Recovery from fatigue

I appear to have recovered from the fatigue that had hamstrung me in mid August. In recent weeks I have described the way in which my return to training following the episode of illness in June and July was thwarted by a peculiar inability to raise my heart rate during exercise.  I found it very difficult to maintain a pace faster than around 6 min/Km. The most dramatic illustration of the problem occurred in the final stages of a staircase session on the elliptical cross –trainer, when I found it crushingly difficult to maintain an output of 240 watts for 4 minutes.  When I subsequently examined the record of my heart rate, I discovered that it had reached 143 bpm at the 200 watt step on the staircase, and had not risen at all when I increased the power output to 240 watts, resulting in the need to generate the additional power via anaerobic metabolism.  The Poincare plot of R-R intervals between successive heart beats demonstrated extensive spread of the points across the 45 degree line, confirming excessive parasympathetic output.  My parasympathetic nervous system was clamping my output in an apparently over-vigilant attempt to protect my heart from doing too much work 

The morning orthostatic tests corroborated the evidence of parasympathetic excess.  The rise in heart rate from resting to standing was typically only 2 or 3 beats per minute, compared with my more usual heart rate rise of around 9-10 BPM.  On one occasion, on the day following a very sluggish 16 KM run, my hear rate was actually lower while standing than when lying down, providing an additional illustration of an excessive parasympathetic response. 

 Today

Today, the pattern was much different. Here is a chart showing my heart rate during the orthostatic test, and also the Poincare plots representing R-R intervals in the 3 minutes before standing and during a 3 minute interval starting 30 seconds after standing (once the immediate heart rate variations associated with the work done in elevating by body had settled). 

 

Orthostatic test on 12th September 2009. The upper figure is the trace of heart rate while resting for 3.5 minutes and after standing for a similar period.  The lower figures are Poincare plots of heart beat R-R intervals during the final three minutes of rest (left) and during a three minute period starting 30 sec after standing (right).

Orthostatic test on 12th September 2009. The upper figure is the trace of heart rate while resting for 3.5 minutes and after standing for a similar period. The lower figures are Poincare plots of heart beat R-R intervals during the final three minutes of rest (left) and during a three minute period starting 30 sec after standing (right).

 

The features of note are:

1)      The orthostatic increase in heart rate is 14 bpm – a little greater than my normal increase of 9-10 bpm and much greater than the -1 to 3 bpm characteristic of the period when I was fatigued.

2)      There is much greater variability of heart rate while resting than while standing.

3)      While both resting and standing, the heart rate shows prominent fluctuation in time with my breathing.  I tend to breath naturally at a rate of around 6 to 7 breaths per minute when relaxing, a rate that corresponds to the 6 to 7 peaks per minute (0.1 – 0.12 Hz) in the heart rate trace.

4)      While resting, the breath by breath fluctuations exhibit a steady rise followed by a sharp descent.  I was aware of breathing out immediately prior to standing, a period in which the heart rate trace shows a sharp descent, confirming that the sharp descents arise as a result of the increase in parasympathetic output during expiration. These sharp descents are much less pronounced during standing.

5)      Comparison of the Poincare plots reveals not only a much greater variation in R-R intervals during rest (note the different scales marked on the axes) but also a different shape.  During the resting period, there is a cluster of points located far above the 45 degree line to the left side of the chart.  These points represent long intervals (ie slow heart beats) immediately following shorter intervals (faster beats), and reflect the sharp descents during expiration seen in the heart rate trace.   In contrast, the Poincare plot during standing is shaped like a comet with a flared tail.  It shows limited spread across the 45 degree line and relatively greater spread along the 45 degree line (though the actual extent is substantially less in both directions compared to the resting period).

 

Overall, today’s orthostatic test confirms that my parasympathetic nervous system is no longer over-active.  If anything, the balance has tipped further towards sympathetic activity compared with my usual state, though this degree of sympathetic output is well within the normal range.

 What led to recovery?

I am inclined to attribute my recovery over a period of 2-3 weeks to my program of low-volume, moderate intensity running.  I have done 3-5 runs per week, over distances of 3-6Km, either at an easy pace interspersed with a few moderate intensity stride-outs for a distance of 200-300 metres, or moderate intensity tempo runs. In addition I have done 1 or 2 staircase sessions on the elliptical cross trainer spanning the aerobic range (though on the one occasion noted previously, following an ill-advised attempt at a longer run the previous day, I found myself in the anaerobic zone at the top of the staircase, due to my parasympathetic system clamping my cardiac output).

 A decision about the Robin Hood half marathon

I am now ready to resume normal training.  This presents me with the need for a decision.  Tomorrow is the day of the Robin Hood half-marathon, which I had set as a target race four months ago.  The fact that I have not been able to train normally for the past twelve weeks has torpedoed any prospect of a fast time, and in any case, I would be unwise to push myself really hard on the first day back into normal training.

I am uncertain about what pace to set.  The greatest uncertainty is about how well my legs will cope with 21.1 Km, due to the marked truncation of training volume.  Here is a chart of my training volume in the period May to September this year, compared with the same period last year, when I ran the half-marathon in 101:50. 

 

Training volme (Km per week, averaged over 5 week intervals), May to September 2008 and 2009.

Training volme (Km per week, averaged over 5 week intervals), May to September 2008 and 2009.

My training volume was greater last year, but most of that running was at low intensity.  This year, a higher proportion of the training sessions have included at least some moderate intensity running, and as a consequence, I think my aerobic capacity is probably not much less than last year despite my illness and its aftermath.   In several of my runs in the past two weeks, my heart rate has been around 650 beats per Km – over distances of 2-4 Km.  Last year, I rarely achieved lower rates than 650 beats/Km, though my endurance was much greater.

Although it is usually not sensible to set race pace according the heart rate on account of the risk of being misled by the higher sympathetic output associated with racing, in my present circumstances it is crucial that I avoid stressing my heart too much, to avoid precipitating another parasympathetic clampdown or perhaps an even more serious rhythm disturbance.  Hence, I think that the best strategy is to aim for a heart rate in the range 134-137 (upper part of the mid-aerobic zone) for the first 14 Km, and then adjust my pace according to how well I am coping at that stage.

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5 Responses to “Recovery from fatigue”

  1. Ewen Says:

    Canute, that’s a great analysis of your recovery from the fatigue. You ran the half, but I’m yet to read that post.

    Would you say that parasympathetic excess is typically revealed by a small difference between lying and standing HRs? I’m just thinking of what might be a good test for myself without the HRV monitor. Typically my difference is around 15-20 beats (low to maximum). I can roughly pick up the HRV when looking at the monitor when lying – as it doesn’t settle on a HR, but varies quite a bit, up and down around an average.

    Also, is an inability to push the HR into the high end of the aerobic zone a symptom of parasympathetic excess?

  2. canute1 Says:

    Ewen, does your HRM record average HR over individual laps? If so I suggest that you set the monitor to record one lap of 3 minutes duration starting 30 sec after lying down (assuming you are already in a reasonably relaxed state); a second lap from zero to 30 seconds after standing up and a third lap for three additional minutes of standing. The difference between the average for the first and third ‘laps’ that is most informative. It is best to avoid having to concentrate on the HRM during the test. A quiet alarm to inform you when to stand is also useful. In general, results are more consistent if you can empty your mind of any concerns during the test.
    As for what might cause inability to push the HR into the upper part of the aerobic zone, it could in principle be either a deficit of sympathetic input or excess of parasympathetic input. Sympathetic input can fail in some disorders of the autonomic nervous system (and also in old age), but during my recent fatigue, I think the problem was excess parasymaptheic input – this was indicated the Poincare plots, especially during the elliptical session when my HR remained at 143 despite an increase in workload from 200 to 240 watts. On that occasion, the Poincare plot showed an abnormal amount of spread across the 45 degree axis indicating excessive parasympathetic input.

  3. Ewen Says:

    Yes, it does. I think I might start doing that on a regular basis and get some data that I can relate to how I felt during that day’s running.

    One thing I’ve noticed when not stressed or tired, is that when running on my undulating 7k course, the HR plummets quickly on all the descents. When I’m stressed it doesn’t.

  4. Elliptical Says:

    Elliptical Machine…

    […]Recovery from fatigue « Canute’s Efficient Running Site[…]…

  5. Monitoring stress, recovery and fitness | Canute's Efficient Running Site Says:

    […] output might be regulated by a governor led me to reconsider an observation that I reported in my post of 12th September 2009 and have repeated on several occasions since: namely that following a period […]

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