Escaping the Choke Point

Performance-minded cyclists often spend heavily on drivetrains, wheels, and shifting systems in search of small gains. But one of the most overlooked sources of inefficiency sits at the top of the pedal stroke, where hip and knee flexion are at their greatest.

Understanding the Choke Point

At the top of each stroke, your hip and knee reach peak flexion at the same time. When both joints flex deeply, a two-joint muscle like the rectus femoris becomes shortened at both ends simultaneously. This creates a problem called active insufficiency, where the muscle loses its ability to generate effective force right when it is needed most.

Peak quadriceps torque occurs around 60 degrees of knee flexion, well short of the deeper flexion the joint reaches at top dead center.

There is a good chance you have noticed this in action. You reach the top of the stroke, hesitate briefly, and then produce a burst of power on the downstroke to compensate. Over time, this can lead to premature quadriceps fatigue and, in some cases, pain beneath the kneecap.

Common signs include:

• A hitch or hesitation you can feel, or hear if you ride on an indoor trainer, near the top of every pedal stroke.
• Quad fatigue that appears disproportionately during climbs or high-intensity efforts rather than steady riding.
• Pain located under or around the kneecap instead of along the sides or back of the knee.

On their own, none of these signs automatically means you have a fit issue. However, if several occur together, there is a good chance you would benefit from a shorter crank.

Where Crank Length Comes In

For decades, crank length has largely been treated as a one-size-fits-most decision, with most production bikes shipping with 170mm or 172.5mm cranks regardless of rider proportions. That standard can worsen the choke point and aggravate existing joint issues for riders who fall outside that narrow range.

By shortening crank length, you can open the knee and hip angles, reduce strain on the knees, hips, and lower back, and create a smoother, more consistent pedal path. A Cal Poly kinesiology study tested 18 elite cyclists across six crank lengths ranging from 180mm down to 150mm while measuring hip and knee motion throughout each pedal revolution.

As crank length decreased, hip range of motion dropped from roughly 51 degrees to 45 degrees, while knee range of motion fell from about 75 degrees to 67 degrees. Another study found that reducing crank length by as little as 5 to 10mm measurably decreases knee flexion during the pedal stroke.

Many riders assume that shorter cranks automatically reduce power output, but the research tells a different story. One study found no significant difference in maximum power output across a range of crank lengths during a 30-second maximal effort, suggesting the feared power loss often does not materialize.

Matching the Bike to the Body

When changing crank lengths, saddle height should be raised by the same amount to preserve the rider's extension at the bottom of the pedal stroke.

Because the bottom of the stroke stays the same, nearly all of the resulting geometry change occurs at the top of the pedal stroke, exactly where riders tend to run out of room.

That is why crank length and saddle position should be treated as one bike fit decision instead of two separate adjustments. Installing shorter cranks without repositioning the saddle leaves much of the potential benefit on the table.

The goal is to fix the bike's geometry instead of training around its limitations. That philosophy is central to JCOB, where crank length and saddle position are selected according to the rider's actual proportions rather than industry averages.

A shorter crank reduces how far the knee travels at the top of the stroke, while a forward-riding saddle helps prevent the hips from closing excessively. Together, they create more room where the rider needs it most.

The result is a smoother pedal stroke that feels like one continuous circle instead of a noticeable dead spot at the top.

Shorter cranks also make it easier for many riders to achieve a lower, more aerodynamic position without the thighs crowding the torso during every revolution. For some riders, this translates into improved comfort, easier breathing, and a position that is easier to sustain over long efforts.

The Takeaway

The dead spot at the top of the pedal stroke is rarely just about fitness. More often, it is the result of a crank and saddle setup designed around an average rider instead of your body. Before investing in a new drivetrain or chasing marginal gains elsewhere, ask whether your bike has been built around your proportions or whether you have been forced to adapt to the bike.