A lady with jogging tech catching her breath

Sports technology: Fitness Trackers

'Wearables' are among the fastest growing tech items of 2015, with fitness trackers being near the top of the list. But how can they improve your fitness?

During my very brief career as a schoolboy athlete, training generally consisted of running around the school athletics track, timing yourself, then running around again, ideally a little bit faster.

Today, things are rather more technical. The latest 'training device' that can be used by anyone is the fitness tracker. Part of the 'wearables' market and one of the fastest growing technology trends of 2015, fitness trackers are light, unobtrusive wristbands that can monitor a whole host of body functions, from the number of steps you've taken in a day to whether you've been stationary for too long and ought to start moving about.

More sophisticated models, such as the recently released Microsoft Band, feature smartwatch functions such as alarms and timers, calls, messages, calendar and weather.

The information is paired with an app on your phone or a web-based portal and used as part of a training or fitness programme. But what purpose do they really serve?

Motivation

Gary Willis, race director at Race the World, an amateur round-the-world cycling race, sees fitness trackers as a way of monitoring your everyday lifestyle as much as a training device for athletes. As the former Olympic talent coach for British Cycling and performance manager at Scottish Cycling, Willis has worked with individuals who train and compete at the highest level.

He says that whilst top athletes may use fitness trackers to monitor their everyday life, they have coaches and sophisticated training programmes to assess their actual training and competition, so fitness trackers are of far more value to ordinary people looking for a motivational tool to improve their fitness.

"The most basic fitness trackers are little more than glorified pedometers, although more sophisticated trackers are getting increasingly smarter in terms of the information they can provide," he says. "They're especially good for allowing less active individuals to set goals - like how many steps they take in a day - and keeping an easily accessible record of their progress in achieving them.

"But whilst it's easy to set specific goals like this, unless they can be readily measured a lot of people find it hard to achieve them; fitness trackers act as a focus for monitoring your progress in doing so. That said, you do need to get into a routine of downloading the data and using the information the tracker provides, otherwise it just becomes another high-tech gadget rather than a tool to improve your fitness."

Another benefit of fitness trackers is that they provide a record of your everyday lifestyle as well as specific fitness goals, from the aforementioned number of steps you take in a day to the amount of time you spend at rest and even the time you spend sleeping. "If you lead a sedentary life as so many people do these days, a tracker can also inform you of just how little you've done in a day and thus works as a reminder to be more active," says Willis. "Essentially it monitors the effects of everyday life on your overall fitness and wellbeing, whether you're being active or inactive".

This sentiment is echoed by Chrissy Winchcombe, marketing executive for wellness at Garmin, which produces a range of fitness trackers as well as a selection of high-tech watches incorporating the activity-tracking element. She says that the company has found its vivofit and vivosmart bands are used by "everyone; we've found a really even split between male and female users of all age groups. The common link is an interest in health and wellbeing, whether they want the motivation to improve or just to keep track of their activity level".

Winchcombe feels that "the key to Garmin's activity trackers is motivation. They give you the encouragement to move a little more, keeping track of this over time using Garmin Connect, an online training tool that allows you to review, relive and share your steps, goals, sleep, weight and calories burned."

What's inside?

But what's actually in a fitness band? This will, of course, depend on the sophistication of the device. All fitness bands contain accelerometers, which measure orientation and acceleration force, and as such can tell whether the device is moving and whether it is horizontal or vertical. This is used primarily for counting steps, usually via a three-axis sensor which is able to measure the band's position in three dimensions.

GPS is often incorporated into trackers as the chips become smaller and more efficient in their use of battery power. The system is required to lock on to four satellites at any one time to pinpoint your location and consequently map your activity.

Heart rate monitors may also be found on more sophisticated fitness bands, although these are of the optical variety and use a process known as photoplethysmography to monitor the volume of an organ. The arteries and arterioles under the skin are distended with each beat of the heart, and this change in volume is detected by illuminating the skin using an LED and then measuring the amount of light transmitted or reflected (depending on the site) to a photodiode in the tracker.

Each cardiac cycle appears as a peak, and because blood flow to the skin is affected by exercise (or lack of), the readout can be used to monitor heart rate. There are some issues over the effect of skin tone as this must be compensated for in the device's measurements and, although useful, the accuracy of readings obtained from optical heart rate monitors can vary.

Interestingly, heart rate can be linked with skin temperature - measured by a thermometer within some fitness trackers - to inform the wearer of potential illness. If there is a rise in skin temperature but no increase in heart rate, this may be an early sign that the wearer is going down with a virus or other illness. In more benign circumstances, an increase in skin temperature is an obvious sign that the wearer is exerting themself in some way.

Also relying on skin temperature, galvanic skin response sensors in fitness trackers measure electrical connectivity of the skin; as you warm up your skin conducts electricity more efficiently and the sensor within the band can monitor this.

Light can also be measured in both the UV wavelength, which allows the band to warn that you may be in danger of getting sunburn, and in the form of ambient light level, which can be used to adjust the brightness of the screen (if the device has one).

Several of the above features may be measured by just one bioimpedance sensor. In the case of Jawbone's new UP3 tracker, the sensor measures heart rate, respiration rate and galvanic skin response by detecting very small impedance changes.

But as Gary Willis points out, "None of this will get or keep you fit, but it will help you monitor what you're doing on a daily basis and ideally encourage you to do what's required to improve or maintain your fitness level".

So shouldn't we all be sporting a fitness band? Perhaps one day we will.

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