Punctuated equilibrium

Hanging upside down was one of
the treatments I tried for my chronic
back injury.

When I was in my running prime, I gave little thought to athletic decline.  I knew many veteran (masters) runners and recognised my potential as a runner would decline as I aged.  However, I never thought much about the process.  If anything, I expected the decline to be a smooth glide path.  Each year would see slightly slower times for benchmark distances and I would be chasing podium places as I entered each new age group.  It was a naive and simplistic view of the process, and my only defence is that these issues seemed remote and I didn't give them sufficient thought.

Now, with ageing parents and my own ageing body, it has become obvious the process of ageing and athletic decline is more akin to the evolutionary biology theory of "punctuated equilibrium".  This postulates that, over time, long periods of stability with little change are punctuated by events causing significant change.  Rather than being on a gradual descent to our ultimate demise, or the end of our running career, we have periods, often lasting years, when our abilities and capabilities remain relatively static.  As runners, these stable periods may include various soft tissue injuries and oscillating fitness, but our basic capabilities are essentially unchanged.

Looking towards North Avoca from Avoca Beach
during this morning's walk.

Significant events for runners are those injuries from which we never really fully recover, despite how hard we train.  There were no more Personal Bests for me after a back injury (spondylolisthesis) sustained  in 1979 brought to an end the steady improvements I had seen in the preceding years.  Likewise, a serious knee injury in 2006 meant a lot of time off running and a limit on training load I could sustain in subsequent years.  I could plot other significant injuries over the years that have also had a lasting impact on my running capability.

Looking from Copa, low cloud covers Mount Bouddi
during this morning's walk.

Now I'm trying to reconcile myself to the capability change that will result from my Deep Vein Thrombosis and associated Pulmonary Embolism and Atrial Flutter.  I'm still in the midst of this "event" and don't know the level of capability I will emerge with, but it will almost certainly be less.  Goals will have to be recalibrated, or frustration will build.  I'm not reconciled to these changes yet, but can sense I am in the midst of the process and will eventually accept what must be.

This morning, I walked a comfortable 10km in misty rain beneath low cloud.  It was a nice change from the relentless summer weather of the last three weeks.

When to run again?

My walking route this morning took me through the
Avoca Beach Markets.

When I went to bed last night I had decided that today's exercise would include some light jogging.  It's not so much that I'm desperate for an endorphin high, or even the satisfying fatigue that follows a run.  It's more that I was very fit four weeks ago and I can feel that condition ebbing.  I know these feelings are familiar to all injured runners, but this time around I'm conscious that a miscalculation on when to start running again could feasibly have fatal consequences rather than just a setback in recovery time.

Avoca Beach Markets.

So, this morning, while enjoying my cup of decaffeinated coffee, I surfed the Web and pondered the most rational approach to a return to running.  I don't want to take stupid risks, but I don't want to be too timid either.  Finally, I decided to just walk 10km today and use the time to work out a rational strategy.  I do my best thinking while walking.

The first conclusion I reached was that the Deep Vein Thrombosis (DVT) diagnosed seventeen days ago was still at significant risk of throwing off small clots that could impact my lungs and heart.  Many sites on the Web indicated a minimum of four weeks and usually six weeks for DVT's to resolve themselves.  I should probably wait another three weeks and possibly an "all clear" from another ultrasound exam of the lower right leg before resuming jogging.

Avoca Beach Markets.

The second conclusion I reached was that my exercise, whether walking or running (when the time comes), should be at a pace which does not push my heart/lungs into what I'm calling the "Amber Zone".  Twice during today's 10km walk, near the top of steep and longish hills, I could feel myself beginning to struggle for breath and an unpleasant sort of pressure (not pain) building in the base of my chest as my heart began to race.  It was as though the clutch was slipping and no drive was being transferred from the engine to the wheels.  This was the same feeling I had when running faster up hills just before being diagnosed with Pulmonary Embolism (PE), so I'm becoming familiar with it.  I didn't have to stop walking for the sensation to abate today, but did need to slow right down to a dawdle.  I would define the "Red Zone" as being the need to stop and sit down, and I have not reached that point yet, nor do I want to.

Avoca Beach Markets.

Like most chronic injuries, I feel like I'm starting to get a handle on how to manage it, but know it is not wise to look for the "edge of the envelope" as has been my inclination in the past.  I also know that, even after the DVT has resolved itself and the clots in the lungs are no longer an issue (which could take months), I will still likely need some sort of medical procedure to address the Atrial Flutter problem before I can start running hard again.  Patience!

[I have posted my Post-DVT Training Diary here, or it is accessible from the Links menu at right.]

Caffeine

45mg of caffeine in my
favourite tipple

Early in my running career I consumed quite a lot of caffeine.  In my twenties, I routinely drank six or seven cups of strong coffee a day, including a cup just before bed which didn't seem to affect my sleep.  At 150mg of caffeine per cup, I would have been consuming about 1000mg of caffeine per day, way above the recommended daily dose (600mg according to the New South Wales Health Department).  At some point, I decided that this was a bad thing because on weekends, when I didn't consume cups of coffee as regularly as when working, I tended to get headaches.  I went "cold turkey" and after two weeks of mild headaches and irritability, the addiction was gone and I did feel generally better.

My running regime makes it important to drink large amounts of fluid, and I have got into the habit of always having a drink at hand.  It's easier to keep hydrating if you enjoy the drink and I have never enjoyed drinking just water.  For a few years I managed to stay caffeine-free, drinking decaffeinated coffee and soft drinks, but when I began my expatriate working life in 1987, and was constantly travelling to different countries, these were not always readily available.

Gradually I settled into accepting the caffeine content of diet colas (Diet Coke seems to be available in most places), which I enjoy drinking (way too much, according to my friends), and trying to limit the consumption to about four cans a day.  I also accepted the occasional coffee.  This would have added up to about 200mg to 300mg of caffeine a day, not an addictive quantity and within the recommended daily maximum.

My "heart-starter" in the last 10 years has been my
pre-run cup of strong black coffee (~175mg of caffeine)

After retiring from work in 2003 and joining Terrigal Trotters in 2004, I changed my regime to having an early morning strong cup of black coffee when I got up and before going for my early morning run.  It helped wake up my body at a time when advancing age seemed to be making the early miles of any run harder and harder, especially the Trotters' 6:00am, or earlier, starts.  I calculate my morning coffee as having about 175mg of caffeine, which is quite a large dose, and though it had the desired effect of pumping me up for the run, it was not always a pleasant feeling and I could often feel veins pulsing in my temple.

The reason for discussing caffeine now is that my research has shown it can be a risk factor in the Atrial Flutter with which I have been recently diagnosed.  Although not the likely cause in my case, it has been a trigger for me to reevaluate my caffeine intake.  My sense is that eliminating the strong early morning coffee and limiting myself to four diet colas a day (or 200mg of caffeine a day), will be a positive move, and that is what I did from last weekend.  I noticed a head-achy feel the first few days and then yesterday morning, after a very early start for the Thursday track session at Terrigal Haven followed by a 10km walk, this developed into a full-blown migraine that had me in bed from about 1:00pm through to 7:00am this morning.  I can't say that it was a withdrawal headache for sure, and given the clots in my bloodstream and the Warfarin I'm taking, there's always a nagging concern it could be something more sinister.  However, today I feel a bit better, though my weekly INR test this morning showed my anti-coagulant level is significantly above the target range (4.8 when it should between 2.0 and 3.0) and I wonder whether this was a factor somehow.

Caffeine is a legal stimulant and research has shown benefits to long-distance runners.  I have experimented with its use and will talk about that in a future blog post.

Fibrillation or flutter

Part of my walk around Copa today

I wasn't really anticipating any good news when I had a long consultation with my GP today, just a summary of the tests so far and referrals to some specialists.  If anything, I came away a little more positive.  She confirmed that all of the blood tests for more sinister underlying conditions had come back within normal range, and provided more detail on the cardiac tests and leg ultrasounds.

Apparently, the cardiologist diagnosed Atrial Flutter (AFl) rather than Atrial Fibrillation (A-fib) as being my heart condition, and according to the GP, this is the better diagnosis to have.  I gather A-fib is chaotic disorganised beating of the Atria while AFl is regular, but way too fast, beating of the Atria and may be a little easier to treat and sometimes stops of its own accord.

Looking north from Captain Cook Lookout
during today's walk

The leg ultrasound report found "some occlusive thrombus in one of the peroneal veins from 7cm below the knee crease to 20cm below".  The GP says her starting theory would be that the thrombosis in the leg has thrown off small clots that have impacted both my lungs (Pulmonary Embolism) and heart (AFl), but has referred me to a respiratory specialist and a cardiologist to try and confirm the diagnosis and prescribe treatment.  In the meantime, I continue with the Warfarin anti-coagulant.  The earliest specialist appointments are six weeks away, but I guess the fact that I'm not seen as an urgent case is a good sign.  It probably means, however, that my exercise is going to be limited to walking until at least the end of February and any prospect of returning to serious marathon training in time for the Gold Coast Marathon in July is remote.

Looking south from Captain Cook Lookout during
today's walk

I won't abandon the marathon goal until I speak with the specialists, and dearly want to resume regular running.  However, I am already mentally more focussed on the need to be fit for my next planned adventure, a 3500km southbound hike along the Appalachian Trail from Maine to Georgia in the eastern US starting in Autumn (October) and finishing in the Spring (March).  I know there is a possibility that this too could be scuppered by my current health problems, but I'm trying to be optimistic.

I walked about 8km today, not particularly quickly, and felt fine the whole way.  I gather that regular leg use is recommended in the treatment of Deep Vein Thrombosis, so being able to walk 8km without pain or other problems must be a good thing, I reckon.

More theories

I unexpectedly struggled midway through a long trail run
near the Barrington Tops four months ago.

The longer it takes to see specialists about my Pulmonary Embolism (PE) and Atrial Fibrillation (AF), the more time I spend on researching the conditions on the Web, talking to other people, retrospective self-analysis and theorising about my prognosis.

I was quite depressed following the surprise (to me) AF diagnosis, but after researching athlete experiences for yesterday's blog post (see Endurance athletes and A-fib), I'm starting to feel cautiously optimistic that I will be able to resume running.  Maybe I have had Paroxysmal (occasional) AF for some time, triggered by exercise fatigue.  Many people have AF and are unaware of it.  Maybe AF explains the unexpected and sudden onset of severe fatigue during some long runs in the past six months, including the Melbourne Marathon (see blog post Reality check).  I had put them down to lower back issues affecting my stride, for want of a better explanation.  When AF occurs, the heart beats inefficiently and less oxygen reaches the muscles causing fatigue.  The long runs when I had trouble were all at a time when I was building from a lay-off and possibly going a bit too hard for my level of fitness.  Later long runs, when I was fitter, but running within myself, were faster without trouble.

Struggling in the Barrington Tops

This is all amateur conjecture, and perhaps there will never be certainty, but it does make me think, that once the PE and Deep Vein Thrombosis conditions are resolved through time and Warfarin, I will be able to make a return to running, much more aware of my situation and more able to manage it.

It was a beautiful summer morning for the regular Terrigal Trotters Saturday run.  I was there early to take care of runner registration as Kev, the Club Registrar was away in Parkes for the Elvis Festival, and enjoyed greeting the 100+ runners who turned out.  Many kindly asked after my health and I later had the benefit of talking to a couple of club-mates who recently had surgery for similar heart issues.  My regret at not being able to join everybody for the 11km "Round Drive" run was somewhat tempered by a pleasant 6km walk with some great coastal views and the usual post-run bonhomie.

Perseverance is not always good

Deep Vein Thrombosis is the formation
 of a blood clot (thrombus) in a deep
 vein, predominantly in the legs.

There are whole worlds out there that I know little or nothing about.  I'm a bit of a current affairs nut, and an avid reader on a wide range of subjects, but there's nothing like a new injury or illness as motivation to expand your knowledge of a subject.

During my running life I have had serious injuries to my Achilles tendons, knees and lower back, as well as the usual torn and strained muscles, tendons and ligaments.  In each case, I've learned a lot about those injuries, including through missteps I have made in dealing with them.

I like to think that my own experiences allow me to offer soundly-based views on the running-linked injuries of friends when asked.  In the case of soft tissue injuries, I generally advise patience and the avoidance of activities that worsen the symptoms.  If something seems more serious or inexplicable, I usually suggest starting with a doctor.  They have a range of diagnostic tools at their disposal and a broader range of knowledge about the possible causes than ancillary or alternative health care professionals.  I'm not a fan of starting with the latter because I believe their field of knowledge and the tools they have available make it less likely they will consider all of the possible sources of a problem.  This can lead to misdiagnosis and a delay in recovery.

Pulmonary Embolism  is a blockage of the main artery
of the lung or one of its branches by a substance
 that has travelled from elsewhere in the body
through the bloodstream (embolism).

In the last two weeks, through doctors, the Web, and articles given to me by others, I've become a lot wiser about the subjects of Deep Vein Thrombosis (DVT), Pulmonary Embolism (PE) and Atrial Fibrillation (AFib), and their associated symptoms, treatments and prognoses.  Of course, there's much more I don't know about these subjects, but one thing I have learned is that runners need to be much quicker in seeking the opinion of a doctor if they start to feel inexplicably short of breath, dizzy or light-headed, or experience chest pains, hyperventilation or persistent leg pain.  There can be life-threatening medical conditions underlying these symptoms and endurance runners are at higher risk of developing them, especially if they have a long background of endurance training.

Atrial Fibrillation is the most common cardiac arrhythmia
(heart rhythm disorder).  The normal regular electrical impulses
generated by the sinoatrial node are overwhelmed by
disorganized electrical impulses usually originating in the
roots of the pulmonary veins, leading to irregular conduction
of ventricles impulses which generate the heartbeat.

Many runners, and particularly males, think seeking medical advice about these symptoms is a waste of time and/or a sign of weakness.  All endurance athletes get used to dealing with fatigue and injury "niggles" and there's a strong temptation to dismiss them as a "cost of doing business".  Two friends, both distance runners, have recently been diagnosed with PE, but only after persevering with their symptoms for much longer than me and ending up in hospital emergency wards.

I will now be quick to advise any runners suffering from the symptoms described above to urgently seek the advice of a doctor.  Early intervention is important and delay could be fatal.  It's just not worth the risk of persevering.

After mentoring this morning's track session at the Terrigal Haven, I walked for about 6km, feeling fresh and healthy the whole way, and wishing I could be running my usual post-track session 11km.

Trotters

Terrigal

Last night was the monthly Terrigal Trotters Committee Meeting at the Terrigal Surf Life Saving Club.  I always get a sense of privilege rocking up to the Surf Club on a Monday evening during holiday season.  Terrigal is a very popular holiday destination and during the summer you have to make your way through throngs of holiday makers knowing that by next month's meeting they will all be back at work or school and you will still be here, continuing to enjoy the delightful beach, hinterland and weather that have attracted them for their vacation.

Terrigal Surf Life Saving Club

Over my athletic career, I have belonged to a succession of running clubs - Melbourne High School Old Boys (defunct), Kew Camberwell District (defunct), Croydon Harriers (UK), Colchester & Tendring (UK), Watford Harriers (UK), St Louis Track (US) - and now Terrigal Trotters.  Along the way I have served in various Committee positions in some of these clubs and Terrigal Trotters stands out as unique.  Most Clubs seem to rely on two or three people to do much of the work assisted occasionally by other club members.  At Terrigal Trotters, without counting the numbers, I would guess that there are 20 people who make a very significant contribution to the Club's activities and many more who are willing to help out with particular events.

Terrigal Trotters Santa Run

The Committee is energetic and the Club inclusive.  Membership is growing and there are new people showing up for every Saturday's run, many of whom soon become hooked on the format and camaraderie.  It's fun to be a part of and volunteers enjoy involvement in professional and successful events.  Such success feeds on itself, drawing in more volunteers and participants.

Each month, one of the Committee Meeting agenda items is to nominate people who have made an exceptional contribution to the Club in the previous month and then select a Club Person of the month.  It is illustrative that there were 30 members nominated for their efforts in the past month.  Surely a sign of a vibrant club doing it's bit to promote fitness, health and fun.

Terrigal Trotters Christmas Party

My exercise today was another 5km walk around Copa.  I felt good and really wanted to be running.  Unfortunately, resumption still seems to be some way off.  My Echocardiogram this morning revealed significant Atrial Fibrillation in my heart and the specialist immediately sent me off for an Electrocardiogram (ECG) which confirmed his diagnosis.  The results still have to be reviewed by a Cardiologist, so I don't have a detailed report, but Googling the condition makes it plain that I have been lucky, will remain on Warfarin to reduce the risk of Stroke, and will need to consult some specialists before daring to run again.

The Prom

The boardwalk through Sealers Swamp on
Wilsons Promontory

Not unexpectedly, I was unable to get my Echocardiogram done today.  The first day back at work for the clinic after the Christmas/New Year break was always going to be busy.  I was lucky enough, however, to receive a call from the clinic later in the morning to say they had a cancellation and I'm now booked for the test tomorrow.  The chest X-Ray last week found that my heart was "borderline enlarged" but it seems reasonable that it would be in an endurance athlete.  If I did an hour of chin-ups most days for 45 years, my biceps would be "borderline enlarged" as well.  There is a condition called Athletic Heart Syndrome (AHS) that would explain the size, but it's hard not to be a bit anxious about what they will find.

Refuge Cove, Wilsons Promontory

My exercise today consisted of a walk around my usual 5km in Copa listening to an audio version of "The Economist", one of my favourite reads/listens.  Walking by the beach on a nice sunny morning, it was easy to think about better things and I recalled one of my favourite long training runs that included some great beaches.  I have only done it a handful of times, because it is on the remote Wilsons Promontory, the most southerly point of Australia's mainland, and one of Australia's best National Parks.

Oberon Bay, Wilsons Promontory

There are a number of running routes available on The Prom, short and long, and over the years I have spent weekends and weeks camping there with family and friends.  All of the runs are worth doing, but my favourite is a 43km loop that includes beaches on the western and eastern side of The Prom and two climbs over the spine that provide views and some quintessential Australian bush trails.

Tidal River, Wilsons Promontory

Going in a clockwise direction the run starts with a steady climb up to the Oberon Car Park along a tarred road for 4km before joining the walking track to Sealers Cove that starts with some hillside running, crosses Windy Saddle, and then descends to boardwalks across an eerie swampy world behind the spectacular Sealers Cove.  From there the trail follows the coast southwards past Refuge Cove to Waterloo Bay, offering some fabulous views over the pristine coast before turning westwards, back across The Prom to Oberon Bay.  It's easy to imagine that nothing has changed here for thousands of years as you run along the flat hard Oberon beach with the breakers to your left and the imposing Mount Oberon ahead.  The last section of the run returns to the starting point at the Tidal River campground around a rocky cape and you can finish along the beach or along a trail through the ti-tree.

I have run the course quite quickly in days gone by, but it is just as enjoyable at my slower pace of today, and I look forward to my next visit.

Mixed feelings

Ultra-running legend, Pat Farmer, running
with friend, Dina, near the end of the
"Round the Bay"

Today was Terrigal Trotters' "Round the Bay" run, which is traditionally held on the first Sunday in the New Year.  At just over 37km of roads and concrete bike paths, and usually in humid conditions, this a tough run.  Three weeks ago, I had been planning to use it as a long training run, but the Pulmonary Embolism diagnosis a week ago changed all that.

The event, which circumnavigates Brisbane Water, and is followed by a picnic breakfast, has become increasingly popular within the running club, and today was no exception.  Fifty-five people completed the circuit, including one group of walkers who began at 2:00am!  Some slower runners started at 4:00am while the main bunch set out at 5:00am.

Despite injury, Wayne nears the end of
his 13th consecutive "Round the Bay"

To get some exercise, I drove down to the start in Gosford and then walked 4km out and 4km back along the last section of the course with my camera, photographing the runners and walkers as I encountered them.  It was inspirational to see so many of my friends out testing themselves, including some suffering from injuries and/or a lack of preparation.  In just about every case, I managed to coax a smile out of them, despite their exhaustion.  My friend, Wayne, who is the only person to have run every one of the twelve editions so far, and has had a bad couple of years with various injuries, still found the determination to finish and preserve his record.  We have had a few good tussles on this course in past years.

Trotters gather for breakfast and a low-key presentation
after the "Round the Bay"

The inspiration provided by my friends this morning was, sadly, somewhat offset at frustration with my own situation.  It was only eighteen days ago that I ran the same course on my own without pressing the pace in quite a reasonable time.  I need to remind myself that eighteen days is not that long, and that I was still running up until a week ago.  Assuming next week's Echocardiogram is clear, I may be jogging in another week, and won't have lost much fitness.  Other people with my condition would just be thankful to still be vertical, and I need to remember that too.

Lost opportunities?

Boney Mountain

I joined the usual throng of Terrigal Trotters at Terrigal beach this morning for the regular Saturday 6:00am run.  I was sad not to be joining them for "Bob's Hill", another of my favourites, but reflected that I was lucky to be there walking and sharing time with friends.  Several Trotters who share my demographic are dealing with significant health issues, including one who recently suffered a more serious and life-threatening episode of Pulmonary Embolism than me.  Fortunately, he seems to be on the road to recovery, but it's another reminder to live for today, particularly when you get older.

A year ago, almost to the day, I enjoyed one of my happiest racing experiences for some time.  Sharon and I were on the last day of a three-week vacation in the western U.S., and ran in the Boney Mountain Trail Half Marathon west of Los Angeles.  After a steady start, I worked my way through the field in the second half, which included a 2000ft climb, and after a helter-skelter descent, finished in 18th place in a field of over 300.  The next runner in the 60+ division was 33 minutes behind.  I didn't believe I could still run so fast and thought then that it was likely to be the racing highlight of 2013 for me, and that's how it turned out.

Reaching the bottom of the descent
from Boney Mountain

I do get frustrated when I miss races and other running opportunities, but know that physical brittleness and vulnerability come with age.  I can accept the injuries and illnesses, so long as I don't feel I have given up my quest to be the best runner I can be, and don't incur them through making stupid choices.  All runners have those moments when injury strikes and they just wish they could have a "do over" and avoid whatever caused the problem.  Sometimes it results from doing something foolish, but often it's just plain bad luck and could not reasonably have been foreseen.  The challenge is to strike a balance between testing your limits and being foolhardy in pursuit of your potential.

I would like to think I didn't make any poor choices leading to injury or illness since Boney Mountain last January, but know I have learnt a few things about myself, particularly the growing need to warm up longer and/or start slower for anything fast.  Good choices or bad, I still had plenty of downtime and failed to produce any performances comparable to Boney Mountain.  However, it was only a year ago, and common sense tells me that not too much athletic potential can have been lost in just one year.  I still believe that if I can string together three or four months of consistent and smart training and racing, there's no reason why I couldn't get back to that form.  This is what keeps me going.

Some cause for optimism

Near the start of the Dubbo Gully Run

As the early test results come back, I'm becoming more positive about a return to running.

So far, no evidence has been found of more sinister underlying conditions that could have led to a blood clot forming in my veins and migrating to my lungs.  However, I still need an Echocardiogram early next week to rule out any heart disease or other heart issues, so am not out of the woods.

On the other hand, an Ultrasound Doppler examination of my right leg yesterday, found a small clot just beneath my right knee and close to the site of severe knee pain I experienced following a 30km trail run on the Dubbo Gully course three weeks ago.  There is no pain there now, and there hasn't been for several weeks, so it seems reasonable to surmise that the clot may have been larger when the pain was greater.

Crossing Mangrove Creek on the Dubbo
Gully Run

What led to such a clot forming, and why didn't I pay more attention to it?

Firstly, I have had significant right knee pain for more than six years now (see Post titled "Adaptation"), so I expect it to be sore after a long run.  However, I recently switched from wearing Nike Pegasus shoes, a model I have worn for decades, to another brand that promised more cushioning.  I was wary about changing shoes because I know different brands and models can change the stresses and strains imposed on the legs making you potentially more vulnerable to injury.  However, I have also been struggling with a painful chronic right Achilles tendon injury and been stymied on several long runs, including the Melbourne Marathon, by lower back pain and associated sciatica.  A shoe offering a softer ride and different pressure on the heel was worth trying and I bought a pair.  After a couple of weeks and several long runs in the new shoes, positive signs were that my Achilles tendon was less painful and there had been no back trouble.  Offsetting this was a minor worsening of my knee pain, which seemed to have moved to just below the patella on the inside front of the leg.  Following the Dubbo Gully run, the pain was particularly intense, especially on the hour-long drive home, and was sufficiently painful to cause sleeplessness the next two nights.  It now seems likely this pain was associated with deep vein damage.

Part of the Dubbo Gully route

Three risk factors probably compounded the development of a clot in the vein.  I was dehydrated after the run, but drank sparingly in the next four or five hours, increasing the viscosity of my blood.  Unusually, I had a three hour nap (while still dehydrated) on my bed when I got home, during which my heart rate would have dropped to its usual low resting rate (~45 bpm).  Finally, I have low blood pressure anyway.

My guess is that the coincidence of the new shoes changing the stresses on an already damaged knee, dehydration, a post-run nap, and low blood pressure led to Deep Vein Thrombosis.  The next ten days saw parts of the clot break off and travel to my lungs and the development of Pulmonary Embolism.

Through gradually increasing the daily dosage of Warfarin, my International Normalized Ratio (INR), a measure of the clotting tendency of my blood, has reached 2.1 (the desirable range is 2.0 - 3.0) and the daily Clexane injections have ceased.  I'm still not allowed to run, but I played golf this morning and have been walking about 5km per day this week without ill-effects.  I haven't discussed it yet with the doctor, but I'm hoping I can resume unpressured jogging after a scheduled visit in a week's time, provided the Echocardiogram doesn't yield any concerns.  Fingers crossed!