They could dry out your hands or if they are strong enough could burn skin
warm ups and cool downs are necessary in an exercise because they help the body get through the exercise easier.
warm ups-
•Jumping jacks, start slow then faster.
•Walking or slow jogs, same with jumping jacks, start up slow then faster.
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cool downs-
•Cool down after runs, walk for 10 minutes
•Cool down after jumping jacks, skip jump for 10 minutes