Shortness of breath in the last few miles of a marathon?

Mousey4

Wondered if anyone could answer what Google can not. I did Manchester marathon last week and had for me a brilliant run at 3.59 (I train every day cycling/ swimming/weights but VERY rarely do any actual running so I was beyond happy with this.) I ran the whole thing at a completely even pace (following a pacer and using my own watch) so I know that mile one was the same speed as mile 26. The first 15 miles felt like they were a very comfortably slow speed, the following 7 were getting harder but still fine. From mile 22 though I started to get more and more out of breath even though my pace remained unchanged. I was determined to go under 4 hours so just kept pushing through it and accepted that it was going to hurt. I thought it was weird though just how much I was huffing and puffing. I could understand it if I'd picked up the pace and tried to sprint as I would at the end of a half but I hadn't, yet was seriously out of breath and feeling very sick for the last mile. I understand oxygen debt but surely that shouldn't come into it if I was running aerobically?

I feel like I've recovered really well and am full of energy. I've trained a bit this week (but reduced to allow rest) and felt fine doing a couple of high intensity fitness classes. I've just been out for a cycle though and found I was more short of breath than normal. Out of curiosity I just checked my resting pulse and found it's very high compared to normal (15bpm.) I'm guessing that means I'm not as well recovered as I thought! Did I just push too hard in the marathon?

Any ideas welcome!

Mousey4

P.S This is not my first marathon; I've done 4 in the last year (mainly trail) as well as quite a few halves. I rarely run in between them but I didn't mean to give the impression I'd done this with no previous running. 

cougie

Three threads? You're keen. Go and have a rest.

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