Date of Award

2009

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Exercise, Biomedical and Health Sciences

First Supervisor

Robert U. Newton

Second Supervisor

Michael R. McGuigan

Abstract

Study 1: Relationship between ground reaction force and ball velocity during windmill softball pitching The purpose of this research was to (1) determine the reliability of measuring ground reaction force (GRF) in multiple pitching trials and (2) investigate the relationship between ground reaction forces and pitch velocity in elite fastpitch softball pitchers. Seven female softball pitchers (19.6 ± 3.9 years; 167.4 ± 7.2 cm; 77.3 ± 7.6 kg) from the state, national and international level pitched six fastballs for maximal velocity and the fastest three pitches were used for analysis. Vertical peak forces (Fz1, Fz2), anterior-posterior peak forces (FAP1, FAP2), resultant peak forces (FR1, FR2) and maximal pitch velocity (PV) were measured using a force plate (Type 9287BA, Kistler) and a JUGS radar gun. Intraclass correlation (ICC) and coefficient of variance (CV) was determined for all variables and the relationship between PV and GRF was evaluated by Pearson product-moment correlation coefficient. Statistical significance was set at α level of p < 0.05. The ICC for all GRF variables (0.922-0.985) and PV (0.914) were high. CV for GRF variables ranged from 2.2% to 4.9% and 2.4% for PV. Fz2 and PV were significantly correlated (r = 0.89; p < 0.01). Fz2 relative to bodyweight (Fz2/BW) was also significantly correlated to PV (r = .801, p < 0.05). No other GRF measures were significantly correlated to PV. A high ICC and low CV across the variables support the reliability of GRF and PV over multiple trials. The strong correlation between Fz2 and PV provides evidence that a transfer of force to the lower body has a large contribution to windmill pitching performance. This supports prescription of lower body strength exercises to improve the ability of pitchers to effectively transmit forces through the lower body for improved PV.

Study 2: Relationship between strength, power, speed and change of direction performance of female softball players The purpose of this study was to investigate (1) the cross-sectional relationship of strength, power, and performance variables in trained female athletes and (2) determine if the relationship between these variables changes over the course of a season. Ten female softball players (age = 18.1 ± 1.6 years, height = 166.5 ± 8.9 cm, weight = 72.4 ± 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (1RM), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, unloaded countermovement vertical jump height (VJH) one base (1B) and two base (2B) sprint performance and change of direction performance on dominant (505 D) and non-dominant sides (505 ND). The testing sessions occurred pre, mid and post a 20 week pre/in-season training period. Relationship between body weight (BW), relative strength (1RM/BW), VJH, relative PP, relative PF, PV, speed and change of direction variables were assessed by Pearson product-moment correlation coefficient at each testing session. Significant relationships were found across all time points with BW, speed and change of direction measures (r = 0.70 to 0.93) and relative strength and measures of speed and change of direction ability (r = -0.73 to -0.85). There were no significant relationships between VJH and any measure of performance at any time point. In conclusion, body weight and relative strength have strong to very strong correlations with speed and change of direction ability and these correlations remain consistent over the course of the season. However, it seems as if many relationships vary with time and their relationships should therefore be investigated longitudinally to better determine if these cross-sectional relationships truly reflect a deterministic relationship.

Study 3: Changes in muscle architecture and performance during a competitive season in female softball players The purpose of this research was to (1) examine the performance changes that occur in elite female softball players during 20 weeks of concurrent softball training and (2) examine the relationship between percentage change in muscle architecture variables and percentage change in strength, speed and change of direction performance. Ten female softball players (age = 18.1 ± 1.6 years, height = 166.5 ± 8.9 cm, weight = 72.4 ± 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (1RM), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, one base (1B) and two base (2B) sprint performance, change of direction (505) on dominant (D) and non-dominant (ND) sides, aerobic capacity and vastus lateralis (VL) muscle architecture characteristics including muscle thickness (MT), fascicle length (FL) and pennation angle (θp). The testing sessions occurred pre, mid and post a 20 week pre/in-season training period. Changes over time were analyzed by repeated measures ANOVA. Relationship between percentage (%) change in muscle architecture variables and strength, speed and change of direction variables from pre to post were assessed by PPM correlation coefficient. Significant improvements in PV and PP occurred at all JS loads pre-mid and pre-post. Significant increases occurred pre-post in absolute 1RM, relative 1RM, 505 ND and 2B sprint. The strongest relationships were found between % change in VL MT and 1B sprint (r = -0.800, p = 0.06), % change in VL FL and 2B sprint (r = -0.835, p = 0.02), and % change in relative 1RM and 505 D (r = -0.702, p = 0.04). In conclusion, gains in strength, power and performance can occur through the season in elite softball players and are correlated to changes in muscle architecture.

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