When taking part in a ballet or Graham technique class it is often important to have a rigerous structure. This would include a warm up. Warm ups allow the tendons and ligaments to stetch and create friction. This literally warms them up and makes them more stretchy and flexable. This is usefull in Ballet as you often have to stretch your legs to their limmets. Warming up ensures that you can do this to your full potential. It will also prevent injury. In Graham technique sometimes when you suddenly contract or twist the ligaments are put under sudden strain and could snap or ull. Warming up makes them more pliable so injury is less likely.
When sticking to a structure that often means you repeat the same exercises. Repeating exercises that are specific to a dance move can strengthen you and increase flexibility. Repeating evercises over and over will increase your cardiovascular and muscular edurance / stamina for it. Repeating sequences or movements will improve muscles memory which means you can focus on more details when dancing, rather than the getting the basics right.
When sticking to a structure it also helps you get into a mental rutine as well as a physical one. It will often make participants feel more proffessional as they can be left to cary out their warm up or cool down. Having a structure also mentally prepares you for the dance. This comes from the theory that you perform better if you practice the same way in which you perform.
One example of a ballet warm up often used in a class is repeated pliates. This will help strengthen the quadracepts and hamstrings, which in turn could make you jump higher and hold positions for longer. When doing this you could use the idea of progressive overload. This is where you make it harder each time so that you gain something from the exercise. For example repeating a pliate over and over would increase your