There is great potential for power as a running metric but a number of issues to consider before applying it in everyday training.

 

Price: $199 (circa £159.90)

Purpose: Power monitor for running

Website: www.stryd.com [Stry Gen II ‘FOOT POD’]

Summary –      Pros:    Accurate, repeatable, syncs with training peaks /    Cons:  Lack of ability to select specific metrics in IQ stryd watch app / No effective integration of run-power into WKO4

The use of power as a metric for measuring the impact of training and as a tool for optimising performance has revolutionised cycling. However, beyond real time GPS little has changed beyond measuring heart rate from the late 70s and early 80s. This may just have changed with the introduction of power measurement for runners. One version of power meters for running making the headlines has been ‘Stryd®’. I have being playing about with the Stryd over the past few weeks and thought I would share a few findings thus far.

Figure 1. Photos of the Stryd. Super small & light-weight!

 

Benefits of power for running

Many of you will already be using power for cycling but the application to running has some significant differences –  for example in cycling the more power you put through the pedals the faster you go. However, in running you could theoretically have increases in power but no increase in speed, but why? The simple reason is you’re locked into a certain position on a bike and the measurement of power simply represents what goes into the power meter via the pedals. This is very different during running as we use power ideally fwd motion, but as you know when we run we move up and down and side to side. All of this non forward movement could result in a loss of forward propulsion from our power production. The take-home not all power results in fwd movement.

Therefore, the Stryd could be a great tool in  assessing the point at which power peaks in faster running and at what point any additional power does not further increase speed.

 

This type of data can provide guidance in technique development by helping modify our form so that any wasted power (excessive up and down and side to side) can be corrected to result in better fwds movement.

So from a personal point of view I have used cadence on Garmin’s to be more economical in my running. However,  I did not know how to ‘effectively’ apply form changes to impact other metrics such as ground contact time (GCT), vertical oscillation (VO), stride length (SL), vertical ratio (VR) that then show up as faster running or faster running for less effort (thats the goal right!).

Sometime to much information can be damaging if you cannot find a practical home for it. I am all about practical application rather than just measuring something because we can. To that end lets have a look at the Stryd and how we can use it at a practical level.

 

How Stryd Works?

In essence the Stryd works using 3-dimensional accelerometer and some clever algorithms to estimate power production. According to the Stryd team the product and its data has then been then validated against force plate embedded treadmill in a lab (gold standard of directly measuring force/power).

As such Stryd can measure force production in 3 dimensions (up and down, sided to side and forwards and backwards). This is at a theoretical level is superb as with the right software to extract the data you could not only look at the metrics we see currently on the likes of Garmin 920xt but also some other metrics such as ‘breaking’ during running (something you get if you’re a heal toe runner). Therefore, the Stryd could be an affordable micro-biomechanics lab that could be used not only to measure power (next section) but also to monitor and manipulate in real time, running economy and form (#Free Speed).

 

Power measurement and running

I have to say this blog has been a bit delayed because I have had in my possession the Stryd for a few months. However, I wanted to have a play about with the stryd in multiple conditions and paces (Intervals vs long runs etc etc) to see what it can and cannot do. Being from a wet and windy part of the UK this has made for a challenge when it comes to finding a dry and non-windy day.

There are a few metrics that are a must have for me when running – pace, heart rate, distance and time. As a new bonus power is now a possible ‘new’ metric to add to that list.

 

The Stryd App

At present there are 2 apps available for Stryd when using watches such as Garmins 920xt or similar. These can be accessed by the IQ connect and include:

• Stryd IQ (official app)
• Stryd 10s power (non-official / unsupported app)

Then we have additional ways to see the data when using and for post analysis:

• The stryd app for your phone (during running on a treadmill)
• The stryd online power centre (post run data analysis)

I have had a play with all of these and the phone is nice if you want to see a big screen whilst in the gym, but on the road is not practical. So I will focus on those ‘other’ apps and the data given from the watch displays and via Stryd’s own website ‘the power centre’.

Before that I want to just give a quick overview of some metrics you can get from the Stryd outside of those typically available with a Garmin such as cadence, hr, vertical oscillation, ground contact time etc.

• Power: The stryd records real-time (instantaneous power) however, there is a workaround app to give 10s average as discussed below.
• Leg Spring Stiffness: Based on variance in ground contact times (typically less ground contact means running faster and to a point more economically). In general we see swimmers having very flexible ankle (not stiff) and as such transitioning from swimmer to runner is harder.
• Form Power: This is the power to raise one’s centre of mass against gravity with each step and is independent of speed and gradient. The application of this is when your form (body position etc) is altered to decrease this number is associated with improved economy and reduced vertical oscillation.

 

My testing of the Stryd

To look at the way the Sytrd works I wanted to check out a few different types of sessions that are typical for most runner and triathlete training sessions. These are the long run (outside) and intervals (treadmill). These are a nice mix of sessions on different surfaces and should be able to highlight the pros and cons from using the Stryd and its related software.

Before we start using the Styd we need to find out our training zones. For me these are carried out during a lactate threshold test (see previous blog on BSx). From that test set training zones are based on Hr, Pace and Power.

 

The Power Centre: Analysis (Pro’s and Cons)

The 1^st session was intervals (warm up, then 3 x 11Min reps at 3.45/3.45 min/km or 6.15min/mile if you like imperial). As you can see below (Figure 2) we get some nice square wave power level shapes (orange line) for each fo the 3 intervals. When doing bike intervals and using a power meter these shapes are very similar, and like using power on a bike we can see a lag in the heart rate (purple line) getting up to 160bpm (the goal pace for mid to upper Level 3 work).

Figure 2: Stryd’s online power centre – Data analysis from Interval training on a treadmill.

 

The lag in Heart Rate for me was about 5-6 mins before hitting what would be level-3, therefore power allows us to instantly work in the right zone rather than consistently upping or lowering pace until you hit the right the heart rate. However, it could be said why not just set our training zones off pace as that’s a way to cut out the delay (lag) in heart rate rising to the hight level?

Well again we have external issues than can increase or decrease the physiological demand (effort) of maintaining a specific pace. Pace does not take into consideration the effort it might take to get up or down a hill or running into a head wind. What’s great is that (theoretically) using power would make issues as weather (wind) and terrain (hills) irrelevant to a large degree – resulting in consistently hitting the right training zone in every session.

Figure 2: Stryd’s online power centre – Data analysis from easy long run!

 

The figure above shows some metrics from a very easy zone 2 run and from it you can see the blue line showing pace (min/km) and its nice and steady and tracks closely with orange line (power) below.

At present what I don’t like from using the Stryd is the variability. The power measurement (see the orange line above) is taken in real time. As such its readings of power jumps quite often (unlike the trace we get on a treadmill – see orange line on Figure x) as power can fluctuate from second to second. The result is constantly checking your watch to try and stay in the right power zone. This is not great and a distraction when it comes to pacing a workout on the road.

The solution to this would be to have the ability to see and average of power measurements over say 5-10 seconds as we can do with power as measured using a Garmin on our bikes or like average pace on a watch. The averaging effect would smooth the values (variability) you see on your watch, making running at a constant power more achievable and less stressful. I will discuss the possibility of a workaround for this in the ‘Watch App’ section below.

Figure 3: Stryd’s power centre – Lots of metrics available on the power centre for data freaks.

 

When you use the power centre there are a whole host of data fields that can be looked at (See Figure 3 above). But for my own view there are only a few that seem of interest at this time. ‘Form power’ (see the ‘Stryd app’ section above for what this metric means) and ‘cadence’ are the main 2 beyond power.

When you run (On a treadmill) is easier to keep a check on ‘form power’ during the session. My view is that keeping form power low is typically due to leg turnover (cadence) and also how you toe-off when running. It provides some pretty quick feedback and typically as form power drops you will also see the power to maintain a set speed falls (more efficient?).

What I cannot say is how this metric is useful across a range of abilities. For myself whilst I don’t have a very high VO2_max, my running economy is very good as is my cadence. Therefore, I do not see a huge benefit for an economic runner. However, in others I see run cadence a major issue in them becoming more economic. Many can achieve high (>180) cadence figures when running at 5-10k pace but this drops of significantly as the distance increases and pace drops. I believe that truly economic runners with good form will hold a cadence of circa 180 almost irrespective of run pace (recovery vs. marathon).

As such I see some nice options from the metrics but outside of ‘form powder’ and ‘cadence’ I think they are just nice metrics to perhaps compare overtime (something you can do in the power centre i.e. compare metrics from one workout against the same workout a few weeks later).

 

 The watch app

The biggest downfall of the Stryd is the watch app. The primary App is available from the GARMIN connect store (Stryd IQ). The app allows you to download the data post run to the power centre and also to training peaks. the issue is that there is no ability to decide what metrics you can see on each data field. You simply have to accept the data fields the app allows you to see with power.

Figure 4: Watch metrics – well at least the useful ones!

 

You also cannot alter the sampling rate for power i.e. per 3, 10, 30 Seconds etc. As above this causes some issues. There is a workaround for those wanting average power and that’s in the form of an app from the Garmin Connect IQ store called ‘Avg Power 10s’. This is the metric I now use on my runs but unfortunately it does not record the power data from that session – so although you can see the data field during the run (average 10s power) and your other chosen metrics such as heart rate and pace etc its not downloadable. It’s also not supported by Stryd.

https://apps.garmin.com/en-IE/apps/ae28e863-89d6-408c-b4a6-94a1683aec7e;jsessionid=A8BF8154DDBF09E083FF08EEB10F970A

 

Is it fit for purpose: Future proofing?

There is great potential for using power for run training and racing but there are still some significant issues to be resolved. I live in the north of the UK and we can get some real windy days and the effort to run in side winds are not fully transferred into the Stryds power measurements in my experience. As such to measure physiological effort in such conditions you need to fall back to heart rate.

However, in days where wind is below 10mph the Styrd is spot on in its accuracy and reproducibility. You can set you training zones using the stryd but take care on what surface. You will get different readings depending on the surface you run on. In my own testing the harder the surface the higher the power recorded. From one treadmill to another despite the same gradient and speed there is circa a 10w difference. Therefore, you will need to build in this when considering your training zones and perhaps power to use if for a race on the road vs. off-road / x-county.

The app needs a major makeover – its very ridged and at this time its not very intuitive in setting it up. What you want is the ability to connect to Stryd as you would a heart rate monitor and for your Garmin to know that and then you have in the field data options all the potential metrics available. Metrics such as those in the power centre plus and ability to look at average power for laps, 5, 10, 30 seconds etc. This will no doubt require more co-operation between Stryd and Garmin and other watch makers.

 

Downloading Data

The final issues relate to training peaks. The only data that gets downloaded is power but no ‘form power’ or ‘LSS’ or similar metrics seen in the Stryd power centre. The other major issue for me personally is the data that shows up as power on training peaks does not sync with WKO4. As such when you want to do some in-depth analysis your cannot use power i.e. the whole point of using the Stryd.

There is also I am sure some other great metrics that you could get from the Stryd but just not accessible ‘yet’. Because it measures 3d power with the right software we could get values related to heal striking (breaking). This would be a valuable metric for helping alter run form and from what I hear from Stryd its something possible for the future.

I know from following the Stryd forums and asking staff about the issues of setting up the app etc that they are trying to resolve these early adopter issues. Similarly, the WKO4 team are working on an update for Stryd but as of yet not timelines have been released.