Development of a netball specific dynamic balance assessment
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The purpose of this study was to design a netball specific balance assessment. A literature review revealed a lack of suitable assessments for this athletic population. Existing tests failed to replicate sport specific movements, measured variables inappropriate for dynamic balance assessment, failed to indicate the origin of balance deficiencies, disregarded the quality of the movement being performed, failed to indicate the movement strategy used for balance corrections, gave no indication of segmental orientation, used equipment that is not accessible to many practitioners, only assessed static balance, used non sport specific conditions such as eyes closed and unstable surfaces or failed to report the reliability of the tests. Prior to designing a netball specific balance assessment two elite level games of netball were analysed for the frequency of jump landings by jump direction, bi-lateral and uni-lateral landings, turns in the air, and jumps upon landing. Jump landings were chosen for analysis because previous research reported that jump landings and twisting on jump landings represented the greatest injury risk in netball (Otago, 2004; Powell & Barber-Foss, 2000). Forward jumps were performed most frequently (42%) followed by vertical (32%) and lateral jumps (26%). Uni-lateral landings (67%) were most common, as were jumps with no turn in the air (60%). It was less common to perform a second jump immediately upon landing (28%). There were marked differences between player positions in terms of jump direction and the number of jumps performed whereas whether a turn was performed in the air or whether the jump was landed on one or two limbs was more consistent between positions. In general, players could be split into end court and mid court by their landing profile. The exceptions were goal attack who had much in common with the mid court players and wing defence who had much in common with end court players. 12 Based on these findings and previous research on injury mechanisms, three movements were chosen for assessment: A single leg squat, a forward jump, and a forward jump with a turn in the air. The single leg squat was performed to a self selected depth whilst intensity of both jumps was standardised by controlling jump distance and jump height. Deviations from the line of gravity were calculated at the knee, hip and trunk as calculated from video footage using SiliconCoach to assess balance. Fourteen female netballers (16.8 ± 2.4 years) performed three successful trials of each movement on two separate testing occasions approximately one week apart. The reliability of the assessment was determined for within day and between days. The mean ICC values for each body segment, during each movement across the four variables ranged from 0.62 – 0.81 indicating ‘moderate’ (ICC > 0.61) test- retest reliability. The typical errors averaged across all body segments for the single leg squat, forward jump and jump with a turn were 1.1 cm (ICC = 0.71), 1.8 cm (ICC =0.72) and 2.6 cm (ICC = 0.62) respectively indicating ‘moderate’ reliability. The errors were considered too great for use in indicating the magnitude and origin of balance deficiencies and a more sensitive measure is required. The tests may be useful to give an indication of an athlete’s movement competency prior to engaging in training for example knee movement in a single leg squat may indicate knee movement in a more dynamic forward jump.