PolarFit 4 calories burned questions....

hookilau

So I got a PolarFit 4 in order to get my heart in better condition and keep my BG under control.

I weight train regularly & have heard that the 'calories burned' calculated by my HR monitor is inaccurate.

My question is, if my heart rate is elevated to within my 'zone' for the duration of my workout, (over 60 min. yes, apparently I need more conditioning) then can I trust what it says as far as calories burned?

BarackMeLikeAHurricane

No. Volume load vs pressure load. Subtract around 70-80% of the calories burned for a more accurate estimate.

vorgas

justsomerandomgirl is right.

When considering fuel sources there are two basic types of workouts: aerobic and anaerobic. Aerobic exercise combines fat with oxygen to create fuel. Anaerobic exercise uses glycogen (carbs) in your muscles as fuel. Lifting weights is anaerobic. What most people call 'cardio' is aerobic.

Your HRM is designed to measure aerobic exercise. Your heart is beating faster to push more oxygen through your body. If you try to use it to calculate calories burned during anaerobic exercise it's not going to be accurate. Sorta like using your fuel gauge to measure how fast you're driving.

The amount of energy needed to lift a weight is well established. It's 4.184 calories (that's .004184 Calories) per kilogram per meter. So to burn 1 Calorie that we track on mfp (technically a kilocalorie) you need to move about 250 kilograms (550 lbs) a meter (3.2 feet). Average weight motion is about half that, so you need to move 1100 pounds total, or 11 reps with a 100 lb weight.

Of course, your body is terribly inefficient and so requires a lot more calories to apply 4.184 calories per kilogram per meter. But as you can see, it's nowhere near as many calories as your HRM would indicate.

This is why MFP doesn't really track calories burned from weight lifting. For most people it's pretty negligible. Weight lifting isn't about the calories burned while doing the exercise. It's about a whole host of other health benefits, including looking thinner and burning more calories while just going about your day.

hookilau

justsomerandomgirl is right.

When considering fuel sources there are two basic types of workouts: aerobic and anaerobic. Aerobic exercise combines fat with oxygen to create fuel. Anaerobic exercise uses glycogen (carbs) in your muscles as fuel. Lifting weights is anaerobic. What most people call 'cardio' is aerobic.

Thank you both for your responses. I think I understand now, but have an additional question.

I recently started 'shuffling' (that slow jog that folks who never ran before do, lol) intermittently with walking as I seem to be in fair cardiopulmonary health and it's all I can manage right now.

I'm restricting my starchy food intake because my blood sugar goes damagingly high.

I've noticed that a 20 minute 'shuffle' can drop my BG quite a bit & bring me to near normal levels, meaning that because I'm testing before and after, I know this to be true for sure. Aerobic, so fat+O2=fuel.

What happens during weight training if my starchy food intake is severely limited? Please forgive if these questions seem odd, I've recently been given new parameters within which to 'work' this body in & am having trouble understanding what a new 'normal' for me is.

vorgas

You get carbs from all kinds of sources. Fruits, vegetables, sugars, honey, etc. Your diet is closed so I can't really comment on where you are, but MFP does track macros. Find other sources of carbs and you'll be fine.

If you don't have enough glycogen to fuel a lift, the most common response is form failure. In other words, you will re-position your body to lift the weight instead of using the correct muscles. Sometimes this is no big deal, such as leaning into a tricep pull down thereby using your body weight to get it moving. Sometimes it can lead to injury such as rounding your back during a deadlift. Best thing to do is take it easy, and focus on form and technique, especially in the beginning. Quit as soon as you get to form failure.

hookilau

Thank you again that makes alot of sense to me. I'd never had trouble before but after changing my diet
due to metabolic disorder, I *have* noticed I was having some difficulty with certain exercises that I had never had before.

I just chalked it up to 'my new normal'. Yes, I'm getting carbs from non-starchy veggies but clearly functioning at a deficit compared to 3 wks ago.

My diary isn't open because I haven't been tracking my macros in this manner lately, rather, much to my dismay, I'm having to use other parameters to track my health...my glucometer.

Thanks for taking the time to explain, often I find I have to ask the same question a number of different ways to get an answer I can use or understand. :drinker:

I think I'll try some toast & cheese before the gym to see if that makes a difference. I had done that a wk or so before but not completely knowing the why's and wherefore's, I hadn't made the connection that it's fuel I can use without adverse effects in the short term.

PriceK01

I've been logging my Starting Strength workouts in the cardio section under "strength training, weight-lifting." Is that a safe guesstimate?

vorgas

Safeish, but it does come with a warning about it's accuracy. It simply has no idea.

For example: Lets say you are doing arms for 60 minutes and so am I. We both weigh the same and are lifting the same weights. However you only use one arm at a time and I use two, as a result I lift more weight. Incidentally, you can use this to test the inaccuracy of HRMs for weight lifting as your HR will be nearly the same despite 2x as much weight.

Lets further say you rest 90 seconds and I only rest 60 seconds. Who burns more calories? None of this is tracked by the calorie tracker.

As long as your daily deficit is over 250 it will probably even out in the end and won't be a big deal. This is one of the reasons I so strongly recommend that you set your weight loss goal to 0 lbs, eat all those calories, and not eat back exercise calories. Weight loss comes from exercise, which results in a healthier you overall. You don't have to worry about accuracy in an inherently inaccurate system. Just pick up heavy things, put 'em back down, and look and feel a lot better

JoanB5

You may be a good candidate for "In Place of a Road Map" post (see my profile for the link if you like). I calculate my TDEE by their method (then use HayBaler's excel sheet), and then only eat the full amount if I get my workout in that day. Otherwise, I subtract a couple hundred calories.

HIIT training nor strength training are handled well by HR monitors.

hookilau

You may be a good candidate for "In Place of a Road Map" post (see my profile for the link if you like). I calculate my TDEE by their method (then use HayBaler's excel sheet), and then only eat the full amount if I get my workout in that day. Otherwise, I subtract a couple hundred calories.

HIIT training nor strength training are handled well by HR monitors.

I'm not sure if this comment was directed at me, but TDEE won't work for me as I do not respond to some foods favorably. I'm not concerned with my caloric intake or burn as much as I am with being able to fuel my workouts effectively. (if that makes any sense, lol)

In other words, my original question was less about whether I could eat those calories burned and more about why the HR monitor was inaccurate since my heart is working hard according to the numbers I see.

Due to recent life changes, my primary goal is conditioning my heart, conditioning my body with far less emphasis on calories burned vs calories consumed.