So, if we're riding, say, a 20-minute interval, we press the "interval mode" start button and then constantly adjust our pedaling effort so that the interval's resulting average power reading (in Watts) is within our 20-minute training power zone. If the reading is too low we pedal harder; if too high we back off a bit. We then dutifully record this reading in our training logs for future reference. Just for an example, here are my training zones (we rarely train below Level 4 unless we're too dog-tired to do any better):
- Level 4: 246-285W
- Level 5: 286-332W
- Level 6: 333-600W
- Level 7: as high as possible!
Others of us use the current ("instantaneous") power display. It shows the power we're producing at any given moment. I do this to learn how to pace myself as smoothly as possible. The experts agree, as do my legs, that smooth and steady is more efficient. And more efficient is faster and more sustainable over time. Per Matt Russ: "A variable effort is more fatiguing to the body when compared to an even, steady effort." I am pretty much always able to hit my power training zones on every interval, day after day, week after week. I suspect my even pacing gets some credit for that.
So, which is best? Neither; both can work just as well. Try both and see how they work for you...
OK, I admit I prefer current power since our intervals are designed for a specific power level, not the average of wildly fluctuating power. And constant power spikes tire us out; that can jeopardize our power during a tough workout. Check out the following graphs, which charted my power during two similar intervals (the yellow line is power in Watts):
Which one do you think yielded the best average power? The left one did, which may not be surprising if you look at how smooth the yellow power line is on it, compared with the jumpy yellow power line on the right graph. I hope those graphs make my point for me: Use the current power display and try to keep the power exactly where you want the average to be when you're done with the interval.
But it brings up another topic: pacing strategies for time-trials (solo races against the clock). The steady pace that is best for intervals isn't always best for TTs (or other races). But even then I'm convinced current power display is better because it allows us to nail our power level exactly to suit the TT course. But... that is a big topic worthy of a separate blog post. In the meantime, here are some links to pacing articles:
- Research Institute for Sport and Exercise Sciences: Pacing strategies during a cycling time trial with simulated headwinds and tailwinds
- John Hawley: Pacing: A Matter of Strategy
- Joe Friel: Time Trial Pacing
- BioMedSearch.com: Effect of pacing strategy on cycle time trial performance
- Matt Russ: Using a Power Meter for Triathlon Pacing