The relationship between age and baseball pitching kinematics in professional baseball pitchers

https://doi.org/10.1016/j.jbiomech.2006.01.008Get rights and content

Abstract

Joint range of motion and physical capacities have been shown to change with age in both throwing athletes and non-athletes. The age of professional baseball pitchers could span from late teens to mid-40s. However, the effects of age on the pitching kinematics among professional baseball pitchers are still unknown. In this study, 67 healthy professional baseball pitchers were tested using a 3D motion analysis system. Their mean age was 23.7±3.3 years (range 18.8–34.4). The 12 pitchers more than one standard deviation older than the mean (i.e., older than 27.0 years) were categorized into the older group, and the 10 pitchers more than one standard deviation younger than the mean (i.e., younger than 20.4 years) were defined as the younger group. In all, 18 kinematic variables (14 position and 4 velocity) were calculated, and Student's t-tests were used to compare the variables between the two groups. Six position variables were found to be significantly different between the two groups. At the instant of lead foot contact, the older group had a shorter stride, a more closed pelvis orientation, and a more closed upper trunk orientation. The older group also produced less shoulder external rotation during the arm cocking phase, more lead knee flexion at ball release, and less forward trunk tilt at ball release. Ball velocity and body segment velocity variables showed no significant differences between the two groups. Thus, differences in specific pitching kinematic variables among professional baseball pitchers of different age groups were not associated with significant differences in ball velocities between groups. The current results suggest that both biological changes and technique adaptations occur during the career of a professional baseball pitcher.

Introduction

The baseball pitching biomechanics of adults have been extensively studied (Barrentine et al., 1998; Dillman et al., 1993; Elliott and Grove, 1986; Feltner and Dapena, 1986; Fleisig et al., 1995, Fleisig et al., 1996; MacWilliams et al., 1998; Matsuo et al., 2001; Pappas et al., 1985, Pappas et al., 1995; Sakurai et al., 1993; Stodden et al., 2005; Vaughn, 1985; Werner et al., 1993). These studies have shown that baseball pitching is a highly demanding task, and proper pitching mechanics are very important in preventing pitching injuries and improving or maintaining performance. A previous study (Fleisig et al., 1999) of baseball pitching among various levels of development revealed that adult pitchers did not demonstrate different position or temporal patterns than younger pitchers. All the kinetic variables that were analyzed increased significantly with competition level, which was most likely due to increased strength and muscle mass in the higher-level athletes.

Aging changes the physical capacities and therefore the performance of athletes considerably. In a study of track and field athletes, Fung and Ha (1994) found that the running, jumping, and throwing events most affected by age were the 400-m run, long jump, and javelin, respectively. There are systematic relationships between the age of peak performance and specific athletic events. Stones and Kozma (1984) developed a second-order polynomial model to quantitatively describe the relationship between age and performance in track and field events. The model fit the data very well and accounted for approximately 81% of the mean variances. Schulz and Curnow (1988) found that performance in swimming, sprinting, jumping, and tennis tended to peak in the early to mid-20s, whereas performance in long-distance running, baseball, and golf peaked in the late 20s and early 30s. In major league baseball players, the athletic performance on key indicators (e.g., ERA, Strikeouts) rises relatively quickly from age 19 to a peak age of 27 and declines gradually thereafter (Schulz et al., 1994).

The age of professional baseball pitchers ranges from late teens to mid-40s. Even though some researchers have investigated the relationship between age and pitching performance in major league baseball pitchers (Schulz et al., 1994) and the pitching biomechanics among various development levels (Fleisig et al., 1999), the variations in pitching mechanics of professional baseball pitchers among different ages are still unknown. Therefore, the purpose of this study was to investigate the differences of pitching kinematics between two different age groups of professional baseball pitchers. We hypothesized that kinematic variables will be significantly affected by age.

Section snippets

Methods

Sixty-seven professional baseball pitchers were tested in an indoor laboratory. All participants had no previous history of neuromusculoskeletal disorders. The average age of the subjects was 23.7±3.3 years (range 18.8–34.4). Those subjects older than one standard deviation above the mean (>27.0 years) were categorized into the “older group”, and those subjects younger than one standard deviation below the mean (<20.4 years) were defined as the “younger group”. There were 12 subjects in the

Results

The average age of the older group was approximately 10 years older than that of the younger group. There was no significant difference between the two groups in body height, body weight, and ball velocity. Players in the older group played at higher levels (Table 1). In fact, an analysis of date-of-birth data provided on Major League Baseball's website (www.mlb.com) showed that the mean age of the older group in this study (29.5) was very similar to the mean age of current Major League

Discussion

In all, 6 out of 14 position variables were found to be significantly different between the two groups: stride length, upper trunk and pelvis orientation angles at lead foot contact, maximum shoulder external rotation angle during arm cocking phase, and lead knee angle and trunk forward tilt angle at ball release. The joint range of motion of the human body has been demonstrated to degrade with age among both the general population (Allander et al., 1974; Barnes et al., 2001; Clarke et al., 1975

Acknowledgments

This study was supported in part by funding from Smith & Nephew, Inc.

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