Baseball throwing mechanics as they relate to pathology and performance - a review

Abstract

It is a commonly held perception amongst biomechanists, sports medicine practitioners, baseball coaches and players, that an individual baseball player's style of throwing or pitching influences their performance and susceptibility to injury. With the results of a series of focus groups with baseball managers and pitching coaches in mind, the available scientific literature was reviewed regarding the contribution of individual aspects of pitching and throwing mechanics to potential for injury and performance. After a discussion of the limitations of kinematic and kinetic analyses, the individual aspects of pitching mechanics are discussed under arbitrary headings: Foot position at stride foot contact; Elbow flexion; Arm rotation; Arm horizontal abduction; Arm abduction; Lead knee position; Pelvic orientation; Deceleration-phase related issues; Curveballs; and Teaching throwing mechanics. In general, popular opinion of baseball coaching staff was found to be largely in concordance with the scientific investigations of biomechanists with several notable exceptions. Some difficulties are identified with the practical implementation of analyzing throwing mechanics in the field by pitching coaches, and with some unquantified aspects of scientific analyses. Key pointsBiomechanical analyses including kinematic and kinetic analyses allow for estimation of pitching performance and potential for injury.Some difficulties both theoretic and practical exist for the implementation and interpretation of such analyses.Commonly held opinions of baseball pitching authorities are largely held to concur with biomechanical analyses.Recommendations can be made regarding appropriate pitching and throwing technique in light of these investigations.

Keywords: Baseball; analysis; biomechanics; injury; pitching; throwing.

Figure 1.

Total number of throws made as described by fielding position from data of Barrett and Burton (Research Quarterly for Exercise and Sport. 73(1), 19-27, 2002). 1B denotes first baseman; 2B': Second baseman; '3B': Third baseman; 'SS': Shortstop; 'OF': Outfielders.

Figure 2.

Distance thrown and position of player making the throw for the data described by Barrett and Burton (Research Quarterly for Exercise & Sport. 73(1), 19-27, 2002). Note that the vast majority of throws were made through the distance 46 to 60 feet, and that these throws were made principally by pitchers and catchers. Note also that almost all of the longest throws (180 feet and above) were made by outfielders.)

Figure 3.

Delineations of the six stages of the pitching motion are displayed here, viewed from six perspectives. The top row shows a perspective view from the third base coaches box, the second row shows a view from home plate, the third row shows a view from above, the fourth row shows a view from the first base side, the fifth row from second base, and the bottom row shows a view from third base. The six stages of the pitching motion are windup, stride, arm cocking, acceleration, arm deceleration, and follow-through. The delineations of these stages are shown here, and are: Rest, maximum knee height, stride foot contact, maximum arm external rotation, release, maximum internal rotation, and follow-through

Figure 4.

Calculation of stride length, stride offset, and lead foot angle at the moment of stride foot contact. Distance 'A' measures the length from centre of the trailing ankle to the centre of the lead ankle. Distance 'B' measures the distance from the leading edge of the pitching rubber to the centre of the lead ankle. Distance 'C' measures the offset of the centre of the lead ankle from a line drawn from the centre of the trailing ankle through to the centre of the target (home plate). Positive values being on the non-throwing arm, or 'open' side with our example showing a positive value. Angle Theta (Ө) measures the angle made between the long axis of the leading foot and a parallel line drawn from the centre of the trailing ankle to the centre of the pitching rubber. In this case Theta measures approximately 9° toward the 'open' side. Fleisig's (1994) PhD thesis gave normative values for each of these variables as follows: A: 75% of height, ± SD: 4%; B: 87% ± 5%; C: 0.4cm ± 8.3cm; Theta: 15° ± 10°.

Figure 5.

Depiction of elbow flexion at moment of Stride Foot Contact. Commonly pitching coaches will assert that the elbow shoulder remain at less than 90° of flexion (i.e. “straighter”) during the throw, however the results of several investigations reveal that this may need reappraisal in light of reduced stressful forces at both the shoulder and elbow where a higher amount of elbow flexion is displayed.

Figure 6.

Arm external rotation at Stride Foot Contact. In the investigation of Fleisig (1994) Arm external rotation was found to be 53°±26°. An increase in the amount of displayed external rotation at this point in the throwing cycle is termed “Early External Rotation” and was shown to be associated with increased stressful forces at both the shoulder and elbow, whilst a reduction in external rotation is termed “Late External Rotation” and was shown to be associated with increased stressful forces at the elbow, but a reduction in potentially damaging forces at the elbow.

Figure 7.

Maximum displayed Arm External Rotation. Maximum displayed figures for arm external rotation during pitching have been recorded in excess of 210°, and routinely are reported in the order of 180°. The clinical assessment of a thrower’s passive rotational range of motion needs to be made with these figures in mind.

Figure 8.

Maximum arm horizontal abduction during pitching.

Figure 9.

Comparison of glenohumeral external rotation in horizontal abduction and horizontal adduction. The image on the left depicts the proposed effect of performing the shoulder external rotation during the cocking phase whilst the arm is “left” in horizontal abduction of the early cocking phase. The subject on the right would be susceptible to less attenuation of the anterior capsular structures through performing this external rotation in the plane of the scapula, and hence less horizontal abduction coupled with the required glenohumeral external rotation.

Figure 10.

Arm abduction during pitching from the point of Stride foot contact to Maximum External Rotation, and then to release.

Figure 11.

Lead knee position during pitching. Significant variations are seen in the amount of knee flexion from the point of stride foot contact to release and then follow through. The lead knee may increase, decrease, or remain unchanged in terms of flexion. The rate of knee extension has been shown to be associated with an increase in ball velocity (Matsuo et al, 2001).

Figure 12.

Depiction of Pitching styles. Pitching style is termed according to the angle of inclination of the trunk and the forearm of the throwing arm. The leftmost image shows a pitcher sideflexing his trunk toward the contralateral (to the throwing arm) side, and an almost vertically placed forearm at release. This throwing style is termed 'overhand'. The third image shows a thrower standing erect with an almost horizontally placed forearm, this is termed 'sidearm' throwing. The second image shows a thrower with only a small amount of contralateral sideflexion and a forearm inclined between the extremes shown in sidearm and overhand throwing, this is termed 'three-quarter' throwing. The right-most image shows a thrower displaying ipsilateral trunk sideflexion, and a lesser amount of arm abduction than the first three images, this is termed 'submarine' throwing.

Figure 13.

Image taken from Burkhart, S.S., Morgan C.D. and Kibler, W.B. The disabled throwing shoulder: spectrum of pathology Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy 19(6), 649, 2003. The original caption to the image reads: 'Ideal mechanics involve abduction in the plane of the scapula (A, dotted line) with the elbow high enough to keep the upper arm at or above the horizontal plane. (B) With a “dropped elbow ”(solid line), the upper arm hyperangulates posterior to the plane of the scapula. (C) This pitcher has excellent mechanics, with the arm abducted in the plane of the scapula and positioned above the horizontal plane.' Note that this image shows an overhand thrower at or close to maximum external rotation of the arm.

Figure 14.

Image taken from Burkhart, S.S., Morgan, C.D. and Kibler, W.B. The disabled throwing shoulder: spectrum of pathology Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy 19(6), 650, 2003. The original caption reads: 'This pitcher has excellent mechanics, with the arm abducted in the plane of the scapula and positioned above the horizontal plane. This pitcher shows abduction in extension, with angulation of the arm posterior to the plane of the scapula rather than in the plane of the scapula. Note the “dropped elbow ”in this pitcher, causing the arm-body angle to drop below the horizontal.' Note that this image shows a pitcher soon after stride foot contact, and before arm cocking has been undertaken to any great extent. Therefore it is not an unusual finding to have a reduced amount of arm abduction, and an increased amount of arm horizontal abduction at this point in the throwing cycle.