Why smart cyclists train with watts

Watts don't just brighten your indoor existence; they can light up your ride, too. The same energy used to make bulbs glow is similar to what you can create on your bike (stationary, road or mountain) without a plug. Your manmade power comes from within—or more specifically, the combination of RPMs (i.e., your cadence) plus how much torque you put on the pedal, explains seven-time Ironman triathlete and Equinox cycling instructor Robert Pennino.