Unlike chest straps, wrist - based trackers fit comfortably into everyday life, providing continuous heart rate
for up to several days
without recharging (vs. a couple hours at a time) to give a much more informative picture of overall health and fitness trends,» Fitbit representatives said in a statement, adding that their internal tests showed an accuracy rate of 94 % [or a
margin of
error that was about 6 %.]