If our bodies are not strong， our spirit to do things will certainly be quite dull。 And at the same time， we are lack of energy (ies) to study。 Diseases will only attack the weak， but not the strong。
Why are our bodies not strong? Because we do not pay attention to exercise。 For this reason， we students must often take different kinds (sorts) of exercise in the gym。
Exercise helps us (to) strengthen our bodies and avoid disease。 It also teaches us cooperation， for most exercise is played by team。