Leading into ‘what’s strong with me’ day 4, is to describe what the cost of cadence/rpm is on your heart rate. My background is in the cardiac field and since the early days when polar heart rate (HR) monitors were introduced, since HR is a physiological manifestation of the body’s response to exercise; or load (power and volume) on the system, HR has been the means to measure that response.
Back to cadence and an exercise in what I mean by ‘cost’. Do this next time on the bike; warm up gradually over 5 minutes, starting at 85 rpms and up to 105 rpms maintaining a light gear and low tension. Note how your HR picks up as the cadence picks up, as the load is gradually picking up as well. Respiration goes up, your cardio/resp system is adjusting cardiac output, increasing it as a response to the need for O2 and fuel.
Now quickly increase your cadence to 120 rpms for 10 seconds; HR will increase quickly. Then HR will drop back down when cadence goes back down. Do this 3 times and the ‘cost’ to your system is the increased need for more HR in response.
Then do the same with load/tension, by increasing the gearing while reducing cadence so that power gradually increases – measured by Watts. At this point you’re warming up the skeletal muscle and you’ll find that the HR doesn’t respond the same way – it will eventually go up to a similar HR but the load and perceived exertion will be higher than it was with cadence.
An efficient rider will have a cadence (and load) that provides the most power over time with the least ‘cost’ to the system. Mashers (low cadence) are using more skeletal muscle, the fatigue factor will be higher even with a lower HR. Spinners (cadence over 105 rpms) will fatigue due to the cardiac system working too hard; both types will experience the ‘cost’ of high or low cadence.
Where is all of this leading? 2 things.
- Find your most efficient leg speed, one that you can maintain power without pushing up the HR.
- Practice different leg speeds during your repetitions to have your muscles become efficient at them, without driving the HR up.
That ability, is what’s strong with me.
- more on how to increase power without increasing the ‘cost’ on day 5