A yoga ball is a large, inflatable ball that can be used to perform several types of exercises, including yoga, physical therapy, and core-strengthening workouts. Yoga balls come in various sizes to accommodate different body sizes and types of exercise, typically ranging from 18 inches (45 cm) to 34 inches (86 cm). Manufactured from durable materials such as vinyl or silicone and polymer blends, yoga balls are intended to be able to withstand several hundred pounds of weight, though special slow-leak, puncture-resistant or burst-resistant models are often available for the cautious buyer. The surface of a yoga ball is usually smooth but not slick, allowing skin and clothing to easily grip, and preventing the ball from slipping out from beneath the user.
When a yoga ball is inflated to full capacity, it feels very firm, and may be uncomfortable to sit, lie, or roll on. Many distributors suggest buying a size larger than is needed, and then under-inflating it so it remains soft. Some users may feel more comfortable with a smaller or larger ball than normal, so it is also recommended that potential buyers test out several exercises on different ball sizes before purchasing. Generally, beginners and users with back problems prefer larger balls as they provide a more stable platform on which to balance.
Using a yoga ball for balance, physical therapy, or yoga exercises provides support, while still forcing the muscles to work to maintain balance. A favorite of many Pilates and core-fitness enthusiasts, the yoga ball allows the user to isolate and train specific muscles or muscle groups in the core of the body. For many exercises, a yoga ball can be used in conjunction with other equipment, such as exercise bands, medicine balls, or free weights to increase the intensity of the workout.
Some people use a yoga ball in place of an office chair to encourage proper posture and possibly alleviate back pain. This also provides an opportunity for a relatively passive workout, lightly engaging the legs and core muscles continuously throughout the workday. Using yoga balls in place of chairs has become so popular that many yoga ball distributors offer ball-stabilizing bases or stools with inflatable dome seats. Some chiropractors express concerns about the absence of back support, possible muscle fatigue, and injuries from falling, but do not deny the potential benefits of using yoga balls instead of office chairs if used correctly.