How is Cardio load calculated?

[patilu]

In response to a prompt, I indicated I wanted to improve my cardio load. The first few cardio load scores in the '40s based on treadmill workouts seemed reasonable. Then yesterday I got a score of 1 for a 30 minute  intermittent interval spinning workout where my average heart rate was 132 which is well into the vigorous range for me and more challenging than my typical spinning workout. According to Fitbit, My cardio fitness score is 39 to 43 which is considered excellent for my age. I don't understand the why discrepancy between the treadmill scores and the spinning score.

Moderator edit: updated subject for clarity

[jbatchellor]

I totally agree. It should be better with Google you would think. My
husband bought a new fitbit and it's not working right either. Maybe they
are steering us to the Google watch and not putting much effort into the
fitbit.

[shrlzi]

I’ve noticed that if my hand is still - eg pushing a grocery cart - my steps are not always counted - think it’s related? I wonder if wearing watch on ankle would help

[RiekoC]

Hello @shrlzi 

This help page explains how Fitbit devices track steps (<-- click link). As a wrist worn tracker, the device uses arm movements for step tracking, which is why you don't see as many steps when you're pushing a grocery cart or using a treadmill while holding onto the handrails.

I have seen where some users will wear their Fitbits on their ankle during a treadmill session so they get a better step count. However, I'm not sure if they get good heart rate tracking when they wear their devices on their ankles.