Going out with a bonk - my last long training run for the Beacons Ultra

Well, I've logged my last proper long run before the Beacons Ultra and it wasn't for the faint hearted. I figured I might as well try to re-create some of the likely experience of the final stages of the ultra. So, Friday evening's run was a carb-depletion run.

Carb Depletion Runs

I've posted about doing one of these before, basically, you start the run either fasted (i.e. first thing in the morning) or after a low carb diet during the day. Then you don't take on any fuel during the run. The logic is that this will lead you to exhaust your stored carbohydrate supplies faster than on a normal run . This helps your body learn to adapt to using fat as fuel in favour of carbs [1]. It also helps you mentally prepare for having to carry on running in that condition.

Essentially, the whole point of a carb depletion run is to reach the point where you bonk. It's definitely not a training exercise you should plan to do often. Nor one you should look forward to, unless your masochistic streak is exceptionally strong.

Training Prep

On Friday my daytime diet was a cheese, ham and spinach omelette for breakfast and a green salad with mackerel in tomato sauce for lunch. I snacked on a couple of handful of almonds and a protein shake. Total pre-run carbohydrate consumption = 20 grams. On a more typical day, this would be between 120 and 150 grams.

So, I was "ready" for my 23 mile run. I took on a moderately hilly route, mainly off road, with the last seven or so miles of the route on road. I planned the last bit on road mainly because it was going to be dark by that point and also because I knew that I would be struggling.

The route plan was to do one and a half laps of the Slaughterford 9 route, then follow roads down into Box, slog up Box hill and run any remaining miles on the roads around home. This would mean that I could adjust the final miles to feel and time. I'd promised H I wouldn't be out for much longer than 3:45, so I needed to stick to that.

Pushing the pace

When I started the run I actually felt pretty good. To maximise the chances of bonking, I wanted to push along at a reasonable pace. The easier you run, the longer your carb reserves will last [2]. At a moderate pace, even in a relatively fasted state, I've probably got enough stored carbohydrate to support at least a 22 mile run.

I managed to tick along at a reasonable pace. The main problem I had was that I had to stop and re-tie my shoelaces about six times. This got so frustrating that I eventually gave up and changed the way they were tied altogether. It was particularly annoying to feel like I was losing time to something so simple. I need to have a proper look at this ahead of the ultra, because I don't want to have a repeat during the race.

In spite of the frustration of continually loosening shoe laces, I managed to cover the ground pretty well. I ran at least part way up most of the steep sections of the route. On a normal easy training run around this course, I walk the hills. In face, even when I ran the Slaughterford 9 race I walked the main steep sections (this seemed to work pretty well for me, because I finished strongly).

After some gusty wind and a few brief heavy showers, the skies cleared and it turned into a beautiful evening. The sun was fairly low in the sky. There are several points on the back half of the route where you're running along a hill side with a valley below. The low sun casts some beautiful shadows and it feels liberating to be out in the countryside, trotting along in peace.

At about 16 miles I stopped to re-fill my water bottles and then the route turned back towards roads. I tried to kick on a bit, especially as the first road section was downhill. I managed to push a bit, but I could already feel that I didn't have much pace in my legs.

I dropped into Box at about 18.5 miles. This is more-or-less the lowest point of the run. More importantly, it's the start of a long climb of about two miles continuous uphill. It's not aggressively steep. It climbs about 350 feet in those two miles (I have to do 1300 feet in a similar distance during the ultra). It is definitely persistent though.

Time to bonk?

The climb up the hill was definitely hard work. It's hard to say if I was bonking at this point. I don't think so, it was just a tough slog after a fairly decent run. But, when I got to the top, I was definitely aware that I had nothing left in the tank. The last few miles were a real slog. This was definite "just keep putting one foot in front of the other" territory. Mentally, I felt tired, but I fairly clear headed. I've read reports of people bonking and hallucinating. Maybe I didn't totally bonk. I certainly had an empty fuel tank and I couldn't kick on at all. My final miles were paced at about 9:45 - 10:00 min / mi pace. I'd normally comfortably run along an easy paced long run at just over 8 min / mi. So, this was definitely a big difference.
Moderately hilly, still plenty enough to bonk!

Post Run Takeaways

After the run I immediately scoffed a banana and downed a recovery drink. I wasn't feel great, but it felt good to get something restorative in my system. Then H and I treated ourselves to a "that's the last really long run for a while" chinese takeway. I felt vaguely justified, even though I am trying to keep my weight right down ahead of the race.

The biggest lesson from the run was that I'm not going to make up much time along the flat canal sections at the end of the race.
The other lesson was that fuelling matters. A lot. So I need to make sure I get this right on race day.

From here on, it's reduced mileage, easier paces and a bit more rest. Let the taper begin!

[1] There are lots of articles and received wisdom about glycogen depleted running. A relatively good starting point is http://www.scienceofrunning.com/2009/11/evidence-for-doubling-training-in.html
[2] For a great explanation of this, see http://www.runningwritings.com/2014/08/brief-thoughts-long-easy-runs-in.html

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