Guest Blog – How to run a marathon…

Lessons from my first negative split marathon


This is written as a follow on to my last guest blog post, how not to run a marathon (which I wrote after my ill-prepared but ultimately fun attempt at Brighton). I went into London this year, 3 weeks after Brighton, without huge expectations – I’ve been on and off with injury since January, had only just run a marathon, and in the 12 marathons I’d run so far, I had faded (usually quite badly) in the second half.

Most of us know that feeling… where your legs get fatigued, your mind won’t fight and you end up slowing down or even walking. Well, for the first time ever for me, that didn’t happen. Whilst London wasn’t a PB, I do consider it my most successful marathon. I felt strong, and ran my first ever negative split, with the second half over a minute faster than the first – according to London marathon chip timing, each of my 5k splits were within 3 seconds of each other, whereas at Manchester in 2022, I ended up over a minute per mile slower. This has raised a few questions in my mind, biggest of which is what made this happen, and can I replicate it to get a PB.

Quite a few things were different this time, so it is quite hard to isolate what had the most impact. And of course, this is a study of one, so what worked for me this time may not work for me next time, and may not work at all for you. That said, there are a few things I will definitely be doing again, playing with and improving:

Training and pre marathon:


  1. More cutback weeks / recovery time
    Because I have had on and off injury issues this spring, I have run lower mileage overall – 600 miles in the run up to London this year, compared to 960 in the run up to Manchester last year (I did replace some of the mileage with cross training, but no more than another 100 miles equivalent). On top of that I did fewer 20 mile + runs (4 compared to 6) and less speedwork this time round because I couldn’t risk it with a dodgy achilles.
    In summary, more cutback weeks and a better balance between mileage and speedwork meant I built aerobic fitness but was able to recover properly. I have no secret answer for the magic balance, but be aware of the signs of under recovering – poor sleep; getting irritated; unable to hit paces etc. and don’t be afraid to drop a session to run easy, or an easy run to rest.
  2. Build a strong base – run miles, strength train and do the prehab
    I was able to maintain fitness through my injuries, and keep going for longer because I have been consistent and diligent in building base mileage and doing strength work prior to this training cycle. It is what you do consistently for months and years that holds you in good stead for a marathon, rather than just one training cycle. Don’t neglect the non-running stuff!
  3. The controversial one – running the distance (or over the distance) in training.
    Please take this one with due caution. I felt running Brighton Marathon three weeks before London really helped me. I walked sections of Brighton, so it wasn’t done as a hard effort, but it did give me confidence and the full distance miles in my legs. I felt this helped and I would do it again. However, I know that other experienced runners and coaches disagree, and I bow to their expertise. Martin suggests that whilst a time on feet easy run (where you run for your intended target time for the marathon but at a much slower, easier pace) is very useful, running the full distance is risky and produces too much fatigue.


Lessons for the marathon itself:


  1. Pacing – get it right. Hold back in the first half, hold on in the second.
    This is one I often get wrong, going out too fast, and then struggling after half way (at which point my mind gets to me and says you still have so far to go, just slow down / walk). A key learning point for me is that going out too fast doesn’t just mean faster than your proposed marathon pace, it also means listening to your body. Is your proposed marathon pace right for that day, those conditions, that training cycle? Too often I’ve focused on the end goal time I want, and not listened to my body. As, for London, I had a soft target for me, I could afford to pay more attention to what my body was asking.
    GPS in London this year seemed worse than usual, so I had to rely more on effort and heart rate than usual. My target pace was 8.40-8.50, but I couldn’t always tell what I was running at using my watch, so whilst I did use average pace as a rough guide, I also had heart rate visible, and kept it below 150 for the first 12 miles where I could (about 5-10bpm lower than I have done for a marathon in the past), and focused on my breathing. If I felt it rise too much, I pulled back. I did a lot of holding back in those first few miles. My splits reflect the fact that London is downhill for the first 3 miles, but after that I just sort of found a rhythm and went with it.
  2. Fuelling – fuel lots, often and practise it in training. Find what works for you.
    I don’t like taking gels. I often skip one or two. This race I didn’t – 40g carbs from a sports drink on the start line then a 20g carb gel every three miles. In addition, I decided to play with timing of caffeine in London. I love coffee, and have normally had at least three strong cups by midday. My first coffee is always the most impactful and gives me a productivity boost, so I decided to not have any caffeine in London until after mile 12. I was flagging by that time, but after a 70mg caffeine gel after Tower Bridge, I felt great. Not buzzy, but bouncy and full of energy. Every gel taken after mile 13 had caffeine in. Please note – I have practised this a lot and am comfortable with taking a lot of gels, including with caffeine. Don’t try this for the first time on race day!
  3. Mindset – break down your run into small chunks. Running ten miles on tired legs is hard. Running just one more mile until you get to [insert target here] is a lot easier on your poor tired brain!
    One thing I realised at Brighton Marathon 3 weeks ago, is that I wasn’t breaking my run down enough. At mile 16 of Brighton, I was overwhelmed by the thought of 10 miles to go (I was still poorly so not really a surprise) but instead of saying just one mile and then I’ll see, I let it overwhelm me and started walking. This time, I took the pressure off in my head a little bit more and broke it down into cutty sark (6 miles), Tower Bridge (12), half way… and then focused on each kilometre, and each 5km chip timing mat. I visualised the people tracking me seeing even splits and no fading, just for that one 5k “parkrun equivalent” section. When I hit 22 and started to get more tired, I aimed for the 40km mark, and then the MH Runners cheer squad at 25.5 miles and by then I was nearly home… different ways of chunking work for different people but this is the first time I’ve actually got it right. For me, the key was really believing I could back off if I want, but would try just one more kilometre first. Find what works for you.

Finally, I have been asked a couple of times if the fact I didn’t fade means it wasn’t hard. No, it was – all marathons are hard , it’s a long way and every time I do one I remember just how far it is! (you would think I would have learned by now, but if you’ve run a marathon, you’ll know what I mean!). But because I managed to keep a consistent pace for longer, when it did get hard, I had the confidence behind me to try and carry on. That hasn’t happened before, but I do hope it will again – it was a whole lot more enjoyable than going out hard and fading. I would trade that feeling for a PB if I had to, but hopefully, with these lessons under my belt, I can aim for both next time.


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Martin Hulbert

Running Coach & Personal Trainer Leicestershire

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