Scientific
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As a service to our visitors, Simbex provides a handy source of publications, references and whitepapers that we believe would be of interest.  Abstracts and/or full publications are not available through this web site or Simbex.  We hope you find this resource useful.  

Publications on Other Topics

Batting performance of wood and metal baseball bats.
Crisco JJ, Greenwald RM, Blume JD, Penna LH
Department of Orthopaedics, Brown Medical School/Rhode Island Hospital, Providence, 02903, USA.

INTRODUCTION/PURPOSE: Although metal baseball bats are widely believed to outperform wood bats, there are few scientific studies which support this. In a batting cage study, Greenwald et al. found that baseballs hit with a metal bat traveled faster than those hit with a wood bat, but the factors responsible for this difference in bat performance remain unidentified. The purpose of this study was to determine the effects of swing speed, impact location, and elastic properties of the bat on batted ball speeds.

METHODS: The pitched ball, batted ball, and swings of two wood and five metal baseball bats by 19 different players were tracked in three dimensions at 500 Hz using a passive infrared motion analysis system.

RESULTS: Increases in the batted ball speeds of metal bats over those of wood bats resulted from faster swing speeds and higher elastic performance with an apparent increase in the ball-bat coefficient of restitution. The contribution of these variables to batted ball speed differed with metal bat model. The "sweet spot" associated with maximum batted ball speeds was located approximately the same distance from the tip of wood bats as it was from metal bats.

CONCLUSIONS: The variables that correlated with differences between metal and wood bat performance, and most notably differences in the percentage of faster batted balls, were identified using a novel kinematic analysis of the ball and bat. These variables and their correlation with bat performance should be applicable to other players and bats, although more skilled players and higher performing bats would likely result in even faster batted ball speeds.

Med Sci Sports Exerc. 2002 Oct;34(10):1675-84.

Volume Management: Smart Variable Geometry Socket (SVGS) Technology for Lower-Limb Prostheses.
TECHNICAL NOTE
Greenwald, Richard M. PhD; Dean, Robert C. ScD; Board, Wayne J. MS

Smart variable geometry socket (SVGS) technology provides a method of dynamic volume management for lower limb amputees. Because amputees experience residuum volume changes during the day and over time, the fit of their sockets may vary. Currently, socks are often added or removed to maintain a stable and comfortable fit. SVGS technology automatically and continuously accommodates for residuum volume changes to maintain the fit of the socket. The system functions by adding and removing liquid from the intrasocket environment, regulated dynamically by intrasocket pressure. SVGS rationale, theory of operation, alternative approaches, and clinical relevance are described.

JPO Journal of Prosthetics & Orthotics. 15(3):107-112, July 2003.

Dynamic Impact Response of Human Cadaveric Forearms Using a Wrist Brace
Richard M. Greenwald, PhD*,, Peter C. Janes, MD, Stephen C. Swanson, MS* and Thomas R. McDonald*
* Orthopedic Biomechanics Institute, Salt Lake City, Utah  High Country HealthCare, P.C., Vail/Frisco, Colorado

The purpose of this study was to compare the dynamic impact response of braced and unbraced cadaveric wrists using a commercially available wrist guard. Twelve arms were harvested from six cadavers. Each pair of forearms, one with and one without a brace, were impacted using a modified guillotine-type drop fixture placed over a force platform. Using a piece-wise linear regression analysis, we identified four phases of dynamic loading in the vertical force profile before fracture. These phases included an initial linear loading phase starting at impact, followed by a nonlinear phase, a second rapid linear loading phase, and a final nonlinear loading phase to failure. Three transition points were identified that defined the boundaries of the linear loading phases. Vertical force and impulse were significantly higher (P < 0.01) at each transition point and at failure in all braced specimens compared with unbraced specimens. However, the most noticeable differences were found during the initial two loading phases. Time to each transition point and to failure was not significantly different (P > 0.27) between the braced and unbraced wrists. The results of this study differ from those obtained under more quasistatic loading conditions. Dynamic impact testing suggests that wrist guards may have a prophylactic effect during low-energy dynamic impact situations.

The American Journal of Sports Medicine 26:825-830 (1998)