Everyone goes to the gym and works out once in a while but who would know that physics is part of lifting weights and running on the treadmill. Forces everywhere. When you are are lifting you are applying a force against the wights but gravity is also a force that is present as well. Work is also being done on the weights because you are applying a force on an object. And how many reps you do can be considered power because power is the rate which the force does work.