I must say that it is tricky to remember to do everything you intend while filming a class. I had planned to explain the alternative to the box and honestly thought that I did. After reviewing the class, I realize I did not. Sorry about that. To modify the box exercise, kneel with knees very close to edge of reformer carriage and have your bottom close to feet. Try to keep low back from rounding throughtout the exercise! Thanks for watching.