Sex is great. Everyone knows that. After a while though, you and your partner might want to change things up in order to keep it fresh and have new sexual experiences. You two might even want a challenge. Here are also the most dangerous sex positions and bizarre injuries that happened while filming porn.These are the most difficult sex positions ever conceived by mankind. In fact, none of these can really be recommended because most of these positions require superhero-levels of strength, and taffy-like flexibility. So, you've been warned. In any case, read all about, and rank, the 10 hardest sex positions of all time.