different qualities. It’s not either/or.
So how do we classify what we’re actually seeing? In this case, it’s efficient energy recycling with minimal loss, a quality that supports sprinting and explosive jumping.
You could
Both are valuable. Both train different qualities. It’s not either/or.
So how do we classify what we’re actually seeing? In this case, it’s efficient energy recycling with minimal loss, a quality that supports sprinting and explosive jumping.
You could
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label this athlete “elastic,” but the more important question is…elastic relative to what and in what context?
This is why definitions matter. Just like saying someone is “too tall” or “too low” when sprinting, those descriptors are meaningless without the athlete’s build,
This is why definitions matter. Just like saying someone is “too tall” or “too low” when sprinting, those descriptors are meaningless without the athlete’s build,
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posture and task in mind.
Stiffness, elasticity, compliance, these are not absolutes. They’re tools in our vocabulary and the value comes from applying them precisely.
This type of critical lens is what I built into Speed Kills, understanding which qualities matter, how to
Stiffness, elasticity, compliance, these are not absolutes. They’re tools in our vocabulary and the value comes from applying them precisely.
This type of critical lens is what I built into Speed Kills, understanding which qualities matter, how to
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develop them, and how they fit into weekly or yearly programming. From sprinting to lifting to plyometrics, I break down mistakes, progressions, and structure, and then show it all in a complete program.
Right now, I’ve bundled Speed Kills with The Art and
Right now, I’ve bundled Speed Kills with The Art and
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Science of Sport Preparation, over 130 pages combined. If you want to move beyond buzzwords and start applying concepts with clarity, it’s available on my site now.
fredduncantraining.com/product/projec…
fredduncantraining.com/product/projec…