You could run. You could do a fast walk. You could jog or do jumping jacks. You could do jumping rope. Or you could walk at a faster pace than normal for a minute or two.
assistant
Swimming is a great way to do this, or if you prefer cardio exercises, then you could ride a bike.  You could also run, and do some light stretching exercises to get your body ready.
assistant
How should I warm up prior to working out?
user
There are many different things you could do, if you want to increase your fitness.
assistant
Okay, like what?
user