2. Happy baby pose! This pose is very good to your legs and lower back. And who wants an aching leg and stiff lower back while having sex? Happy baby pose will stretch the spine while it looses up the hamstrings and the adductor muscles. These muscles are very much used in positions such as missionary, and if youre a fan of this position, you better improve it! You can hold in this pose for 3 to 5 minutes for optimal results.