The first study we're going to look at is one by Dr. Alan Jung while he was at the University of Alabama.
Jung AP. The impact of resistance training on distance running performance. Sports Med. 2003;33(7):539-52.
This study is an analysis of the scientific literature related to endurance training and it has two big takeaways.
1) Resistance training improves running economy in trained athletes by up to 8%: In other words, athletes who had been training for years were able to improve their running efficiency simply by adding a well designed resistance training program. If you want to do the math, this means shaving about 10-20 minutes off your marathon time.
2) Resistance training improves neuromuscular characteristics and reduces ground contact time. To put it simply, the ability of the nervous system to recruit muscle fibers is improved which in turn causes the muscles to function more economically and reduces fatigue. Reduced ground contact time equates to greater stride frequency and increased speed at a given effort.
There is also some indication of Lactate Threshold improvement for less trained runners that's not as prevalent in well trained runners. Regardless, the benefits of resistance training for endurance athletes is quite obvious. So don't be afraid to add a well designed strength program to your training schedule. As always, please let me know if you have any questions...
Exercise Physiologist, CSCS