This occurs when the body is confused and contracts both muscles at the same time. This background information will help you understand why sprains and strains happen. You probably all know about sprained ankles and strained elbows, but the back is an area where strains and sprains often occur. Back sprains and strains are also the most costly to the individual. A strain occurs whenever a muscle is stretched beyond its limit.
Muscles do a great deal of work.
However, they must be conditioned if they are to perform in a given way. Professional athletes condition their muscles through rigorous training. We also must condition our muscles. A worker who is accustomed to manually handling a large number of pieces of material in a given workday can do so with ease. Those of us who have different duties would find it difficult to do that same amount of work without paying for it with aching muscles.