The Coaching Files: Everything You Need to Know About Power To Weight Ratio
Chris Carmichael

To reach the top of Cheyenne Canyon in Colorado Springs in 20 minutes, you have to have a power-to-weight ratio (PWR) of 4 watts per kilogram. When he was with Discovery Channel Tom Danielson set the record on this climb during a 2006 visit to Carmichael Training Systems, stopping the clock at 13:34 (6.7 watts/kg). PWR is the great leveler; it’s the measure that allows us to compare the strengths of cyclists side-by-side, even when the riders vary greatly in size. Take for instance, two of my coaches, Craig Griffin and Lindsay Hyman, who made a deal to see who could be first to break 20 minutes up the 5-kilometer, 1200-vertical feet ascent. The winner got coffee for a month. Griffin is 5-foot-10 and weighed 76 kg and Lindsay is 5-foot-3 and weighed 55 kg, four weeks before their final showdown, they were both sitting within .25 watts/kg of reaching their shared target.

There’s far more than free coffee riding on the PWRs of the world’s top riders – it can translate to minutes gained and lost on the steep slopes of the Alps, Pyrenees, and Dolomites. The Holy Grail is a maximum sustainable power of 6.8 watts/kg for 30 minutes – the power to weight ratio necessary for winning the Tour de France. And as more and more cyclists buy power meters, questions and confusion abound about this crucial measure of performance.

How do I determine my PWR?
First of all, power to weight ratio isn’t a static number, but rather a number that corresponds with a specific time. For instance, 6.8 watts/kg for 30 minutes. For 60 minutes that same rider would average lower, like 6.4 watts/kg; and average higher, maybe 7.0 watts/kg, for 15 minutes. Following a good warmup, a 20- or 30-minute time trial effort is a good test for most amateur cyclists because they can maintain both consistent power and focus for the entire time. Determining weight is much easier; just divide your weight in pounds by 2.2 to convert to kilograms. Then divide your weight into the average power from your time trial. Example: Griffin weighed 76 kg and his 20-minute time trial power was 275 watts, so his PWR for 20 minutes was 3.6 watts/kg (Lindsay’s sat at 3.8 watts/kg. Craig had some work to do).

Is the weight of my bike factored in?
Not typically, but a light bike will help because cutting weight on the bike will effectively increase your PWR. The danger with factoring bike weight into your numbers is that it provides athletes with a way to “buy” their way to their goal PWR, and that means they often stop working to optimize power output and bodyweight. I prefer to maximize a rider’s PWR regardless of the bike, and urge athletes to consider a weight-savings on the bike as an added race-day advantage.

Does PWR change throughout the year?
Yes, and that’s perfectly normal. Elite racers aim to be as strong as possible when they are also as light as they can be, but this is a delicate balance that can’t be maintained for very long. Most experienced cyclists can expect to see a 15% change from the lowest to highest PWR they see during the year. Since it’s far easier to make PWR go down than up, changes greater than 15% within a year often indicate that experienced cyclists either gained too much weight or decreased their training load too much during the fall and winter.

Which is more important, losing weight or gaining power?
For novice cyclists and experienced riders who are carrying around more than 10 extra pounds, losing weight and gaining power are equally important and equally achievable through focused training and good nutrition. This also means that heavier cyclists can make bigger improvements in their PWR because they can attack both parts of the equation. Between the two coaches in my office, this favored Griffin and put Hyman at a disadvantage because she’s already very lean.

Let’s use Cheyenne Canyon and a 75-kg rider with a max sustainable power of 250 watts as an example of the impact of weight and power output. The climb averages an 8% grade for 5 kilometers. Dropping 2.5 kilograms (roughly 5 pounds) with a power output of 250 watts would cut 38 seconds off this rider’s time. Improving power output by 10 watts without any weight loss cuts 41 seconds off his time. This increases to 85 seconds if you improve power output by 20 watts. When you combine losing 2.5 kilograms of bodyweight with a 20-watt increase in sustainable power (both of which are attainable for most cyclists), this rider would go 2:03 faster up Cheyenne Canyon.

Can PWR make a big guy into a super-climber?
Sorry Sasquatch, but no. Losing weight and improving your sustainable power output will help any cyclist go faster uphill, but there are physiological limits on how light you can get while maintaining a high power output. And here’s the test: if you’re leaner than you’ve ever been and you’re average power output on climbs starts to decline, you’ve reached the tipping point for PWR. Back off on your training, gain 2-4 pounds, and you’re likely to see your power comes back up. From now on, that represents your minimum allowable weight, and improving PWR depends on training.

Does PWR matter if I’m not climbing big mountains?
Unless you’re a downhiller, there’s no place in cycling where it pays to be heavier. And yes, that means even track sprinters, criterium specialists, and time trialists. The gravity tax may be less extreme when you’re riding on flat ground or a velodrome, but acceleration is paramount in racing and riding with groups, and a higher PWR means you can handle accelerations better.

Where do you stack up?
There’s more to winning races than PWR, and there are exceptions to every rule, but a rider’s 30-minute PWR gives a good indication of whether you have the strength to compete at the next level. Differences in the size/depth of the fields and nature of the races lead to different PWRs for men and women in this chart.

Warm up for 15 minutes, including some fast pedaling efforts to loosen up your legs and get your heart pumping. Then you’re doing sets of three 5-minute climbing efforts. In each set, the first interval is at a Tempo pace (88-90% of time trial heart rate, 81-85% of time trial power), the second is at your Max Sustainable pace (95-97% of time trial heart rate, 95-100% of time trial power) and the third is the Extra Gear (95-105% of time trial heart rate, 100-105% of time trial power). Recovery between intervals is 5 minutes, recovery between sets is 10 minutes. Beginners should do two sets, intermediate cyclists (Cat 3, Masters) should do three sets, and advanced riders should do four sets. Be careful with these, they won’t seem terribly hard in the beginning because their short, but they’ll kick your butt by the end.

Last Updated: 5/14/2008