" The benefits of weight lifting on running performance were demonstrated in a 2008 study by Norwegian researchers (Støren et al. 2008). Seventeen well-trained runners were divided into two groups. Members of one group continued with their normal run training, while members of the other group added to their routine three weekly strength sessions consisting of four, four-repetition sets of half-squats using their four-repetition maximal load (i.e., the heaviest weight they could lift four times). After eight weeks, members of the strength group exhibited not only the expected gains in maximal strength and rate of force development, but also significant improvements in running economy (5 percent) and in time to exhaustion at maximal aerobic running speed (21.3 percent). The control group showed no improvement in any of the measured parameters. "

― Matt Fitzgerald , Racing Weight: How to Get Lean for Peak Performance