The art of pedalling may sound simple but to get the most from your effort takes skill and work. Andrew Pruitt, is the founder of the Boulder Centre for Sports Medicine and has worked with elite athletes for years. He has become one of the world’s foremost experts in 3D bike fit analysis. Here he explains the biomechanics of pedalling to help you become more efficient in the saddle.
Written By: Andrew Pruitt
Cycling biomechanists often use a so-called clock diagram to illustrate the forces involved in pedalling. For the purposes of this feature, I’ll offer a simplified version. Call it the lay person’s guide to pedalling mechanics. Here’s what we’ve learned.
Pedalling Is a Restrictive Athletic Motion
The pedalling motion takes place through a relatively small range of motion. If you’re using 170 mm crank arms, the legs move in a circle with a diameter of only 340 mm. Contrast that to the huge mobility required by basketball players, gymnasts, or triple jumpers.
So while cycling is less likely to cause muscle pulls due to excessive motion, a stretching programme is crucial since the muscles aren’t stretched in their daily routine of pedalling.
The bicycle is a fixed machine that can be adjusted by such means as raising or lowering the saddle and changing the reach to the handlebars. Humans are also machines, and while adjustment isn’t possible (short of an operation to lengthen your femurs), the human body is adaptable.
The Foot Rarely Pushes Straight Down on the Pedal
The only point at which the foot is pushing straight down is at about the three o’clock position. The rest of the time, force is applied tangentially to the pedal, increasing shearing force and reducing the percentage of power from the quads that’s actually applied to the bike’s forward motion.
Fast Pedalling Lowers Force, Slow Pedalling Increases It
Lance Armstrong has made it popular once again to climb at a fast cadence. He and his coach, Chris Carmichael, know that low-cadence pedalling (60 to 80 rpm) requires large muscular forces, while fast cadences (around 100 rpm) lessen the load on the quads and transfer it to the cardiovascular system. Because the quads fatigue faster, and recover more slowly, than the heart, it makes sense to train your cardiovascular and neuromuscular systems to pedal rapidly.
The Best Cyclists Don’t Produce Power When They Pull Up on the Backstroke
As mentioned earlier, force-measuring pedals show us that no cyclists, not even track pursuiters who are capable of silky smooth pedal strokes at 130 rpm, really exert upward force when the pedal is coming up from dead bottom centre.
Mountain Bikers Most Closely Approach the “Ideal” Pedal Stroke
How could it be that mountain bikers get closest to the ideal pedal stroke? We tend to think of mountain bikers using a forceful, hammering pedal stroke as they ride up technical climbs. But in fact, riding loose surfaces and steep climbs requires an extremely smooth pedal stroke. If the rider emphasises the downstroke, the surge of power applied to the rear wheel causes it to lose traction on sand and gravel trails.
This phenomenon is painfully evident on Moab’s fabled Slickrock Trail. The surface isn’t loose; rather, it’s smooth sandstone that provides incredible grip to the tyres. So it’s possible to climb insanely steep pitches—but only if you avoid any power surges to the rear wheel. The slightest jerkiness in the pedal stroke breaks loose the rear wheel and causes a painful slide down the “slick rock.”
Getting your skin rubbed off by Utah sandstone provides instant feedback, teaching skilled off-roaders to apply power all the way around the pedal stroke. They still can’t pull up, unless they’re pedalling at a very low rpm, but they come close.
Even Though There’s No Such Thing as a Perfect Pedal Stroke, It’s Still a Goal to Work Toward
You can improve your pedal stroke by doing the following drills:
Concentrate on the top and bottom of the pedal stroke. At around 90 to 120 rpm the pedalling motion is so rapid it’s nearly impossible to focus on and modify the different parts of the stroke. The feet simply go around too fast. The trick is to anticipate the motion you want and initiate it early. That means starting the upward pull of the pedal when the pedal is at dead bottom centre and initiating the downward push as the pedal comes over the top and begins its descent.
Greg LeMond first described pulling through at the bottom of the stroke saying it’s “like scraping the mud off your shoe.” The image still works. But pulling through at the bottom is only half the story. You should also concentrate on pushing the knee toward the handlebars as it comes over the top and begins the power phase of the stroke.
By starting both motions well before you want their actions to take effect, you’re assured that by the time your command is sent from your brain to your legs, they’ll do the right thing at the appropriate time.
Do one-leg pedalling drills. Set your bike on a trainer and warm up. Then unclip one foot and rest it on the rear trainer support or on a chair or stool. Pedal with the other foot, emphasising good form. Then switch feet and repeat. Start by doing several sets of one minute for each leg in a low gear, and increase to sets of five minutes and larger gears.
One-leg pedalling forces you to pedal all the way around the stroke. It will be awkward at first, but with practice you’ll improve rapidly. And the pedalling efficiency you acquire will transfer to normal two-leg pedalling on the road.
Ride rollers. Most cyclists now use indoor trainers, but old-school rollers can help you improve pedal form. The reason is that it takes a smooth stroke to even ride the things!
If you pedal awkwardly on rollers, you’ll weave all over the rollers or be unable to stay upright. Rollers are the ultimate biofeedback device for smooth pedalling.
Ride off-road. As I mentioned earlier, riding loose-surfaced, steep climbs on a mountain bike is a great way to work on your pedal stroke. You don’t have to live in the mountains to get the benefits of this pedalling workout. Even short climbs are helpful.
This article was excerpted with permission of the publisher from Andy Pruitt’s Complete Medical Guide for Cyclists by Andy Pruitt, Director of the Boulder Centre for Sports Medicine, with Fred Matheny. The book is available in bookshops, bike shops and online. Cordee.co.uk