Relationship between knee angle in squat test and defence or reception efficacy in amateur volleyball players

Introduction: Defending and receiving successfully in volleyball is necessary to produce good attacks. The most used technique of defence and reception is dig. It was found that performance of dig influences the performance of spike (Palao et al., 2006). Key points for the effectiveness of dig are anticipation, decision-making, and movement speed. However, it is legit to hypothesize that knee joint angle (KJA) in the starting position of the dig may have an influence on defence and reception efficacy. Therefore, we aimed to investigate the relationship between KJA during an overhead squat test and both defence efficacy (DE) and reception efficacy (RE) in amateur volleyball players. Methods: Fifteen amateur volleyball players were recruited (20.27±3.08 yrs, 76.60±9.27 kg, 184.53±6.63 cm). Players performed three trials of the NASM overhead squat test (Clark 2001) aimed to detect the minimum knee angle value just before losing inverting the normal lumbar lordosis. The KJA was assessed using Microsoft Kinect™. After that, DE of each player was assessed in response to 15 test spikes performed by the same player, as well as RE was assessed in response to 15 test services performed by the same player (Palao et al., 2015). After checked for the normality of the distributions, Pearson correlation coefficient was calculated between KJA and both DE and RE. A p-value lower than 0.05 was considered statistically significant. Data are presented as means ± SD. Results: The KJA in the squat test was 103.9±13.4 deg; DE was -41.3±22.9 % and RE was 46.6±20.9 %. Correlations between KJA and DE and KJA and RE were -0.7 (p=0.004) and -0.14 (P>0.05), respectively. Discussion: The significant inverse correlation between KJA and DE suggests that the players with knee angle lower just before losing the normal physiological lumbar curve had a better efficiency during the defence position. From a speculative point of view, the major depth reached the quality of movement in the squat test reflects a better technical performance the quality of movement in the defensive stance; generally, the squatting depth positively influences the lower-body jumping and postactivation potentation (Esformes & Bampouras 2013). Conversely, the non-significant correlation of KJA and RE was probably due to the more time from the service to the dig, allowing the receivers more time to prepare the reception. References: Palao JM, Santos JA, Urena A. (2006). J Hum Mov Stud 51(4), 221-238. Palao JM, Giménez-Ibarra MI (2015). Cent Eur J Sport Sci Med 12(4), 25-34. Clark M. A. (2001). National Academy of Sports Medicine. Thousand Oaks, Ca. Esformes JI, Bampouras TM. (2013). J Strength Cond Res 27(11), 2997-3000.