In massage therapy, the Sims’ position is basically a semi-prone, side-lying variation that allows you to work on areas that are tricky to access in fully prone or supine positions — especially glutes, piriformis, lateral hip, and sometimes lower back — while keeping the client comfortable and stable. . Advantages for Massage Work • Better glute access: Especially for deep work on piriformis, glute medius, and deep rotators. • Client comfort: Great for clients who can’t lie fully prone (pregnanc