This is a repost from the SB Tri Club Coach’s Corner blog, April 2013, in case it looks familiar to anyone…
I just re-read parts of Joe Friel’s latest book, Power Meter Training, which got me thinking. As athletes gear up for the next set of early season races, I wanted to present some data to help you with the pacing of your bike ride. Friel discusses the concept of a Variability Index (VI), the ratio of normalized power to average power for a ride, which in non-power user’s terms means even pacing of your effort over the course of the whole ride. For this discussion let’s focus on the half Ironman distance, specifically the Wildflower Long Course race, which many of us are familiar with. The same concept will apply to the Olympic distance race, except you just have to push the pace a little harder.
If you think about racing a bike race versus a triathlon, in a bike race there are lots of surges, very hard and short efforts, while in a triathlon there are very few surges (not including the pros and/or top age groupers, who may be battling with the fellow competitors in draft free battles.) Hard surges produce lots of acid that the body has to deal with, and in a bike race it’s possible to sit back and draft and hopefully recover from the hard effort to get ready for the next attack. In a triathlon that would mean slowing down, losing time, so it’s better to maintain a steady level of effort (lower VI), and if you’ve got a power meter that means knowing your race goal power. For non-power meter users, that means knowing a HR or HR zone that you want to stay in.
Friel adapts Alan Couzens concept called The 50-40-30-20-10 Rule, as seen in the following table, so that a person that averages 19 MPH (~30 KPH), can use their speed on a particular part of the course to judge how hard they should be working. (If you average 40 KPH, adjust the numbers accordingly.)
|The 50-40-30-20-10 Rule|
|If your goal (power) for the race is expected to produce an average speed of about 19 MPH, then…|
|When your speed is||You should|
|Greater than 31 MPH||Coast – get aero and stop pedaling|
|About 25 MPH||Decrease your power output below your goal power|
|About 19 MPH (~30 KPH)||Ride steadily at goal power|
|About 12 MPH||Pedal a bit harder above goal power|
|About 6 MPH||Go well above goal power|
|Note: Borrowed from Joe Friel’s book, Power Meter Handbook, which he adapted from Alan Couzens concept on when you should pedal hard during a triathlon, and when you should coast and enjoy the ride.|
If you were riding a flat course, averaging 19 MPH, then you would ride the entire distance at your goal power, maybe something like the Ventura Tri course, multiple loops on a flat course, only dealing with the wind, your VI would be around 1.0. As we know, the Wildflower course is anything but flat, so here’s how you should be doling out the effort.
Ignoring the first hill out of T1 to the top of the bike course, you should be riding in an easy to moderate effort to get settled in on the bike, taking your time to find your rhythm through the part of the ride where you hit the first downhill after the entrance to the park where they check you in. You’ve got two short climbs after that when you’ll have to start adding more power/effort before exiting the course, turning onto Interlake Road. From here on out follow the guidelines from the table, coasting on the faster downhills, recovering, while pushing the uphill sections, remembering to finish over the top of each hill to gain momentum heading down the next downhill.
The reason you should not be pushing hard as your speed increases is that to go from 24 to 30 MPH (a 25% increase), you’re fighting wind resistance, the effort involved changes exponentially, not linearly, so you have to add so much more power to go a certain percentage faster, which just doesn’t give the same return in time saved. Racers in all sports, car, motorcycling, bicycling, have learned that to go faster overall you have to go faster in the slower sections of the course, where you make up the most time. As they say, everyone can ride (drive) fast in the fast sections, it takes more skill/power to ride (drive) fast in the slow sections.
If you were riding the hilly parts at 8 MPH and want to go 10 MPH (the same 25% increase as above), the amount of power increase would be less than going from 24-30 MPH, so more bang for your buck, as you ride away from people that are conserving on the hills, trying to push hard on the fast sections, while you get aero and recover.
How does this help you with your Variability Index? By not over-doing the faster sections, controlling your hard efforts on the hills, your power spikes will be reduced, meaning less acid build up in the body, lessening the need to slow down to recover, so you can maintain a high level of effort/power.
Dave Scott said years ago that he hardly ever went anaerobic during his Ironman races, maybe 1-2 times during the entire 112 mile bike ride, as he did not want to slow down to recover to get back on pace. Six Ironman World Triathlon Championships later, Dave’s advice is still sound today. Put that together with the 50-40-30-20-10 Rule, pace your bike ride correctly, evenly, and come off the bike ready to put in a hard effort on the run.
Try this in you final training days leading up to the race, your race focus training, and see how you can smooth out your power delivery to get ready for a Wildflower PR day. Good luck with your training!