Background Softball pitching is a strenuous task that accrues high forces at the shoulder resulting in frequent overuse injury, potentially exacerbated by increased pitcher body fat.
Objective To examine differences in injury rate, pain prevalence, and throwing shoulder kinetics between pitchers with high and healthy body fat percentage (BF%). We hypothesized pitchers with high BF% would display increased kinetics and higher rates of injury and pain.
Design Cross-sectional; retrospective.
Setting Indoor biomechanics laboratory with high-school league softball pitchers.
Participants Forty-three female pitchers volunteered (1.69±.07 m, 75.97±16.85 kg, 15.2±1.2 years) and were analyzed. Participants were currently on team rosters and surgery/injury free for the last six months.
Assessment of Risk Factors BF% was determined using dual-energy x-ray absorptiometry and pitchers were grouped into healthy (<32 BF%; n=17) and high-fat (≥32 BF%; n=26) categories.
Main Outcome Measurements Throwing shoulder distraction, superior, lateral, and anterior forces (normalized to body weight * pitch velocity) were measured via an electromagnetic motion capture system. History of softball related injuries and the presence of pain was self-reported on a health history questionnaire.
Results 83.3% of pitchers currently experiencing pain (total n=12) and 72.2% of pitchers who had suffered a softball-related injury (total n=18) were high-fat pitchers. Statistical parametric mapping was used to determine differences in throwing shoulder forces between groups during foot contact to follow-through of the pitch. Analyses revealed high-fat pitchers had higher normalized distraction force over most of the first 27% of the pitch (tcrit=3.112, p<.008) and lower normalized superior force during 80–91% of the pitch (tcrit=3.141, p=.004).
Conclusions High BF% alters shoulder kinetics during the pitch and may increase high-school softball pitchers’ injury risk. Athletes, coaches, and clinicians should understand this increased risk and safely emphasize the importance of attaining a healthy body composition.
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