Using a Power Meter for Triathlon Pacing

Thursday, September 17, 2009 | By TrainingPeaks
 
 
 
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Power meters are by no means perfect devices.  A robust design with simple functionality has yet to be created in my opinion (although they are getting better); and they are expensive to boot.  A power meter requires a level of technical and analytical aptitude that not every athlete will possess.  However, if used to correctly, a power meter is a powerful tool that can increase training accuracy, efficiency, and facilitate a much higher level of post race or workout analysis.  Utilizing a power meter within a multisport pacing strategy may give a tactical edge as well.  If you are an athlete that attempts to gain speed by working all the angles, it may be appropriate to add a power meter to your arsenal.

Road cyclists were the first athletes to really adopt and capitalize on the value of power training and racing.  Road cycling is very multi-disciplinary, combining time trials, critieriums, and road races into single events.  Non draft triathlon cycling by comparison is a simple time trial with a swim and run on the respective ends.  Can racing with power be as important to a triathlete interested in sustaining power?  I believe it can if used correctly.

Metering out your energy and using it most effectively is the basis of pacing.  An athlete that spends their first hour of an Ironman at their threshold wattage would likely not make it to the run; or even complete the bike split.  Wattage is a great metric as it is not directly affected by environmental factors such as heat, hydration, humidity, altitude, and cardiac drift.  It is a measure of “pure” output.  Which is a better pacing metric, heart rate or wattage?  I never throw out a data stream and use both metrics to design a balanced pacing strategy.  By combining the two you obtain an even clearer picture of how your body is reacting both externally and internally.  For instance a sharp deviation between heart rate (high) and wattage (low) could be an indicator the athlete became dehydrated and that their body was working harder to circulate a more limited amount of blood volume.  This would be a red flag and perhaps cause for examination of fluid intake.  The three metrics I use for designing a multisport pacing strategy are cadence, wattage, and heart rate.  A fourth metric would be time, mainly to stay on track with fluid and calorie intake.

A variable effort is more fatiguing to the body when compared to an even, steady effort.  The body likes homeostasis, and a stochastic power output is similar to performing intervals. You may have experienced how fatiguing it is to ride in high, gusting winds when compared to a calm and windless day.  I have found that my best athletes are very good at sustaining a steady cadence and power output; even over varied terrain.  They are able to find their “groove” and stay in it.  There is an algorithm called “variability index” (VI) that analyzes how smooth or consistent an athletes power output was during a race or work out.  These athletes have comparably low VI’s and more steady heart rates.  VI may also be a good indication that the athlete is focused on the process of racing vs. the external stimulus (ex. chasing other athletes) that may pull them off their game.  A pacing strategy of a smooth and consistent power delivery will reduce fatigue and pay dividends on the run.

How do you balance these various metrics including wattage during a race?  It will depend on the distance and even course.  For short course triathlon a power meter may be used as a “redline” to keep you from “blowing up” and producing too many over the top anaerobic efforts that send you into oxygen debt.  Remember these debts have to be paid back and the only way to do this is by slowing down to re-oxygenate the working muscles.  An athlete that is familiar with their power outputs knows what is sustainable and what will degrade their run.  For longer course aerobic level events such as 70.3 and IRONMAN a power meter can be used to flatten power delivery throughout the event and reduce fatigue.  I may use a heart rate range to keep the athlete aerobic while using power as metric to avoid too much variability.  Again, the best athletes often have a relatively consistent power delivery throughout the event.

How do you test for and design a pacing strategy based on power?  I prefer to use the athlete’s actual performance during their work outs, specifically key bricks, to formulate a strategy based on known performance.  I avoid using formula based strategies (ex. % of Functional Threshold Power) as it relies on a test that may or may not be accurate at the athlete’s present fitness level.  I prefer to observe power outputs at various heart rate levels, in race like conditions; and the athlete’s ability to run off the bike.  A cycling pacing strategy that does not promote a strong run is useless.  I believe this strategy offers more data points and a broader, more consistent picture of the athlete’s abilities.  It is important to note that any pacing strategy is not absolute or precise and only on race day, after the taper, will true performance be revealed.  I prefer to think of pacing strategy as a “close field goal range” that may need to be adapted and modified slightly by the athlete on race day.

The course must be considered as well.  A hilly course will require a different strategy when compared to a flat course that is more sustained.  An athlete can expend a lot of energy attempting to hold wattage during a descent that is offering little speed gain in return.  Conversely low cadence climbing wattage may be slightly higher at a given heart rate.  The athlete must know how to factor the terrain into their pacing strategy.

A power meter can work both as a carrot or a stick.  It can indicate to increase energy slightly, or tell you to hold back and save it for the run.  Some athletes pace extremely well naturally.  Others are easily distracted and are pulled off their games producing large, fatiguing, power surges throughout an event.  I find that once an athlete is acclimated to training with power it improves their ability to find their pacing “groove” more naturally even without devices.  By breaking a race up into a process and a strategy you will optimize your performance.  No device is perfect and it is important to note that an overly complicated strategy offers more chances for error to occur.  An athlete has to be able to function when all devices fail.  A good drill for this is to “fly blind” for brief periods of a work out and compare these periods to the ones monitored with devices.  An athlete must “feel” their pace as well as monitor it.

This article was written by Matt Russ.

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