Workout balls have become increasingly popular as fitness equipment. The term workout ball can refer to one of several different balls, each with a different size, weight, and workout function. A medicine ball, for instance, is usually the size of a volleyball or basketball, and it comes in a variety of weights. Some trainers have clients throw medicine balls against a wall, to another client or have them lift the ball overhead and side to side, sometimes in conjunction with a balance exercise. Balance balls also are popular. These are usually large enough to sit on and can be used for a variety of balance exercises, abdominal exercises and back-strengthening exercises.
The most common type of workout ball is the Pilates balance ball. This ball, which measures 2 feet by 2.5 feet (about .6 meters by .8 meters) in diameter was originally known as the Gymnastik or Pezzi ball; it was developed in 1963 by an Italian plastics manufacturer. The balls were first mainly used by pediatricians for children undergoing neurological rehabilitation. Swiss physical therapists later introduced the ball to the rest of Europe as a means of adult physical rehabilitation; it ultimately became known as the Swiss ball.
After the aerobics boom of the late 1980s, gyms and exercise studios were looking for new classes to teach. Pilates studios had become popular in many United States (U.S.) urban areas, and fitness centers saw Pilates classes as a source of revenue. Some women were already familiar with the workout ball, having used it as a birth ball in hospitals. But gyms quickly moved away from the discipline of traditional Pilates and incorporated the balls into other exercise trends.
The large workout ball is used most commonly for core-strength workouts—exercises that strengthen your abdominal, back, and pelvic muscles. These might include modified sit-ups while sitting on the ball, squats, hip flexor exercises, modified push-ups, or even pure balance exercises, such as keeping your body stable while sitting on the ball and lifting one leg off the floor.
BOSU brand balls also come in a half-ball size, called a balance trainer. These are used for core work also, but primarily are used for balance training. Balance trainers may be used in place of steps for step aerobics, or as challenging platforms for lifting hand weights or other, smaller workout balls such as medicine balls.
Other ball sizes and functions have also been integrated into fitness center workouts. 9-inch (about 23 cm) diameter soft-sided mini balls can be used as headrests, back supports, or to strengthen inner thigh or calf muscles. Other, smaller workout balls, between 5- to 7-inch (about 12.7 to 17.8 cm) in diameter, can be used in place of hand weights or to strengthen balance and coordination by transferring from hand to hand or throwing in the air during cardiovascular workouts.