Anal sex positions involve anal penetration. Most anal sex positions are adaptations of vaginal penetrative positions:
Doggy style penetration maximizes the depth of penetration, but can pose the risk of pushing against the sigmoid colon. If the receiving partner is male, this increases the chances of stimulating the prostate. The penetrating partner controls the thrusting rhythm. A variation is the leapfrog position, in which the receiving partner angles their torso downward. The receiving partner may also lie flat and face down, with the penetrating partner straddling their thighs.
In the missionary positions, to achieve optimal alignment, the receiving partner's legs should be in the air with the knees drawn towards their chest. Some sort of support (such as a pillow) under the receiving partner's hips can also be useful. The penetrating partner positions themselves between the receiving partner's legs. The penetrating partner controls the thrusting rhythm. This position is often cited as good for beginners, because it allows them to relax more fully than is usual in the doggy style position.
The spoons position allows the receiving partner to control initial penetration and the depth, speed and force of subsequent thrusting.
The receiving partner on top positions allow the receiving partner more control over the depth, rhythm and speed of penetration. More specifically, the receiving partner can slowly push their anus down on the penetrating partner, allowing time for their muscles to relax.