RUNNING METRICS: A CLOSER LOOK AT WHAT YOUR WATCH IS TELLING YOU

As our season of racing begins to wind down, you may find yourself looking back at the year and evaluating how you did with your running. You may even find yourself setting some new goals, and thinking about all of the tools available to you and how they can help you get to the next level. One of the best tools you have could very well be the one strapped around your wrist.

Two months ago I spent a little time going over some of the very useful running metrics that some running watches keep track of; heart rate, cadence, vertical ratio and ground contact time (GCT) balance. Running metrics are becoming more and more popular; they were even featured during the broadcast of this year’s New York City Marathon, so for this week’s Corner I wanted to dive a little deeper into each of these metrics and talk a little more about the data behind them and what they are really telling us about our running.

HEART RATE

As I mentioned in my previous post, heart rate (HR) is one of the best, if not the best, indicator of running effort. After all, the heart never lies. Understanding how your heart rate responds to different types of runs can really benefit your training by guiding you to make better decisions about your pace and your effort. Understanding HR training begins with knowing what your maximum heart rate is. Your device most likely tracks both average and maximum heart rate. Maximum heart rate is generally described as 220 minus your age. This is a good formula, but keep in mind that maximum HR can be a little lower or higher than what the formula predicts, and this can only be determined through a fitness test or over time.

HR training is also classified into HR zones, which correspond to different levels of running intensity. Garmin identifies these as zone 1 (Z1), zone 2 (Z2), zone 3 (Z3), zone 4 (Z4) and zone 5 (Z5); the higher the number the higher the intensity. When using the Percent of Max Heart Rate method, your maximum HR defines the upper limit of the highest zone (Z5) and every other zone under that is a percentage of your maximum HR. Each zone is also a heart rate range, so for example, my Z1 range is 95 to 114 beats per minute, or 50 to 60% of my maximum HR.

Generally speaking, this should be the intensity level of each HR zone:

Z1: Warm-up

Z2: Slow jogging

Z3: Easy running

Z4: Fast running

Z5: Very fast running

Here is a snapshot of one of my 5K races, my corresponding HR zones, and the time (in minutes and in %) spent in each zone:

Yup!! That’s a 5K for you!

Understanding how to train using HR means understanding which zones your training runs should fall in, and this is where running becomes more of a science. It’s very common to see this kind of breakdown (chart above) from a race, especially a short-distance race, but the real challenge lies in how to plan your training runs in order to maximize the benefit of HR training. At the very least, it’s fascinating to observe what your HR zones look like after each type of run; you will most likely find that your longer runs are in the lower zones and your shorter runs or workouts are in the higher zones.

There are other methods of HR training:

The Percentage of Lactate Threshold Heart Rate method uses lactate threshold HR rather than maximum HR to determine the zones. Lactate threshold is the level when your body begins to accumulate lactic acid faster than you can flush it out.

The Percent of Heart Rate Reserve method measures your resting HR and then calculates your heart rate reserve, which is defined as the range between your resting HR and maximum HR (HRmax-HRrest = HRreserve). Then it determines your training zones within this reserve. The more fit you become, the lower your resting heart rate gets, giving you a larger reserve to work with.

While there are several schools of thought on which method is best, it's most important to be able to accurately measure your heart rate, using the right sensor. Then you can decide which method to use, to inform your decisions on targeting the correct zone, based on the timing of your next run within a training cycle.

You can usually choose which HR zone method to use within your device’s user settings. You may also notice that your device tracks something called training effect. This metric uses your HR to measure the accumulated effect of exercise on your aerobic fitness, to determine if you are maintaining your current level of fitness or improving it. Another very useful by-product of HR training.

CADENCE

Cadence is defined as the frequency at which your feet land on the ground while running, and is measured in number of steps per minute (spm). There is a popular belief that the optimal cadence for a runner is 180 spm but in general, the higher the cadence the more efficient a runner becomes, and more running economy usually translates into faster times and less chance of injury. This is what makes running cadence an important metric to track.

Garmin has researched many runners of all different levels and in general, more experienced runners tend to have higher cadence. Here is a chart that you can use to compare your cadence to that of other runners:

Much like HR, cadence often varies within a particular run but unlike HR, the more useful metric to focus on is average cadence over maximum cadence because it provides more information about the entire run. Generally, a runner starts off with a lower cadence in the first few steps or first mile, then gradually builds to a higher cadence hovering around the average for that run. Cadence can also vary depending on the type of run (for example, a long run vs. a workout) but maintaining a cadence as close to 180 spm is ideal!

To illustrate how cadence can vary depending on the run, here’s my cadence from a long run, compared to my cadence during the 5K I mentioned before:

VERTICAL RATIO

Vertical ratio (VR) is another metric that can be very useful because it demonstrates a runner’s efficiency. It compares a runner’s lift off the ground (vertical oscillation or VO) to the distance traveled with each stride (stride length or SL). The calculation is VO/SL = VR. Garmin uses the bounce in your torso to determine your oscillation, and the length of one footfall to the next to determine your stride length.

There are two ways you can affect your VR and improve your running efficiency:

1. Lower your vertical oscillation by running less with a forefoot strike and a “bounce” in your step and more on your midfoot.

2. Increase your stride length by applying more power off the ground INSTEAD of reaching with your legs to cover more ground.

Here are the vertical ratio ranges of the runners that Garmin has researched, and the percentiles of each range:

GROUND CONTACT TIME BALANCE

Ground contact time (GCT) is the amount of time in each step that you spend on the ground while running and it’s measured as a percentage of contact time between the right foot and left foot. GCT demonstrates a runner’s leg symmetry and it could also indicate strength imbalances and leg length discrepancy. As you would expect, a symmetrical gait is preferable when it comes to running efficiency, running performance and injury prevention.

Of the runners that Garmin has researched, GCT balance tends to deviate further from 50-50 when running up or down hills. The camber angle on a road can also affect your GCT balance so this is something to be very aware of, especially in terms of injury prevention and the longer a run is.

Here is a breakdown of GCT balance among the runners they researched:

As you can see, the majority of them tend to favor their right foot over their left foot. However, it is possible to have near perfect symmetry! Here’s the data from my long run:

If you’re fortunate enough to own a running watch that tracks some or all of these metrics (I use a Garmin Forerunner 630 with a chest strap heart rate sensor) take the time to study them a little closer. You may be surprised and informed by what you find. These metrics are fascinating and there are even more out there that your watch can track! If your watch doesn’t have these features, well, it may be time to get a new watch

Run better. Run smarter. Run for life.

Coach Mwangi