Although the traditional view is that underhand pitchers have minimal risk for sustaining pitching-related injuries, Loosli et al. found a high incidence of injuries to underhand pitchers.58 Thirty-one percent of these injuries were at or distal to the elbow. Unfortunately, research investigating the motion involved in underhand throwing is limited.
Barrentine et al. estimated the amount of force experienced at the elbow during underhand softball pitching.59 During the acceleration phase, a compressive force equivalent to 445 N is exerted to resist elbow distraction. Elbow distraction is caused by the centrifugal force on the forearm resulting from the upper torso rotation of 650°/sec, the arm rotating about the shoulder at 5260°/sec, and the elbow flexing at 880°/sec. A valgus torque of 45 N-m is generated at the elbow to resist varus stress caused by the combination of elbow flexion and shoulder internal rotation. After ball release, a compressive force of 356 N is exerted to resist distraction at the elbow during follow-through. The compressive force exerted on the elbow is smaller during underhand softball pitching than during overhand baseball pitching, and the timings of the maximum loads differ. Peak compressive force loads during underhand pitching occur during the acceleration phase, and peak forces during baseball pitching occur just after ball release during the deceleration phase. Varus torque observed in baseball pitching does not occur in underhand pitching, so fewer elbow injuries result. Elbow injuries often are related to improper mechanics, such as hitting the medial elbow against the hip before ball release. Obvious differences, such as sex, size of the ball, and pitching environment (height of mound), prevent a direct comparison between overhand and underhand pitching; however, based on the results, the elbow in the underhand motion may not be as safe from overuse injuries as previously thought.
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Since World War II, there has been a tremendous change in the makeup and direction of kid baseball, as it is called. Adults, showing an unprecedented interest in the activity, have initiated and developed programs in thousands of towns across the United States programs that providebr wholesome recreation for millions of youngsters and are often a source of pride and joy to the community in which they exist.