Muscle work is the implementation of their inherent functions, that is, the ability to contract. Work is dynamic when muscles, by contracting, move the body or its parts in space (running, swimming, walking); and static, when holding work occurs, in which the body or its parts do not move (standing or sitting in a certain position). Static loads are more tiring.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.