Austin Tri-Cyclist Blog

Saturday, August 24, 2013

Pacing on the Bike

by Jack Mott
Missy Ruthven of ATC Racing finishing the Mopac TT

Position, power, and pacing are three keys to a solid time trial or triathlon bike leg performance. Obviously, you want to be capable of producing as much power as possible by training hard. We previously talked about position and equipment setup. Now let's talk about pacing. Optimal pacing gets you the most speed for your available energy. To a very close approximation, the best pacing strategy on a flat course is to hold constant power for the whole course. The most common mistake is to start out too hard because you feel good, which you pay for later.

40k TT - a little too hard the first half, but not bad
To illustrate the kind of time that can be wasted by bad pacing, we can run some numbers through the website Analytic Cycling. Suppose a 75kg rider is capable of producing 250 watts for an hour, and completes a flat 40k time trial with perfectly even pacing. This rider would complete the 40k in about 59 minutes and 24 seconds.  Now suppose that this rider makes the classic mistake of going out too hard and does 275 watts for the first 30 minutes, then starts to blow up and has to average 225 watts for the rest of the ride. This would result in a finishing time of 59 minutes and 32 seconds, about 8 seconds slower for the same average power.  That doesn't sound too bad, but in fact it would be impossible for the rider to maintain that power output of 225 watts after going out too hard.  The harder you push, the bigger the physiological price you pay, and if you start out too hard you will not be able to maintain the same average power.  A more realistic scenario is that the rider would have to drop down to something like 200 watts after starting out that hard, which would bump the time to 1 hour and 53 seconds. Almost a minute and a half slower.

So you don't have to have the new Cervelo P5 to see significant gains. You can potentially save more time by pacing properly than you can by upgrading your bike (of course, you could do both!). All you have to do is practice and ride smarter!  The most sure-fire way to nail your pacing perfectly is to use a power meter, but with practice you can do quite well without one. We will discuss how to approach both situations.

Pacing with Power

The first step to pacing an upcoming TT or triathlon bike leg is to pick a power goal.  For time trials, you should estimate about how long the event will take you to finish, and then look at your past power data to figure out what power you are likely to be able to do for that duration.  The Mean Maximal Power chart (or MMP) is very useful for this.  At a glance you can see what your best ever power production is for a given duration. For example, suppose you have an upcoming event that will take about 20 minutes.  Load up your MMP chart with some of your recent training history. In Golden Cheetah it will look something like this (WKO+ has a similar chart):

Click to Zoom
At a glance I can see that the best 20-minute power I've done is around 280 watts, but I can also see that there is a little bump around 17 minutes, where my best power is 300 watts.  This implies that I've never done an all-out 20-minute effort, and am probably capable of doing a little more than 280.  So a reasonable power goal might be 290 watts for the upcoming TT.  Be sure to take into account weather conditions and your fitness and fatigue levels when setting your goal. Hot weather will often lead to significantly less power, for instance.

Triathletes will usually want to set their power goals by doing practice bricks or by extrapolating from past races.  A great way to set a power goal is to do a bike ride that simulates race conditions as closely as possible, and then do a short run afterwards to be sure the pace left you fresh enough to run well.

Once you have your goal power, you don't want to follow it blindly on race day.  You might be capable of more, or you might have aimed to high. You need to listen to your body to some extent, but you also need to try to defy it sometimes when it tells you to slow down!  Since the most common mistakes are to start out too hard and to give up too soon, I like to use the following protocol:

1. For the first half of the event do not ever go above your goal power, but if you feel terrible, you may go under it.  This is especially important in the first few minutes.  It is okay to surge for 4 or 5 seconds to get up to speed, but then settle down, no matter how amazing you feel. It will pass, I promise.

2. For the second half, never go below your goal power, but if you feel great, start trying to raise it up gradually.  This ensures you won't totally miss out on any unexpected fitness or heroics.  We are all naturally capable of more than we think, so no matter how bad it hurts, never drop below that goal power in the second half, you can do it.

That is all there is to it. With this general approach you can almost guarantee you nail your bike legs and time trials every time. However, don't skip the section below where we talk about pacing without a power meter, because sometimes mechanical problems will leave you without your power meter, and you should be ready to perform well, and without stress, when that happens.

Pacing by Feel

The challenge with pacing by feel is the incredibly strong tendency to start out too hard.  The adrenaline of race day and your fresh anaerobic stores will leave you ready to go 100 watts or more too hard for the first few minutes, for which you will pay dearly later on.  Do not go out too hard. Do not go out too hard!

The most important thing you can do is practice. If you have a 40k event coming up, practice 40k TTs a few times. If you have a half iron race coming up, practice a 56-mile bike ride, evenly paced with as few stops as possible, and then run afterward.  Pay attention to the wind, your speed, and how you feel to get an idea if you have paced it well.  An evenly paced time trial will generally feel very easy for the first few minutes.  As you get near the halfway point, things will start to be very hard; you will not believe that you can keep up the effort the whole time.  After halfway begins the ultimate suffering that you must fight through and never give up. A well-paced triathlon bike leg will be quite different. Ultimate suffering should be avoided and used on the run instead!

With practice you will get to know what it feels like to pace evenly.  You can even borrow a power meter or use the CompuTrainers upstairs at ATC to practice.  If you do own a power meter, occasionally practice with the display covered by tape, and then review how you did after the fact. This will leave you capable and confident on race day even if something goes wrong with your power meter.

Pacing the Hills

Hills will disrupt the simple plan of holding even power. The proper approach to maximize speed on hills is to go a little harder on the uphills and a little easier on the downhills. The most common mistake is for people to launch out of the saddle and throw an extra 100 or 200 watts on the uphills. This is too much; instead, raise power by 20 to 50 watts depending on how steep the hill is, and lower it by about that much on the downhills.  For longer distance triathlons, consider putting a cap on your power output about equal to your threshold or one-hour power to ensure you don't dip into anaerobic reserves.  If you don't have a power meter, just remember to raise your power on the uphills, but don't hammer like a mad man. On the downhills don't give up and coast; keep a little bit of effort on the pedals and shift as necessary to keep moving well.  Again, longer distance triathletes may want to consider coasting on any decent downhill to conserve energy for the run to come. Time trialists and short distance triathletes should keep pedaling whenever possible!

Pacing the Wind

Wind follows the same pattern as hills, but to a much lesser degree.  The harder the headwind, the higher you should raise the power, and the stronger the tailwind, the more you should reduce your effort. However, the optimum change is very small, only 2 to 4 watts in either direction.  This is so small of a difference that it can be hard to put into practice even with a power meter, so you can feel free to just ignore it and pace evenly for the most part.  Exceptions include cases where the tailwind on one part of the course will be so strong that you run out of gear. In extreme cases like that, you will want to push much harder into the headwind since you will get a forced rest with the tailwind.


  1. Great info, what do you watch for power on a Garmin, current power, 3 sec, or 10 sec average?

  2. If your head unit allows it, I like to have one display showing the average or normalized power for the whole TT, and another showing a current average. Use whatever time duration (3, 5, 10 seconds etc ) works for you. The ideal one will depend on your typical cadence, and type of power meter. Be sure your head unit is set to *include* zeros!