London Marathon: Technical report

First up, here are the splits compared with my 'perfect marathon' at Abingdon.

	London		Abingdon
1	07:43	135bpm	07:59	no hr
2	07:27	144bpm	07:27	144bpm
3	07:06	146	07:36	146
4	07:23	147	07:53	148
5	07:24	147	07:22	146
6	07:45	147	07:48	146
7	07:39	145	07:32	145
8	07:32	146	08:36	145
9	07:40	146	07:30	144
10	07:37	146	07:38	146
11	07:38	144	07:44	146
12	07:37	145	07:39	146
13	07:39	145	07:38	146
14	07:37	145	07:40	147
15	07:37	145	08:02	149
16	07:37	145	07:48	148
17	07:46	145	07:32	151
18	07:34	146	07:55	151
19	08:02	146	07:58	152
20	07:53	144	07:53	154
21	07:57	145	07:48	153
22	07:56	144	07:50	155
23	08:00	145	07:47	154
24	07:43	145	07:53	154
25	08:30	144	08:24	156
26.2	09:54	146	07:25	158
			01:38	160

10 km	0:46:27
20 km	1:34:00
half	1:39:07
30 km	2:21:38
40 km	3:11:21
finish	3:22:22

The main factor to consider when looking at the above results is the heat. It was anything from 23°C to 27°C according to which report you believe. The heat pushes your heart rate up as blood is diverted from the muscles to the skin for cooling and makes the heart work faster to get oxygen to the muscles. Unfortunately you can't simply run at a higher HR because the restricted blood supply makes the muscles less efficient and lactate levels rise. Your only option is to slow down back to your usual HR level. This year's marathon was full of stories of people who tried to run at their normal pace and then had to slow dramatically when they lost the battle with their blood chemistry.

Apart from the effects of the heat slowing my overall pace, what disappointed me at London was the fact that I slowed quite significantly in the final miles, despite running cautiously, whereas at Abingdon I was strong to the tape. At Abingdon I only lost 90secs in the last half, whereas at London I lost 4 minutes. At London I couldn't keep pushing my HR up like I did at Abingdon, although my pace wasn't as slow as the difference in HR between the two races might suggest. Incidentally, the slow 25th mile in both races are in fact due to displaced mile markers rather than my pace, which was still around 8:00/mile according to my GPS.

I was telling everyone that I went off at too high a HR and paid for it at the end. To some extent this is true, as I was trying to maintain a 7:25/mile pace in the face of a raised HR, but in fact the HR splits for the opening miles compare favourably with Abingdon where my pacing was spot on.

Was it the heat causing dehydration and loss of performance in the closing stages? Maybe.

Was it the late start to the training and the loss of January to illness and lack of 20-milers causing a lack of endurance? Maybe.

Could it be that in the heat you have to be conservative and go off at an even lower HR to avoid overheating later? Maybe.

Could it be a lack of warmup which caused an early rise of lactate which caused problems later on? (I've been reading about VO₂ kinetics and the importance of a proper warmup). Maybe.

Was my lactate threshold lower due to lack of marathon pace training runs or tempo runs, and so not able to tolerate such a high HR? Maybe.


Questions aside, I ran a sensible race. I took a sip of water every mile and sloshed the rest over me. I took a gel (SiS Go gel) every 4 miles. I felt spent at the end but not unduly distressed, just a little dehydrated maybe. I just seemed to lack strength in the last 3 miles.

I'm not going to obsess about my 'failure', which of course in many people's eyes is a resounding success. It always pays though to look at your performance and analyse what went wrong and what you need to do better. Regardless of how I ran the race, the main reason for being a lot slower than anticipated was the sudden heat, for which I was unprepared.

So what would I have done differently? Not much really. I could have taken it easier after Abingdon and avoided injury, but I doubt I could have avoided the illness. Maybe running Ryde 10 after a week in bed wasn't such a good idea though - it probably extended the illness. The injury and illness combined to restrict the time I had for the build up - this would seem to be the main problem apart from the heat.

I'll now work towards an autumn marathon to go for 3:15 again. As I felt before London I was already on 3:15 form in cool conditions, given another 6 months of injury free consistent training I should be able to get 3:15 comfortably. I hope so!

It's been 2 weeks since the marathon and my recover is going well, in that my legs feel OK. I have been rather tired since the marathon though - more so than for previous marathons I think. I've been getting at least 8 hours sleep per night, but by mid afternoon I'm falling asleep at my desk, and then falling asleep in front of the tele. Is this psychological, ie a lack of focus after the marathon, or physical? A bit of both I think.

I have a 5k race on Wednesday, so a chance to gauge my physical recovery. I think I should do well, although maybe not at my absolute best. Then it's back into full training for that 3:15!