I lift semi hard during my base training phase, which i'm doing right now. I lift 3 days a week, monday, wednesday, and friday. Monday and Wednesday I lift for endurance, 3 sets of 15 to 20 reps of straight bench, incline, decline, then I do bicep curls, then I do push-ups and sit-ups and reverse push ups following the same number of sets and reps, but with push ups and sit ups, i'll do 20 push-ups, then sit-ups, then reverse push-ups with no rest in between. On friday I do pure strength lifting, only 3 sets of eight reps and no floor exercises(like push-ups, etc). People say runners shouldn't strength train their upper body's, that's a bunch of crap. Just keep an eye on the scale. When you first start phasing in hard core strength training, you'll probably actaully lose weight. But if you start to gain weight, like over 5 pounds, then it may be time to lay off a little on the strength training. I think if you have week muscles anywhere on your body they are slowing you down. In the last couple of seasons I have lost weight, I weigh 120lbs, yet I can bench 167. There are runners out there that weigh more than me, are slower than me, and think that it is okay, and natural, that they can't even bench 100 pounds because they're runners. They think lifting will make them gain weight. I try to explain to them that by working their entire body they become fat burnign machines, and will probably actually lose weight if they do it right. If they trained their entire body's like I train mine, then they could probably have a chance at beating me. But you're running pretty decent times, you'll only get better from here, and lifting will definately probably help you out. When I was in high school I only broke the 5 minute barrier twice. Now a few years later, I'm going to try to run sub 5's the whole way through the 5K on the track.