Heart rate monitor confusion wrt calories burned

I'm a bit curious too. I've been burning fewer calories on my runs. I am running longer, but my HR doesn't peak as high as before, because I am in better shape. I believe we are supposed to push "harder", but I am honestly pushing about as hard as I can right now based on my strength levels.

I guess this is a very "first world" sort of problem.

I still burn a lot...just not as much as before, unless I simply add more "time".

With regard to improved fitness levels burning less calories.......yes and no.

Yes.....If you are doing the same 15km bike ride route in 30mins now that you are fitter, then certainly the stress on your body is lower and the caloric burn therefore lesser.

No......If you are doing the same effort for 30 miins now that you did then, I'd expect the calorie burn to be in the same ball park as before. The key is in the effort. If you were doing 80% of max HR before for 30 mins then 80% now for 30 is the same amount of stress. You're probably able to cycle further in that 30 mins than you used to for the same effort.

Does that make sense?

The level of calorie drop you report seems unusually large to me. Have you changed any of the settings on the Polar? If you've altered your weight downwards and/or your working heart range, then this can have a large effect.

I've read that if you "confuse" the muscles it will do exactly that! I mix it up by walking, running and throw spinning in the mix. My first choice is running but I hit a plateau. The spinning helped rev things up it seems. Also, changing the time of day I work out I think has helped. Just a guess based on things I've read.

It is necessary to vary the training stimulus (in a planned and controlled way) to continue making training improvement, and cross-training can be helpful for the recreational athlete to avoid excessive fatigue and injury, but the idea of "muscle confusion" is just marketing gibberish--a concept that was concocted to sell second-rate workout videos.

For you to keep progressing you have to keep pushing harder and harder. I don't do any cardio but it would make sense to me that it would work much like lifting weights. If I keep lifting the same 15 lbs dumbells for bicep curls for a year I will get little progress compared to increasing the weight along the way.

Re: "Randomly changing activities will not consume more calories. Actually, just the opposite will occur. A less fit or untrained body will burn fewer calories because mechanical limitations prevent it from pushing to a higher workload.

The concept of "muscle confusion" is a pernicious lie that will lower the overall quality of your routine."


I disagree with that , based on my personal experience and one other. Adding other activites and varying the times doesn't make one "less fit" After hitting a plateau AND changing it up has worked for "me", I'm more fit than before sinceI work differing muscle groups instead of "just" running. But everyone is different.

That said, my calorie expenditure by minute is significantly less now that I can run for that hour, given that my running form is significantly better than it was when I started.

It may be a little less, but likely not "significantly" less.

When one starts a new activity (in this case, running), there is an initial period of adaptation. Meaning that the body has to learn the basics of how to do the movement, and, internally, the body has to learn to shunt blood flow and make some other neural adaptations. During this initial time (which is short), the body will not have a consistent, stable response to the exercise.

If one uses these workouts as a "benchmark" for comparison, then, yes, the difference will seem dramatic. Often with a new exercise, esp if somewhat strenuous, HR will skyrocket, the body feels out of control, and an HRM will show you burned 1,000,000 calories. But these are not real numbers and cannot use them as a reference. When researchers want to study the effects of a new exercise machine, or to compare the effects of two or more machines, the subjects always go through a habituation process, so that the entry data is consistent.

Studies on the effects of mechanical efficiency have shown only a small effect over a long period of time--on the order of 3%-6% over several years for trained athletes. Heart rate may drop more dramatically, and that can affect HRM readings, but actual VO2 and calorie burn will not change that much.

And even if "mechanical efficiency" does play a larger role, there is no reason why calorie burn has to decrease for the individual. If one has become, for example, 10% more "efficient", then one, by definition, has the capability to run 10% faster to compensate (at the same perceived exertion level).

In other words, if someone is running at "X" miles per hour and that speed results in a calorie burn of 500 per hour, and after 5 years their economy of form has improved by 10% (meaning they are now burning 10% fewer calories running at "X" mph), then they must be able to now run at "X" mph + 10% at the same level of perceived exertion. This would increase calorie burn to what it was before.

If improved efficiency lowers calorie burn, it's because it has also lowered exertion level. If you are moving more efficiently, then you aren't working as hard. But you are not restricted to that level of effort. If running at 6 mph represented a 70% effort, and the person was comfortable working at that level, and mechanical efficiency reduced that to a 62% effort, why would the person just stay at 62%? They would certainly notice the difference. The logical thing to do would be to increase workload so that you were back at a 70% effort. And by increasingly workload, one would burn more calories.