Cadence

Cycling is a power sport. The more power (watts) delivered to the back wheel, the faster your speed. Total delivered power/minute = power per pedal revolution x revolutions per minute (cadence). For any set level of power, the slower the cadence, the more force delivered to the pedal (via leg muscles, ligaments, and joints) per revolution. And conversely, the higher the cadence, the less force on the pedal and muscles/knees per revolution.

Cadence impacts:

1. muscle and joint (especially knee) complaints
2. the rate at which you will fatigue
3. your maximal power output.

There have been multiple studies attempting to identify the "optimal" cadence for an endurance cyclist, that is the one that is presumably the least fatiguing. The four I found most relevant:

• One - the least amount of oxygen used per watt of power generated lies between 60 and 80 rpm.
• Two - the lowest level of lactate production is at a cadence of 70 - 80.
• Three - As work load increases (more watts are generated) most riders increase their cadence from 60 towards 80 rpm. Perceived exertion (RPE) was lower at low cadences (60) but when the need was there, the naturally selected cadence moved up to the one that is also the most efficient, 80 rpm.
• Four - For a group of trained cyclists, the best results in a 30 minute time trial were at a cadence of 80. Results fell off above and below this rate.

And there is an upper cadence limit (i.e. 120 rpm) above which performance (i.e. maximum wattage) and anaerobic threshold deteriorates.

If you're new to cycling, you are probably riding at a cadence that is below your optimum. Most new riders think they are getting a better workout if every pedal stoke is a strain and the quads are burning. Lance Armstrong has popularized high-cadence pedaling. He'd spin at about 90 rpm on even the steepest climbs, and he's regularly over 100 rpm in time trials. Does this mean you should be pedaling at a high cadence as well? Although your cadence can be increased through training, it may not fit with your personal physiology and biomechanics.

Your optimal cadence is the one that let's you spin as fast as you can (in a coordinated manner) while still feeling some pressure on your pedals. Generally this will be around 80 rpm. The make-up of your leg muscles (the ratio of fast-twitch to slow-twitch fibers) and your fitness self-select the ideal initial cadence. Non-cyclists tend to start at 60-70 rpm. and as they ride more frequently move up towards 80 rpm.

For those of you just getting into cycling, here is a bit more detail from a Dr. Mirkin blog: "The best way to learn how to ride a bike efficiently is to try to keep your cadence between 80 and 90 pedal strokes per minute. However, you may not be able to do this yet. Most experienced bicycle riders do best when they chose gears low enough to allow them to pedal at this cadence. You will learn to anticipate increased resistance on your pedals. You do not wait for your cadence to speed up or slow down. Eventually when you feel that the pressure on your pedals is going to slow you down to a cadence below 80, you will lower your gears. When you feel that your cadence is going to go faster than 90, you will raise your gear ratio."

Increasing your power (and cadence) means increasing your quad strength. Most serious riders want to avoid the gym during their training season as weight training leads to muscle soreness which in turn impacts their training rides. A good alternative is adding hill sprints twice a week to your program - standing while keeping a high cadence.

This exercise may be helpful in picking the ideal cadence for your level of skill and training.

1. Locate a protected 2-mile stretch of road (without significant cross streets or traffic). Ideally slightly rolling.
2. After you warm up for 15 minutes, ride the route hard in your biggest gear. Note your finish time and your heart rate if you have a monitor.
3. Recover for 15 to 20 minutes with easy spinning.
4. Ride the course again at the same heart rate (or perceived exertion if you don't have a monitor). But this time choose a rear cog that's one or two steps larger and allows you to keep your cadence about 100 rpm. Note your time for the same course.
5. After a day or two of rest, do the test in reverse - larger rear cog (lower gear ratio) first.
6. Compare your times. For most riders, the lower gear and higher cadence will produce faster times for less perceived effort.

• Use a down hill to practice. Spin in a small gear on a slight descent, then gradually increase your cadence until your pelvis begins bouncing on the saddle. Back off about 5 rpm so (the bouncing stops). Hold that cadence and concentrate on a smooth pedal stroke for one minute. Cruise back up the hill and do it again. Relaxation is the key to pedaling at a high cadence without bouncing. Keep your elbows, shoulders and hips loose.
• Use a that tailwind that you have stumbled across. Shift into a moderate gear and gradually increase your cadence until you're at 100-110 rpm. Hold it there for 30 seconds, then gradually ease back to 80 rpm. Repeat several times.

And if you don't have a cadence function on your cycle computer, the following is the way to estimate your cadence. Set your computer display to show seconds. Using your right foot, count the number of times it is at the bottom of a stroke during a 15 (or 30) second interval. Then multiply by 4 (or 2).

Reader's Questions

It got me thinking that if I could have gone to a lower gear and used a higher cadence I could have maintained the same speed and maybe used similar power to my lighter friends? Then the conversation went to crank length (mine is 175) and the whole think started to seem overly complex with too many theories and a cafe seemed the best idea! - Bill

A. A complex question, but these comments may help to make it a bit clearer.

1. Let's assume you measured your power output at the back hub. That tells you how much work you are doing (work done by your leg muscles - generally expressed in work/minute or watts). Training is the way to increase your total power output (per minute).
2. Assume you are putting out your maximum effort and producing a certain number of watts. You can deliver this power at multiple cadences. If your cadence is higher, the work per stroke is less, but total work per minute as measured at the rear wheel is the same as if you used a lower cadence with more work per stroke. You are not going to get "more power" by spinning faster. The reason you are going slower as you go up the hill (at the same work/minute output) is that you are not only working to move the bike forward at a set speed but also doing additional work to lift yourself and your bike up the elevation of the hill.
3. The reason I encourage riders to spin at a faster cadence (90 - 100 rpm) is that there is less stress on your knee per revolution (remember, assuming a similar work output per minute, a faster cadence = less work per revolution = less stress on the knee joint, than a slower cadence while maintaining the same speed).

   An example might help. I have found the calculators at this website very helpful in sorting out questions such as this. Assuming you use the basic assumptions suggested on this webpage, and only change the cadence, you get the following:

   • 60 revolutions/minute = 260 units of force on the pedal
   • 75 revolutions/minute = 208 units of force on the pedal
   • 100 revolutions/minute = 156 units of force on the pedal
   Thus maintaining the same speed (work output) you get a significantly decreased stress on the leg (and knees) at a higher cadence.

4. Crank length is beyond me. A longer crank arm acts as a longer lever to allow more power per stroke, but again you will get more stress on the knee per revolution and I am not sure you deliver any more overall total work per minute to the rear hub than with a shorter crank and a faster RPM.
5. Heavy guys generally do better on the flats as they have more mass (and strength) per square meter of body surface area facing into the wind (which is producing resistance) than thin guys. But when you climb, you lose the advantage as you have to pull so much extra mass up the elevation gain. Basically this means you are probably putting out more work/minute) watts than your buddies and can capitalize on this on the flats. But then on a hill, you still are putting out more work per minute than you riding group, but now have the disadvantage of needing to use more of it to move a bigger mass up the grade. (see the section on energy requirements of cycling).

I was fine on gentle to average climbs because I could maintain a cadence of 90 but on any long steep climbs this would drop to 60 and I found it hard work. Using Sheldon Brown's tables I could see that a cadence of 90 on a 29 ring gave more speed and was easier on the legs than a cadence of 60 on a 25 ring. So for the mountains I have a cassette that allows me to do this which helps get my 90 kgs up the hill! Thanks again.