So, it seems that fitness is quite reliant on your max and min heart rate. Well, there are tables, surely, but what do they mean? There is a handy little calculator here that supposedly clarifies my garmin's estimates.
I enter my age, 42; gender, female; resting heart rate, 60bpm...then hit calculate. Why 60bpm? Because I've been too lazy to check it for the first precious moments when I wake up and am still in bed. Seems though, that this 60bpm is a fairly fit person (not amazingly so, but not a couch potatoe either), so I'll work on the assumption that I am fairly fit.
I don't know my max...and most people don't. Now, my garmin assumed it was 187, but if I let this tool estimate it, its 180. I'll stick to the 187, just because I like that number better :)
Now, if you really want to try to find out your max HR (which a lab test is the only true measure), there seem to be quite a few different methods online to estimate this...go and google!
Most zone charts are based on at least one of the following:
- Lactate Threshold
- VO2 Max
- Maximum Heart Rate
Zone 1: Healthy Heart(40-52%), eg Walking Briskly
Zone 2: Easy(52-64%), eg jogging, can carry on a conversation
Zone 3: Aerobic(64-76%), eg running briskly, can speak in short sentences
Zone 4: Anaerobic Threshold(76-88%) , eg Going Hard, can speak in one word only
Zone 5: VO2 Max(88-100%) , eg All Out!
For me, this equates to the following heart rates (BPM), per the online calculator:
Zone 1: 110-126
Zone 2: 126-141
Zone 3: 141-156
Zone 4: 156-171
Zone 5: 171-187
Basically, I want to be in zone 3 or 4 at my level. Zone 3 will maintain/slightly improve my cardio base, while Zone 4 will push it into a 'safe' overdrive while still burning the "mommy weight" which is one of my goals :)
But, what about that dreaded "fat burning zone" .... In a nutshell, the higher your zone, the more your body will rely on carbs (rather than stored fat) as a percentage of energy. So, yes, Zone 3 will burn more fat than carbs....but if you punch it up to Zone 4, you may be burning more carbs than fat (as a percentage)...but you are burning much much more overall (and even the fat burned in Zone 4 is most likely more than the fat burned in Zone 3). In other words, pushing up to Zone 4 will technically burn more fat than Zone 3.
Now, what is this dreaded Zone 5? From what I understand, this is your anaerobic exercise. Still feels like serious cardio, I know, so the term anaerobic seems foreign to me, as I usually equate this to lifting weights and the like. This phase requires your body to use the sugar, or lactic acid, stored in your muscles. However, this phase does continue to burn calories and can result in weight loss.
That being said, if you want to return to ketosis, you will most likely want to maintain your workout in zone 4-5 to burn off that Dairy Queen Peanut Buster Parfait from earlier in the day :) Otherwise, you will be burning fat, but sugar will definitely remain in your system, so ketosis is never reached.