KINEMATIC AND KINETIC COMPARISON OF FULL-EFFORT AND PARTIAL-EFFORT BASEBALL PITCHING

G.S. Fleisig, N. Zheng, S.W. Barrentine, R.F. Escamilla, J.R. Andrews, L.J. Lemak
American Sports Medicine Institute, Birmingham, AL 35205

Presented at the 20th Annual Meeting of the American Society of Biomechanics
Atlanta, Georgia. October 17-19, 1996

INTRODUCTION

The kinematics and kinetics of full-effort and partial-effort baseball pitching were compared. Differences may help determine the best use of partial-effort pitching in training, warm-up, and rehabilitation of baseball pitchers.

REVIEW AND THEORY

Partial-effort pitching is often used by baseball pitchers during training, warm-up, and rehabilitation. The intent of these throws is to progressively increase the loads on the athlete's body to the high levels produced in full-effort pitching while reinforcing proper timing, coordination, and movement patterns (Wilk et al., 1994). While the biomechanics of full-effort pitching has been well- documented (Dillman et al., 1993; Feltner et al., 1986; Fleisig et al., 1995; Fleisig et al., 1996; Sakurai et al., 1993; Werner et al., 1993), the biomechanics of partial-effort pitching has not been published. Although it has not be scientifically verified, many baseball experts believe that compared to full-effort pitching, partial-effort pitching has similar kinematics and decreased kinetics. The purpose of this study was to evaluate this hypothesis.

PROCEDURES

Twenty-seven healthy college baseball pitchers were tested. Their height was 1.84 ± 0.07 m, and their mass was 81.6 ± 8.8 kg. After providing informed consent, history, and physical information, each pitcher was tested in an indoor laboratory. Reflective markers were attached to 14 bony landmarks. After stretching, the subject threw three balls from seven different conditions (i.e. 21 total trials). The conditions were: 100% effort from a standard-height 10" mound, 75% effort from a 10" mound, 50% effort from a 10" mound, 180' crow-hop throw, 120' crow-hop throw, 60' crow-hop throw, 100% effort from a 13" mound. Only data from the first three conditions listed were used for this study. The order of conditions was randomized for each subject, and warm-up time was provided before testing each condition. For all trials on a mound, the subject pitched from a portable pitching mound (B&P Sports Products Inc., Amelia, OH) towards a strike zone ribbon located over a home plate at a distance of 18.4 m (60.5 ft) from the pitching rubber. Ball velocity was recorded with a Tribar Sport radar gun (Jugs Pitching Machine Company, Tualatin, OR).

Three dimensional coordinates during the second trial of each condition was determined with a four-camera 200 Hz automatic digitizing system (Motion Analysis Corporation, Santa Rosa, CA). Root mean-square error in calculating three-dimensional location was 1.0 cm. Using the digitized data, and published anthropometric data, 23 kinematic (Figure 1) and kinetic (Figure 2) parameters were calculated as previously described (Dillman et al., 1993; Fleisig et al., 1995; Fleisig et al., 1996). A one way repeated measures Analysis of Variance was performed, using a Bonferroni t- test to identify significant (p<0.05) differences between full- effort pitching (i.e. control group) and the other conditions.

Figure 1. Kinematic parameters: (a) elbow flexion; (b) shoulder external; (c) shoulder abduction; (d) shoulder horizontal adduction; (e) lead knee flexion; (f) forward trunk tilt; and (g) pelvis angular velocity ( P) and upper torso angular velocity ( UT).

Figure 2. Kinetic parameters: (a) shoulder forces; (b) shoulder torques; (c) elbow forces; and (d) elbow torques.

RESULTS

Means and standard deviations for all parameters are presented in Table 1. Significant differences between partial-effort (75%, 50%) and full-effort (100%) pitches are indicated. In order to simplify interpretation of the results reported in Table 1, mean values for 75% and 50% effort pitches were expressed as percentages of values for 100% pitching. A summary of these percentages, approximated within 5%, is shown in Table 2.

DISCUSSION

Coaches, therapists, trainers, and pitchers often discuss pitching at "75%" or "50%." However, what 75% or 50% means is not well-defined. In this study, pitchers were given similar vague instructions, and their kinematics and

Table 1. Kinematic and kinetic parameters for 100%, 75%, and 50% effort pitching

* Significantly different (p<0.05) from 100% effort.

Table 2. General description of 75% and 50% effort pitching, relative to 100% effort pitching.

kinetics were quantified. At 75% effort, pitchers produced approximately 90% of the velocity and 85% of the force and torque as produced during full-effort. At 50% effort, pitchers produced approximately 85% velocity and 75% force/torque. Reduced effort pitching also corresponded with reduced arm rotation during cocking, increased horizontal adduction, and a more upright trunk (less knee flexion and less trunk lean) at ball release.

These results were similar to a previous study of partial golf swings which found that compared to a full golf swing, a 50% effort swing generated less backswing rotation, 75% as much torque (based upon angular acceleration), and 87% as much velocity (Lemak et al., 1994). Standard deviations were noticeably greater during partial golf swings, compared to during full swings. In the present study, standard deviations were fairly consistent among the different effort throws. This implies that while golfers had varied interpretations of partial-effort, pitchers had fairly consistent interpretation of partial effort. In summary, reduced force/torque and reduced rotation were produced during partial-effort pitching. As a result, reduced body and ball velocity were generated. Although there were some differences in mechanics, pitching with reduced effort appears to be useful for a pitcher in training or rehabilitation who does not want to overload his arm.

REFERENCES

Dillman, C.J. et al. J Orthop Sports Phys Ther, 18(2), 402- 408, 1993.

Feltner, M. et al. Int J Sport Biomech, 2(4), 235-259, 1986.

Fleisig, G.S. et al. Am J Sports Med, 23(2), 233-239, 1995.

Fleisig, G. S. et al. J Appl Biomech, 12(2), 207-224, 1996.

Lemak, L.J. et al. Science and Golf II, (pp. 14-19),E&FN Spon, 1994.

Werner, S.L. et al. J Orthop Sports Phys Ther, 17(6), 274-278, 1993.

Wilk, K.E. et al. The Athlete's Shoulder, (pp. 669-678), Churchill Livingstone, 1994.

ACKNOWLEDGEMENTS

The authors would like to thank B&P Sports Products for donating the mounds. The assistance in data collection and analysis provided by Andy DeMonia and Phillip Sutton is also greatly appreciated.