To be honest, I don’t think this forum is busy enough to warrant subforums for each body part. That just disperses all the active topics, giving the impression the site is even quieter than it already is. As a forum admin on another site, I wouldn’t recommend this.
Also - I have had laser on my legs, abs, and chest as one block of treatments. Similarly with back, shoulders, and arms. Which section would I put my log under?
A better approach is either to encourage people to use the search function, or if the software supports it, create tags that can be applied to topics. Then people can tag a log with as many or as few body parts as needed.