For most of cycling history, riders gauged their effort in steady-state events such as time trials, centuries, brevets and solo breakaways by their perceived exertion. Canny riders got really good at apportioning their energy for the length of the event. They quickly learned, by trial and error, how hard they could pedal and still have enough left to avoid slowing drastically in the final miles.
It isn’t very difficult on a flat, windless course, but skilled riders learned how to dole out their effort on hills and into headwinds as well. The goal was to finish at top speed but at the same time with nothing left in their legs. It was a calculation with little room for error.
When heart rate monitors first appeared, they promised to transform the art of pacing into a science. It seemed simple: Just figure out in training the highest heart rate you could maintain for the duration of the distance and then keep effort at an intensity that elicited that heart rate. Presto! The perfect pace.
Unfortunately, it doesn’t work that way. Heart rate turns out to be a slippery beast, changing from day to day for a given power output because of factors that include hydration status, lingering fatigue and even mental state.
A phenomenon known as cardiac drift plays a role, too. If a rider keeps his power constant over an effort of, say, an hour, his heart rate will inexorably rise even as the effort stays steady. So if he gauges his effort by heart rate alone, he’ll slow down when he might have been able to go faster.
And pacing with a constant heart rate means that you must slow on hills and into headwinds. But studies show that it’s better to increase the intensity a bit in those conditions, then recover slightly with the help of downhills or tailwinds. Pacing with a constant heart rate makes that impossible.
With the advent of power meters a new way arose to find the perfect pace. In theory, you can simply keep the monitor on the wattage you know from training that you can sustain for the distance. Power meters tell you exactly how many watts you’re producing, so they’re a much more objective measure of effort than heart rate. But power meters are expensive — though more and different types of units are coming out all the time, driving the cost down.
What’s the best way to ride at your unique optimum pace for a given distance? At a conference we attended in the past, Joe Friel, author of The Cyclist’s Training Bible and other well-known books, shared three key techniques for riding the fastest possible time.
Ride a Negative Split
In any event that lasts 10 minutes or more, years of experience have taught us that it’s better to ride the second half slightly faster than the first half. According to Friel (right), the first half should take 51% of the total time and the second half should take 49%.
“If you go too slowly in the first half of the race,” says Friel, “you’ll never catch up in the second half. Start too fast and you’ll build up too much lactate. That’s inevitable in steady-state events lasting less than 60-75 minutes, but it’s easier to tolerate high lactate for a short period at the end of the race than to fight it all the way.”
Most cyclists neglect this advice, start too fast and crawl to the finish in misery. Why? Friel argues that many riders lack confidence. They take off at blazing speed to prove to themselves that they can do it. Then they blow up. They seem to believe, irrationally, that time gained early in the race is greater than the time gained later. Finally, Friel argues, many riders lack self control in competitive situations.
Of course, a 51/49% time split isn’t your best bet depending on terrain and wind. For instance, in an out-and-back time trial with a strong headwind going out and the corresponding tailwind for the second half, the time split may be more like 60/40% while the intensity (due to thechanging wind) is 51/49%. Experience and a finely honed sense of perceived exertion aid riders in these situations.
Maintain Nearly Steady Power
Suppose you had a power meter and used it for several time trials. You’d quickly see what studies show: Power is a more sensitive metric than heart rate or perceived exertion.
And you’d learn another fact unearthed by exercise scientists: A steady power output results in less fatigue than a variable power output.
For instance, with a power meter you could compare how you felt after two training rides done at the same average wattage. Suppose in ride No. 1 you rode steadily at a moderate pace. In ride No. 2 you alternated flat-out efforts of 3 minutes with 3 minutes of easy pedaling. Even though your average wattage was the same, I bet you were much more tired after the second ride.
But we also know that it’s advantageous to increase power on climbs and into the wind because you can gain more time in these slower parts of the course. You spend a greater percentage of total time on slow sections because — surprise! — you’re going slower. So the opportunity to gain time is greater.
Friel argues, based on research, that fit athletes can manage a 5% variability in pace without paying dearly for it. So the greatest gains come from riding about 5% harder on climbs and into headwinds and then reducing intensity about 5% on descents and with tailwinds.
Tune in to Cardiac Drift
According to Friel, heart rate is input — how does your body feel? Power, on the other hand, is output — how hard are you working?
Comparing input to output is a good measure of stress. Time trials are won with high power, not with high heart rate. No one gets on the podium because they recorded the highest number of heart beats per minute on the course. But monitoring both indicates the direction of adaptation: Is training making you better or worse?
As we have seen, it’s normal for your heart rate to slowly rise over the course of a steady-state effort even when you’re keeping power output the same. The less of this cardiac drift you experience, the fitter you are. If you can generate more wattage with less variability in heart rate, it’s a good indication that your training is going well.
This power/heart rate variability index has other functions:
- It indicates aerobic endurance. If you can maintain higher wattage for a given period today than you could a month ago — without having your heart rate creep up — you’ve gotten fitter.
- It shows your adaptation to heat and altitude. Good adaptation means that power goes up and heart rate goes down — and stays down — for a given power output compared to earlier in your training program.
Friel discussed a Phoenix triathlete who, because of his job, had to train for the Hawaii Ironman at midday. Because he became accustomed to riding hard in temperatures over 100F (38C) degrees, he didn’t have problems in the heat of Kona. Using the variability index allowed him to track his adaptation and cut training short when he was in danger of heat illness.
- It helps determine your power/heart rate ratio. The key is whether it changes from the first half of the event to the second half. The goal, Friel says, is a change of less than 5%.
Power Meters vs. the Alternative
It’s easier to follow Friel’s three suggestions for more efficient time trials if you have a power meter. Using one with the appropriate software enables you to chart the power/heart rate variability index and keep your uphill and headwind power within 5% of your downhill and tailwind power. It makesnegative splitting easier, too, because if you know the wattage you can average for the distance, you can work at a few watts less in the first half of the race, saving something for a faster finish.
What if you don’t want to invest money in a power meter and software, and time in analyzing all the data? Old-school perceived exertion still works. It’ll take some trial and error and you’ll need to listen carefully to your body. But many successful riders have found that they can feel the difference between the pace needed in the first half of a race compared to the second, faster half. They can also feel the added 5% effort on hills and into headwinds.
Pacing by perceived exertion has two other important benefits. You’ll become keenly attuned to your body’s reaction to varying conditions. And you’ll be able to spend the money you saved on something else to help make you faster.