Our sources say Yes! This often debated issue was the subject to one scientific review in which the author concludes that strength training is not likely to improve either your aerobic capacity (VO2 max) or to boost your lactate threshold. However, it could increase running economy by up to eight percent. Even a small improvement in running economy of even a few percentage points could have a large impact on distance running performance, particularly in longer events, such as marathons or ultra-marathons. Don't let pumping iron substitute any of your other training, but work upper and lower body exercises into your routine. Just make sure you give yourself enough time to recover before launching into speedwork or some other hard workout.