Assessing fatigue

9 Jun

You may well ask, if I can’t feel my legs, how can I tell whether the exercise I am doing on my FES bike is overdoing it or not? Good question. I use a couple measures to help me determine I level of fatigue:

  1.  if the level of stimulation goes up to 100%, and then the automatically controlled resistance begins to reduce and reduce and reduce, that’s a sure sign that my legs are getting tired.
  2. When I am doing an intense interval with manual control of resistance, then the machine will not reduce my resistance even if my legs are getting tired (though the RPMs will fall). In this case, I can look at the average power per lap during the session and see whether it was falling towards the end. Also, I can monitor my power output during the exercise and see whether it is stable or decreasing.
  3. In addition, when I do more than one session of the same type I can monitor whether my power output was higher in the second session than the first, or whether it is beginning to decline with each succeeding session. A variation of this, when I am doing an easy session, is to see whether the level of stimulation required increases in each successive easy session.
  4. Lastly, though I can’t feel the skin on my legs, it seems that after an intense workout my brain can sense that the legs are tired. There’s a heaviness that I don’t sense prior to my workout. This is fascinating, because my injury is considered complete, which means my brain receives no sensation from nerves below the entry level. How is it possible then that I can sense fatigue?
  5. Related to this, if I had a really hard workout, afterward I find that I cannot stand in my chair for very long without my consciousness fading away. When I am fresh, I can stand much longer.
  6.  If I have pushed too hard during a workout, when I stop, my blood pressure may fall precipitously and I will bonk seriously. If I have trouble remaining consciousness after a workout, that’s a sure sign that I have overdone it.
  7.  And finally, if I do two identical workouts several days apart and experience much worse results on the second workout, that’s a sign that I am either fatigued, or coming down with a cold, or something similar. It’s a clear indication that I should take it easy for the next couple of workouts.



There are a few graphs from today’s workout illustrate my points.




In the graph above, the black line shows average power per lap during this session. Average power was higher in the second left in the first as my legs got used to the level of work required, and was only 10% less in the third lap. After a 15 minute break, the average power during the last lap was nearly as high as in the second lap. Conclusion: in this session, fatigue is not an issue.


Well now, let’s look at the two easy sessions I did during this workout. In the first, below, the stimulation level (blue line) rose to nearly 100% and then stayed fairly constant around 95%. In the second easy session, further below, the stimulation level only rose to around the 80% level, indicating that my legs were not worn out yet. However after two hours of riding, I was ready to take a break!


LSD (long slow distance) session 1:



LSD (long slow distance) session 2:



Any questions?

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