The larger or heavier the catcher, the greater the health risks associated with repeatedly assuming a crouching or squatting position; knees and backs are especially vulnerable to "wear-and-tear" injuries. Catchers also have an increased risk of circulatory abnormalities in the catching hand. A study of minor-league ballplayers showed that, of 36 players in various positions, all nine of the catchers had hand pain during a game, and several had chronic pain in the catching hand. Catching high-speed pitches can, in some cases, cause the index finger on the gloved hand to swell to twice the size of the other fingers. Ultrasound and blood-pressure tests showed altered blood flow in the gloved hand of five of the catchers, a far higher incidence than in the hands of players at other baseball positions.