Scuba divers cannot pass gas at depths of 33 feet or below because the human body is not able to exert enough pressure to produce gas. Paintball is one of the safest extreme sports. Only 20/1000 players sustain any type of injury, including slight bruising from close hits or sprains from stumbling during games. In 1926, women were banned from competing in marathons because it was believed to cause infertility. Bill Russell was the first black head coach of a major league sports team.