Tuesday, 17 October 2017

One on marathon nutrition

As a bit of winter base training, and just for fun, I ran the Bournemouth marathon last weekend.  I wasn't aiming at a time, just to enjoy the run, take advantage of the water stops, and to be part of a big event.

Coming out the other side, there were actually some learning points.  But first....

A quick word on gait - now that I'm not ramming my heels into the tarmac 40,000 times in 3.5 hours, I found that I recovered incredibly quickly.  I can't believe how little damage I did to my legs.  I was waiting for DOMS for the next 48 hours, but it never came.  So 54 hours after hitting the finish line in Bournemouth, I was running in the club's Tuesday evening 6x800m off 60s session.  Sure, I ran the first efforts easy in case something broke, but the last two efforts I was hitting sub 2:50 which is up with my best for this session!

Anyway, this post is more about the nutrition learnings.  

The following graph shows heart rate, but I also selected elevation (the thin green line) as it explains some of the heart rate variations.

The very flat sea-level sections represent the flat seaside promenade on Boscombe, Bournemouth and Poole seafronts.  The black line is heart rate.

Click on the graph for a full size version!

In terms of effort, that first 4k felt very easy.  I was letting people pass me (and I had started in the third pen back), I was chatting, and I hit 4:50/km on average.

Then as you can see, there was a downhill section at 4km, that flattened out.  I suspect that the pace and cadence increased, because as the downhill flattens out, you can see that the heart rate raises as I must have tried to maintain the faster pace (the red box).  Certainly I was now overtaking people.  I remember looking at my watch at about 10k and seeing that the average pace had come down to 4:41/km.  From 5km to 21km the heart rate is higher, and as I would soon find out, above the fat burning zone!!

From half way, I was in trouble!  10 miles of burning glycogen had left me depleted.  I took a couple of gels from the feed stations (I think about half way and again at about 30 km).  At 30km I thought I was going to have real trouble finishing.  Walking the two hills had taken their hit on the average pace, and I was down at 4:57/km.

[At this point, I have to confess that in general my HCLF regime is not going as well as it was this time last year (Healthy Fat Low Carb).  It's hard work! Autumn 2016 I was frying vegetables and pork belly, I was avoiding all rice and pasta, I was only having one roast potato with Sunday Lunch.  OK so I haven't gone back to the muffins 3 or 4 times a week, and I never buy chocolate bars now, so sugar intake is still way down.  But I've slipped out of my most efficient fat burning abilities that I enjoyed at the Portsmouth Marathon last December.]

Back to the Bournemouth Marathon.  30km.  You can see that the heart rate comes back down (the green box).  And this is where I start to recover.  I remember, from the 6 marathons I did between 2001 and 2006, when I hit the wall, I REALLY hit the wall.  Half Foster territory.  Once in London, I had to walk from Tower Bridge to Canary Wharf.  But not at Bournemouth last weekend.  The wall never came, I think it was about half a mile down the road the whole last half.

This time, I believe I had enough retained ability to metabolise fat that I experienced a bit of a recovery, and the pace never dipped slower than 4:57/km.  

Going through the 24mile marker, I realised I had 19 mins left to get under 3:30, and I thought "what the hell".  So for the last 2.2 miles I really picked up the pace, bringing the agerage back down to 4:56/km.  I hit the finish in 2:29:50!!  Boston Qualifier by 10 seconds!

So, although the highest heart rate at which I can run on fat alone has probably come down a bit, the ability is still there.  

Not exactly scientific, but I am still enjoying this experiment with a sample size of 1....

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