Currently, I'm using strength training to keep my body strong and injury free as I get higher mileage. I'm focusing on lower body and core mainly but I am also incorporating upper body moves as well. What works for me best (with the limited time I have) is doing supersets of a lower body move followed immediately by either a core or upper body move. This cuts down the rest time between reps and allows me to get in a full body workout in 30 minutes.
I know that my body works better in life and running from working these muscles, even if I'm not making it my main focus. I can feel when I'm running how my legs work less to get me up and down hills. I can easily lift up my fifty pound dog. And I know it's cutting down on my injury potential because I have less weight on my body and my muscles and joints are strengthened from the different ways I'm working them outside of running.
Once I go into off-season training, I'll probably up my strength training days once again to give my body recovery from heavy running and get it set up for the next race. It might not be a long off-season depending on if I decide I want to tackle a spring marathon or half marathon but I know even two months of focusing on lifting weights three times a week will translate into faster, stronger runs in 2018.
How do you incorporate strength training into your running schedule?