Originally Posted by Brian Stone
I'd like to finish in under 2 hours, which I understand is pretty reasonable for a start. I 5k is probably the longest distance I've ever run, and I've only done one of them. I believe I did it in maybe 23 mins, but it was also on a treadmill which is hard to count. I recently did a 5k row in 20:33, which I understand translates pretty well to comparable run times in most athletes.
I currently do the CrossFit WOD with usually some jumprope or semi-heavy lift as buy-in.
To run it in under 2 hours, you will need a bit of training. There is a big difference between a 5K and a half marathon. I would keep it simple and target 3 runs per week. Do one longer run building to 10 miles. The other two can be whatever you want. As long as the long run is progressing, you will be fine. The other two runs can be interval sessions, easy miles...whatever. You should have no problem with losing muscle mass if you are running less than 20 miles per week. Honestly, as a long time runner, I can tell you that 20 miles per week is not much at all. You can mainain muscle on that type of mileage easily. Not sure when you half marathon run is scheduled but I would target a 12 week program along the lines of what I outline below. I am only showing week 1, 6 and 10 but you can fill in the weeks in between with a reasonable progression.
Mon: 1.5 miles easy
Sat: 2 miles easy
Mon: 3 miles easy
Sat: 6 miles easy
Mon: 3 miles easy
Sat: 10 miles easy
Just fill in the weeks in between with a reasonable progression to those mileage goals. That will keep you under 20 miles per week, with only 6 weeks or so over 10 miles per week. Week 11 and 12 should be slightly reduced mileage for the long run. Maybe cut it back to 7 miles and then 5 miles but add a few quarter mile intervals in during those long run sessions in week 11 and 12. That simple program would more than prepare you to survive a half marathon without hurting too bad and you should not have any problem with muscle loss as long as you refuel adequately.