Developing an satisfactory strength base is essential to meeting the demands of any sport, in particular running.
Some runners are hesitant to strength train, believing --mistakenly-- that strength training will muck up their running performance. just the opposite, proper strength training has been reliably proven to increase performance in runners and any athlete who time and again engages in knee bending.
Researchers exposed that runners who will live with injury move in a different manner than those who don't come to be injured, and that most injuries are associated to poor running mechanics. The latest studies show that injured runners have poor alignment of the foot, knee and hip, as opposed to well runners, who are able to keep their joints in a neutral position.
While you may conclude your leg muscles are to blame for changed mechanics and poor running performance, it's really the core muscle groups that are responsible for proper joint alignment. Unfortunately, although they are primary to healthy running, core muscles don't get trained when you run. In fact, it's just the opposite: the inadequate range of motion involved in running tends to weaken all the core muscles surrounding your legs and hips. Running just involves back-and-forth motion in one dimension, not really any lateral side-to-side movement, so the core muscles that work to balance your trunk get weaker truly with each mile...
If you look at other aggressive sports such as basketball, football, baseball, soccer, and for the most part any other sport you can think of, you see that athletes perform sport specific exercises in the off season to get stronger, broaden their effectiveness, increase core strength, and cure common sports injuries. Strength training allows athletes to perform at a higher level.
So, let's go over again so we can really drill this in: core muscles don't get trained when you run, but they are ideal to healthy running.
The healthy and successful runner needs to conceive that pain-free, fast running is as much about the strength of your core as it is about your legs.
What I've seen over and over again is runners who like to just run. Strengthening is seen to be a distraction or annoyance and not an atypical part of running. This is chiefly the case for recreational runners who often are trying to fit in' a run before or after work. Or, many runners are motivated to run to keep weight under control and anticipate that strengthening leads to bulking up.
What you must envision is that strengthening your core muscles does not translate into getting 'bigger' or regaining weight. Simply, it's a critical part of running that is about upgrading the muscles among runners that inevitably get long and weak -- the muscles you rarely use in running -- into strong muscles that can stabilize your pelvis and allow explosive power from your limbs.
To sum it up, a strong core is as effective as getting comfortable sneakers -- it is a TOOL of healthy, pain-free running. You have to think of strengthening as an integral prerequisite of running, not as something that's tangential or as a bonus when you have extra time. In fact, your schedule needs to allot specific times during the week for a set amount of must-do strengthening exercises. If not, you're surely going to get injured (almost all runners do) and lose even more time by having to finally stop running.
Runners often conclude that running more is the only way to increase their performance. It turns out the desirable way for runners to help performance and prevent injury is to increase strength and the stabilization that results originating at a strong core.