Pressure sensor calibration for measuring stud-player impacts

In rugby union, laceration injuries can occur from players stamping on opponents in the ruck. To measure the stud-skin interaction during stamping movements, pressure sensors can be used. Pressure sensor calibration techniques have highlighted the need to perform calibrations using appropriate impact dynamics. A pilot study with seven rugby players informed the expected peak forces and loading rates of rugby stamps. Subsequently, a custom calibration procedure was developed, using a drop hammer and force platform to replicate the experimentally observed forces and loading rates. The conventional calibration of the pressure sensor system, supplied by the manufacturer, overestimated total force by 132%. The method described in this paper resulted in a mean error of 7.5%. This study describes a simple and effective calibration procedure for using pressure sensors when measuring the peak force from stud-player impacts. The method has potential to be used as an improved calibration protocol when the expected peak force range of the measured event is between 1800 and 3000 N. The calibrated pressure sensors will be used to obtain kinetic data from stamping events in the ruck in rugby union

Measuring wearing time of knee-ankle-foot orthoses in children with cerebral palsy: comparison of parent-report and objective measurement

Purpose State Orthotic wearing time may be an important confounder in efficacy studies of treatment in children with spastic cerebral palsy (SCP). Most studies measure parent-reported wearing time with questionnaires, but it is questionable whether this yields valid results. This study aims to compare parent-reported wearing time (WTparent) with objectively measured wearing time (WTobj) in children with SCP receiving orthotic treatment. Method Eight children with SCP participated in this observational study. For one year, they received knee-ankle-foot orthosis (KAFO) treatment. WTparent was measured using questionnaires. WTobj was measured using temperature sensor-data-loggers that were attached to the KAFOs. The 2.5th and 97.5th percentiles and median of differences between methods (per participant) were used to calculate limits of agreement and systematic differences. Results There was no systematic difference between WTparent and WTobj (0.1 hours per week), but high inter-individual variation of the difference was found, as reflected by large limits of agreement (lower limit/2.5th percentile: -1.7. hours/week; upper limit/97.5th percentile: 11.1 hours/week). Conclusions Parent-reported wearing time of a knee-ankle-foot orthosis differs largely from objectively measured wearing time using temperature sensors. Therefore, parent-reported wearing time of KAFOs should be interpreted with utmost care

Causation events of stud laceration injuries in rugby union

Laceration injuries in rugby union account for approximately 6% of all injuries sustained during match play. Commentators often cite the design of studded footwear as a causal factor in laceration injuries. In order to assess the laceration injury risk of different stud designs, there is a need to develop a testing protocol that is able to replicate the laceration injury event. This study used a questionnaire to identify the play scenarios that result in laceration injuries. The questionnaire was answered by 191 rugby players, of which 72% had experienced one or more stud injuries during their career which hindered them playing rugby. Half of the laceration injuries described by the respondents came from the ruck, and 27% from a tackle. When analysing free-text responses, a deliberate stamp was described in 35% of the responses and a tackle from behind was described in 14% of responses. These injury scenarios are considered to be the dominant cause of laceration injuries. In future work the identified injury scenarios will be replicated in simulated play and kinetic and kinematic measurements will be recorded. This will inform test parameters for future assessment of laceration injury risk of stud designs

Pressure Sensor Calibration for Measuring Stud-player Impacts

In rugby union, laceration injuries can occur from players stamping on opponents in the ruck. To measure the stud-skin interaction during stamping movements, pressure sensors can be used. Pressure sensor calibration techniques have highlighted the need to perform calibrations using appropriate impact dynamics. A pilot study with seven rugby players informed the expected peak forces and loading rates of rugby stamps. Subsequently, a custom calibration procedure was developed, using a drop hammer and force platform to replicate the experimentally observed forces and loading rates. The conventional calibration of the pressure sensor system, supplied by the manufacturer, overestimated total force by 132%. The method described in this paper resulted in a mean error of 7.5%. This study describes a simple and effective calibration procedure for using pressure sensors when measuring the peak force from stud-player impacts. The method has potential to be used as an improved calibration protocol when the expected peak force range of the measured event is between 1800 and 3000 N. The calibrated pressure sensors will be used to obtain kinetic data from stamping events in the ruck in rugby union