Measuring Exertion, Part 2

We talked about cumulative metabolite load (q) previously. This load is the resistance for the exertion to work against, rather than the exertion itself. The effort is then perception of the exertion made against the metabolite load. (The nerve system must work harder against the increasing metabolite load in order to tell the muscle to burn the same amount of fuel and maintain the constant performance level). For a sustained activity of constant intensity, we can reasonably use the heart rate as the proxy for the exertion. And if we conservatively assume a linear relationship between the effort and the exertion, we have:

effort = q * hr

(Though heart rate may also be raised to clear out the metabolites, the heart rate increase required to produce the energy during an exercise should be larger than the increase to clear the metabolites. Hence, the heart rate accounts for the exertion, but not the metabolite load, during a sustained exercise).

Metabolic Load for Crash vs. Non-crash

2x700m walk normally does not cause post-exertional sickness for me. But it does if I increase the speed. the walk on 7/3 was such a case. The comparison of effort for this walk (in red) with the one on 6/24 (in black) that did not cause the sickness is shown on the right.

Effort  for Crash vs. Non-crash

We see that the peak  effort for 7/3 is higher than 6/24 while the peak metabolite load is slightly lower. Since hr are similar on both dates, it must be only the patterns of q and hr that conspired on 7/3 that produced higher peak of effort.

Now, if I was walking faster on 7/3, you'd think that both q and hr should be generally higher on 7/3. That there wasn't much difference between the two seems to indicate that the tracker's heart rate and calorie measurements are not sensitive enough to account for the speed difference of a few steps/min and the higher effort peak on 7/3 must be just a coincidence. The tracker may be accurate enough for the purpose of healthy people, but it may not be for CFS patients who react sensitively to slight differences in exertion. If that difference is within the margin of error of the tracker, the tracker data would be useless.

In the next installment, we'll talk about how to get around this sensitivity problem of the tracker. To be continued..