Half Marathon vs 10k speeds

So I have been running seriously for around 8 months now. My 10k speed is just starting to break the 40 min mark. I am running about 40km a week with speed intervals, speed session and one Long run a week. I have been filling in the gaps with easy runs.

Anyway. Last weekend I decided to run my first half marathon in Dundee ( The Half DRAM) I had a great time and finished with a 1:43 with a half way split of 44min. I am happy with that for a first attempt, but to be honest I was looking for something a bit faster. I have done the pace calculators online and they tell me I should be running around 1:30. This seem fast to me. What am I doing wrong Is it training? Miles? Intensity? or just bad race tactics?


Any advice or help would be much appreciated.


  • DT19DT19 ✭✭✭

    How did you feel at various stages of the half? Its taken you 59 minutes to cover the last 11k compared to 44 for the first 10k so a fairly substantial drop off.

    When did that start? If you went through 5k in 17 minutes then its a very different story. With a 40 min 10k you should in theory be around 90 min hm mark.

    How long is your long run? what do the speed interval and speed sessions look like?


  • Cheers for the response DT.

    My Speed sessions have consisted of

    • 10 x 1km with 1.30 rest,
    • tempo runs around race pace
    • 2 x 5km with 3 mins rest
    • laps going from 1200m to 400m with 400m rest jogs between. 

    My long runs have been 10 miles for quite a while but I have upped them over the last month to 12 miles. These have felt fine, I have been running these at about 4:45min/km. 

    As for the race. There was a long hill drag at the start and it was very congested. I ran my first couple of miles at around 8-9min miles and sped up after that to try and get some time back. I really started to struggle around the 11 mile mark. I had nothing left in my legs and the last mile was hell! Again around the 11 mile mark there was quite a long uphill drag.

  • MillsyMillsy ✭✭✭
    Some good points from DT19

    my only comment is that you can often "blag" decent times at the shorter distances off relatively low milage (40k a week for you).

    Similar levels of success at the longer distances usually need a bit more weekly milage, unless you are naturally very talented.

    Most sub 1.30 runners would be running long runs of at least 15-18 miles
  • Millsy thanks for the reply. From what I have read 40k a week is a good amount km to be covering at my level and speed. 

    I have been concentrating on getting my 10k speed down since I started. Would running a 15-18 mile run on a weekend be beneficial or detrimental to my 10k? What would you recommend as a mileage for a week?

  • MillsyMillsy ✭✭✭
    What do you want to improve on? 10k or Half marathon?

    If you want to do well at the Half then a longer long run (run at an easy pace) will be beneficial, I can`t really see how it would harm your 10k stuff either.

    40k a week may be good enough for your level at 10k but it seems like you lack a bit of endurance and the best way to improve that is usually more milage.

    ask some people you know around the times you want to hit and see what sort of training they do.
  • I don't think you need to be doing 15-18 mile long runs but increasing overall weekly easy paced mileage should bring big gains.

    Those interval sessions look fairly heavy. What pace are you doing them at?
  • Last weekend. Was it a hot, humid day where you were? 

  • DT19DT19 ✭✭✭

    When I have a target half coming up I draw my long run (usually around 90 min at 8 mm) to closer to two hours for a month or so. You might benefit from a mid week easy medium length run ie about 8-9 miles, probably more from a hm view than speed work. I'm about 40 10k right now and would expect to hit about 1.28 for a half from past experience. 

  • Thanks for all the replies. I think adding another 8-9 mile run midweek would probably benefit me. I am going to try an increase my weekly mileage also.

    I do think that the conditions had  a part to play as it was quite hot and humid. There is another half that I might give a go next month and see how I get on.

  • Do longer long runs with a fast finish. I did 1.37 and my 10k is 42.40.

  • Frosty10k wrote (see)

    Anyway. Last weekend I decided to run my first half marathon in Dundee 

    It sounds like a bit of a last-minute decision rather than something you've specifically trained for, so it's not surprising you haven't matched the pace calculators on your first one.  They work on the basis that you're in optimum shape for each distance (and in good conditions rather than hot & humid weather), not a 'run X at 10k one weekend, so Y at half marathon next weekend' basis.

  • Frosty - your training looks reasonable to me and I would suggest you suffered due to pacing.

    Let us say you did 17 minutes for 2 miles (you say you did 8-9 minute pace) that means you did the next 4.5 miles to half way in 27 minutes. That is 6 minute pace and is quicker than your 5k pace. Okay that may not be the exact numbers but a some point you ran 5k at or better than PB pace. If I did that then I would expect to suffer as you did second half.

    If you had set off at 7:00-15 pace I suspect you could have maintained until the end for a good time.

  • NayanNayan ✭✭✭

    your 10k time is a decent platform to train for a 3:15 marathon or 1:30 half. The point is that you have to train for it, and you certainly wont get there quickly /off low mileage  unless you are genetically blessed.

    It needs a proper mix of various runs broadly, (intervals, tempo, and long slow run). Your basic speed and form is ample sufficient if you are nudging sub 40 for 10k. I dont think you need to do hard intervals more than once a week and could even switch to alternating that session with a proper tempo run every other week.

    Threshold pace and easy pace  runs will do you a world of good, and give you the aerobic capacity + stamina over  that your basic speed can support.

    I havent done a HM for a bit (last 1:36 about 6 months ago when I was 42:30 10k all off 35miles a week). These days I'm 41:54 10k and would target 1:33 for HM. off 40-45miles per week

  • Nayan - all good points but even off his current training he could have ran a decent half if he had paced it better image

  • DT19DT19 ✭✭✭

    There can be very little question that pacing was a major issue. A 1.43 half is 7.51mm against a 10kp of 6.30. That on an even paced outing would be close to easy pace.

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