Written By Rebecca Johansson
Rebecca Johansson is a sports scientist and founder/coach of The Performance Project. She specialises in program design for runners and triathletes and sports performance education for coaches and athletes. You can follow Rebecca on Instagram, Facebook, and YouTube @_theperformanceproject_.
It seems that, with each new generation of GPS watch, there is more and more data available. Heart rate, oxygen saturation, respiration rate, sleep scores, the list goes on! And that doesn’t even include the main reason you probably bought the watch – to track distance and speed. With so much data available to you it can be hard to make sense of it all. Which metrics are the most important to track?
Running distance and speed
Don’t let the fancy bells and whistles detract from the original function of these watches – to track distance and speed. These functions are valuable in tracking training load and they also have good accuracy (Johansson et al., 2020). There are two helpful calculations for training load that take both distance and intensity into account.
1) Training Stress Score (TSS)
If you do most of your training on the road or flat trail, a training stress score can be calculated as follows:
TSS = duration (hours) x (intensity factor) (McGregor et al., 2009).
The intensity factor is a ratio of the session speed divided by a speed you could maintain for approximately one hour in a race situation.
2) Session Training Load
For trail runners, calculating session training load is useful since running speed is highly variable depending on terrain.
2) Session training load = session rating of perceived exertion x duration (minutes) (Foster et al., 2001).
Plot your weekly training load to see how your training is progressing, what value you can consistently hit without injury, and to plan safe increases to your training in the future.
Heart rate is an accurate way to determine intensity, but it’s important to take into account that chest strap monitors are more accurate than wrist-based monitors (Pasadyn et al., 2019). Heart rate can also be affected by ambient temperature, altitude, hydration level, caffeine, sleep, and stress.
When calculated as a percent of maximum heart rate it can be used as a tool to help pacing at ultra-trail events. If the event is going to take several hours, you should spend a majority of your time under 80% of your max heart rate.
These include metrics such as ground contact time, vertical oscillation, stride length, and cadence. It can be useful to look at these metrics as a race goes on and fatigue increases.
While most of these metrics are more useful in road running, cadence can be useful for trail running. Start looking at your cadence as you do climbs in your training. What is your cadence for uphill running and hiking and how much does it differ? Similarly, how does cadence change as the gradient of the climb changes?
One downfall for many trail ultrarunners is not spending enough time practicing efficient uphill hiking before races. Using cadence in your training can help you be better prepared.
Vertical gain and loss
One of the first things you should do when studying an ultramarathon race is to look at the course profile. The amount of vertical gain and loss in a race gives you an idea of what to target in training.
GPS watches use a range of technology to provide data on vertical gain including GPS based altimeters and barometric altimeters. The accuracy of vertical gain and loss is not as good as distance travelled horizontally. For example, if you finish a race and pool together the vertical gain reported from everyone’s watches there will be more variability than when comparing distance reported on everyone’s watches. However, vertical gain and loss is still a useful tool in training to help you adequately prepare for a race. But be warned not to assume that there is no more climbing left in a race simply because your watch has hit the race specifications for vertical gain.
With any metric that you have access to, consider the following questions: 1) How accurate is the metric?, and 2) How can this metric be used to maximise your performance and decrease your risk of overuse injury, if at all?
Foster, C., Florhaug, J. A., Franklin, J., Gottschall, L., Hrovatin, L. A., Parker, S., & Dodge, C. (2001). A new approach to monitoring exercise training. The Journal of Strength & Conditioning Research, 15(1), 109-115.
Johansson, R. E., Adolph, S. T., Swart, J., & Lambert, M. I. (2020). Accuracy of GPS sport watches in measuring distance in an ultramarathon running race. International Journal of Sports Science & Coaching, 15(2), 212–219.
McGregor, S. J., Weese, R. K., & Ratz, I. K. (2009). Performance modeling in an Olympic 1500-m finalist: A practical approach. The Journal of Strength & Conditioning Research, 23(9), 2515-2523.
Pasadyn, S. R.,. Soudan, M., Gillinov, M., Houghtaling, P., Phelan, D., Gillinov, N., Bittel, B., & Desai, M. (2019). Accuracy of commercially available heart rate monitors in athletes: a prospective study. Cardiovascular diagnosis and therapy, 9(4), 379.
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