Variation in Calories Burned

aschroeder2749
aschroeder2749 Posts: 172 Member
in Fitness and Exercise
Hi there. As training for my 5k I'm running next month, I'm doing the Couch to 5k program. Sometimes, even during the same exact interval layout, I burn significantly more calories one day than the next. I wear a heart rate monitor and the calories burned during a 30 minute workout vary from 220 to 350.

I'm just curious what factors contribute to such a variation? It's discouraging to think I'm about to torch 350 calories only to hit 220. Is it because I'm becoming stronger and it's less of a strain for me? Or is it something else, like the amount of sleep one has had, or what time of day it is?

New to this; thanks!

Replies

  • brianpperkins
    brianpperkins Posts: 6,124 Member
    HRMs don't do well with intervals. Their calculations are based on relationships between heart rate and specific steady state activities. When you move from higher to lower intensity and your heart rate remains high while your actual activity level drops .... running to walking or ending a workout ... the HRM keeps counting heart beats and calculating as though you were still running.

    If your heart rate remained elevated for a longer period during the less intense parts of your intervals, the HRM then calculates more calories burned although it really isn't the case.
  • aschroeder2749
    aschroeder2749 Posts: 172 Member
    What would be the best tool to calculate calories burned during interval training? This sounds like I'm not nearly burning as many as I thought. This week, the workout is 5 min warmup, 5 min jog, 3 min walk, 5 min jog, 3 min walk, 5 min jog, 5 min cool down.

    My heart rate stays within my "zone" during the walking, but slows down tremendously. During the jogs, it's at the highest part of my zone (165).

    I also have a fitbit if that would be more accurate for interval training. Once I'm jogging for most of 30 minutes, would the heart rate monitor then be more accurate? Thanks!
  • brianpperkins
    brianpperkins Posts: 6,124 Member
    What would be the best tool to calculate calories burned during interval training? This sounds like I'm not nearly burning as many as I thought. This week, the workout is 5 min warmup, 5 min jog, 3 min walk, 5 min jog, 3 min walk, 5 min jog, 5 min cool down.

    My heart rate stays within my "zone" during the walking, but slows down tremendously. During the jogs, it's at the highest part of my zone (165).

    I also have a fitbit if that would be more accurate for interval training. Once I'm jogging for most of 30 minutes, would the heart rate monitor then be more accurate? Thanks!

    A fitbit will track steps ... not necessarily calories. The reality is that short of getting hooked up to machines there is no accurate way of measuring caloric burn ... everything is an estimate.

    Zones are also pretty much garbage. The "fat burning" zone was based on testing of fit people in a lab setting and only indicates that the body is burning a higher percentage of fat than carbs for fuel. As long as you don't reach the point where the body switches from aerobic to anaerobic processes you burn more total fat at higher intensities.

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