Question: Should I Lift Weights Before or After Running?
"I don't have time in my schedule to dedicate an entire training session to strength-training. So if I want to run and lift weights on the same day, which should I do first?"
Answer: Strength-training is very beneficial to runners, so it's definitely good to work strengthening exercises (either weight-lifting or bodyweight exercises) into your training schedule. And, yes, it's fine to strength-train on the same day that you run.
The answer to the question, What should I do first -- run or strength train? really depends on which activity is most important to you -- that's the one you should start with. As runners, our focus is to build and maintain our cardiovascular endurance, so we should run first.
One of the reasons runners should run first is that your run will be more effective when your energy supplies (available fuel) are highest. If you strength train first, you'll deplete some of that energy, and you most likely won't run as long or hard as you could if you ran before strength-training.
Also, if you lift weights or do strength training before running, your muscles will be fatigued, which could increase your injury risk. Another benefit is that you'll burn more total calories than if you lifted first. That's because most people will be able to run longer and at a higher intensity if they run first because they won't be fatigued from a pre-run strength-training session.
Of course, you definitely don't want to strength train every day or after every run. Two to three sessions of strength training each week is enough to get the benefits of strengthening.
Also see: Strengthening Workouts for Runners