Appropriate negative splits for races

Can anyone suggest appropriate negative splits (in percent of overall pace if possible) for races? I'm particularly after estimates for half- and full-mara.Thanks!

I've seen suggestions of 2 or 3% i.e., start off 2-3% slower and gradually rise to 2-3% quicker than your overall average.  For example, if I expect to run a 1:40 half, this is a 4:50min/km pace. If I run 3% (9 secs) slower at the beginning rising in a line to 3% quicker by the end, this means 4:59/km rising to 4:41/km.

If I get a reasonable % figure, then I can program a series of laps into my Garmin. But I have seen a figure just in a couple of places - most people just talk about two halves, the second quicker than the first. One calculator here allows one to program in a negative or positive fade. Another here in Norwegian allows one to draw a graph, even curvilinear, to match a desired finish time. But neither offers advice on the right amount of negative split per unit distance. 

 I know this sounds a bit finicky, but at my age (54) I need every last bit of help to crack upcoming pbs image I've read the general argument that if you conserve some glycogen early on, it helps to burn fat+glycogen later on, which is faster overall than going out flat or faster in the first half. e.g. this strategy and calculator.


  • PhilPubPhilPub ✭✭✭

    Hmmm... I've given this a lot of thought and from my experience I still think that EVEN splits is the way to go, for pretty much all distances. 

    For a half marathon, you're running reasonably close to threshold.  (I know it's only elites that are running very close to actual lactate threshold, but I'd still argue that the build-up of lactic acid at sub-threshold pace is an important consideration.)  I've found that the optimum pacing strategy is to feel a little uncomfortable nearly all the way round, and I would fear that if I set off too slowly, I just wouldn't be able to pick it up enough to run the last few miles at quicker than average pace... crucially this would risk increasing lactic build up too quickly and would make the closing stages too hard to maintain the quicker pace.

    I think the marathon is more complicated and I don't pretend to know the right answer. If anything, a small positive split may be the optimum pacing strategy, because you could argue that no matter what pace you went out at, fatigue will catch up with you towards the end, so allow for a little slowing.  On the other hand, my most pleasurable marathon experience was one where I ran a one minute negative split (1:22:30 - 1:21:30 = 2:44 roughly) BUT in hindsight maybe I could have run a couple of minutes quicker if I'd set out slightly faster.  The last 10k may not have been so pleasurable since I would have been hanging on, but that's beside the point, you're asking about optimum pacing.

    Running a negative split, after the event, and in terms of comfort when racing, is a very satisfying experience, BUT if you can handle setting out at a harder pace and hanging on, I believe this will get you round faster.

    So there you - even splits gets my vote.  image

  • Thanks for being the first person to stick your neck out with an answer, Phil!

     Especially in view of your comment "Running a negative split, after the event, and in terms of comfort when racing, is a very satisfying experience" I'm tempted to try an A race half on Sunday with a slight negative split of say 1 to 2% while still shading into a pb because I have a mara not long after and I don't want to be totally wiped out for that. I suppose I want everything really image

  • My head's spinning!! I must sit down and get my head round this: too technical! What sort of time, at 54, are you trying to get Steve C?
  • Just faster than before is all! Maybe 1:35.
  • oooo. I long for that. Did a 1hr38 last time out and felt good. Started a little too fast... maybe a fade is what I need! And yours is fantastic for your age. Hope I can still approach that in six years' time.
  • Stevie  GStevie G ✭✭✭

    Steve C, you don't look too bad for 54, unless that pic is from years back   image

    I've done 19 halfs, and admittedly the early ones were just a case of running it and finishing. The later ones I've had a pace per mile ideal.

    The idea of going faster in the 2nd half is one I've never been able to crack. As Phil Pub suggests it's hard to lift the pace later when you're fatigued. My own personal preference is to have a target pace per mile in my mind, set off, and if in pb shape get a little bit in the bank for the inevitable slow down later on.

  • Thanks; Peter but my new WAVA for 54 is not specially brilliant at 67% but at least I'm still improving! Stevie, yes, that picture is a bit out of date, but not far wrong; I should update it image

    So far I tend to agree with Phil that a half could be run flat, but I still want to try a full with a negative taper because I'm persuaded by the analysis that you need to preserve some glycogen to help burn fat towards the end of a marathon. That's not so relevant for a half or shorter, where threshold is more the limiting factor, not glycogen stores.

    Anyway,  yesterday I got a new half pb, behind target time by only 14 seconds, finishing 1:42:12, cf. the same course last year at 1:43:24. that's the fifth time I've run that race.

    I aimed for a slight negative split by setting an average pace of 5:40/km on my watch, then purposely trying to run 6 secs/km slower for the first third, then at overall target for the middle third, then faster than overall average for the last third to get back to target. The plan pretty much worked in that it stopped me going out too fast, but I was only 3 to 5 sec/km slower in the first third.

    First third: 1.4% slower than target
    2nd third:  -0.4%
    3rd third:  -0.8%

    In hindsight, 1.4% is plenty for a half, if any. The first third felt pretty easy, the middle was OK (even though I was already over my previous pb pace). The last part was tough but it was not many km so I knew I could manage it.

    I liked this way of having a fun race, but there's a lot going on in the head balancing speed and heart rate, also because I couldn't program every individual km into my Garmin. I'm keen to try this for a marathon now, perhaps using that MARCO calculator I linked to in the first post, with a couple of percent negative split. I could program in a target time for each segment of the race that it suggests.

  • Steve in Norway - you may want to read up on the subject of Teleoanticipation. The theory is that the brain is always calculating your current effort level and the effect this is having on the diminishing of your energy reserves. In an effort to ward off death (which would be the inevitable result of continuing to run at near threshold pace...), your brain and nervous system work together to increase the stress on your body to make you stop using your energy up so quickly.

    A better understanding of this theory may help you to work out why negative splits are so hard to achieve (and only elite runners who do so much mileage that their brains can better balance experience against teloanticipation), that they are able to dig deeper into energy reserves in the 2nd half of a race.

    Last year, I ran Amsterdam mara in +ve split of 17s. Yesterday I ran Paris in a couple of minutes quicker (but it was much hotter in 2nd half of the race) and ended up with a +ve split of about 4 mins (4.7% slower). I would advise that if you are going to target a negative split, you go for something less than half of that. So effectively you are talking about marginal differences. Overall, I think going for even splits is the most reliable way to run a marathon, because ultimately you have to be adaptable. Local conditions on the day can have a huge impact over planning.

  • PhilPubPhilPub ✭✭✭

    Teleoanticipation.  That's an absolute doozy!  I'm guessing this ties in with Noakes and his central governor theory, although I could be wrong.

    Wise words TD.  If someone did manage a 4 mins -ve split in a marathon, I would argue that they set out far too leisurely and could have run a lot quicker if they'd got a bloody wriggle on.

    Steve - congrats on the PB!

  • Hey Phil - I just did a quick search for related articles and guess whose name i found attached to THIS introductory sentence?  BTW, have you had that op yet on your hip?

    "Fatigue is hypothesised as being the result of the complex interaction of multiple peripheral physiological systems and the brain. In this new model, all changes in peripheral physiological systems such as substrate depletion or metabolite accumulation act as afferent signallers which modulate control processes in the brain in a dynamic, nonlinear, integrative manner."

  • I think I'll keep repeating that sentence to myself during VLM on Sunday.

    By the end of the race I'll either have a) understood it or b) my brain will have exploded  image

  • PhilPubPhilPub ✭✭✭


    Thanks for asking, progress continues to be slow on that front.  I've got a final CT scan booked for next week before I finally get on the waiting list (!) for an op.  The frustrating thing is that my physio recommended a CT scan back in January but he was over-ruled by my (seemingly clueless, quite frankly) GP who referred me to another specialist.  It's basically taken three months to have someone else come to the same conclusion.  image

    Still, cycling seems OK and the days are getting longer, so it could be worse.

  • I wish luck to anyone who thinks about these things so much, but when I do an HM, I train with some degree of organisation, but then run the race with a certain pace overall in mind and the vague idea of enjoying it too. It's certainly not harmed my pb potential, though I suppose I could run faster with more of a plan - I just don't think I'd enjoy it that much having to think about it all the time.
  • loulabellloulabell ✭✭✭
    me too PC , im a fairly even paced runner as a rule, i dont time splits or anything -ever. as like you although i try to better myself i think it would strip the fun /enjoyment out of it sure i could get faster too with rigid plans..but i think im preferring runner further rather than faster...
  • Thanks for the input, everyone. Based on what you say and what I read, I think I will try for a conservative slight neg split in the coming Vienna marathon (B race for me) so long as the course is reasonably flat,  it is not windy and it is not too hot. If any of these are true I will go by effort/heart rate as I have always done in the past. In every other race I have done this has produced a fade in speed.

    The plan will be based on your opinions and the Marco calculator linked int he first post, which equates to split halves of 50.6% and 49.4% of the total time. Put another way, I get behind by 1:25 mins  in the first third, run at target 5:20/km pace in the middle third and recoup the 1:25 in the last 14 km. Also, this lets me keep to the pace of my mrs, who is doing the half, so I have a plan image 

  • Curly45Curly45 ✭✭✭

    We've discussed pacing tactics in quite some length on MG...

    I'm very much in the go out and hold on camp (suicidal pacing we call it) and have run all my pbs that way, but it means I cannt pb very often because it involves going to the well during the second half to find extra energy from somewhere. It also means the second third of races can be particularly mentally difficult and I do have a rather larger number of DNFs than most people.

    All that said, I still get my best results (when ready and A racing), by this kind of pacing. Even if it means a slight positive split. When I go out easy I cannot pick it up during the second half and I am left wondering 'what if'.

  • Hi Curly45, what's MG, please?

  • Curly45Curly45 ✭✭✭
    Sorry its our thread - the Middle Ground - where we hash out ideas like pacing image
  • PhilPubPhilPub ✭✭✭
    The Middle Ground's got its own abbreviation.  It's now bigger than J-Lo.  image
  • OK thanks, here.
  • I read somewhere that a 49/51 split is particularly 'ideal'. It was in a book written by a RW-USA chap, and aside from the language etc, it was well written i think.....will update with link shortly

    Ultimately it is an individual choice as to what works for you.  I like metronomic even splits

    Joe Henderson....

  • Thanks for that, Nick. I found what Joe Henderson was saying here, and it is an extract from the book you link to. He accepts anything from even (50/50%) up to 51/49% half-split, the first half being a little slower, but in reality that's not much - a few seconds per mile, as he says.
  • Steve - yep, thats what he them the wrong way round!

    I really enjoyed reading that book - another thing he goes on about, which makes a lot of sense, is to stop trying to chase PBs all the will only get disappointed, and that really you should only compare the same course time, rather than some races are so different you cant compare a flat fast half in early spring, with a hilly half in the middle of summer!

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