Getting Started with Running Power Meters
- Mar 13, 2017
- 5 min read
The use of power has become the gold standard for measuring intensity in the cycling community over the years. The metrics delivered by a power meter are so well known that some bikes now have the meters built directly into the bike (Unicorn). Running with power, just like cycling, allows athletes to gain efficiency, achieve better pacing, and really control the intensity of a training session if they understand how to get started; which this article helps to pave the way for.
Let’s first go over some terms used in training with power specifically Functional Threshold Power (FTP) and Critical Power (P. Crit). The key here is that these two terms are different, but overlap based on the protocols used to determine them. Functional Threshold Power is based off the body’s ability to sustain a power for 1-hour similar to Lactate Threshold Heart Rate (LTHR) and thus is a common term used both in cycling (FTP) and now running (rFTPr). It is common to add a “W” or “R” when talking FTP for running because before there were powermeters for running FTP was usually Functional Threshold Pace. Critical Power just like rFTPr is a representation of the body to maintain an average pace at max effort for a given time. In the case of critical power, the time is undefined. Thus, you could talk about Critical Power for 5 mins or Critical Power for 60 minutes.
Currently there are a few power meters for running on the market. The team at Stryd produces the current market leader and back it up with ever growing research in their online community. Stryd builds their training zones off of Critical Power and aligns them closely with the 3-Zone training system of “low,” “moderate,” and “high” intensity within their online training platform and app. They do break “high intensity” down into two additional zones. The research at Stryd is based on aligning power to blood lactate threshold testing which allowed them to determine the pace at which athletes reached their blood lactate and then defined that as their critical power. From scientific research on LTHR and FTP we know that a blood lactate of roughly 4 mmol/liter is the transition from moderate to high intensity and is what cycling FTP and running LTHR is set on. This said, the current research from Stryd shows an error rate of 8-9% with getting their power zones to align with the LT tests.
In the coaching community the current subject matter expert is Coach Jim Vance who built a body of research using the Stryd while writing his book Run with Power. His test protocol to determine rFTPr is one of the protocol options currently used by Stryd to determine Critical Power. Coach Vance used his rFTPr research to design a zone breakdown that aligns with the zones developed for cycling by Andy R. Coggan, PhD in his book Training and Racing with a Power Meter. Coach Vance’s research and simpler equation claim to have an error rate of 3%.
The testing protocol is a five part test consisting of a warm-up, 3-min max effort, 30 min active recovery, 9-min max effort, and a cool-down. The recommended version looks like this:
Warm-up: 15 mins
Main Set:
Part 1: 3-min max effort
Part 2: 30 min active recovery (5 min walk, 10 min jog, 5 min walk, 5 min jog, and 5 min walk) -
Part 3: 9-min max effort
Cool-Down: 15 mins
You can determine your Critical Power and rFTPr from this testing protocol. Currently, there are other test protocols to determine zones, but we will focus on this test as it works for both Stryd’s Critical Power equations and Coach Vance’s rFTPr equation which means there is an ability to check pacing through math. Additionally, I like this method because it doesn’t put the stress of a 20 to 30 minute all out effort on the athlete.
The equation for Run Functional Threshold Power is
While the equation for Critical Power is:
*P3 and P9 are the average power values for the three- and nine-minute running intervals
From my research I have found that a well paced hard effort on the testing will get you within 3-5% of the two values. If your two values are greater than 5% the test is invalid due to pacing and a retest is needed.
Training zones as established by Coach Vance's research for the book Run with Power align to the 7-Zone system common in cycling training and thus easily translate to most training philosophies. The percentage values do not align with the values set by Mr. Coegan for cycling, but as I have seen in my research they do align well with expected efforts in both racing and training validated through Rate of Perceived Effort (RPE), LTHR and pacing. Coach Vance’s zones are:
- Zone 1: Recover <81%
- Zone 2: Endurance 81 - 88%
- Zone 3: Tempo 89 - 95%
- Zone 4: Threshold 96 - 105%
- Zone 5a: Threshold Improvement : 106 - 115%
- Zone 5b: VO2Max: 116 - 128%
- Zone 5c: Anaerobic Capacity: >128%
As you begin to work with power in racing and training realize that this new technology will continue to adapt as the body of research expands. Recommend testing your zones against set LTHR and FTP zones to see how they relate over time and training. Once you have an established body of data in your training logs begin to look at other metrics such as Efficiency (EF), Normalized Power (NP), Variability Index (VI) and training Intensity Factor (IF) during key sessions to gauge adaptations. Also, use power when testing shoes and stride corrections in real time such as using a controlled pace on the treadmill and seeing what adjustments allow you to maintain the pace at a lower power thus improving your running economy. Just learning to control your power variability (VI close to 1.00) could be what allows you to pace to your next PR!
About the Author
Coach Dave is a USAT, USAC, HRV Performance, and IRONMAN Certified Coach who has been coaching triathletes since 2016. Coach Dave believes an athlete centric coaching process backed by science and data is the best way to achieve overall wellness and performance. Coach Dave is the head coach of Triple Victor Racing and under his guidance these athletes worked throughout the season to reach a top team ranking with IRONMAN of 7th in the world for 2016. Coach Dave is a 9x time 70.3 and 6x IRONMAN finisher to include racing at the IRONMAN 70.3 World Championships in 2015 and 2016. Coach Dave is a 4x IRONMAN All-World Athlete, 2x USAT All-American, 2x Team USA member, and finished 2016 ranked #1 in his state for Age Group 30-34. Coach Dave's athletes have raced around the world at every distance and he takes great pride in helping his athletes achieve their wellness and endurance athletic goals. You can learn more about Triple Victor Coaching here.
*The purpose of this article is not to be a general review that is applicable to the endurance athlete and is not meant to take the place of professional coaching or training.
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