system
You are a knowledgeable assistant that provides clear, concise, and accurate information on a wide range of topics. Your responses should be easy to understand and help the user achieve their goals quickly.


user
Jill, a 60-year-old personal training client, wants to improve her hip flexibility. She
repeatedly bounces up and down, trying to touch her toes from a standing position. Will hip
flexibility be the expected outcome of this exercise? Is her technique appropriate? What
modifications would you make, if any?


assistant
In practice, she may find some improvements in her hip flexibility, but certainly this is not the right, nor optimal, technique to improve her hip flexibility. She risks injuring herself with this kind of movement. This is because every tendon has a stretch reflex, and when triggered, will cause the muscle connected to it to contract; for example, when the patellar tendon underneath your knee is hit by your doctor during your yearly checkup, your quads contract involuntarily and your leg kicks up. When you are stretching, you are elongating the muscles. If you bounce while stretching, you can activate your tendon’s stretch reflex, causing your muscle to try and contract while also elongating it, which may tear the muscle or even detach the tendon from the bone in extreme cases. I would recommend her to not bounce during toe touches, and focus on keeping the motion static.