While running is very good for you, it's not an all-inclusive exercise. If all you do is run, eventually you'll end up overdeveloping some muscle groups (hip flexors, hamstrings) and under developing others (leg abduction/adduction, and upper body).
Over the years I've noticed these deficiencies becoming more pronounced. When I was younger, I could get away with just running and always felt strong. Now, I know which muscles need the most attention because I can feel it!
1. Weak Back- Neglected by most runners, I feel back discomfort during hilly runs. The fix is back extensions - I do mine on an exercise ball, locking feet under a heavy piece of furniture and resting my waist on the ball. I like to do light dumbbell reverse flys in that position also.
2. Hip Flexors- Mine are very tight. I like to open my hips and stretch the flexors using a standard yoga posture (seen here)
3. Tight Achilles, Lower Calf- Mine are very tight. Fortunately I have no problems but I can feel they need regular stretching with a Pro Stretch , by lowering heels carefully off of an edge or the standard wall push.
4. Upper body- I am weak! I do regular push-ups with push-up bars- only 1 set of 30 followed by another set of 30 arm curls with 15# dumbbells. If I had access to a pull-up bar I would be doing those along with overhead presses.
5. Weak Abs- I do the bicycle and reverse crunches.
6. Tight Hamstrings- Mine are tight and one that is weaker than the other, so I work it with standing curls using an ankle weight- 3 sets of 50. Evening stretching is mandatory.
7 Leg Abductors are weak- Side leg raises using the ankle weight solves this one nicely. I just have to make sure my leg is kept straight and parallel. This exercise is effective for reducing some of the strain on the IT band.
8. Quads are weak- I am a terrible uphill runner. I like the uphill repeats on a bike that I mentioned in #13.
9. Overall lower body weakness: I like the Hindu Squats for developing gluts, quads, and hamstrings. An overall great lower body exercise for runners.
My problem, of course, consistency with all of this. Sparkpeople.com is a great site with pictures of exercises you can do at home.
The bottom line: Don't neglect muscles that never get used, and stretch the muscles that get used the most. Focus on the muscles that you know are a problem. Establish an alternating routine that takes a few minutes a day, and work one set of muscles every other day. Stretch every night!
(c) Dave Elger 2008, All rights reserved.