Sports watch relies on optical technology to continuously measure heart rate

February 21, 2013 // By Julien Happich
With the Mio Alpha sports watch, Nordic Semiconductor has unveiled what the company claims to be the world's first strapless continuous heart rate monitor for athletes.

The sports watch employs a Nordic µBlue nRF8001 Bluetooth low energy Connectivity IC to communicate live or stored training data directly from the wrist to any Bluetooth v4.0 enabled smartphone or device.

The Mio Alpha is designed for both serious amateur and professional athletes and employs a unique electro-optical cell with a pair of optical sensors on the underside of the watch to track blood flow volume in the wrist as it pulsates with the rhythm of the heart to extrapolate heart rate.

An on-board motion detector and built-in noise filtration software developed by Philips compensate for arm movements and perspiration typical of fast running and cycling, which can all interfere with blood flow measurements.

The watch's built-in rechargeable lithium ion battery offers up to 10 hours of 'live' heart-rate smartphone-linked monitoring (its most energy intensive operating mode). This ensures reliable performance even in demanding 2.4GHz operating environments such as busy, modern gyms that can house numerous local active devices and emitters (in particular Wi-Fi) all working on the same frequency.

In operation, the Mio Alpha can be used as a standalone device and includes features such as workout timers, continuous heart rate display and audible heart-rate zone alerts, or in conjunction with popular smartphone apps such as MapMyRun, RunKeeper and Wahoo Fitness.

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