Humeral torsion and throwing

This thesis is concerned with the act of throwing, and particularly with a variation of a skeletal feature — humeral retrotorsion — which has been shown to be associated with high level throwing. In the introductory chapters 1 to 3, the importance of throwing is established, followed by a description of humeral torsion, and an account of the development of humeral torsion. It is noted that there is a lack of consistency in the description and measurement of humeral torsion, along with some technical and practical difficulties in the currentlyemployed methods of its quantification. In the chapter 4 the rationale for an alternate method of measuring humeral torsion using the relation between the bicipital groove and the orientation of the humeral head is proposed. In the first of a series of experiments, the inter-rater reliability of two methods of measuring humeral torsion both of which involve standardising the position of the deepest portion of the bicipital groove and measuring the inclination of the ulna are explored. In the first method direct palpation of the bicipital groove is employed, and this is compared to ultrasound-assisted visualisation. Excellent inter-rater reliability is demonstrated for the ultrasound-assisted method in the dominant and non-dominant arms of 16 non-athletic adult subjects (ICC2_1=0.98, and 0.94) while the reliability of the palpation method was seen to be poor (ICC2,1=0.51 and 0.49). For the remainder of the experiments, the ultrasound-assisted method of visualisation was employed to measure humeral torsion. The next experiment investigated the side-to-side difference in humeral torsion in a group of throwing athletes (85 adult males, 16 adult females, 35 adolescent males, and 37 adolescent females), swimmers (l9 adolescent females, and 10 adolescent males), and 16 non-athletic adults. Greater dominant arm retrotorsion (11.90 :I: 105°) was displayed in the arms of the throwers irrespective of age or gender. The swimmers showed a lesser inclination toward increased dominant arm retrotorsion (6.4° d: 9.9°), and the non-athletic adults showed no detectable sidedness effect (13° :|: 89°). A wide range of between-subject variation was displayed in this data, with values for the throwing athletes varying from a maximum of 38° greater dominant arm retrotorsion to 18° greater dominant arm antetorsion. In the following experiment, the relation between humeral torsion and obtained proprioception was examined in 16 high-level adolescent male baseball players. In the non-dominant arm, a strong (F088) and significant (p