Introduction to Running Power

Often the butt of many jokes on Twitter and dismissed by many experienced athletes, I believe it’s a misunderstood technology which can provide an athlete with unparalleled insight into their training. 

The running power meter was inspired by the bicycle power meter, which collects data from a strain gauge in a pedal, crank arm or wheel hub to calculate how much force is being applied by the athlete. This allows them to pace and race better on hills, into headwinds, at altitude and in the heat. The running power meter is not a true power meter in the respect that it is based on an algorithm, using accelerometers rather than a strain gauge. Combined with the pace at which an individual is running to generate a number measured in watts, this gives the athlete an insight into how much energy they are expending to achieve forward momentum. 

As a runner, I would put money on you having trained with pace, heart rate and RPE in the past. So to start with I’ll break the pros and cons of each method down to help you make the right decision for your training.

RPE
A runner participating in a race

Rate of perceived exertion is how hard you feel you are running, whether you are going eyeballs out in a race (RPE of 10) of gently jogging along on an easy run (RPE of around 4). It’s an important skill to develop for runners of all abilities even if they also use technology, as data doesn’t have all the answers and can fail at any point.

Pros:

  • If you are having a bad day, RPE will make sure you don’t over exert yourself and push you towards exhaustion or overtraining
  • It removes the risk of setting targets that are too high/low for an event
  • Free

Cons:

  • Newer runners will struggle to understand what their bodies are telling them, and may be based on what they perceive as “getting a good workout” rather than achieving the goals of the session
  • Will cause most runners to head out too fast when fresh, then fade as they didn’t pace themselves well enough 
  • Difficult to accurately measure training load, fitness or fatigue
  • Requires many years of experience to dial in, and even then the best of us make mistakes
Heart Rate
A pair of heart rate monitors

Pros:

  • Heart Rate gives us an unparalleled insight to how the body is performing, if your heart rate is outside of normal parameters, your body is trying to tell you something. This helps us avoid overtraining by pushing too hard
  • Relatively inexpensive, most modern running watches will come with a heart rate monitor built in or come with a free chest strap
  • Tracking your heart rate over time provides a valuable insight into how well your body is adapting to exercise.

Cons:

  • There is a large delay between your body’s exertion and and an increase in heart rate, so it is difficult to use it to pace races with lots of hills/surges as the feedback isn’t immediate, and your heart rate may continue to rise for up to 30 seconds after a tough section
  • Lots of factors outside of training can artificially inflate our heart rate. A lack of sleep, high levels of stress, temperature, altitude and mensural cycle to name but a few will all affect our heart rate and may result in us running faster/slower than we should
  • Prone to dropouts or false readings. Where 10BPM is a huge difference, battery or connection issues can leave you vulnerable
  • Sticking to heart rate based training can be incredibly frustrating for new athletes as they feel they need to walk to keep their heart rate in the correct zone
Pace
A Garmin wristwatch displaying a pace field

Pace is probably the most popular method of measuring running intensity, and is still the most important. If I put a running power meter on the foot of every athlete starting a 5K run, the winner wouldn’t be the one who put out the highest number of watts or the best horizontal power, it would be the one who ran the fastest. However there are issues when using a GPS watch to measure pace

Pros:

  • Cheap, comes with all fitness tracking devices, or you can use you phone
  • The winner of the race is the athlete who runs the fastest, so it’s the purest way of tracking intensity

Cons:

  • GPS watches can lose signal, or struggle to find it in areas such as woodland or around high rise buildings
  • Large events place so much strain on GPS systems that they cannot keep up. This resultis in athlete’s watches giving false readings, and getting out of sync with the race organiser’s distance markers. This can result in widespread confusion and frustration
  • GPS watches are very sensitive to changes in direction. They expect you to continue running in a straight line, so making a U turn or sharp corner can leave the GPS struggling to catch up
  • It does not take gradient or headwind into account, if you are running up a hill or down a hill, pace data is of very little use
  • Susceptible to headwinds
Power
A Stryd run pod

Finally, this brings us onto the running power meter, which for my money goes a long way to correcting the flaws of other methods:

Pros:

  • Takes hills and wind into account (new generation Stryd only)
  • Provides advanced running metrics such as stride length, ground contact time, running efficiency, form power and leg spring stiffness
  • Reliable data in all situations
  • Measures distance precisely using the accelerometer inside the power meter, giving you an exact pace rather than GPS estimate
  • Allows you to track improvements easily
  • Unparalleled treadmill accuracy

Cons:

  • Can be confusing at first, requires time investment
  • Expensive, at £200 for a Stryd unit, on top of a compatible watch, it’s a definite investment in your running
  • The data can become all consuming, and athletes run the risk of losing sight of the bigger picture (running faster)
  • Any long term changes in athlete weight require re-calibration and redundancy of previous data
  • Can be tricky to use if you are aiming for a specific finish time

The biggest benefit for running power for me is consistency and the low margin for error. While the algorithm behind running power is up for scrutiny, as long as the data that is outputted is consistent that’s the most important thing. Whether an athlete is running on a treadmill, up an alpine pass, a road marathon or simply on a jog with friends, I know I have good data which represents their effort, using it to track improvements and calculate fatigue.

Hopefully that has given you an insight into the advantages of using running power over other methods, next up I’m going to delve into a bit more of the science:

What is running power?

Running power is measured in the arbitrary measurement of a running watt. This is a combination of force (in newtons) and speed (metres per second), with higher numbers translating into faster running. When you hit a hill the power meter will recognise this and increase the power to represent the additional effort you are using to fight gravity, while on the downhills it will recognise the gravitational assist and lower the power number to represent the reduced level of force you are having to generate yourself. This helps us pace our runs much more accurately.

Training with Running Power

Hopefully by now the concept sounds appealing at the very least. So how do you get started? First off you need a running power meter. I would recommend against any power meter which generates numbers based on speed derived from a GPS signal. This will normally involve an algorithm which looks at your cadence and your speed to generate an estimation of power. For my money though, it’s not worth the paper it’s written on. Running power in itself is an algorithm, so an algorithm that is required to generate another algorithm has a large margin of error. I use a Stryd footpod which is the most popular running power meter available currently, and will be writing the rest of this article on the assumption this is what you are using.

These numbers, like those from a cycling power meter are fairly meaningless without a benchmark. Is 250W a lot? What should you be hitting in your intervals? Is there a number you should be staying below during your event? When is your run too easy? To find the answer to these questions, we need to find a threshold, a point where an effort becomes unsustainable. The simplest way to use this is to use the Stryd auto CP (critical power) calculator, which harvests the data from all of your runs to give you an estimation of your ability. It’s important you feed it a variety of data points, from sprints to 5Ks and long runs. Don’t expect an accurate number after a few easy runs.

A graph illustrating a runner's personal bests across various timeframes, used to calculate a run power threshold
The WKO5 power duration curve informing us that this runner’s threshold is 231W

Zone training is nothing new as we have zones for pace and heart rate, but the fact that threshold is calculated by looking at thousands of data points rather than a single point, means our threshold is more accurate. It also updates automatically with time. Smash out a big hill session which included your best two minute power? Your threshold may improve by a couple of watts. Absolutely storm that cross country race? You may see a nice big boost to represent that. It’s important to note that these are based on a 90 day rolling average, so any data older than 90 days will disappear. This can result in sudden increases/decreases to your threshold power even if you’ve spent the day on the sofa.

The way our power threshold updates itself automatically reduces the need for formal testing every 6-8 weeks to check for improvements, which is arguably the biggest benefit of running power for me, ensuring your threshold is always up to date.

Indoor Running

I don’t like running on a treadmill, and I’m going to go out on a limb and suggest that you don’t like it either, but sometimes it’s a necessary evil. This can be due to the weather or when we’re in a country where wearing sports clothing in public is not appropriate. One of the frustrating issues I encounter as a coach is accurately recording treadmill workouts. Treadmills vary significantly in accuracy, and the indoor running mode included on sports watches leaves a lot to be desired.

You may be lucky enough to have access to an indoor running facility such as a sprint track or even a full 400M. The lack of GPS signal can be a issue if we want detailed information from our session, but a running power meter provides us with all the information we need, without the GPS accuracy issues which plague even outdoor tracks.

Running with power is the perfect way to record your indoor runs as we get meaningful figures that can be directly compared to your outdoor runs. In fact, I’d go so far as to say that if you’re a serious runner who trains indoors regularly, a power meter is an essential purchase.

My preferred way to train on the treadmill is using Zwift, software which takes you through a virtual world as you run where you can join races and complete workouts. It’s free for runners and pairs with your power meter, so download it and give it a go.

A runner on a treadmill in front of a screen displaying Zwift, which she is using to record her run
Image copyright Zwift

Post Run Analysis

A graph depicting various data points during a run
Fatigue Indicators Chart developed by Steve Palladino, available on WKO5

Once you get back from your run your watch will upload your data to an analysis platform of choice. Most software now supports running power, however the level of support varies considerably. If you are a basic user the Stryd Power Centre will offer enough information for you, with the bonus of being free, although they will be offering a premium subscription in the near future to access some features. TrainingPeaks offers some basic functionality, but if you are a serious runner only looking to analyse data, and have little to no interest in purchasing a TrainingPlan then I recommend using WKO instead. It costs the same as a year of TrainingPeaks premium with far greater support for running power. There’s a steep learning curve however, so if you’re a recreational runner this is probably overkill.

Assuming your threshold is accurate, you will be able to see in detail how hard you ran. This data will be far more insightful than pace or heart rate, and pick up small, rapid changes much better, such as jumping over a fallen tree or sprinting for a couple of strides to make it across the road before the lights turn green. While these aren’t necessarily actionable data points, the power meter ensures that these efforts are recorded and reflected in your training load calculations. 

If you are so inclined, you can take a real deep dive into your data looking at the advanced metrics offered by WKO where you can see your leg spring stiffness, duty factor, percentage of power generated horizontally or vertically, and all manner of other metrics, which I’m not going to go into here.

Two metrics that are worth paying attention to however are running efficiency and horizontal power. 

Running efficiency (RE) looks at how effective you are at turning watts into speed. As you may remember, higher speed means higher watts, but you can also create power simply by jumping up and down on the spot, so this metric looks at how efficient you are. Running efficiency is quite a finite metric, but when running at threshold, anything below 0.97 requires improvement, 1.0 is a good score, and 1.03 or above is likely the realm of elite runners. An improvement in RE over time at the same pace/power suggests that you are improving as a runner.

Percentage of power generated in a horizontal plane (or horizontal power) tells you how much power generated is transferred into forward momentum. As mentioned above, you can create power by jumping up and down on the spot, which would create 0% horizontal power, and 100% vertical power. You can’t create 100% horizontal power, but if you can get it up to around 75-80% this suggests you are moving fluidly.

These metrics will vary from run to run, and will be lower on easy or hilly runs so make sure you’re only comparing these with like for like runs.

The real danger here is getting lost in the numbers and over analysing every single data point, or believing you aren’t capable of more than the software’s predictions. We should still be runners at heart, hitting the roads/trails for fun and the challenge of pushing our limits. Running power data is so in depth we can run the risk of becoming data analysts first instead of athletes.

Running Power for Triathlon

So, if you’re a triathlete, how does this fit into your training? How can you use it to run faster off the bike? The answer is in form power.

When we run off the bike we’re never going to run as well as we will at a standalone event. Depending on your event and ability you may be up to ten hours into the race at this point, and your legs will be stiff from the repeated pedalling action on the bike. Your mobility may be impaired and your legs will be fatigued. This can mean you find yourself not running as quickly as you’d hoped. Add to this the accumulation of fatigue over the rest of the run and we’re looking at a very different picture to training.

Running power takes this into account, recognising that you’re putting in the effort, even if you’re not travelling as quickly as you would normally. This is form power, it looks at the vertical and lateral movement from the foot compared to the horizontal power which we touched on above. While generating a high amount of form power is bad news for our running, what’s worse is not taking this into account and pushing harder because we feel we’re slacking off.

This becomes imperative to our pacing. We may know we can hold 5:00 for a marathon when fresh, but after a hard 180Km on the bike this may be 5:20, maybe even 5:30. If we stick to our guns (and pride) aiming for 5:00 per KM we could well be slowly running ourselves into the red and find ourselves walking. Aiming for a power target instead takes our loss of form into account, ensuring we focus on what our body is doing, as opposed to what we think it should be doing.

Conclusion

So, you may be wondering why more people don’t run with power at this point. I’ll break down a few most common issues people have with running power

Elite athletes don’t use it

It’s true, not many professional runners use Stryd, with some notable exceptions such as Ben Kanute and Olympic Triathlon Champion Gwen Jorgennson. More often than not this is the choice of their coach rather than the athlete, who will adapt an “If it isn’t broke, don’t fix it” approach. Truth be told, if I had an athlete who was winning races training with pace and/or heart rate, I probably wouldn’t suggest they switch to running power. Elite athletes are often training at a level where they can’t afford to try something new, especially going into an Olympic year, so they stick to what they know.

Technophobes

Some very successful coaches out there won’t even want their athletes to wear watches. They’ll stand next to the start/finish line of a track with their stopwatch, barking splits out to runners as they complete every lap. While this is an extreme example, many coaches who qualified in the 20th Century aren’t interested in opening their minds to new training methods. There is nothing inherently wrong with this if they’ve been coaching for 30 years and had great success with their current methods, but they may not be getting the most out of their athletes.

This also extends to athletes who may not understand what running power is, how to set it up, or how to use it to make themselves faster, to them it’s just a number that appears on their watch. I hope to demystify it in more detail with more articles in future.

Just not appealing

For some, training with heart rate and pace is enough, or even too much in some cases. If you live a very busy life and don’t have the time, headspace or inclination to look through your numbers after a run. For some, running is a time for them to switch off, lose themselves in nature, or blow off some steam, and there’s nothing wrong with that.

It’s not a “mature technology”

It’s true that our understanding of running power is accelerating at a rapid pace, in fact it could be argued that the entire concept is in beta testing with rapid developments and new interpretations of the data on a regular basis. The concept is based on an algorithm and it’s hard to see how that could be changed currently, so it’s hard to see it becoming as reliable as cycling power any time soon. That being said, look at the way Team Sky and British Cycling advanced the knowledge of cycling power, first developed in the 80s, to emerge as a dominant force in 2012. There is a lot of potential in running power, and early adopters with the right guidance can capitalise on its benefits.

Early versions were poor

Running power meters first arrived on the scene back in 2015, and by the company involved’s own admission more recently, left a lot to be desired. New generations have improved the accuracy and the stability of running power significantly.

The best thing of all though? Just because you record running power doesn’t mean you can’t also run with pace, heart rate or RPE. You can record all four at once, and choose whichever you want to dictate the intensity of your workout. Following a MAF plan? Increases in power can reassure you the training is working.

It may be you want a running power meter simply to record your pace more accurately, or you’re only interested in a single metric such as leg spring stiffness or horizontal power. As with everything in our sport, you only need to take it as seriously as you want. If you have the cash I recommend you give it a go though, it may be just what you need to take your running to the next level.

Further Reading

There are limited resources out there for running power, but I have a few recommendations:

Palladino Power Project

Steve Palladino is an accomplished running coach who has invested heavily in running power, and has created a Facebook group to act as an open forum to discuss running power. With up to date information and good discussions, I recommend you join: https://www.facebook.com/groups/PalladinoPowerProject

Run With Power by Jim Vance

Unfortunately this book is slightly out of date now and I’m hoping for a second edition, but it’s still the primary source of information for running power.

Cover of "Run with Power" book

The Secret of Running by Hans van Dijk and Ron van Megen

This is a more up to date book which includes useful information on Running Power

Cover of "The Secret of Running book"

Stryd Materials

As a company, Stryd have done a good job of creating a number of resources for runners. This includes articles on their website, their podcast and their Facebook group where runners can ask questions and discuss training with Stryd staff https://www.facebook.com/groups/strydcommunity

I hope this has opened your eyes to the potential benefits of running with power. If you have a running power meter and are struggling to understand your data, why not book in a coaching consultation with us here where we can talk you through the process and help get your training on track.

Aerobic and Anaerobic- What You Need to Know

Aerobic and anaerobic are two words that many in the endurance coaching world including myself bound around on a daily basis, yet for the aspiring triathlete these can cause confusion at first.

The terms refer to how the body generates energy, imagine a six year old at sports day, belting across the school field towards the finishing line. When they finish their run they will likely be breathing heavily, exhausted from the 25M sprint they have just completed. When they move into secondary school and start running the 1500 on the track and cross country they soon realise something, if they want to run longer distances they have to slow down.

Once they run longer distances at a lower intensities they are not nearly as out of breath at the end of the effort. They may be exhausted and collapse in a heap with sore legs and no energy left, but their lungs will not burn in the same way as before, they will not be recovering from what is known as an oxygen debt.

The reason you experience an oxygen debt after short efforts is due to the body relying primarily on its anaerobic system heavily for short, hard efforts, this is where your body creates energy without oxygen. I won’t go into the science of how it works here, but what you need to know is that the anaerobic system can only function for around 2 minutes before the athlete accumulates a large oxygen debt and has to slow dramatically, this is our fight or flight reaction that allows us to escape from danger. Many predators in the animal kingdom rely on their anaerobic system heavily as they sprint after prey, if the gazelle manages to slip from the cheetahs grasp or zig zag enough to tire the cheetah, it can avoid becoming lunch as the cheetah has created an enormous oxygen debt it must recover from, akin to the six year old who has sprinted full pelt over a short distance and has nothing left at the end.

Cheetah_hunting_impala-photo-safari_Masai_Mara_3285.jpg
A Cheetah relies on its strong muscles and high anaerobic prowess to hunt down its prey, but if it mistimes its sprint or the animal escapes, it is unlikely to make the kill (photo credit Federico Veronesi)

On the other side of the equation we have aerobic fitness, this is energy created using oxygen. This is much more efficient and is one of the leading reasons for our dominance as a species, where our prey relied predominantly on their anaerobic system to escape danger, we were able to keep them in sight and slowly run them into exhaustion as they were unable to hold the pace that we were over longer distances.

As triathletes we are focused almost entirely upon the aerobic system, as it is very rare that we will be putting the hammer down and become predominantly anaerobic when racing even a sprint distance triathlon as we will need time to recover from this effort. The exception to this is in draft legal triathlon where you may launch an attack off the front of the pack to try to bridge to the next group, which upon joining you will be able to sit in the wheels of for a minute or so while your body recovers from the oxygen debt.

This is the reason that so much triathlon training is done at an “all day” pace, to ensure we are building and strengthening our aerobic system and not our anaerobic system. The mistake that many athletes make is doing all of their training way too fast and making very little headway on the aerobic development side of things. You may be able to run a very quick 5K, but that doesn’t necessarily translate into a great marathon experience, I can vouch for that one personally!

This is where things get confusing, I am a fairly gifted anaerobic athlete, I can push myself harder and go deeper than many others over shorter periods, but tend to suffer over especially long efforts. Normally when I mention that I have a strong anaerobic system and that 5K is my best distance to an athlete a metaphorical finger is waved in my face. “Aha! But a 5K is over 2 minutes, so it’s not an anaerobic effort”. This is of course true, but what people don’t always realise is that your body is never generating energy on a 100% aerobic or anaerobic basis. If that were the case a 100M sprinter could run with his mouth gaffer taped shut and still hit the same time as his rivals.

Anaerobic energy is created in addition to the energy that is being generated aerobically, you are using anaerobically generated energy while reading this. It is only an incredibly tiny fraction of the energy being created (think several decimal places), but is it ticking over like a pilot light, ready to leap into action at a moment’s notice.

To illustrate this more clearly here is a graph created using WKO4 (more information here) that visualises the energy systems used by an athlete at different timeframes. The data is collated using the athlete’s best performances at the time periods listed on the X axis, with the maximum power than can sustain for that period on the Y axis. I use these graphs to help athletes gain a better understanding of their individual physiologies to help us understand where we need to focus our training effort.

Screenshot 2019-01-11 at 12.46.41

Today we want to focus on the green and the blue lines, the green line represents aerobic contribution, the blue line anaerobic. If we start to the left of the chart we can see that at 1 second there is very little contribution from the aerobic system as the body has not started increasing the rate at which it pumps oxygen to the muscles yet, but using glycosides the body can create energy within the muscles and get us moving immediately. As we look closer towards the 10 second mark the aerobic system is really starting to get up to speed now, additional oxygen has been absorbed from the lungs and is being pumped to the muscles to get them fired up.

For this athlete, it is at one minute 6 seconds that the crossover occurs, and the aerobic system takes over as the primary fuel source. The aerobic system has fuel, it can continue indefinitely for as long as it has fuel, the anaerobic system making a tiny contribution that can increase on hills or when accelerating hard.

Looking at the 20 minute data point, the anaerobic system is still contributing 10W of power, which is still a respectable amount, I’m sure if this athlete saw their FTP drop by 10W they would be mortified. Remember, this is looking at the athlete’s best 20 minute effort, not all 20 minute efforts use such a proportion of the anaerobic system.

Going back to the graph, it would look very different for a track sprinter compared to a time trialist (which this athlete is classified as). In a sprinter the anaerobic system would make a much greater contribution, it would continue for much longer before the intersection with the aerobic system as sprinters need to hold maximum power for as long as possible. Their aerobic system will be very weak comparatively and they would struggle to keep up on a gentle Sunday club run as a result.

So now we’ve gone through the science, let’s have a look at the takeaway points, and how a better understanding of the two energy systems can aid your training:

-There is no benefit to developing your anaerobic system for most triathletes. I know an extremely successful athlete who has raced at Kona, yet claims he can’t sprint for toffee (never seen him sprint so can’t confirm this). He doesn’t need to train or develop his anaerobic system, he’s happy to let it fall by the wayside almost entirely to focus entirely on his aerobic system. That’s not to say that he won’t start leaning on anaerobic pathways during some sessions (such as hill reps), but the goal of these sessions is to develop muscular force, not to increase anaerobic ability although this may come as a byproduct.

-You’re never completely aerobic or anaerobic, the body is always using both, even if in very small amounts. Your anaerobic threshold is where you start to produce energy primarily from the anaerobic pathway and should be avoided for the majority of your sessions

-Avoid using large amounts of anaerobic energy in your training. It feels good as it leaves you feeling more fatigued, and changes in your anaerobic system are faster to gain and easier to track than gains in your aerobic system (“I’m 5 seconds faster up that hill!”), but are of little use to the vast majority of triathletes when it comes to race day. I know I’ve certainly fallen foul of this one in the past.

-Many fitness tests require you to use large proportions of anaerobic energy, as triathletes we are not testing you for improvements in these areas, rather trying to assess your current weighting between aerobic/anaerobic energy sources. If an athlete puts out the same amount of watts over a set period as his previous best but the anaerobic contribution is lower then the previous test, this will result in an increase in FTP when uploaded to WKO4.

I hope this has given you a better understanding of the role that aerobic and anaerobic pathways play in endurance sport, leave any questions in the comments below and I’ll do my best to answer them.