Isotonic, isometric, and resistive isometric are three categories of exercise. They are classified
according to the type of muscle contraction involved. Of the following exercises, which are
considered isotonic?
a. Bicycling, swimming, walking, jogging, dancing
b. Tightening or tensing of muscles without moving body parts
c. Push-ups, hip lifting, pushing feet against a footboard on the bed
d. Quadriceps set exercises and contraction of the gluteal muscles