Masters Theses

Date of Award

5-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Human Performance and Sport Studies

Major Professor

Songning Zhang

Committee Members

Wendell Liemohn, Craig A. Wrisberg

Abstract

The windmill style fastpitch involves an array of motor skills requiring sequential coordination of the upper and lower extremities. Characteristic of the motion is a powerful drive and rapid transfer offeree on to the striding lower extremity. This may result in a substantial breaking force over a short period of time. The purpose of this study was to determine the kinematic responses and magnitude of ground reaction forces (GRF) created by the stride leg in selected windmill pitches. Five female intercollegiate fastpitch softball pitchers (age: 22.6 yrs, body mass: 69.0 kg) performed 5 pitches of the fastball (FB), changeup (CH), dropball (DB), curveball (CB) and riseball (RB). Simultaneous recordings of video (60hz) and GRF (1000 hz) were obtained and synchronized for each trial. Kinematic variables evaluated included stride length, ball velocity, joint angle at contact (JAC), maximum angle (MAX), time to maximum angle (TMAX), minimum angle (MIN) and time to minimum angle (TMIN). Primary kinetic variables evaluated were first peak force (F1), second peak force (F2) and maximum brake force (Fb). Single factor ANOVAs revealed significant kinematic differences (p < 0.05) between pitches for MAX and MIN for hip, knee and ankle, as well as, differences in JAC for hip and knee. Stride lengths of the participants in this study indicate that different strategies were used in the delivery of the various pitches. Stride lengths were longest for the riseball and shortest for the change-up. In general, the pitchers adopted a style characterized by extended hip and knee joint and plantarflexed ankle joint. Comparison of stride lengths to total body range of motion at contact indicated that longer stride lengths are associated with a less upright position of the body. In general the fastball, curveball and riseball had longer stride lengths and greater total body range of motion. In contrast, the body assumes a more upright position in pitches with a shorter stride length, such as the change-up and dropball. The results also indicated trends of slower ball velocities with a more upright body position. Peak vertical forces during pitching are higher than those reported in walking and low impact aerobics. In addition, peak vertical forces experienced during pitching appear to be similar to those reported in distance running and high impact aerobics. However, peak forces are lower than those reported in jump/landing skills in basketball and volleyball. Maximum braking forces of pitching are higher than those reported in running and walking. In addition, the braking forces produced in pitching are higher than common movements performed in basketball, with the exception of landing after a layup shot. The riseball had the highest braking force followed by the fastball, whereas the lowest braking force occured in the change-up. The findings indicate a trend that pitches with the highest F1 values are accompanied by high maximum braking forces and vice versa for pitchers with the lowest F1 values. These findings indicate trends that the pitches with the highest F1 values are accompanied by high maximum braking forces and vice versa for pitchers with the lowest F1 values.

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