Re-evaluation

I am now completely recovered from the illness that afflicted me seven weeks ago.  The main symptoms had resolved after 4 weeks and I have gradually resumed training in the past few weeks, though prior to this morning, I my longest run had been 6.5Km, and the only session at a pace faster than 5:30 min per Km was a 4 Km tempo run.

This morning I faced the question of whether or not to abandon my plan to run a half marathon in early September. Seven weeks ago my training was progressing according to plan, and my target time of 99 minutes appeared reasonable.  After four weeks of quite debilitating illness and 3 weeks of very light training, that target is probably beyond me.  Is it even feasible to contemplate a half marathon at all, within the next 6 weeks?

Last night I had vacillated between planning a 10Km run as the first step in a prudent program directed at recovering endurance, or a moderately paced 15Km to force an answer to the question of whether or not I should persist with my plan for half marathon in early September.  This morning, the rain was beating down from an oppressive leaden sky, and my initial inclination was towards a prudent 10K.  However, rain often looks worse when seen though a glass window than it feels splashing on your face.  So I decided on the 15K, starting slowly, but with the intention of increase pace gradually to around 5:15 min/Km.

The rain was invigorating and I gradually built up pace.  During the second Km my heart rate monitor revealed some brief bursts of tachycardia (discussed below) but I felt fine so I continued to increase pace gradually, and still felt comfortable when I reached 5 min/Km.  The rain continued to pour down and my clothes and shoes became water logged.  I had set off in a pair of old, very heavy, reebok shoes because I suspected that the intrinsic muscles of my feet might have become de-conditioned in the past seven weeks, and I wanted to protect my awkwardly angled metatarsophalangeal joints from the stony sections of the riverside path.  It was probably a wise decision, but nonetheless as I splashed through the mud and slush, the water-logged reeboks felt like soggy clogs.  I had images of Emil Zatopek training in army boots and re-assured myself that I was probably giving my hamstrings and hip flexors a good work-out.  From 3 Km  to 15 Km I maintained a constant cadence of 186 strides per minute (except on the short steep hills) and I gradually increased my stride length from 104 cm to 110 cm.  I finished comfortably with an average overall pace of 5:11 min per Km and a heart rate of  664 beats/Km.

So what conclusion should I draw?  I felt relaxed and comfortable throughout.  My only subsequent musculo-skeletal discomfort is some tenderness of the tissues overlying my metatarsophalangeal joints, confirming the anticipated de-conditioning of my feet during the past seven weeks.  My larger muscles appear to have coped well.  I could almost certainly run much faster in a half-marathon race.  The heavy shoes and muddy surface probably cost me several minutes.

However, I am not sure that my former target of 99 minutes (4:42 min per Km) is within reach   Today’s performance is very similar to my training runs in early June.  At that stage, with three months preparation ahead of me, I was confident of achieving my target. Now, with only a month of training ahead, I doubt that 99 minutes is feasible, but am fairly confident that if all goes well during August, I can achieve a time of 102 min; maybe even 100 min.  So I have set myself a provisional target of 100 min.

The Polar RS800CX

My new Polar RS800CX Heart Rate Monitor has provided me with lots of fascinating information, but at this stage, I am not sure what to make of it all.

Quality of the engineering

My first impression is that it is not as well engineered as I had anticipated for a Polar product.  Sometimes the facilities if offers do not appear to work reliably; for example the first time I attempted to use the Own Optimizer test of training stress and recovery, it failed to give the beep after three minutes to signal that it was time to stand up.  At other times it gives warnings of problems that do not appear to exist.  At this stage I am monitoring the situation to determine whether any of these problems is sufficiently troublesome to justify returning the device to Polar.  On account of the large number of clever options it provides, I suspect that have yet to learn many of its subtleties.

I am not sure about the S3 foot pod. It definitely gives unreliable estimates of distance if not mounted very firmly.  I am not yet convinced that it is reliable even when firmly mounted.  Sometimes it fails to communicate with the wrist-mounted watch/computer for a period of 10-15 seconds, and I am trying to ascertain if this is caused by running near large metal objects.  However, despite occasional evidence of minor unreliability, my interim conclusion is that it is useful to have a reasonably reliable estimate of pace during training.

Heart rate variability

The more interesting thing is the information the RS800CX provides about my heart. There is no doubt the information is interesting, though whether this will allow me to train more effectively remains to be seen.   I have been doing a recording each morning while seated and relaxed.  This confirms that I produce a healthy amount of high frequency heart rate variability at approximately the respiratory frequency suggesting good function of the parasympathetic nervous system; the system that promotes relaxation and recovery.    Figure 1 shows a typical 5 minute segment of resting heart rate.  The fluctuations occur at approximately the breathing frequency (6 breaths per minute).

Figure 1: Five minutes of resting HR

Figure 1: Five minutes of resting HR

I will be interested to see how the resting heart rate variability changes once I beginning training more heavily.  As I anticipated, I am frustrated by the Polar Own Optimizer, which merely gives a single number indicating recovery status.  It maybe that for a person who is not interested in the physiology, a single number is all that they want, but I suspect that reducing the relatively complex information contained within the heart rate recording to a single number creates the risk of erroneous interpretation in some circumstances.

So far, I am finding a strong correlation between the various indices of parasympathetic function derived from HRV and low resting heart rate.  Maybe a simple observation of resting heart rate would be less prone to misinterpretation, though it should be noted that in the more severe form of the over-training syndrome, resting heart rate is likely to be mis-leadingly low due to over-compensation by the parasympathetic nervous system.  So even a simple measurement such as resting HR needs to be interpreted in light of the overall evidence

Erratic HRV

The most interesting thing I have discovered about my own heart is that despite a healthy amount of heart rate variation associated with parasympathetic activity, my heart rate also exhibits some more erratic variability.  Sometimes during warm-up I get brief runs of rather dramatic tachycardia, during which my heart beats much faster than the anticipated maximum rate of the normal pacemaker in the sinus node.  With my old primitive HRM, I occasionally observed these events, but attributed them to malfunction of the monitor.  However, with the detailed record of R-R intervals provided by the RS800CX I can examine these events in much greater detail, and they do appear to arise from aberrant initiation of the heart beat.  However I cannot be certain of their origin until I record a full ECG.   Figure 2 presents a comparison of a selected (atypically bad) one minute segment of the HR record during warm-up, with a typical one minute segment recorded in the mid-aerobic range.  During the atypical warm-up segment, there is no evidence of fluctuation at the breathing rate, but instead there are erratic fluctuations including bursts of a few beats at a heart rate over 200 per minute, which is far above the maximum rate of my normal sinus node pace-setter (around 160 bpm).  In the mid-aerobic segment the fluctuations are fairly regular at approximately the breathing rate (around 45 breaths per minute).

Figure 2: One minute segments of HR during warm-up and in mid aerobic zone

Figure 2: One minute segments of HR during warm-up and in mid aerobic zone

I am re-assured by the fact that there is growing evidence that ventricular tachycardia (which is potentially a precursor of fatal ventricular fibrillation) tends to be a predictor of cardiac death when it is observed during recovery rather than during exercise itself.  In my case, the abnormalities are mainly present during warm-up.  When I am working fairly hard, my heart rate exhibits an apparently healthy pattern of variation. As expected, the parasympathetic influence decreases markedly as I approach maximum heart rate, but there is still an appreciable variation at the respiratory frequency.  Furthermore, during the recovery period, the parasympathetic influence re-asserts itself rapidly.  So overall, I think I have a quite healthy heart (for a 63 year old) but it may be that there is an irritable bit of muscle in the walls of my ventricles that gets impatient with my well-regulated sinus node during warm-up.   I will experiment with a more gradual warm-up.

In conclusion, perhaps my previous ignorance was bliss, but I am inclined to think that it is better to understand the situation more fully.  Any middle aged person who runs vigorously faces a small risk of a heart attack.  I suspect that in most cases, the increase in life expectancy due to the improved cardiac function produced by training far outweighs the small risk of catastrophe.   I hope that the additional information provided by my HRM will allow me to improve the odds in favour of increased life expectancy.

However, for the person who would rather avoid the intricacies of interpretation, maybe the most sensible thing is simply to measure resting heart rate each morning.  For the gung-ho individual, maybe even this seems over-academic – always looking both ways before crossing the road might provide a greater improvement in life-expectancy in proportion to effort spent.  However I am enjoying the exploration of the intricacies of heart rate variability, and I am increasingly confident that it will allow me to regulate my training more effectively.

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5 Responses to “Re-evaluation”

  1. Ewen Says:

    That was a good 15k test Canute. A sub-100 still looks possible.

    With the monitor, if there are continued problems, get the unit replaced under warranty – I know a runner who got a 600 series Polar replaced.

    With the high readings during warm-up, check that it isn’t just a contact problem. I know with my RS200 I used to get high readings during the early kms of a run. What I do now is soak the strap in warm water just before running. Also, make sure the strap is sufficiently tight. Sometimes I’ll get a 00 reading if the strap becomes slightly loose. Polar sell a conductive gell, but I haven’t had to resort to that.

    I’ll be interested in the HRV readings once you’re into full training.

  2. Andrew(AJH) Says:

    I had a couple of mechanical issues early in the life of my Polar rs800sd and got it replaced under warranty. Whilst it wouldn’t do for your purpose of detailed HR analysis, I far prefer my Garmin 405 to my Polar.

  3. Derrick Says:

    “Muscle-memory”: How much credit do you give to this phenomenon? Given that your heart is a muscle, and you were previously well on track to run 99 minutes, I don’t think meeting your goal will be as daunting as it seems.

    If you had previously reached 99 minutes, or its equivalent, I am sure it will be easier to reach the goal again, than it was to achieve it for the first time. Every body is different, but of this I am certain: it is much easier to lose aerobic capacity than it is to lose muscle mass.

  4. canute1 Says:

    Derrick,
    Thanks for that optimistic comment. I think you are right that muscle mass is lost relatively slowly. However I did suffer a quite debilitating illness and I suspect my cortisol level was quite high at the time. Cortisol is a catabolic steroid that causes muscle loss so I have probably lost some muscle power. I can normally do 3x2x20 one leg squats (body weight) quite easily, but at present I struggle to achieve this. Sadly, the older one gets the harder it appears to regain muscle strength and power, probably because growth hormone and anabolic steroids are less active. Nonetheless, I suspect the major loss of fitness following a break of a few weeks is due to loss of blood volume, which results in less efficient filling of the heart and hence decrease of stroke volume. However I anticipate that the deficit in blood volume can be made good within a few weeks. My resting heart rate is almost back to previous levels which I think implies that stroke volume is almost recovered. Other aspects of fitness such as capillary density in leg and heart muscle probably did not deteriorate too much in a few weeks. So I think I am almost back to where I was 8 weeks ago. However, I now have less than 4 weeks of sold training ahead of me so I will probably will not gain as much between now and the beginning of September as I would have gained if I had not been ill. I think 100 min is now a sensible goal, but I will review the situation in three weeks time. At least I am training with a feeling of freshness now; maybe if the next few weeks go well I will reset the target at 99 min
    Canute

  5. Paul Says:

    Great to hear you are ‘back in town’ as we say. It is very frustrating when an injury or illness turns up to spoil a well-laid plan. I am certainly not going to say you can recover all that training-effect you have missed, but I am a big believer on pulling out a great performance on race day if your head is in the right spot (and I don’t mean sitting on top of your neck!) Train sensibly as you normally do then just GO FOR IT on race day. What’s the worst thing that can happen … you don’t run 99 mins … which is exactly what will happen if you don’t go for it! Godspeed.

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