I'm a relatively new runner – I’ve been going a few months now.
It’s summer time here in NZ and I’ve been getting out pretty much every day, I’ve been alternating one day longer (about8 – 10 kms – I guess 5 or 6 miles) and the next shorter 5 kms – about 3 miles but on hills / trails.
I’d like to be able to run further – but less often, my goal would be to be able to run say 20kms (12miles) comfortably maybe once a week and then perhaps a little trail work in between.
What’s the best way to approach this – I’m thinking of just adding a kilometre to my run each week, but perhaps there is a better way – keen to hear from you experts!
That's the basic thing to do. Pick one run per week and add to it. Your increased distance for the week should preferably not exceed 10% of the previous week's total distance. Every four weeks or so take a "back-off" week with decreased distance. Try to run at a different pace (slightly faster) for one or two of your shorter runs. Take a day off each week. A lot of good runners have come from New Zealand. You might also look for a local group or club to run with and for further advice.
Here's the regimin I used to go from 5km to marathon. It's not my own, it's how two training programs I did (one trail running, one marathon) went about it.
First, find a comfy pace that suits you - not a fast pace but one in which you could comfortably talk. Then run 3 times a week:
weekday 1. Easy run, for about 1 hour.
weekday 2. Middle run, about an hour.
Weekend run: Long! Start at an hour and a half and then each week increase the time by between 15 minutes.
For hill runs, I always slow down and don't stress the distance that much. I found by training myself to run longer (time-wise), I ran further without the stress of counting miles.
I run Mon, Wed and Sat.
Like Len said, make sure to run "recovery" weeks and I absolutely agree with him about joining a group or training program. I wish I'd done that sooner.
My own recommendation is to increase time til you hit about 15 miles then back off back to your preferred 12 mile and increase speed on your short run days to increase speed naturally in the long one.