title: Variability of a "force signature" during windmill softball pitching and relationship between discrete force variables and pitch velocity.
abstract: This study assessed reliability of discrete ground reaction force (GRF) variables over multiple pitching trials, investigated the relationships between discrete GRF variables and pitch velocity (PV) and assessed the variability of the "force signature" or continuous force-time curve during the pitching motion of windmill softball pitchers. Intraclass correlation coefficient (ICC) for all discrete variables was high (0.86-0.99) while the coefficient of variance (CV) was low (1.4-5.2%). Two discrete variables were significantly correlated to PV; second vertical peak force (r(5)=0.81, p=0.03) and time between peak forces (r(5)=-0.79; p=0.03). High ICCs and low CVs support the reliability of discrete GRF and PV variables over multiple trials and significant correlations indicate there is a relationship between the ability to produce force and the timing of this force production with PV. The mean of all pitchers' curve-average standard deviation of their continuous force-time curves demonstrated low variability (CV=4.4%) indicating a repeatable and identifiable "force signature" pattern during this motion. As such, the continuous force-time curve in addition to discrete GRF variables should be examined in future research as a potential method to monitor or explain changes in pitching performance.
authors.affiliation: Centre for Exercise and Sports Science Research, Edith Cowan University, Joondalup, WA 6027, Australia; Hurley Surfing Australia High Performance Centre, Casuarina, NSW 2487, Australia. Electronic address: s.nimphius@ecu.edu.au.
authors.forename: Sophia
authors.initials: S
authors.lastname: Nimphius
authors.affiliation: Centre for Exercise and Sports Science Research, Edith Cowan University, Joondalup, WA 6027, Australia; Sport Performance Research Institute New Zealand, School of Sport and Recreation, Auckland University of Technology, 0630, New Zealand. Electronic address: michael.mcguigan@aut.ac.nz.
authors.forename: Michael R
authors.initials: MR
authors.lastname: McGuigan
authors.affiliation: Department of Exercise Science, East Stroudsburg University, East Stroudsburg, PA 18301-2999, USA. Electronic address: timothy.suchomel@gmail.com.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Suchomel
authors.affiliation: Centre for Exercise and Sports Science Research, Edith Cowan University, Joondalup, WA 6027, Australia; Centre for Clinical Research, University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston, QLD 4029, Australia. Electronic address: r.newton@ecu.edu.au.
authors.forename: Robert U
authors.initials: RU
authors.lastname: Newton
mesh_terms: D000293:Adolescent; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D001484:Baseball / Q000502:physiology*; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D009068:Movement / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Fastpitch; Kinetics; Monitoring; Performance; Pitching; Softball