You got miles and km mixed up?
13.1 mile for a hm (21km)
Ha, no not mixed up.
I think the furthest I went was about 16-18 miles during training. Most of the training was 10-15 miles, hence not much further than 20km.
Seemed to work ok for me, as I completed my first ever marathon in about 3hrs 45 mins. Having never even done a half marathon before.
20+ miles longest run for marathon training, and you need to be comfortably running at least 30 miles a week
We were specifically advised against running as far as 20 miles during training, as it takes too much out of your body to allow for consistent training.
Advice we were given was to work up towards 3hr runs, as your 'distance' training. But mainly concentrate around the 2hr mark, and work on sustaining a decent pace over that time.
Agree on looking to do 30 miles per week though, minimum.
a marathon is a whole different ball game to a 10k or a HM...
3 weeks for HM training is gonna be a long shot IMO - remember you're gonna need a few days rest after your 10k race, and before HM race day too which will eat into that 3 weeks
If someone is currently fit enough to run a 10k, then it's not that hard to push through to a half marathon imo.
Running a full marathon is a huge leap, but the 10k and HM should be within most people's grasp, as long as they're relatively fit.
All just about pacing yourself accordingly.