Reliability of equipment for measuring the ground hardness and traction
- Authors: Twomey, Dara , Otago, Leonie , Ullah, Shahid , Finch, Caroline
- Date: 2011
- Type: Text , Journal article
- Relation: Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology Vol. 225, no. 3 (2011), p. 131-137
- Full Text: false
- Reviewed:
- Description: The aim of this paper is to report the inter-rater reliabilities and intra-rater reliabilities of the Clegg hammer, penetrometer, and studded-boot apparatus used for measuring the mechanical properties of natural turf, and to determine whether the level of experience influences the reliability. Three experienced and three novice testers measured the surface hardness and rotational traction at nine locations on a community-level Australian football oval. A repeated-measures analysis of variance tested for significant differences between the six testers for all equipment, and intra-class correlation coefficients (ICCs) were calculated to determine the inter-rater reliabilities and intra-rater reliabilities. The ICCs for the reliability between the six testers ranged between 0.77 and 0.87 for the Clegg hammer, ranged between 0.55 and 0.73 for the penetrometer, and equalled 0.51 for the studded-boot apparatus. The inter-rater reliabilities and intra-rater reliabilities were greater for the experienced testers than for the novice testers for the Clegg hammer and penetrometer but the novice testers produced greater inter-rater reliabilities for the studded-boot apparatus. This study highlights the potential variability that can exist between testers using the ground hardness and traction equipment, which has implications for future research involving multiple testers both in agronomic-based studies and in linking the surface properties to the injury risk across multiple venues. © Authors 2011.
Clegg hammer measures and human external landing forces: Is there a relationship?
- Authors: Saunders, Natalie , Twomey, Dara , Otago, Leonie
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Sports Science and Engineering Vol. 5, no. 4 (2011), p. 231-236
- Full Text: false
- Reviewed:
- Description: Ground hardness is deemed an important consideration for player safety for sports played on natural turf surfaces. Currently, a ground hardness measure is being determined using a Clegg hammer, with the suitability for play dependent on an acceptable reading. This study aimed to examine whether a relationship between Clegg hammer readings and ground reaction forces (GRF’s) generated by a human during a drop landing exist. Fifteen male community level Australian football players were recruited for the study. Participants performed a single leg drop landing on the right leg from a 45cm box onto the force plate to record GRF’s. Ten trials were conducted for three conditions: no shock pad, thin shock pad (15mm) and thick shock pad (50mm) under a synthetic turf sample. Four consecutive Clegg hammer readings were recorded following each set of ten trials. Variables of interest were maximum vertical GRF (Max vGRF), maximum rate of loading (Max RoL) and Clegg hammer (CH) readings. Pearson’s Correlation Coefficient was conducted to examine the relationship between variables and conditions. Slight to fair relationships were found between the Max vGRF and any of the four CH drops (0.181 ≤r≥ 0.189; p ≤ 0.01). This finding was similar to the relationship with Max RoL (0.209 ≤r≥ 0.217; p ≤ 0.01). When analysed for the specific shock pad condition, the relationships remained poor (r <0.1; p ≥ 0.29), with the exception of the Max RoL and the CH readings on the thick shock pad (0.1 ≤r≥ 0.2; p ≥ 0.03). The results of this study show that the ground reaction forces experienced by a human on different levels of surface hardness are significantly different to the forces on impact of the Clegg hammer. Consequently, the Clegg hammer may not be the most appropriate device for relating surface hardness to player safety, thus it is possible that the Clegg hammer alone is insufficient in globally determining ground safety.
- Description: C1