After about 8 - 10 weeks doing up this weekly session I got a new PB of 39.34 (my previous PB was 42.54!).
This “magic” session really has worked for me.
First find a 2k loop - google maps / mapmyfitness.com / walkjogrun.net
(I found 2 in fact within 200 metres of each other, which I ran in different directions to make more interesting and then repeated my slowest loop again to make 5)
Then I ran the 2k loop with a target pace of 7.55 mins, had a 4 / 5 minute recovery then did another loop. In total you should do 5 x 2k loops (10k split into 5 obviously).
At first I could only do 4 x 2k loops and not even getting under 8 minutes.
Then I managed 4 x 2k + 1 x 1k - still not managing to get under 8 minutes (8.05, 8.10 etc). I eventually manged to do all 5 in one session. Over the following weeks I managed to break the 8 minute barrier and now I regularly range between 7.20 - 740. The key is to be able to complete all 5 loops, even if not at sub 8 minute pace - bettering your loop times will come progressively.
There is a great pysological boost knowing that you run a sub 40 10k albeit in 5 parts. What this session does is to teach you how the sub 40 min pace feels and makes your running more economical & consistant.
Make sure you wam up & cool down properly as you will be nearly replicating race pace conditions. I also was doing a regular 10 - 12 mile long run on a Sunday, 7 -9 miles Club run Tuesday plus the odd 5 - 6 mile quickie when I could fit it in.
I initially started this session to improve my 10k time to under 40 minutes but now use it as part of my half marathon training. It has helped me get under the magic 1.30hr mark - something that has eluded me for some time and which I thought I couldn't achieve.
Good luck - and hope this works for you too.