I burn less calories the better shape I'm in?

forevermaryb
forevermaryb Posts: 108 Member
in Fitness and Exercise
I started a strength training program 4 weeks ago to specifically work on my hips/thighs. This program was given to me by a physical trainer. The first day I did it, I used fairly light weights on my weighted squats, lunges and bench steps and I also completed less reps than I do now with more rest breaks (It was HARD!). That first day, I burned close to 700 calories according to my HRM. So now, after 4 weeks, I've almost doubled the weights I use (I started small), added more reps and take less breaks. At the end, my muscles are like jelly and I'm sweating buckets. I look at my HRM and I've burned 545 calories. Both sessions took about the same amount of time, I've just added more reps while reducing breaks. While YAY for 545 calories burned, I'm a bit confused. I also noticed that I used to burn right around 400 calories for a Zumba class and now I'm lucky to burn over 300 for the same time/effort/instructor. My weight hasn't changed, so I haven't had to adjust that on my HRM settings. Could someone please explain? Isn't there some sciency kind of explanation for strength training=more calories burned or am I making that up?

Replies

  • toddis
    toddis Posts: 941 Member
    Your body becomes more efficient.
  • brianpperkins
    brianpperkins Posts: 6,124 Member
    HRMs are not for calculating calories from strength training. HRMs use algorithms that work for certain aerobic activities.
  • fleetzz
    fleetzz Posts: 962 Member
    I don't know the details but it calculates calories burned based on your heart rate. As you become more conditioned (more mitochondria in the muscle cells), your heart has work less hard to deliver the oxygen because the cells are able to utilize the oxygen delivered more efficiently (think of a little 2 piston engine becoming a 16 piston engine--I am not into cars but you get the meaning). No matter how much gas that little 2 piston gets it isn't going anywhere fast (that is your crappy out of shape muscles). As you get in better shape you become a 16 piston engine, and it sucks all the gas (oxygen) that it is provided.

    So as you get in better shape your heart doesn't have to beat as fast. It delivers more blood per pump and the muscles suck all the oxygen and glucose out of the blood much more effectively. The calculator on the HRM doesn't know that. All it knows is that the heart rate has dropped.

    Some monitors will be able to set these values for you--but you will have to ask somebody else how it is done, and which ones do those calculations.

    You still burn the same or more calories if you work the same or harder.
  • Mr_Knight
    Mr_Knight Posts: 9,532 Member
    No. If your weight hasn't changed, and you're doing the same amount of work, the number of calories burned will be essentially identical. What may happen is that as your fitness improves, you can maintain a higher work rate for longer - in which case your burn will go up, not down. But a typical HRM won't be able to pick up on that.

    HRMs are not appropriate for guesstimating calorie burns for the type of exercises, they will (for most people) vastly over-estimate the calorie burn.
  • forevermaryb
    forevermaryb Posts: 108 Member
    Thank you for the replies. So there is really no way to accurately calculate calories burned during strength training and a HRM may overestimate calories during those exercises? How do you adjust your calorie intake? I'm trying to stay at a small deficit (those pesky few pounds).
  • jasonheyd
    jasonheyd Posts: 524 Member
    Mostly repeating good advice / input above, but...

    In general, the HRM is not good for strength training because it's intended to measure elevated, steady-state heart rates. If you're resting in between sets, your HR drops, the HRM accuracy goes *poof*.

    With that said, if you're doing higher-intensity circuit routines, the HRM can work. If you're moving from exercise to exercise with pretty much no rest in between sets, then you're blending cardio and strength training. Even then, the HRM won't be as accurate as for activities like walking, jogging, running... but it's not 100% terrible. :)

    And yes... the more you get in shape, the lower your calorie burn is likely to be unless you somehow increase your exertion level. HIIT is pretty good for keeping the calorie burn up, and the HRM is good for that -- beyond calorie burn estimation -- because it'll help you target specific heart rate zones to maximize your efforts.

    If you want to estimate non-HRM style activities, I've found MFP's estimates to be fairly good. You can find strength training under "Cardio" exercises for some reason.

    I generally double-check against the Compendium of Physical Activities, which is a research-based standard for estimating the calorie burn of a huge number of activities. I've got a Google Spreadsheet of the Compendium set up where you can input your height, weight, gender & get tailored calorie burn estimates:

    https://docs.google.com/spreadsheet/ccc?key=0Al5RZKHzjd6wdG5pTWVVNXV6MnZMZVVlQUNSenFDWkE&usp=sharing

    It might be more effort than you're interested in but, if you're a numbers geek like me, maybe you'll find it helpful. ;-)

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