What does my running watch or app tell me? How do you use the data?

by | Apr 12, 2017

garmin watch helps measure cadence, ground contact time, and other running metrics

Modern life is filled and affected by technology and we are constantly being bombarded by data. From the budgeting app telling us our saving rate to our car letting us know we have a flat, these things are supposed to make our life easy. However, there are also many situations where we have devices providing data that either we do not understand or know what to do with, or we know what the data means but do not do anything! Running technology (watches, smartphones, activity trackers) is a great example – so much interesting data is available to us, but how can we use it in a practical way to help become better runners?

Many of the runners I’ve worked with use a Garmin or similar device to track their mileage and pace. But these devices provide other highly useful data that can be used to an be used to improve your running! !Let’s take a look at some of these metrics:

GPS distance:

You have heard of overuse injuries. Essentially overuse injuries are relative to load – you don’t want to increase the amount you are ‘loading’ your body too much in the short term, compared to the load it’s been used to over the longer term. My favorite metric to help gauge loading and reduce overuse injuries is called the “Acute Chronic Workload Ratio” (ACWR). You can read more detail about this at my previous blog on the topic, but basically, it is the ratio of your load over the previous week, divided by your load over the previous month. Research so far has shown that the “sweet spot” you want to stay in is 0.8 – 1.3; any higher increases injury risk. (The research so far has focused on team sports that include lots of running, such as soccer and rugby, so these exact numbers might adjust as more data becomes available for other sports, but I’d expect the general principle to stay the same.)

A visual representation of the acute:chronic workload ratio

A visual representation of the acute:chronic workload ratio, adapted from Gabbett et al.

Well, the cool thing about exercising with an exercise tracking device with GPS and/or accelerometer sensors is that you can easily use your device’s data to calculate your ACWR and determine whether your training load is in the “sweet spot”. Of course, you don’t HAVE to have a GPS tracker to keep up with your mileage, but it definitely can make it easy. I’ve even had clients who, upon learning about ACWR, went back and calculated it over their last year of runs, to see when they peaked into the ‘danger zone’ and whether it correlated with their injuries. And guess what? It did correlate! Check out the graph below and notice the spikes in the ACWR soon before the injury occurred

If you’d like a copy of the spreadsheet that I’ve created to use your device’s GPS data to calculate your ACWR for you, shoot me an e-mail and I’ll be happy to send it to you!  As you enter your weekly data, it will calculate the ratio and will plot a similar graph for you. Keeping in this safe range will hopefully help the body to acclimatize to load gradually over time to make it more resilient to overuse injury.


Cadence, or step-rate, is simply the number of steps run per minute. It correlates with ground contact time. Low cadence means you are spending more time on the ground, and high cadence means you are spending less time there. Cadence also correlates with vertical displacement of center of mass (sometimes called “bounce”). As cadence increases, bounce decreases, and loading reduces. So, if you have less contact time, and reduced bounce you will also experience less loading which may help to reducing overuse injury.

I discussed the history and science behind running cadence in much more detail in this recent post. In general cadences around 160 and below are low; if your tracking device reports a cadence in this range, it’s worth trying out a higher cadence to see if it works better for you. Most of the athletes I’ve worked with have felt comfortable in the 170 to 180 region, but it’s important to remember a few things:

  1. Each runner is a unique individual; there is no ‘ideal’ magic cadence you need to aim for; settle where you feel most comfortable
  2. You DO NOT need to run faster to increase your cadence; simply reduce your stride length in order to increase cadence while maintaining the same pace
  3. Make changes GRADUALLY. The 10% rule is a fine one to follow for how much to increase cadence per week.

Technology helps you know what your cadence is, and it can also help you change your cadence! All while listening to your favorite beats! Woo hoo! Here are some tools you can use to help you adjust your cadence:

Music-based options:

Metronome-based options:

  • RunCadence – app for Apple by Seattle PT Chris Johnson which helps you increase you cadence by the percentage you wish – great for making sure you are making gradual, safe changes
  • Irunsmooth – app for Android and apple

But what if you don’t run with a smartphone, or you don’t have a tracking device that gives you run cadence? I recently discovered a cool little device called Milestone Pod that attaches to your shoe, and records your cadence, along with pace, distance, and GPS location. It doesn’t yet give feedback to allow you to use it to adjust your cadence, but for $25 it can give you some great data if you’re not already running with a phone or other running tracker.

Ground contact time

Some Garmin devices (and I’m sure others; I’m no expert on all the different tracking devices!) provide a measure of Ground Contact Time. You will have already got the idea that cadence and ground contact time are very strongly correlated (as is the noise you make as we discussed in our last blog!). Longer ground contact time leads to more load through your body. If you would like to try out a technique change such as increasing your cadence, or ‘running more quietly’ as I discussed in last week’s blog, checking out your device’s ground contact time measurements can help you understand whether these changes are working for you. (Of course, you will also be feeling better as you run if the techniques are reducing loading!) Keeping an eye on this metric might also alert you if you’re falling back into old, less-efficient, running patterns.

Vertical Displacement

If your device tracks ‘vertical displacement’, this can also give you an idea of whether a technique change is reducing or increasing your load as you run. We run to go forwards, not up-and-down, so if vertical displacement is high, that indicates an inefficient running pattern that is also putting unnecessarily high loads on your body. It’s for this reason that vertical displacement is one of the measurements I take during video running analysis, and runners who follow my recommendations typically see this reduce. The two videos below of athletes I have worked with both include examples of measures of vertical displacement:




I hope that this has given you some idea of what you can do with the data that your Garmin, Apple, or other device provides. I meet many athletes who have these devices but do not use the data because they don’t know what it means or how it can be used. This data is useful to the athlete recovering from injury as we can try and understand why injury may have occurred and we can then recover in a way that is hopefully more resilient. For the runner who is not injured, we can use it to be more efficient which can make us less susceptible to injury and even perform better (think, faster, longer, less fatigue).

Even when I have a chance to educate, I do encounter runners who are still not interested as they simply want to run and not worry about tracking or thinking about these stats. I completely understand that mentality as running is a chance to escape the stresses and organization that life places on us. My suggestion to them is that you can monitor for a period of time to see if things need to change and then when you reach a good place you can just periodically check your data. You can then monitor if you plan to make any large changes, such as training for your first marathon, switching to a minimalist shoe, etc.

Don’t waste your investment; at the very least have a look and see what you find!


  1. Chambers R, Gabbett TJ, Cole MH, Beard A. The Use of Wearable Microsensors to Quantify Sport-Specific Movements. Sports Med. 2015;45(7):1065-81.
  2. Available at: http://www.athleticsnovascotia.ca/sites/default/files/Documents/bma10k2007. Accessed September 20, 2016.
  3. Available at: http://www.runnersworld.com/race-training/the-great-cadence-debate. Accessed September 20, 2016.
  4. Lenhart R, Thelen D, Heiderscheit B. Hip muscle loads during running at various step rates. J Orthop Sports Phys Ther. 2014;44(10):766-74, A1-4.
  5. Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc. 2011;43(2):296-302.
  6. Willy RW, Meardon SA, Schmidt A, Blaylock NR, Hadding SA, Willson JD. Changes in tibiofemoral contact forces during running in response to in-field gait retraining. J Sports Sci. 2016;34(17):1602-11.
  7. Wellenkotter J, Kernozek TW, Meardon S, Suchomel T. The effects of running cadence manipulation on plantar loading in healthy runners. Int J Sports Med. 2014;35(9):779-84.
  8. Phan X, Grisbrook TL, Wernli K, Stearne SM, Davey P, Ng L. Running quietly reduces ground reaction force and vertical loading rate and alters foot strike technique. J Sports Sci. 2016;:1-7.

Photo credit:

Photo credit: ShebleyCL via Foter.com / CC BY

Photo credit: akunamatata via Foter.com / CC BY-ND

nakashi via Foter.com / CC BY-SA

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