"Stop! That exercise isn't safe," said Juan, a Job Corps Recreation Supervisor and certified personal trainer.
Megan responded, "But we do it on the Pilates DVD all the time. Why would the instructor do something unsafe?" Megan went back to her Pilates roll up.
Juan stepped back and thought for a minute. Megan has a point; that is a perfectly normal Pilates exercise. It's also a straight leg sit-up. The straight leg sit-up is contraindicated. Any kinesiology textbook will tell you that you should not extend your hip during flexion. That's just plain dangerous.