...comes from experience not just books. In anatomy books we are told that muscles go from a-b, and do this that or other action. Its not true, anyone who has been qulaified long enough, or been priviledged enough to view 10 or 12 real skeltons will know that they are all different, lengths of bones, muscle insertions.
Books are interesting, but then people aren't as the books describe. Doubt I will be back to join in for a few weeks at least. This has been just a fleeting visit