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  • Christopher Breen

What Triathletes Can Learn by Using Power Meters and Heart Rate Monitors

Almost every triathlete nowadays has access to a power meter and many more have access to a heart rate monitor. Every triathlete though has access to their own perceived exertion and knows their pace when training. Each metric separately provides valuable feedback on performance and exertion, but it is when we combine all three where we truly see the benefits.

Heart Rate

Heart rate is an indirect measure of the work our muscles are performing. As we ask our muscles to work, we need to supply them with oxygen. Because oxygen is supplied via our cardiovascular system through red blood cells, our heart rate increases as our bodies demand for oxygen increases.

Thus, heart rate is a great indicator of our physiology and a great metric to follow on the bike and run. Although it can be measured on the swim, it’s not good practice to stop and look at your watch while swimming.

One knock on heart rate is that there is a time lag between our effort and the work we are producing and the heart rate measurement. Again, that is why partnering with the other metrics make it a more powerful tool.


Measured in watts, cycling power is torque (x) angular velocity = watts. It is an immediate snapshot into how hard we are working.

Want to generate more power? Pedal harder or pedal faster. When we push harder on the pedals, we immediately see an increase in watts being generated. This is power’s advantage; we get immediate feedback.

For both heart rate and power, we are able to establish training zones that correlate with one’s lactate threshold thereby allowing us to train specific energy systems. Power, however, is primarily used for cycling and although there has been an emergence of run power meters they are still in their infancy. Power is not used on the swim.

Pace also provides immediate feedback in real time and can and should be monitored with all three sports.

Perceived exertion

If an athlete has been doing this sport for some time and is quite “in tune” with their bodies then perceived exertion is often the best indicator of effort. It is simple, always available and can be used across all three sports. It is simply a scale on one’s perceived effort level.

Are you working easy, moderate or hard? The Borg’s scale of perceived exertion using a scale of 6-20 is the original, but more often the modified scale of 0-10 is used with 0 being the easiest of effort levels and 10 being the hardest.

Triathlon is one sport and should be viewed as such. How we perform in one leg of the triathlon affects our performance in the next. If you had the best bike split, does it really matter if you spent the last 10 miles of the marathon walking?

Metrics for Swim

The best metrics are pace and perceived exertion. It is worthwhile to train with pace all the while being completely cognisant of your perceived exertion for a given pace. During a race, the whole leg is going to paced by perceived exertion.

There are no pace clocks and as mentioned above it is not reasonable to check your watch when swimming. Therefore, perceived exertion gives an athlete their best chance for a successful swim leaving one fresh to get on the bike.

Metrics for Bike

Here once again, as with all things triathlon, the bike seems to be the most complicated. On the bike we can utilize every metric available to us. Often times, more information can complicate things.

We can use heart rate and power zones when training, all the while getting a feel for our exertion in each zone. Here is where focusing on the task and being truly engaged in our workouts becomes so important.

We need to take into account of our heart rate for a specific power zone, all the while being aware of our perceived exertion. This allows us to make educated decisions come race day. Most often after a quick swim exit and a hurried transition we find ourselves with an elevated heart rate once on the bike.

Here is where power might be the best metric to follow early on the bike. Once heart rate settles we can then focus on it relative to the specific power we intend to ride. Heart rate allows us to account for external factors such as heat and humidity, and power can keep us honest when it comes to hills and surges that might spike our watts.

As we settle into a long bike leg, perceived exertion acts as our protection plan for minimizing surges and spikes in effort level.

Metrics for Run

With training, we rely on heart rate training zones and our perceived exertion and pace within those zones. During a race, it is important to come off the bike knowing what our heart rate averaged.

A well-paced bike and run will typically see our run’s average heart rate be approximately 10 beats higher than our bike’s average heart rate. It is important to then come off the bike running at a targeted heart rate zone.

This will allow us to pace our run according to the given external factors for that day, setting us up to utilize perceived exertion towards the last third of the run for a strong finish.

It is important to have all the metrics available to us and to know when to utilize one over the other. One of the most important skills I try to teach my athlete’s is the ability to use technology effectively while also decreasing one’s dependence on it.

Published in USA Triathlon's Multisport Lab October 16, 2018


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