Shorter crank lengths are often discussed for aerodynamic fit or joint comfort, but recent findings point to something even more compelling: energy efficiency. A study by JCOB explores how shorter cranks reduce total muscle energy expenditure without sacrificing power. This is more than a marginal gain, it’s a biomechanical shift. By limiting the travel distance of the foot and hip per revolution, the rider reduces cumulative muscular work across thousands of pedal strokes. For cyclists chasing long-distance performance, this can mean arriving at the final hour of a ride with fresher legs and a steadier posture.

Hypothesis 1: Power output can be maintained by increasing cadence

When you shorten crank length, torque decreases. But that loss can be compensated by increasing cadence (rpm). This means that for the same downward force on the pedals, a rider can maintain their power output simply by pedaling faster. Most trained cyclists can adapt to this without issue, and many find that their natural cadence drifts upward without conscious effort once shorter cranks are installed. This is because the reduced pedal circle encourages quicker leg turnover, much like shifting to a lighter gear without changing actual resistance.

For example, moving from 175 mm to 165 mm cranks requires only about a 5 rpm increase to produce the same power output. The 145 mm cranks may require a cadence increase of about 18 rpm. Importantly, laboratory testing shows that most cyclists can adapt within a handful of sessions, suggesting this adjustment isn’t a limitation but rather a recalibration of how power is delivered.

Hypothesis 2: Shorter cranks reduce muscle energy usage

The human body expends energy not just in outputting watts, but in internal muscle activity. The study highlights how shorter cranks reduce total muscle contraction distance per pedal stroke. That means lower contraction velocity, which directly leads to less heat generation and energy waste, especially in fast-twitch muscle fibers. Over the course of a century ride or an Ironman marathon, those incremental savings accumulate into meaningful performance gains.

In testing, a switch from 175 mm to 165 mm cranks resulted in about 5.8% less foot travel per revolution. That may seem trivial, but multiplied by 5,000 pedal strokes in a two-hour ride, it equates to nearly 300 fewer meters of leg muscle contraction. This translates to lower overall energy expenditure per minute, particularly valuable in long-distance riding or time trialing where efficiency matters most. Riders often describe it not as “more power,” but as “less fatigue for the same power.”

Hypothesis 3: Less energy, same power, better comfort

When you combine Hypotheses 1 and 2, a new truth emerges. Shorter cranks let you ride with less physiological stress while maintaining power. That means longer sustainable effort, better posture, and fewer injury risks. For riders who spend hours in an aerodynamic tuck, the reduced hip angle also means less compression at the top of the stroke, easing strain on the lower back and improving breathing mechanics.

By freeing up hip angle, shorter cranks also improve aerodynamic posture and lung expansion. This has cascading benefits in time trials, Ironman races, and even daily training rides. It’s not just a comfort upgrade, it’s more of a strategic performance lever that influences biomechanics, aerodynamics, and recovery all at once.

Final takeaway

Shorter cranks are not just a fit choice. They are a performance tool. Whether it is reducing fatigue, improving mechanical efficiency, or enabling better aero, the science supports what riders have reported for years. For athletes who race long and train often, the savings are compounding: less strain per stroke leads to more sustainable power, and more sustainable power leads to faster, fresher finishes.