Hi 10,
When performing leg raises, you will also be ‘anchoring’ right the way up to your scalene muscles which run from your colarbones to the spinous processes in the neck. On the way past, pec-minor will of course get in on the action. There is also your Ulnar and Median nerves which run out that way before going down your arms which can get easily compressed by spasming or tight muscle.
You can try to trigger point the muscle, by finding the spot that really hurts, then push your thumb in it till it releases, it’ll hurt but bombarding the nervous system will get it to relax eventually.
When you’re actually doing the raises, try rolling up a towel to place behind you head/neck, this will offload and allow you to stay relaxed higher up whilst still giving your abs the desired workout.
Hope that helps,
Rich
http://www.pedalprecision.com