This is because with young people he was used to demanding movements of a high degree of difficulty, and pushing them to the limits of their physical strength. But here the teacher must constantly be watchful and make quick decisions and adjustments all the time, according to how the old people are coping.
因為對年輕人，他習慣要求高難度的動作和體力極限；而在這裡，老師得不斷保持觀察，視他們的接受度當機立斷，隨時做調整。