Rethinking Saddle Height / Crank Arm Length: Why Flexion Matters More Than Extension
🚴♂️ It’s Not About How Straight Your Leg Is
For years, bike fitting was obsessed with one thing: leg extension. “Get that leg nice and straight at the bottom of the pedal stroke,” they said.
But here’s the thing: you’re not doing yoga on your bike. Cycling is not about static poses—it’s a dynamic, repetitive motion. So why are we only checking how you look in one frozen moment?
Turns out, the real problem usually isn’t at the bottom of the stroke—it’s what happens at the top when your hip, knee, and ankle are crunched tighter than your jeans after Thanksgiving.
🌊 The Pool Float Analogy (It’s Weird But It Works)
You know that feeling when you’re floating on your back in a pool, all chill, until someone yanks your leg under the water?
That’s how most people interpret a hip drop—must be too high of a saddle, right?
Maybe. But now imagine someone’s under the water trying to flip you over. That’s what happens when your body hits its limit in flexion—it can’t absorb the load, so it bails: hips collapse, spine twists, and everything starts to fall apart.
Moral of the story: It’s not always your saddle being too high. Sometimes it’s your joints screaming “HELP!” at the top of the pedal stroke.
🤖 Why AI and Motion Capture Sometimes Miss the Mark
Let’s talk tech. We love a good gadget as much as the next bike geek, but relying only on AI apps or single-angle motion capture to fit your bike is like diagnosing car trouble by only looking at the exhaust.
These tools often:
Capture one side of the body, from one angle.
Spot what’s happening, but not why it’s happening.
Miss whether the problem is from a lack of mobility, poor control, or some other compensation your body’s sneakily making.
That hip drop? Could be extension. Could be over-flexion. Could be your crank length messing with your life. AI can’t tell.
Humans can.
🔍 What We Do at Fit Lab Sports (That Your Phone App Doesn’t)
At Fit Lab Sports, we don’t chase numbers—we chase function.
We look at:
Your actual joint range at full compression (not just how straight your leg gets).
Pelvic control throughout the entire pedal stroke.
Crank length, cleat orientation, and saddle position based on your real-world movement.
Rear-view symmetry and functional tests—not just freeze-frame snapshots.
We close the feedback loop with you—your input matters. If you can’t feel what we want you to feel, we haven’t done our job.
Ready to Ride Better (Not Just Longer)?
Whether you’re chasing watts or chasing the traffic light sequencing, we’ll help you ride stronger, more comfortably, and with fewer weird noises (from your knees, not the bike).
👉 Book your fit today at www.fitlabsports.com
Let’s make your bike match you, not the other way around.