sweeney, good job getting to 40. that's really a big crux. you're right to avoid trails like that. they are more likely than the roads to lead to injury. however, you should be able to find some good level trails, even if you have to drive a bit. that is the key to the higher mileage. don't forget the ice bucket after runs to combat the soreness. you can run good 5k-10k even on 1500-3k training, but the latter is going to be heavier speed-based and so I would think more prone to injury at a time where you don't have as strong a base. to promote speed as you do your longer training, definitely do strides frequently and some shorter stuff. daniels will help and see if you can get a training group or a club in your area. not essential but helps accelerate the improvement.