HIIT Workouts and calories

[Sharples]

I’m having doubts over the accuracy of my data. 

Today I did a 24 minute HIIT workout and apparently burned 138 calories. My heart rate average was 111 and most of my workout was in fat burn zone with 5 mins cardio. 

I also had a 24 minute walk at lunchtime and burned 118 calories with an average heart rate of 113. All fat burn zone. 

I find that when I do intense exercise - HIIT or les mills GRIT then the calorie burn looks really low.  I genuinely work out hard and can’t believe that my heart rate doesn’t need spend longer in cardio or peak zone. 

Can anyone advise me?

i move my ionic up my wrist higher for exercise and ensure it is tighter on the strap before. 

[SilviaFitbit]

Welcome to the Community @Sharples! I appreciate the details you've shared. The reason why you're getting less calories burned when performing HIIT or Les mills GRIT is because, this type of exercises are composed of micro sessions which at the end affects the way your heart rate data. 

Let me share my personal experience, usually when I've done HIIT I get less heart rate average because I stop every 2 or 5 minutes to change the activity and then the average heart rate is lower. This doesn't mean that the intensity of it, is less but since I'm stopping and not doing the same thing for a longer period the heart rate is changing a lot and at the end that's why I get a lower number. 

Remember that the heart rate is measured every five minutes as you can double check on your Dashboard. Because it's an average and not minute by minute data. 

Additionally, you can also try wearing it higher when you're doing a very intense activity and check that your Ionic isn't getting loose or getting down on your wrist. You may want to try higher than two fingers as shown on the image. 

Hope this helps!