A barrier would be a person has an injury and can’t work out or a person lacks knowledge of how to work out correctly. Hope this helped! :)
<span>the activity that requires the action of a first class lever in the body is: D. nodding
First class lever refer to a lever on which the resistance exist in one one side of the fulcrum and an effort is made on the other side.
Another example of a first class lever beside nodding are: Scissors, a crowbar, or a seesaw</span>