Answer:
A muscle strain, or pulled muscle, occurs when your muscle is overstretched or torn. This usually occurs as a result of fatigue, overuse, or improper use of a muscle. Strains can happen in any muscle, but they're most common in your lower back, neck, shoulder, and hamstring, which is the muscle behind your thigh.
Saying its natural, there are no tight laws against putting natural on the product so people do it all the time.