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Type: Journal article
Title: One, two, three or four: does the number of Clegg hammer drops alter ground hardness readings on natural grass?
Author: Twomey, D.
Ullah, S.
Petrass, L.
Citation: Proceedings of the Institution of Mechanical Engineers Part P: Journal of Sports Engineering and Technology, 2014; 228(1):33-39
Publisher: SAGE Publications
Issue Date: 2014
ISSN: 1754-3371
Statement of
Dara M Twomey, Shahid Ullah, Lauren A Petrass
Abstract: The Clegg hammer is currently used to measure hardness of natural turf surfaces to inform performance and safety decisions. However, the number of Clegg hammer drops reported in natural grass testing varies from one to four drops, and the impact of the choice of the number of drops is unknown. The aim of this article is to determine whether significant differences exist between the four Clegg hammer drops on natural grass across a variety of conditions. Hardness readings (using a 2.25 kg Clegg hammer), soil moisture and botanical composition were recorded at nine different sites on seven football fields during an 18-week playing season. A total of 1255 hardness readings were collected for each of four consecutive Clegg hammer drops. Overall, there were significant differences between drop 1 and the other three consecutive drops, on all fields and on all sites. Deep soil moisture was the only factor that significantly influenced the hardness readings. The results of this study demonstrate that the decision regarding the number of drops recorded needs careful consideration as conclusions drawn on playability of a ground or the association with injury risk may vary considerably depending on the number of drops.
Keywords: Clegg hammer; ground hardness; test methods; natural grass testing
Rights: © IMechE 2013
DOI: 10.1177/1754337113501300
Grant ID:
Appears in Collections:Aurora harvest 8
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