Got one of those Fitbits and most of the time when I exercise my heart rate stays in the “fat burn” zone. Occasionally I get into the “cardio” zone. Not sure how it’s calculating these – is it an age thing? Presumably I need to work harder to stay in the cardio zone for longer? And what about resting heart rate is that important? It says mine is low 60s.

220 minus your age (in years) is the typical max heart rate from which all heart rate zones are measured.

So if you’re 40, your theoretical max heart rate is 180bpm. Zone 5is something like 95% of 180 (so 171) and the other zones are just lower percentages.

HR lags behind exercise so you may be working very hard and it may take 15 or so seconds for your HR to catch up…

220 minus your age (in years) is the typical max heart rate from which all heart rate zones are measured.

And is largely completely bollocks.

0 is a bad reading, a very bad one, anything is better than 0. This may be the only “fact” that appears on this thread. 🙂

It’s 220 a age plus or minus 20. The prediction interval is normally left off the equation 😉 . Mine is about 15 bpm higher than predicted, but still within this interval. You need a good estimate from some activity to set zones properly. Most use threshold heart rate rather than max. British cycling website will calculate them for you from a threshold test.

And is largely completely bollocks.

Really? Care to clarify?

FYI – mine coincides almost exactly with that calculation. There are variations,of course, but for a complete noob, it’s a reasonable starting point until it’s tested properly…

207 – 0.7(age)

seems to be the new formula that is supposed to be more accurate

I would hope that Fitbit would be able to figure this out once the user has entered their DoB in the app (or whatever method they use…)
😉

Anyway, back to the OP….
What are you trying to achieve?
If it’s just fat burning, then you may be in the right zone but does the app tell you what the target HR range is for each of the zones?
Have you worked out your own max/threshold HR?

Is your focus on getting faster or thinner? Power or endurance?

Whilst there are very general rules of thumb for heart rate and heart rate zones, max heart rate (and the consequent fat burn, cardio and anaerobic thresholds) are a very personal thing. As a cardiologist friend of mine put it to me, you either have a fast beating heart or a slow beating heart. I’m 44 and averagely fit from a cardio perspective, but will typically excercise at 180 / 185 bpm at the gym, but can push my heart rate up to around 210 if I’m pushing hard doing intervals, neither of which tally with standard HR formulas. Of course I could just be weird or awaiting and imminent heart attack!

The only way to determine your own max HR is to actually test it, the various formulae are just generic guesses, you may align with them but equally you may not.

I’m 58 so I should either have a MHR of (220-58) = 162 or (207 – (0.7 * 58)) = 166. I don’t know what my MHR actually is but I can sit at 175 for several minutes so it is likely to be upwards of 185.

You really need to some maximal efforts to find your MHR – there’s a high level of safety margin in the various calculations based on Joe average living a sedentary lifestyle.