I do not believe Fitbit uses heart rate to track calories.  If it uses heart rate to track calories, it would be able to work well with cycling exercises, but it does not. From fitbit website: &quot;Fitbit trackers are optimized for walking, running, and general lifestyle activities but are not recommended for tracking cycling&quot;[0].  Sounds like it uses the step counter and not heart rate to estimate calorie burn along with your weight and age etc.<p>The Charge HR heart rate functionality could be useful to keep my heart rate in a specific range during cardio.  However, it doesn&#x27;t seem like it&#x27;s good for that either[1].<p>[0]<a href="https:&#x2F;&#x2F;help.fitbit.com&#x2F;articles&#x2F;en_US&#x2F;Help_article&#x2F;Does-the-Fitbit-tracker-accurately-track-calories-from-cycling&#x2F;?l=en_US&amp;c=Topics%3AFood_Calories&amp;fs=Search&amp;pn=1" rel="nofollow">https:&#x2F;&#x2F;help.fitbit.com&#x2F;articles&#x2F;en_US&#x2F;Help_article&#x2F;Does-the...</a><p>[1]<a href="http:&#x2F;&#x2F;arstechnica.com&#x2F;tech-policy&#x2F;2016&#x2F;01&#x2F;lawsuit-claims-fitbit-devices-dangerously-underestimate-heart-rate&#x2F;" rel="nofollow">http:&#x2F;&#x2F;arstechnica.com&#x2F;tech-policy&#x2F;2016&#x2F;01&#x2F;lawsuit-claims-fi...</a>