Many thanks, Caroline
Gary Moller comments:
Caroline, the pain you describe is most likely due to spam of muscles deep in the buttock. It is probably the piriformis that is most affected (But let's not get carried away with the fancy names - it is still just a pain in the butt!). This is probably the most common chronic injury issue that runners ask me about.
Fixing the problem is a three-pronged approach of stretching, nutrition and massage. While working on your core strength is worth doing, it is unlikely to be of direct benefit (As an aside, I think core strength is an over-rated thing that serves mostly to keep a lot of fitness instructors employed teaching and supervising an ever-increasing array of complex exercises).
Caroline, you need to get my book on Back Pain (http://www.myotec.co.nz/ ) and to do the hip and low back exercises with emphasis on the exercises that you will find on pages 59, 65, 70, 72, 95 and 96. Exercise 72 is the most important and you may find that this really hits the painful spot of the butt muscle. Hold each stretch for several seconds at about the point of mild discomfort, relaxing the body. Release the stretch a little for a second or two and then reapply the stretch and repeat the cycle several times, swapping now and then between legs. One good set of stretching per day is more than sufficient.
You can just about guarantee that you are low in various essential minerals, including calcium and magnesium. It does no harm and probably does much good to do a course of mineral supplementation because one of the symptoms of mineral depletion is muscle pain and spasm. I recommend either a course of Nutra-Lifer Calcium Complete or, better still, a course of Floradix Calcium-Magnesium formula. While Floradix is more expensive, its quality and bioavailability is unsurpassed. You should also take a vitamin D supplement, like Red SEal Cod Liver oil, or Thompson's Vitamin D capsules, through winter because low vitamin D prevents proper use of minerals by your cells.(All available through http://www.myotec.co.nz/ ).
I strongly recommend a course of massage of the affected muscles. A good massage therapist will locate the tender and knotted parts and progressively massage them and the surrounding areas to break the spasm, soften up the knotts and encourage circulation through the affected areas. This can be quite painful and takes about an hour per session and must be repeated several times every fourth day. The first few sessions may leave you sore and tired over the next few days. Done right, along with the nutrition and stretching, you should notice a steady improvement by way of less pain and better function from about the third session onwards. By about 21 days, you should be back to striding freely. I provide this massage service here in Wellington.
Let us know how you get on Caroline.