Benita de Witt answers:
For years we were taught that ab exercises cure back pain. After testing hundreds of athletes, I have found the opposite to be true.
In fact, most athletes with lower-back complaints after long runs have weaker back muscles than abdominals.
On a long run, the back muscles keep the body steady in an upright position. As soon as they tire, the connective tissue in the back stiffens up in support, and the muscles go into spasm.
The stronger the back muscles, the longer they can hold you up.
By doing a lot of abdominal exercises (shortening the body in the front) combined with hamstring and back stretches (which lengthen the body at the back), you create an imbalance, which weakens the back muscles and causes back pain.
If you suffer lower-back pain after runs, do the self-assessments shown below, counting how long you can hold each position without any pain.
Fast runners will be stronger on the first exercise (on your back) and hill runners should be stronger on the second (on your tummy). It is important to be able to hold both for at least 30 seconds.
If you can’t hold 30 seconds on the back test, find a therapist who can release the connective tissue in the lower back and then use the same exercise (holding 6×6 seconds), once a day, to strengthen up.