Using a power-to-weight ratio is an easy and effective way to determine the amount of watts to target during various efforts. It is a very simple approach that is easy for instructors to use in classes where bikes with power meters are available. With any simple approach, there will be factors to consider for those who desire to be the exception.
When riding a bike outdoors, our friend gravity gets to flex some muscle. Simply put, because of gravity’s effect, heavier riders must move more mass (weight) to propel the bike up the road, or literally, up a hill. A heavier rider must produce more power in order to climb a hill at the same speed as a lighter rider. Because of this, a person generating more power (watts) than another may not be stronger or faster when the rubber meets the road.
Besides relentlessly pressing your sore glutes into the ever-torturous seat, gravity does not play the same role indoors. On an indoor bike, riders are neither physically propelling their body weight up the road, nor are they carrying their body weight up a hill. However, generally speaking, a rider with more mass can often produce more power than a rider with less mass. Hence, a power-to-weight ratio still applies.
Power CTW: Power-to-Weight