A ‘Data Junkie’ and How the Info is Useful

03/15/2017 - 14:58

By Tracy Green

This morning, 58.9 percent of me was water. My resting heart rate was 57. And I averaged 184 steps per minute on my run. Fitness tracking and wearables are a huge market, and you might even have a device on your wish list. Pretty likely when I mentioned resting HR, you thought about checking yours on the device on your wrist.

I’m a data junkie, so I have a Garmin Forerunner 35 and plus a Garmin Index Smart Scale. So what the heck do all these numbers mean, and which ones matter?

I talked to two guys, both named Matt, and who both know what they’re talking about. Matt Ebersole is the coach of Personal Best Training, based in Indianapolis but with clients across the country. He’s been coaching for 25 years, and works with runners of all levels, from 6-hour marathoners to Olympic Trials Qualifiers. He also has the dubious distinction of being my coach.

I also talked to Matt Fitzgerald, author of “How Bad Do You Want It,” “80/20 Running,” and a bunch of others. "I believe that many of the health and fitness metrics that runners are now able to monitor with wearables, apps, and other technologies CAN be useful,” Fitzgerald said, "Whether they actually ARE useful depends on how they are used."

Resting Heart Rate:
If you wear a FitBit or other activity tracker, you probably have this data. If you record it frequently, it can be a great tool. An uptick in your resting heart rate can indicate you’re not fully recovered, or that you’re overtraining.

“But as with most numbers, people don’t pay attention to it until something is wrong,” Ebersole said.

Similarly, Fitzgerald said his favorite app for monitoring training stress and recovery status is HRV4, which measures heart rate variability. The app uses the camera on your phone to measure your heart rate, so no sensors or straps needed. (Current generation phones include both a camera and a light emitting diode, which can be used for reflection based bio-optical imaging. The technique is called photoplethysmography, or PPG.)

"What distinguishes it from similar offerings is that it is supported by reliable guidance on how to use the information you're gathering about your body in order to train more effectively,” Fitzgerald said.

Iron levels:
Ebersole said knowing your iron levels, both ferritin and hemocrit, is really useful especially for female runners. Again, you need baseline data to make the most of this.

“I have some women who train well at 35-40, but some who are over 100,” Ebersole said. “It makes me wonder what those women could do if they were at a hundred, too, though.”

This wide range points to the need to get your levels checked when things are going well — during a recovery phase, for example. Then, if you’re feeling run down in a period of heavy training, a check of your iron levels can be compared to past data.

“Ideally, we’d track that every two weeks or once a month,” he said. Obviously that’s not feasible for most people, but worthy of routine checking.

Measured in steps per minute, cadence is a way to measure the efficiency of your form. But before we say anything else about it, know this: any changes to your cadence should come from strength training and stretching — not by just trying to take more steps.

While it varies by person and pace, around 180 steps per minute is a general target. More and more running watches track cadence, but it’s also pretty easy to do with just a timer. For 30 seconds, count the number of steps you take on one foot, multiply by 4. If you’re bored on the treadmill, that’s a great place to check your cadence, and you can see how it increases as higher speeds.

Ebersole said a dip in cadence can be a predictor of injury, because it can show a runner is slipping back into old habits. Fewer steps per minute is typically an indicator of overstriding, and also increases impact forces on your legs and decreases forward momentum.

Fitzgerald is more cautious
"Research has consistently shown that virtually any attempt to increase or decrease one's cadence from what is natural worsens running economy. That's because runners naturally adopt the cadence that is most efficient for them.”

But, cadence can change beneficially — "but it has to happen naturally as part of the subtle stride evolution that unfolds as runners keep running.”
If you’re really interested in understanding biomechanics and injury prevention, pick up a copy of Jay Dicharry’s “Anatomy for Runners.” It’s the one my physical therapist uses in her work, and it has a place on my nightstand.

I know I should get 8-9 hours of sleep per night, but if I don’t use an alarm that shows how many hours I have until it’s time to wake up, I won’t get enough. Same for having it logged via my Garmin. It just takes staying up a little later and getting up a little earlier and suddenly it’s Saturday long run day and I’ve had 6 hours of sleep the two nights before.

For me, sleep tracking is a reliable way I can make sure I’m logging enough hours. It can also point to issues you might be having, like if you wake up frequently. Remember, sleep is when your body recovers from training and that fitness gains are made. If you’re not sleeping adequately, your training may be for naught. Sleep deficit can also weaken your immune system.

Two things that don’t matter at all:
— Pace on easy days. Ebersole said some runners focus on this as a measure of fitness, the faster you can run on easy days, the more fit you are. He recommends using heart rate as a key indicator for easy days and not worrying about pace at all.

— GPS and the Strava effect. To some extent, this phenomenon has existed as long as we’ve had any sort of watch.

“I’ve even found myself doing this coming back from knee surgery,” Ebersole said. “I look down at my watch and feel like I have to speed up or I’m going to kill my average pace.”

(Tracy Green is a runner and writer living in Louisville, KY, where she lives with her husband, Chris. She is a Hammer Nutrition sponsored athlete and certified Pilates instructor. Find her at @TGRunFit on Twitter and Instagram,, or

(This column appeared in the March print issue of Running Journal. To subscribe, go to

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