Assessing agility in netball players
Hewit, Jennifer Kate
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Determinants of agility performance include change of direction factors (technical and physical qualities) and perceptual/decision-making factors. This thesis aimed to address the gap in agility literature by developing a netball-specific agility assessment battery which incorporated analyses of various ground-based and aerial change of direction movement strategies/kinematics (technical), multi-directional leg power and leg asymmetry profiles (physical) and pass appropriateness in response to target player movements (perceptual/decision-making). A survey developed and administered to 52 New Zealand netball coaches and staff identified the areas within agility that were of importance to the development of netball players. Feedback from the netball coaches and staff identified several tasks which were thought to be of greatest importance for the performance development of netball players; 1) fast and sharp change of direction movements inclusive of rapid decelerations and explosive accelerations; 2) aerial changes of direction (i.e. the ability to turn fully in the air prior to landing); 3) single-leg jumping ability; 4) awareness of the ball, teammate and opponents; and 5) interception timing and accuracy. A netball-specific agility assessment battery and the associated individual tasks (5.0 m straight acceleration, 90˚ and 180˚ ground-based changes of direction, 180˚ aerial catch and turn task, multi-directional single-leg countermovement jumping, and a reactive passing task) were developed based off of this feedback and further analysed in the experimental studies presented in this thesis. When comparing kinematics of straight and change of direction (COD) acceleration performances, COD acceleration was associated with a more upright torso (28 - 30%, p < 0.001), shorter step length (19 - 22%, p < 0.001) and lower knee lift (21 - 22%, p = 0.00). Faster straight acceleration players were associated with smaller step lengths (3 – 5%, p = 0.02 to 0.05), lower knee lift (7 – 15%, p = 0.02 to 0.05) and greater forward lean than slower players while faster COD accelerations had increased step frequencies (4%, p = 0.03). Technical characteristics of sub-elite netball players that were likely to contribute to more proficient ground-based and aerial COD performances included decreased rotational inertia and large takeoff distance (ground-based COD) and aggressive driving action of the arms/legs at takeoff, rapid head turn and lower body rotation while airborne (aerial COD). Single-leg power profiles/imbalances (average symmetry index – ASI) when performing multi-directional unilateral countermovement jumps were investigated in 22 players. Individual ASI’s ranged from 0.0 to 32.7% while averaged ASI’s ranged from 3.1% (peak force) to 11.4% (peak power). There were ASI differences between vertical force and power (3.1% and 9.2%, p = 0.02), horizontal power and jump distance (11.3% and 4.6%, p < 0.00), horizontal force and distance (8.0% and 4.6%, p < 0.00) and lateral power and jump distance (10.0% and 6.2%, p = 0.05). Increased ecological validity of the reactive decision-making assessment task resulted in relatively high variability (CV = 22.7 to 35.1%, ICC = -0.60 to -0.14) for all three performance times. Decision times to move right or left (0.209 and 0.210 s, p = 0.00) were faster decisions for vertical and upper right locations (0.263 and 0.261 s, p = 0.00). Movement times (0.171 to 0.176 s, p = 0.00 to 0.01) in vertical, upper right, and upper left directions were slower when compared to right and left directions (0.147 to 0.154 s). Passes to the right were faster than passes to the left (0.147 and 0.154 s, p = 0.01). A novel approach to assessing agility was presented in this thesis through technical feature templates, multi-directional unilateral leg power assessments, and an ecologically valid reactive passing task. The prognostic/diagnostic information gained from this assessment battery can be used by netball practitioners to guide individual players’ training programmes to better effect. Practitioners should be aware that grouped data masks individual player’s strengths and weaknesses and the ability to individualize programmes. Throughout the thesis data have been presented in a number of ways to fulfil both the academic needs associated with research as well as the needs of practitioners.