The Triathlete’s Guide to Run Power

Published May 11, 2023 09:24AM

Technology keeps advancing endurance sports—both from a training and racing perspective, and we are seeing technology from one sport expand and progress into another endurance sport. Power meters in cycling have become so commonplace over the years, that most cyclists and triathletes can speak to their best power outputs, threshold power values, and power zone ranges for workouts. Cycling power turned a complex sport like cycling into something very simple, down to a single number. Even swimming has gotten in on the action with power meters you can wear to the pool. But what about power for running? Is power really possible to be measured, and what benefit does it have compared to the years of “tried and true” pace as the central metric?

What is power?

Before answering that question, let’s take a look at what “power” truly means: In general, power is a work rate, telling us how much work a person is accomplishing, over time, expressed as force applied, times speed of that force. On a bicycle this is expressed when an athlete pushes on the pedal and the crank arm with their leg, along with the cadence at which they apply that force. The number on a cycling power meter represents the amount of work accomplished in moving the bike forward—how fast it goes depends on the resistance it faces, affected by climbs, descents, surfaces, drafting, and more.

It is important to remember, just because you apply a force to something, doesn’t mean it can move a distance, and in order for work to be accomplished, something must be moved by force. So if you push against a wall, and the wall doesn’t move, you’ve done zero work—when it comes to the formal definition—no matter how hard, taxing and tiring the effort was when you applied the force to the wall. This is important because you still use energy in ways that are not efficient on a bike, that don’t provide any real force to move it. The power meter only shows what efforts are actually transferred to moving the bike.

Running with power: More than just effort

In running, we apply a force to the ground, with a cadence, that moves us through space, (Work!). Just like on a bike, the speed we are able to run at is dependent on a number of factors, such as uphill, downhill, terrain, and even wind (along with a myriad of physiological efficiencies and inefficiencies). However, while pace may vary on a course with a lot of up and down, an athlete can keep a consistent power, (work rate), which is a much more efficient use of their energy, when running and racing, compared to pace.

In this image, you can see where an athlete starts an overall downhill route, with a big climb at the beginning (shaded portion). In this run, the athlete is to build their pace over 5 minutes, with a 1-minute recovery jog, and each round of 5 minutes the pace is to get faster at the peak and overall for the interval. You can see the green line, (pace), is increasing each round. In round three though, they suffer from some GPS reception issues, (the other advantage of power meters is they’re not dependent on GPS), but as the run goes on, her run power increases a lot more than her pace does. In fact, she spent 64% of the run above her threshold power, but only 47 secs above her threshold pace. This tells me as her coach, I need to consider adjusting her threshold power for the run, or really look at what is happening with her form as she runs faster and faster, as perhaps there are a lot of wasted movements to address.

This highlights an important fact—power relative to pace tells us how well we turn our biomechanics into running speed. There are a lot of movements we make that don’t actually propel us forward, like vertical oscillation of the head. Obviously, vertical movements don’t really help with forward movement, but if you don’t lift yourself off the ground, you can’t actually propel yourself running forward, so it’s a necessary inefficiency. Now imagine your ability to measure these inefficiencies, and work to reduce them, or better yet, reduce them at the same time you increase pace, and you can see how a power meter can begin to help you.

Does this mean pace doesn’t matter? No. In fact, pace matters most, because after all, we race to see who is fastest—not who works the hardest. But what power does give us, is an enhancement of the metric of pace, letting us better understand how to produce a fast pace for the least amount of work required, and to help clarify our effort in changing conditions and courses.

How to use run power in training

The simplest and easiest way to use run power in your training is to simply get a device, and start recording your run power data over the course of three or more months. Observe the power outputs you produce while running easy, while walking, and while running hard, uphill or downhill. These general observations will give you an idea of what a potential threshold power value might be for yourself, as well as what intensities seem to line up with what paces and efforts. Look for any exponential changes in power relative to pace, and see if your perceived exertion is aligned similarly.

Probably the best and most important thing you can do with your running power meter, is to record your race performances, and observe it during the race. Races are what you’re preparing for, so if you need to record and understand what the data says the demands of competition are for what you’re racing.

Post-race analysis with run power data provides a much clearer representation of whether your training matched the specific demands of the race. If you ran at much lower power off the bike than your race specific workouts, it is likely you trained at too high or too low of an intensity for your preparation (or your run failed because of nutritional or pacing issues on the bike).

And of course, all run courses are not equal, with some being 4-10% slower than others, simply based on elevation profiles, not even considering conditions. This only highlights the benefit of a power value to associate with run training and run performance. Power provides a much more fair comparison from race to race and course to course.

Using power to make adjustments

With a new, more consistent metric to normalize the efforts across multiple courses, terrains, and races, we can better compare training from one course to another, one location from another, race to race, and even season to season. Opportunities to better assess and perfect training for better race performances include:

Run power presents an opportunity to take run training to the next level, and dial in race pace performances, to better prepare and execute on race day. If you’re looking to make gains in your run, then run power is a relatively low-cost way to achieve the gains you’re looking for.

Workouts for running with power

70.3-Specific Tempo with Power

Aerobic Threshold Power Run

If you have established a threshold heart rate or pace value at your aerobic threshold—either LT1 or LT2—then run at that power for a 40-60-minute tempo, and later come back and try the same. Tracking the power value from workout to workout can provide specific details of improvement in economy. For example, if you stayed at the same pace and HR, but saw a lower power, this shows an improvement in economy.

How to measure running with power

In running, it is very difficult to directly measure power, given the torsional aspect of forces applied thru the foot during landing and propulsion, but with many advances in wearable technologies, algorithms to accurately estimate and record these movements and power calculations, has helped to make power much more available and accurate. The different ways power is calculated is based on the type of device, are generally categorized as one of three:

Which of these is more accurate? It’s very difficult to say. Which one is more popular? Footpods are probably most popular, but the addition of power algorithms in many different brands of watches are giving wrist watches a jump in speed to market. One thing we can say for sure, if an athlete is using run power data, then the best practice is to be consistent with the device you use. If you’re planning to jump from different brands and/or type of devices, (ie wrist watch to footpod, or vice versa), then data from one device or brand is not likely accurate or easily converted for future analysis or comparison purposes with another device. The algorithms are just too different, although some might find the trends to be consistent and similar.

Coros Pod 2

This update to Coros’ original footpod helps improve smartwatches accuracy outdoors and provides metrics when running indoors (like the Stryd). Also like the Stryd pod, this device gives more advanced dynamics than you’d typically find in an on-wrist device—metrics like ambient temperature, Ground Contact Time (GCT), Left/Right Balance, Stride Height, and Stride Ratio. Oddly, Coros has moved away from the “running power” terminology and now uses “Effort Pace”—a min/mi metric that’s more familiar to more runners—but the result is about the same.

The good news is the Coros device is over half the price of the Stryd, and while it doesn’t have quite the depth of data (nor as robust of a training/logging/data analysis platform), it’s almost the exact same size as the Stryd and can be worn either on a shoe or on the waistband of your shorts. The bad news is the Pod 2 is only compatible with Coros smartwatches, so unless you already have a Coros device or are planning on getting one (and want to upgrade the built-in dynamics capabilities), it doesn’t make a ton of sense.

Stryd Footpod (Next Gen)

Stryd was one of the first brands to really focus on running with power, and it’s no surprise that they’re also by far the most accurate and comprehensive when it comes to running dynamics. Along with ANT+ and BLE-connected running power metrics, Stryd also does even more advanced data collection like Form Power Ratio (FPR), Ground Contact Time (GCT), Vertical Oscillation, Leg String Stiffness (LSS), and wind detection (to quantify the impact that wind has on your effort). The newest version is substantially more responsive—meaning it’ll register quicker changes in power on workouts with short bursts and/or quick recovery—as well as Impact Loading Rate (to calculate stress).

The good news with the Stryd is that it’s compatible with Garmin, Polar, Coros, Suunto, Apple, and more, and even if you don’t have a compatible smartwatch, Stryd will record the data and sync to the smartphone app for post-run analysis (though of course you won’t be able to see your metrics in real time). The bad news is that it’s $250 in addition to a smartwatch purchase, and much of the data is overkill for many athletes.

Coros Pace 2

Though we’ve already included a Coros product in this roundup, it’s worth mentioning the least-expensive way to get into running with power, if you don’t already have a compatible device. The Pace 2 is a wholly underpriced, super lightweight smartwatch that has many of the running with power and running dynamics of devices at twice the price.

The good news is that not only does the Pace 2 have the full suite of running dynamics that most triathletes would need (including Coros’ “Effort Pace” measurement that gives you a more realistic measure of pace taking into account grade and other data), but it also somehow has open-water swimming and multisport modes—something you won’t find on any watches in this price range. The battery life is also a very robust 20 days smartwatch (30 hours GPS training). The only downside with this watch is no navigation or music controls/storage, but for the price that’s hardly missing.

Polar Pacer Pro

Though many of Polar’s smartwatches have built-in running with power (including the Vantage M, the Vantage V2, and the Grit X), this is their most recent offering. Along with built-in running with power (and some handy screens and analysis to match), Polar, as always, has a strong suite of physiological functions, including Training Load Pro, performance testing, sleep tracking, and more. For more features, you could upgrade to the Vantage V2, but for 90% of triathletes, this is more than you’ll ever need.

The good news is the Pacer Pro has running with power built in and enough decent data tracking to really make sense of all of the numbers—it also has a much much better processor than previous versions of their watches, so no more lag. The bad news is it doesn’t have a ton of battery life (six days smartwatch, 35 hours GPS training).

Garmin Forerunner 255

Much like the Polar line, many of Garmin’s latest smartwatches—including the new AMOLED, super-bright color-screened Forerunner 265—now have built-in running with power, along with other running dynamics like Vertical Oscillation, Vertical Ratio, GCT, and Stride Length. The reason we include the 255 is because it’s Garmin’s least-expensive smartwatch with built-in running with power. The Fenix 7 line, the Enduro 2, the Gen 2 Epix, and the Forerunner 955/965 also boast the same metrics.

Again, here you won’t need an external sensor to view your running power in real time (and it has a Grade Adjusted Pace, which is similar to Coros’ “Effort Pace”), and the 255 has a host of physio features like heart-rate variability (HRV), recovery time, training status (using HRV and exercise history), acute load, training effect, performance condition, and sleep tracking—among others. In terms of bang-for-your-buck, the 14-day smartwatch battery life (30 hours GPS training) ensures this is one of the best on-wrist running with power options out there, maybe with the exception of Coros’ $200 Pace 2.