Better shape or faulty HRM?

ChubbieTubbie

I've been riding my bike every day for the last 5 weeks, and when I first began (coming from 'couch potato' status) I was burning 225 calories in 15 minutes when I pushed myself as hard as possible, according to my HRM. 5 weeks later, I'm only burning 175 for 15 minutes, according to the HRM. Before, MFP estimates were super low compared to my HRM, now they're nearly exact. Am I burning less calories doing the same activity because I'm getting into shape or do you think it's a problem with my HRM? It used to take little effort to get in the 75-80% range, and now even when I'm going as fast and hard as I can, I don't get out of the 68-70% range until 10 minutes into my ride, and then I usually only fluxuate between 70-75%. I've started increasing my riding time, since now I don't feel like I'm going to die after only 15 minutes, but I just don't know if it's normal for this to happen after only a few weeks--I'm really new to this exercise thing.

kristinlough

You're in better shape! It takes a lot more to get your heart rate up Congratulations!

meggonkgonk

Yea, that sounds like better shape to me- my MFP estimates are pretty close to my HRM measurements usually (except for weird things like "carrying groceries up 6 flights of stairs")

erickirb

Its not just that you are in better shape but also that your body gets use to the same activity. It is recommended that people switch up their routines every 4-6 weeks for this reason. Muscle memory makes it easier to do the same exercise it is a survival mechanism. Try running, or swimming instead, your heart rate may be slightly lower than it would have bee 5 weeks ago, as you are in better shape, but it will be much higher than doing the same exercise day in and day out.

ChubbieTubbie

Its not just that you are in better shape but also that your body gets use to the same activity. It is recommended that people switch up their routines every 4-6 weeks for this reason. Muscle memory makes it easier to do the same exercise it is a survival mechanism. Try running, or swimming instead, your heart rate may be slightly lower than it would have bee 5 weeks ago, as you are in better shape, but it will be much higher than doing the same exercise day in and day out.

I usually ride my bike every day and I walk/jog (C25K) three times per week, as well as swim 3 times per week. I try to get in an exercise DVD 3 or 4 times per week too. As soon as I get down ten more pounds, I'm going to buy an elliptical machine (250 lb limit and I'm at 262) and add that in to see if I can see a difference. I'm not sure what other sorts of activities I should be doing?

Thank you everyone for your input!

DJH510

What "shape" you are in has nothing to do with calories burned during a given activity (cycling as a certain speed for a particular amount of time). Just because you find it physically easier to perform the same exercises, it does not mean you suddenly require less overall energy to perform them; that would be breaking the laws of physics. Most likely what has happened here is that your VO2 max has increased gradually with exercise (in other words, you have gotten fitter) so the same amount of work requires a lower heart rate than before. If the HRM can be calibrated to account for this change in your fitness level then adjusting that should get you closer to a true reading again.
But remember, there is not reason to assume, as nearly everyone on here does, that the figures the HRM are giving you are accurate in the first place. or even that they are more accurate than the one MFP provides you with. They are both just estimates made using generic formulas, and only provide you with a ballpark figure. For most peoples purposes, a ballpark figure should be quite enough!