Ballet dancers must have a good understanding of the physical capabilities of their bodies. This includes their maximum flexibility. During a class, dancers warm up their muscles gradually. They do this by initially doing a smaller movement, followed by a larger movement. The smaller movement is usually the half-way mark of their full capacity. Here are two examples:
A demi-plie (half bend of knees) bends half as much as a grande plie (full bend of knees).
In a cambre, the dancer stops at the half-way mark (90 degrees) before extending fulling to 180 degrees.