Junior (View All Rackets). Kids tennis rackets ranging from 19 to 26 inches in length for players between 2 and 12 years old. As a general rule, the appropriate size racket length for your child is the distance from finger tip to ground when standing upright.
The ring of muscle at the entrance to the stomach is the lower  esophageal sphincter. This muscle is normally contracted to close  the esophagus. At the lower end of the stoâ¦mach food passes through  the pyloric sphincter and into the duodenum of the small intestine. Making the world better, one answer at a time.
This is called antagonistic muscle action. The working muscle is called the prime mover or agonist. (it s in agony!) The relaxing muscle is the antagonist. The other main pair of muscle that work together are the quadriceps and hamstrings.The prime mover is helped by other muscles called synergists.These contract at the same time as the prime mover. They hold the body in position so that the prime mover can work smoothly.it s in agony!) The relaxing muscle is the antagonist. The other main pair of muscle that work together are the quadriceps and hamstrings. The prime mover is helped by other muscles called synergists. These contract at the same time as the prime mover.