Be Fit For Life

with Ellen Cohen-Kaplan

How accurate are activity trackers?

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Nike+ Fuelband ($99-$149), Fitbit Ultra ($99), Jawbone UP ($99), BodyMedia FitCore ($99) and the Adidas MiCoach ($199)

Nike+ Fuelband ($99-$149), Fitbit Ultra ($99), Jawbone UP ($99), BodyMedia FitCore ($99) and the Adidas MiCoach ($199)

fitbit, jawbone, Nike trainer, mi

Activity trackers like the Fitbit, Jawbone and Nike Fuelband are all the rage in the fitness industry. Should you invest in one? Do they measure what you want them to measure? Can they have a positive impact on your fitness level? Are they light and convenient enough so you’ll be motivated to use them? All these questions are ones you should ask yourself when considering this investment. They all have different strengths, measure a range of variables, and may cost from $100 to $200.  So what does the science say about their accuracy and efficacy? ACE, the American Council of Exercise, the certifying agency for thousands of us fitness trainers, recently teamed up with University of Wisconsin- LaCrosse to conduct a study that shed some light on these issues.

Twenty healthy subjects between the ages of 18 – 44, evenly split between men and women did activities while using the fitness trackers along with portable metabolic analyzers and the NL-2000i pedometers.  The analyzers and pedometers are proven accurate means of measuring fitness parameters. The test subjects walked and ran on a treadmill and elliptical.  Then they did sports exercises such as basketball free throws and ladder drills. The 5 trackers tested included the following: Nike+ Fuelband ($99-$149), Fitbit Ultra ($99), Jawbone UP ($99), BodyMedia FitCore ($99) and the Adidas MiCoach ($199). [Note: Since this study was completed, BodyMedia was purchased by Jawbone.] For more details on the study and its results, go to

All five devices predicted within 10 percent accuracy the number of steps taken during treadmill walking and running, as well as during elliptical exercise .  However, accuracy really takes a dip when assessing steps and moves during agility drills, because the trackers aren’t as good at measuring small or quicker leg movements; hence energy expenditure becomes hard to measure. These small quick leg moves also led to less arm movement, and since the Fitbit is the only  tracker not worn on the wrist, accurate registration is less likely.

People move in a vastly different ways, some more efficiently than others. You have only to watch 10 or 12 people walk by to notice the differences in their gait –  the way they swing their arms, the length of their stride, and their reciprocal movement from side to side are just a few ways that gaits differ. The same is true during athletic movements- accuracy of these measurements as recorded by the fitness trackers, compared to the metabolic analyzers and pedometers was poor.  The fitness trackers also had a variability of 13-60% when it came to measuring caloric expenditure. Once again, this can be explained through the wide range of ways people move their bodies, as well as basal metabolic rate, amount of lean muscle mass, and factors related to each individual’s body composition.

The bottom line is that trackers are best for measuring simple activities like walking and running. Once you bring dancing and complex upper and lower body moves often done in classes into the picture,  trackers really decline in accuracy. However, they may provide motivation to move those 10000 steps a day and they take total daily activity into consideration.  Some people think that exercising 30 minutes a day will suffice, even if they’re sedentary the other 14 hours of their waking time. Just wearing a tracker may motivate you to move more frequently, as the numbers will provide some accountability and is an objective measurement.

Previous studies have shown that people are 30% more active when they wear the trackers, so the main point may be that they do their job of increasing moving and fitness levels over time. Accuracy of measurement of movement and calories may take a back seat to actual minutes of movement. The trackers keep it interesting by seeing (an estimate) of your activity of the day, setting goals and working to exceed them by looking back at where you began.

So, the bottom line when choosing trackers:

  • Pick one that’s easy to wear and program
  • Depend on it less for accuracy and more for motivation
  • Use it to set goals and then continuously try to improve on past performance
  • Use it to track total number of steps (fairly accurate) and frequency of activity (for example, 5-6 days/week, 1 hour at a time)

If you’re considering buying one, find one that best meets your needs based on your exercise preferences, and use a phone application for caloric expenditure like my fitness pal or fitness buddy. If you already own a tracker, consider which functions are most relevant for you; use them for motivation, monitoring your progress and setting goals. The most important function of a tracker is to ultimately increase your sense of well being and fitness level by motivating you to get moving!

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