I didn't find the Band 2 to be the most accurate device at tracking my heart rate with its optical sensor, but now Microsoft is providing information on the device's monitoring and tips on how to get the best results.
According to an article on the official Microsoft Devices Blog, a team of two sports physiology researchers are "responsible for stress-testing finely tuned algorithms" for the Band 2's optical heart rate sensor. Josh Boonstra, one of the researchers, said they use a large volume of data and are constantly tuning their algorithms to provide the best results possible.
Clark Masterson, the other half of the physiology research duo, said their algorithms are most used when a wearer of the Band 2 is active, and the team behind the device created specific activity-based algorithms to best estimate heart rate. The actual information is acquired by LEDs – the "optical" part of the heart rate sensor – that are used to light up the wearer's capillaries to monitor blood flow. Specific algorithms are then used for each exercise mode of the Band 2 – such as running or biking – to provide the best results available.
Lindsey Matese, the senior communications manager at Microsoft who wrote the article, said three tips can help users get better results: wearing the correct size Band, having a tight fit so the LEDs can best track blood flow and using the right tile for the type of exercise you're doing.
For what it's worth, I haven't had the same success as Microsoft's article despite meeting its three recommendations, especially when it comes to high-intensity exercises. Microsoft seems dedicated to providing the best results possible, however, so here's hoping its developers keep improving the Band 2's tracking abilities.
Source: Microsoft Devices Blog