Fitbit Zip Ionic User Manual page 12

For optimized heart-rate tracking while exercising:
Try wearing Ionic higher on your wrist during exercise for an improved fit and
l
more accurate heart-rate reading. Many exercises, such as bike riding or
weight lifting, cause you to bend your wrist frequently, which can interfere
with the heart-rate signal if the watch is lower on your wrist.
Make sure the watch is in contact with your skin.
l
Don't wear your watch too tight; a tight wristband restricts blood flow,
l
potentially affecting the heart-rate signal. The watch should be slightly tighter
(snug but not constricting) during exercise.
With high-intensity interval training or other activities where your wrist is
l
moving vigorously and non-rhythmically, the movement may limit the
12