The Ultimate Ratio
Among athletic circles, it's generally believed that the ideal power-to-weight ratio is about 3 watts per pound [source: Kessler].
Power-to-Weight Ratio Explained
If you're looking for a getaway car, you might think about picking up a motorcycle. They're easier to park, for starters, but they're also much faster. Take a standard six cylinder car for a test drive, and you'll probably be able to top out at no more than 120 miles per hour. Put that engine on a motorcycle, however, and you'll be clocking in at a devil-may-care 300 miles per hour. The motorcycle's advantage is its smaller weight. Rather than hauling around a few thousand pounds of windows, doors and cup holders, a motorcycle is little more than two wheels, some handlebars and a seat. What it all boils down to is more bang for your power buck. Since the engine has less to haul, it can focus more on speeding up.
The same principle applies to athletes. By cutting on down the amount of weight they're carrying, an athlete can increase his or her speed and endurance. The more power an athlete has per pound, the higher the power-to-weight ratio. Generally, athletes measure their power-to-weight ratio by pounds per watt. They take the amount they weigh and divide it by the amount of power they can produce, measured in watts. (Most modern treadmills and exercise bikes come with a function enabling you to measure your watt-output.) Generally, an elite triathlete will produce about 400 to 500 watts -- about half the power needed to run a microwave.
Now, consider two runners: a short, 160-pound runner (let's call him Shorty) who can generate 440 watts of power, and a large, 230-pound runner (let's call him Bruno) who can generate 600 watts of power. Bruno's legs are obviously more powerful, but he would lose a race to Shorty. Bruno has a power-to-weight ratio of 2.6 pounds per watt, while Shorty has a slightly better power-to-weight ratio of 2.75 watts per pound. If Bruno was 218 pounds, then the two runners would be evenly matched. As it is, however, Shorty has the advantage.
For "sedentary" sports such as archery and curling, the power-to-weight ratio is almost irrelevant. But in any sport that involves crossing long distances, it's become gospel truth. Rock climbers will go to great lengths to cut down on the extra weight in their rucksacks -- so you can assume they've given ample thought to slimming down their body weight, too. Rowers are known for their low body fat ratios, and the average professional team will spend tens of thousands of dollars to buy as lightweight a boat as possible. Formula 1 drivers are probably the biggest power-to-weight ratio junkies of anyone. The power-to-weight ratio of a standard Formula 1 car? Four hundred and twenty-two watts per pound [source: Essential Style].
Keep reading to find out how a good power-to-weight ratio can get you airborne.