I suppose it may irritate the tissue more - it may not be that - it could just be flexibility but in the long run you need a strong core. I stopped doing triathlon in the early 2000 because of lower back pain - did nothing for 18 months - felt guilty and started running - and then ran again for more than 10 years running loads of sub 3 marathons, did a few more tris and now do time trials - all of that was made possible by just doing 15 minutes of planks and side planks a week - within 3 weeks of adding them to my regime my back pain had gone and has never returned even though I am now 51 