Extreme Skeletal Adaptation to Mechanical Loading

Stuart J. Warden

DOI: 10.2519/jospt.2010.0404

Athletes who predominantly load their dominant upper extremity are useful models for investigating musculoskeletal responses to mechanical loading, as their nondominant upper extremity serves as an internal matched control. An extreme case of skeletal adaptation was recently observed in a 22-year-old collegiate male baseball pitcher assessed using peripheral quantitative computed tomography. Playing baseball for 17 years contributed to the athlete having 63% greater bone mass and cortical thickness in the dominant midshaft humerus compared to his nondominant side. These changes resulted from combined periosteal expansion and endosteal contraction, and provided the dominant midshaft humerus with a more circular cross-section,which maximizes torsional resistance. These collective changes resultedin the dominant midshaft humerus having nearly double estimated ability to resist torsional forces than in the nondominant side. These side-to-side differences set new levels for plasticity within the musculoskeletalsystem as they are the largest reported within an individual, and are 8-times larger and more than double those observed in sedentary individuals and average baseball players, respectively.

J Orthop Sports Phys Ther 2010;40(3):188. doi:10.2519/jospt.2010.0404

KEY WORDS: baseball, computed tomography, humerus, upper extremity

An extreme case of skeletal adaptation was recently observed in a 22-year-old collegiate male baseball pitcher assessed using peripheral quantitative computed tomography.

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