Real World Power Meter Application In Racing

by: Matt Dixon

Do you have trouble pacing the bike leg of the triathlon? Do you have a power meter but aren't quite sure how you should be using it in racing? Below I share my thoughts and practical tips on utilizing a power meter in triathlon racing to maximize speed and achieve your best performance on the day.

There is little doubt that adding a power meter to your arsenal of riding tools is of high value for most athletes. The measurement of objective output throughout training can supply you with immediate feedback during a training session as well as valuable perspective following the session and over time.  A power meter can also be useful in racing, but successful utilization requires some serious understanding of what happens with your output in different conditions and terrain.

It is not difficult to find articles and resources that outline calculations and algorithms for you to find your ‘race power’ relative to your training or maximum potential.  Many coaches will tell you to get onto the bike portion of the race and simply plug into race power. By way of reference, the most common race efforts are roughly promoted as:

IRONMAN Bike Racing:  70 to 80% of Functional Threshold (lower the longer the bike ride will take you).

IRONMAN 70.3 Bike Racing:  80 to 95% of Functional Threshold (lower the longer the ride will take you).

Easy right?  You ‘know’ your power, so we can remove all of the human element and simply plug and play.  All elements of intuition, internal pacing, and management of terrain are simplified to sticking to a narrow range of power.  While there is nothing wrong with creating a framework for a range of power that an athlete can safely sustain, it doesn’t tell the whole story of triathlon bike riding and can’t be applied universally to every course.

Let me give you a specific example that would unhinge this approach.  If you had a stretch of road that was 3-4% uphill for 5 km, then was 3-4 % downhill for 5 km, your fastest route to navigate would not be to maintain the same power up as you would down.  The grade on the uphill makes the production of power easier to generate for most riders, and the speed return is high for the little extra work.  In comparison, forcing yourself to hold onto the same power downhill causes metabolic stress with limited speed return for the effort.  The faster you go, the greater the work needed to add incremental speed. Unfortunately, using our World Championships as an example, if you flatten the course at the Hawaii IRONMAN you will either leave a lot of unused speed on the course, or you will likely blow yourself to bits with high effort going downhill.

As discussed in previous writing, I identify the power meter as a tool of feedback, not an instrument that should shackle you. Let's consider a few real world influences of power output on the bike, which are ignored if you simply decide to rigidly stick to a narrow range of power.

Different grades: Athletes will always have their own favorite grade that allows them to generate their optimal power for a given metabolic stress.  If you ask any rider to perform a best effort trial on flat terrain, then repeat on a smooth grade, the flat terrain will always produce less power.  This has a real world application to the power you can expect to generate when riding a race as effectively as possible.  Riding the same power on the flats as on a grade isn’t the fastest way to navigate the terrain.

Headwinds and tailwinds:  If you are sitting on a stretch of road with a strong tail wind, you will typically find it more challenging to maintain the designated power relative to riding in the opposite direction.  Interestingly, the reward of retaining the high power output with a tail wind typically results in minimal speed gain, with each 0.5 mph speed gain requiring more and more power to create.  If you stubbornly ‘hold your power’, you have a high risk of under-riding sections that present a headwind, while over-working the tailwind sections with a minimal speed reward.  At the end of the day, it isn’t who holds the most power, but who goes fastest, then runs well off the bike.

Rolling Terrain:  Terrain management is a key component to maximizing speed relative to your output.  By loyally holding to a narrow power range you will undoubtedly fail to utilize the variance of terrain in your favor for the fastest navigation.  Imagine a piece of rolling road which has a grade up, a crest, a small descent, and finally a valley at the bottom leading into the next ‘roller’.  Holding a tight power range throughout this piece of road is not the fastest way to navigate. If you instead push just above any power range or level heading up the grade, accelerate the bike over the crest of the hill with a small ramp of power and/or cadence, carry the speed down the back side of the roller, then hold the speed through the bottom of the valley, you will gain maximal speed over the stretch of road.

A power meter is a super tool, but it is just that…a tool.  It isn’t something that should shackle or govern your riding, and successful utilization requires a real balance and understanding of how different conditions and terrain will naturally affect your power and output that you ride.

Let’s finish by discussing how to utilize your average power review.  Average power review can be mildly interesting but doesn’t provide true insight into the effectiveness of an IRONMAN bike ride. A great example occurred at a past IRONMAN event with a couple of professional athletes.  

Race Scenario: A two-lap race course with the following structure for each loop.

Going Out:  General loss of elevation with a strong tail wind.

Coming Home:  General gain of elevation while battling a head wind.

In this two-loop course, we got to review the data from two female riders.  Both of them are very strong riders with similar posture on the bike.  Power meters were identical, fully calibrated and aligned.

Rider A:  Averaged ~235W for the ride.

Rider B:  Averaged ~ 215W for the ride.

Same weight, same setup, surely rider A goes faster, yes?  

Unfortunately, that was not the case.  

Rider B completed the course about 7 minutes faster than Rider A.  How?

Going Out:  Rider A was determined to ‘hold power’ and charged along with a tail wind holding as close to 240W as she could.  A tough task with a strong tail wind.  The neurological cost was quite high, while the speed reward was minimal.  Rider B ramped to speed and floated along with fluid pedaling, but at a much lower wattage.  She was completing the out section at close to the same speed, but at a much lower output.  Her penalty of speed was minimal, but the energy savings were great.

Heading Back:  Rider A remained at her power goal and maintained cadence.  She pushed, but by the second loop was fighting to hold that average.  Rider B returned both times with great energy, shifting to a bigger gear and lower cadence, she was able to maintain an output above the average. Pushing consistently higher than race average power was a greater general cost than her algorithm would suggest, but the wind and grade, coupled with specific training, meant it was the obvious choice. The speed reward was massive.  

The net result was a faster overall ride, a touch of a variance of load (which the body loves), and a readiness to run well.  By no means do I suggest you freewheel down all hills, spin in tailwinds, then charge and attack every hill.  There is a strong balance, but simplifying down to ‘hold XX power’ is extremely limiting.  This approach needs to be supported by both physiological and technical training. The power meter is not just a way of tracking overall output, but also useful for learning how to maximize your energy resources for speed on any course.

I hope that helps.

Matt Dixon


If you would like to learn more about terrain management and how to maximize power output on the bike, book a time with purplepatch coach Paul Buick by clicking here