The inter and intra-rater reliability of the Netball Movement Screening Tool
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Objective To establish the inter and intra rater reliability of the Netball Movement Screening Tool (NMST), for screening in a cohort of adolescent female netball players. Background Netball is one of the most popular team sports in the Commonwealth. It is a fast-paced dynamic sport that can result in injury, especially to the knee and ankle. The most important factor in reducing costs and disability from sports related injuries is to prevent injuries from happening in the first place. To date there is no screening tool, specific to netball, which is used to identify faulty movement patterns that may be able to predict injury risk. The NMST has been developed to identify netball players with poor movement patterns. For a screening tool to be shown as a valid tool in identifying faulty movement patterns it must first be shown to be a reliable tool. This study investigates the inter and intra rater-reliability of the NMST in a group of secondary school netballers. Methods Forty secondary school netball players were recruited to take part in the study. Participants were screened with the NMST which consisted of; the Movement Competency Screen (MCS), Jump components, Star Excursion Balance Test (SEBT) and Active Straight Leg Raise (ASLR). Twenty subjects were screened simultaneously and independently by two raters to ascertain inter-rater agreement. Twenty subjects were scored by rater one on two occasions separated by a week to ascertain intra-rater agreement. Rater one was a physiotherapist with over 10 years of experience in physiotherapy and rater two was a final year physiotherapy student. Inter and intra-rater agreement was assessed for; overall NMST, MCS, Jump component, ASLR and SEBT overall scores and for the individual tests of the MCS and Jump components, utilizing the two-way mixed intra-class coefficient (ICC), standard error of measurement (SEM), minimal detectable change score (MDC) and weighted kappa statistics. Results No significant differences were found between the demographics of the inter and intra rater groups of subjects. ICC demonstrated excellent inter (ICC = 0.84; SEM = 0.25; MDC = 13.8) intra-rater (ICC = 0.96; SEM = 0.13; MDC = 10.5) reliability for overall NMST score and substantial – excellent (ICC = 1.0- 0.65) inter-rater and substantial-excellent intra-rater (ICC = 0.96- 0.79) reliability for the category scores of the NMST. Kappa statistic showed substantial-poor inter (k = 0.75-0.32) and intra-rater (k = 0.77-0.27) agreement for individual tests of the NMST. Conclusion The NMST was shown to have excellent inter and intra-rater agreement for overall score in a cohort of adolescent female netball players. Excellent-substantial inter and intra-rater agreement for the category scores of the NMST were shown, whereas individual tests of the NMST showed more variable agreement. Decreased variability of scoring and improvements in the MDC score are required to ascertain meaningful clinical change. Future studies need to be undertaken to establish if there is a link between lower NMST score and increased injury risk.