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June 4, 2009
NEWS & RACING BROUGHT TO YOU BY CHAPTER2 BIKES
Torque is a measure of how much a force acting on an object causes that object to rotate. Force per pedal stroke basically. Power is a product of torque and rotational speed (i.e. cadence).
The power graphs below are a good visual example of the difference in torque and power and how it relates to the way you ride.
In the first graph (labeled “Torque”) I did a local climb at 60rpm in a big gear. I averaged 369watts and 27 Nm of torque. This is a great training exercise for building strength endurance.
In the second graph (labeled “Power”), I did the exact same climb and averaged 361 watts (nearly the same ave power). However, the main difference in how I rode this climb is I used a higher cadence of 80rpm. This resulted in 11% less torque of nearly 24 Nm. The speed was over 2.5km/hr faster in the second climb (even though the power was slightly lower) because I’ve lost about 5 or 6kg since. Amazing how much of a difference a few kg’s will make when climbing.
Greater torque and muscle tension is useful in training to increase strength. In the beginning 3-4 weeks of a 12 week training block doing 2 x 20mins of these strength endurance (SE) intervals a couple times a week will have a great effect. However, this isn’t good for racing as the added stress to the muscles cause damage and fatigue. There’s an old adage, “save the legs, not your gears” The biggest thing that you’ll notice when racing with the PROs is their very high cadence – especially in the first half of the race. They are clearly saving the legs in anticipation for later.
Glycogen is stored in fast and slow twitch muscle fibers, with the vast majority in the slow twitch fibers. In other words, fast twitch power is extremely limited (fast twitch is what you’ll use when powering up a hill in a big gear). It makes strategic sense to use the slow twitch fibers as much as possible by spinning quickly up those hills and save that fast twitch muscle glycogen for when it’s really needed (i.e. when the winning move goes up the road).