Here Israel is strengthening his quadricep or thigh muscles! He is having a competition to see who is the strongest, him or his physiotherapist! Who do you think? Israel squeeeezes his knee down into the towel and lifts his foot up as high as he can. He is so strong that now his physiotherapist tries to push his foot down, and they see who can hold it the longest! This helps Israel to stabilise and protect his knee joint because he is hypermobile, he has extra bendy joints!