Workouts for Trailrunning
60 Second Hill Repeats
6-10 intervals, moderately hard for 60 seconds, then on each repeat go to the same point, without looking at your watch. Do it once a week.
Long runs with Strides
Just incorporate 30 second strides on long runs.
Lunges
40 walking lunges, side lunges and rear lunges. Or barbell lunges. Do some jumping lunges if you can handle it.
Downhill Strides
8 downhill. Grade can be slight.
Super Slow
Way slower than you're running most of the time.