Hi Spanner
Yes, you should include a letter from a qualified Sports Massage Therapist. It would help if you could tell them what you want them to include. I always try to tell specialists what needs to be included, because sometimes specialists at any level can say things that hinder an application rather than help.
If anyone gives you a letter that is damaging - never include it in your evidence.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems