Pacing a sportive with a power meter

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Joe Friel is an endurance sports coach best known as an elite triathlon and cycling coach as well as the author of The Cyclist's Training Bible, The Mountain Biker's Training Bible, and many books on triathlon.

In this article, adapted from his latest book The Power Meter Handbook, Joe applies his extensive knowledge of training with a power meter to the demands of training and taking part in sportives.This is an advanced article, aimed at riders who are using a power meter to complement their training. To get the most from his article, you will also be using Training Peaks software to log and monitor your training.

Joe makes a number of technical references in the article, including the following:

Normalized Power

Training Peaks software uses an algorithm to calculate an estimate of the power that you could have maintained for the same physiological “cost” if your power output had been perfectly constant (as on a static bike), rather than a ‘real’ ride. This gives a better estimation of how hard you worked than Average Power. Imagine a session on the road that consisted of 2 hard intervals at 500 Watts and 2 rest intervals at 100 Watts. Average Power for that session would be 300 Watts, but those 500 Watt efforts would have hurt more than that! Variability in a session means that the overall average power for a ride or part of a ride is often a poor indicator of the actual intensity of the effort. Normalized Power would calculate a figure that more accurately described how hard the session felt, based on your:

Functional Threshold Power (FTP)

The power output that you can produce which relates closely to your lactate threshold – the intensity at which lactate begins to accumulate in your blood. This is a powerful predictor of your endurance performance ability. FTP is often is often determined by looking at your Normalized Power over the duration of a 1-hour race, or during a test of c.30 minutes. When training with power, your Zones will be determined by first discovering your FTP, with each Zone being a percentage of this.

Finally, Joe refers to ‘match burning’ and has included a ‘Match Size’ table for reference. What Joe is referring to is that you only have so many hard efforts or attacks that you can make in each event – only so many matches in the box. This is why riding steadily, and the Variability Index to which Joe refers, is so important.

Pacing a Century or Cycling Sportive

Pacing is critical to your performance when it comes to riding a long event such as a century or cycling sportive. This has much to do with how efficiently you use energy—especially your precious glycogen stores. Glycogen is the carbohydrate-based fuel your body will use, along with fat, to produce energy to turn the cranks. There’s some mix of the two fuel sources being used throughout the ride. Your glycogen supply is limited, however; you may have 1500 to 2000 calories of glycogen socked away, mostly in your muscles. If you go hard and fast for a while, you’ll burn more glycogen and less fat. If you slow down, the blend of the two fuels will reverse and your body will rely more on fat.

Since you have only a small amount of stored glycogen to draw from, but lots of fat (even the skinniest rider has 30-40,000 calories of fat stored away - enough to ride for a few days), you’ll need to take in carbs while riding in the form of sports drinks, bars, gels, or whatever you like to eat and drink while riding. The problem is that your gut can process only a limited amount of such stuff—probably 200 to 350 calories per hour while riding, depending on your body size and a few other variables. If you take in more than your digestive system can process, the carbs (and whatever else you may have consumed along with it) will just sit there causing a bloating feeling and perhaps nausea. That’s not good.

Glycogen is clearly a valuable resource, so it is wise to be very conservative in your expenditure of glycogen during your century to avoid premature fatigue. The way to do this is to manage your intensity and strictly limit your surging during the ride. It takes more glycogen to surge than to ride steadily, even if in the end your average power output is the same. Every time you surge, such as when you try to prevent someone from passing you, charge up a hill, or hook up briefly with a fast-moving group, you burn glycogen at a much higher rate. If you do this repeatedly during a long ride, even though you are taking in carbohydrate, you are likely to get behind the fuel output-input curve. In other words, you may start running low on glycogen. If that happens, the party’s over. This is called “bonking” and is one of the greatest challenges facing the serious long-distance rider.

The key to steering clear of the feared bonk is to take in carbs at a known manageable rate and pace your ride fairly steadily. The first part, refueling, has to be determined in your training rides. It’s largely based on experience—trial and error—as we’re all different when it comes to refueling. The second part, pacing, has to do with Intensity Factor (IF) and Variability Index (VI).

Let’s start with Intensity Factor (determined by dividing Normalized Power by FTP). This is your primary pacing guide throughout the ride and is displayed on most handlebar head units. Since sportive and century distances are typically anything from 70 to 160 km (42 to 100 miles), and the rider’s capacity for exercise (“fitness”) may be either very high or very low, it’s not possible to specifically tell you what your IF for the ride should be. All we can say with some sense of certainty is that your IF will be between 0.50 and 0.90 (meaning you’ll ride at 50-90% of your FTP). That’s a huge range that needs to be narrowed considerably through training rides that eventually reach about 80% of event distance.

This IF should serve as your effort focus as you ride in the event. But there will obviously be reasons to go harder or easier due to terrain, wind and drafting. This brings us to the Variability Index.

The Variability Index is a feature of the WKO+ software and that tells you how steadily you rode. It’s found by dividing Normalized Power by Average Power. If they are exactly the same then your VI is 1.0 (again, VI is commonly displayed on head units). That means you rode very steadily. If you changed pace, or surged, frequently then your VI will increase to something greater than 1.0. For your event, and for most of your key, event-rehearsal workouts, you should aim to keep your VI at around 1.15 or less. If it goes above 1.15 then you are likely wasting a lot of energy.

“But,” you may ask, “what if there are hills on the course? Won’t that cause me to not ride steadily?” Yes indeed, hills will affect your VI. How much depends on how aggressively you ride up the hills. If you surge and slow down repeatedly on a long hill or aggressively attack short ones, your VI will go way up. Instead of that, the idea is to ride up hills at an intensity you can steadily maintain to keep your overall VI in the neighborhood of 1.15 or less. That’s the premise of the table below, which you can think of as your match-burning guide. It suggests that on hills you can increase your power output by up to two zones. For example, since most long sportive and century rides are done in power zone 2 (IF of 0.55 to 0.75), depending on how fast the rider is, then hills are best climbed in power zone 4. How long you can safely stay in a higher zone and how much cumulative higher-zone riding you can do in such an event is also suggested in this table. This is only a rough guideline as some people can handle more, and some less. Once again, the only way to learn what you can manage is to rehearse it on your longest training rides.

Goal Base Zone (IF) for Most of the Ride

Zone (IF) That Burns a Match (and Upper Limit of Intensity)

Duration in Zone That Burns a Match (May Vary)

Recommended Cumulative Match Duration for Event (May Vary)

Zone 4

(IF 0.91-1.05)

Zone 6 (IF >1.20)

>1 minute

<5 minutes

Zone 3

(IF 0.76-0.90)

Zone 5 (IF 1.06-1.20)

>2 minutes

<10 minutes

Zone 2

(IF 0.56-0.75)

Zone 4 (IF 0.91-1.05)

>5 minutes

<20 minutes

Zone 1

(IF <0.55)

Zone 3 (IF 0.76-0.90)

>15 minutes

<60 minutes

That brings us to the 50-40-30-20-10 Rule. As you’ll see, it is fundamentally important to your performance. The Rule says that when you are riding along at 50 kilometers per hour (about 30 mph), you’re going down a hill. During your sportive or century, don’t try to go any faster. Instead, conserve energy (that precious glycogen) by getting as aerodynamic as you can and coasting down the hill. As you begin to slow at the bottom of the descent to about 40 kph (25 mph) you can begin to pedal again, but not hard. Keep the effort low. You’ll be in zone 1. As the speed decreases to 30 kph (19 mph) pedal harder. This should be close to your average speed for the flat sections of the ride—within a couple of miles per hour—so your wattage should be what you trained for on flat terrain. That’s your base IF.

When speed drops to 20 kph (about 12 mph), you’re probably going up a hill. At this point, pedal harder so that your power rises slightly above your normal output on flat terrain. This harder pace is likely one zone above your base IF. On really steep uphills you’ll slow down to around 10 kph (about 6 mph), so here you should pedal quite hard. This is when the match-burning kicks in and you’re two zones above base IF (see table).

If the speeds I’ve suggested don’t match up with what you expect to do for the event, change them. Instead of 50-40-30-20-10 you may decide to go with 45-35-25-15-5. That would mean 25 kph (15 mph) is your intended average speed for the century, not 30 kph. So you can make slight adjustments to the Rule, but the concept remains the same.

Without a doubt, Intensity Factor and Variability Index are the most important predictors of a successful sportive or century ride. And, of course, you must take in adequate carbohydrate just as Goldilocks would do—not too much and not too little.

British Cycling Members can save up to 40% off TrainingPeaks Premium Athletes Edtion.

Joe Friel is the author of The Power Meter Handbook, A User’s Guide for Cyclists and Triathletes, and other books on training.

Pacing a Century or Cycling Sportive

Adapted from The Power Meter Handbook by Joe Friel

© Joe Friel 2013


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