Q I know that long runs should be run slower than race pace, but can you explain why. I want to race at eight minute/mile pace at next years Flora London Marathon, so surely I should train at that pace? Also, if I run a half-marathon in January, can I use it to predict my marathon finishing time?A Trying to run at eight minute/mile pace (your target race speed) during 20-mile training runs on a regular basis will have a detrimental effect on your other sessions in the week. Thats why long-run pace is slower than race pace.
Instead of trying to sustain a constant race pace in a long training run, try a segmented long run. For example, run for 40 minutes at nine-minute miling, then increase your pace to 8:40 miling for 40 minutes, and finally run for 40 minutes at 8:00-8:25 miling. This will prepare you for digging deep during a marathon, and perhaps even allow you to consider the holy grail of attempting a negative split a slightly quicker second half of your race.
Id also recommend that at the Flora London Marathon you try to run with the RUNNERS WORLD pacers. Theyll relieve you of the pressure of pacing yourself.
As for the second part of your question, multiplying your half-marathon time by 2.2 (or your 10K time by between 4.66 and 5) should predict your marathon capability, though a race closer to April will give you a more accurate picture than one in January.
Bud Baldaro, coach and RW contributing editor