USE OF MUSCLES IN BOWLING
Showing A thickening of flexors on front of arm, as forearm is swung forward, and B thickening of extensors on back of arm, as forearm is swung backward.
The muscles of the limbs are almost as numerous as those of the trunk of the body, and even more complex. Most of them, on both arms and legs, are in two great groups—one known as the "benders," or flexors, which, when they shorten, bend the limb; and the other, the "straighteners," or extensors, which straighten or extend it.
On the front of the arm, for instance, we have the large biceps ("two-headed") muscle, which runs from the shoulder to the bone of the forearm just below the elbow and, when it shortens, bends the elbow and lifts the arm toward the body.
On the back of the upper arm is the triceps ("three-headed") muscle, which is fastened at its lower end to a big spur of bone, the "point" of the elbow; when it shortens, acting lever fashion, it straightens or extends the arm. If this is done quickly, the fist is swung outward with force enough to strike quite a sharp blow, though, as you know, if you wish to hit really hard, you have to strike with the weight and muscles of the full arm and the body behind it, or, as we say, "from the shoulder."
USE OF MUSCLES IN FOOTBALL
Showing A thickening of flexors on front of thigh and leg, as foot is swung forward; and B thickening of extensors on back of thigh and leg, as leg is swung backward.
