Walking in Place / Calorie Accuracy Questions

I've found that while I am at work or home I am able to walk in place quite a lot. I have been logging it as Walking - 2.0 mph Slow Pace.
I time the minutes that I walk in place, and when I do so I try to add variety - stepping side-to-side, kicking, knees up high, or adding arm movements for example.

When I log the minutes I always greatly under-log the minutes in order to ensure that I don't overestimate calories burned. For example, today I've been timing my boughts of walking, but each time I begin again I don't start timing for 30 seconds to a minute in. Then I'll also stop the timer, but keep exercising. When I finally hit 30 minutes on the timer, I logged it as 20 minutes, which came to 58 calories burned. Then I did another 8 minutes but logged it as another 5.

So what I've logged today as 25 minutes, 73 calories may have been as much as 40 minutes of movement. Am I underestimating by too much? Am I "selling myself short" on the calories I might get to eat back? Should I be logging some of it as walking and some of it as low-impact aerobics? It's hard to tell because it doesn't feel like a lot of physical effort.

I am just having trouble telling how much to log and how much to leave off as just normal everyday living calories - know what I mean? I have MFP set to sedentary, but I know it does account for some normal movement/walking throughout the day.

Also, since what I'm doing is so low-impact, and I'm doing it every day, is there a chance that my body/metabolism/whatever might just "get used to" my movements so that my heart rate won't go up as much when I do it, therefore burning less calories?

Sorry for length - and I hope it makes sense. Maybe I'm way over-thinking it. :blushing:

Thanks in advance and unlike some whiners here, I LOVE gifs and welcome snark.

Replies