Journal of Sports Science and Physical Education 5(2): 9-14, 2016 - Jump squat tests can be
used to investigate the differences in the force - velocity (f-v) profile in movement that is
more a sport-specific than isolated exercises such as open chain leg extension. However,
squat jumps involve multi-joint movement, making it questionable which muscle is the main
contributor for the movement. The main aim of this study is to develop a test of isolated knee
extension that encompasses the entire range of human f-v relationship and to investigate the
correlation between linear encoder and kinematic measurement of angular velocity using a
camera system during unloaded kicking. One healthy male subject volunteered to participate
in the study and performed 10 unloaded kicks (knee extension). A cuff was strapped around
the lower leg, approximately 2 cm above the medial malleoli and connected to a linear
velocity encoder (MuscleLab Ergotest version 4010, Norway). During the test sessions, threedimensional
motion analysis was performed with an Oqus Motion Capture System (Qualisys,
Sweden). Data were transferred to Windows-based data acquisition software (Qualisys Track
Manager). There was a positive linear relationship (r = 0.94). The unloaded kicking test to
determine maximum angular velocity at knee extension measured using the QTM showed
that the mean angular velocity was 362˚.s-1, with the highest value being 528˚.s-1. This
preliminary study suggests isokinetic dynamometry (IKD) can be used to investigate the
entire range of velocities (i.e isometric – velocity maximum) of knee extension in normal
human subjects. Further studies can examine the use of IKD in measuring higher velocities.
Multi-planar forces and moments are known to injure the anterior cruciate ligament (ACL). In ACL injury risk studies, however, the uni-planar frontal plane external knee abduction moment is frequently studied in isolation. This study aimed to determine if the frontal plane knee moment (KM-Y) could classify all individuals crossing a risk threshold compared to those classified by a multi-planar non-sagittal knee moment vector (KM-YZ). Recreationally active females completed three sports tasks-drop vertical jumps, single-leg drop vertical jumps and planned sidesteps. Peak knee abduction moments and peak non-sagittal resultant knee moments were obtained for each task, and a risk threshold of the sample mean plus 1.6 standard deviations was used for classification. A sensitivity analysis of the threshold from 1-2 standard deviations was also conducted. KM-Y did not identify all participants who crossed the risk threshold as the non-sagittal moment identified unique individuals. This result was consistent across tasks and threshold sensitivities. Analysing the peak uni-planar knee abduction moment alone is therefore likely overly reductionist, as this study demonstrates that a KM-YZ threshold identifies 'at risk' individuals that a KM-Y threshold does not. Multi-planar moment metrics such as KM-YZ may help facilitate the development of screening protocols across multiple tasks.
Much inter-intra-tester kinematic and kinetic repeatability research exists, with a paucity investigating inter-laboratory equivalence. The objective of this research was to evaluate the inter-laboratory equivalence between time varying unplanned kinematics and moments of unplanned sidestepping (UnSS). Eight elite female athletes completed an established UnSS procedure motion capture laboratories in the UK and Australia. Three dimensional time varying unplanned sidestepping joint kinematics and moments were compared. Discrete variables were change of direction angles and velocity. Waveform data were compared using mean differences, 1D 95%CI and RMSE. Discrete variables were compared using 0D 95% CI. The mean differences and 95%CI for UnSS kinematics broadly supported equivalence between laboratories (RMSE≤5.1°). Excluding hip flexion/extension moments (RMSE = 1.04 Nm/kg), equivalence was also supported for time varying joint moments between laboratories (RMSE≤0.40 Nm/kg). Dependent variables typically used to characterise UnSS were also equivalent. When consistent experimental and modelling procedures are employed, consistent time varying UnSS lower limb joint kinematic and moment estimates between laboratories can be obtained. We therefore interpret these results as a support of equivalence, yet highlight the challenges of establishing between-laboratory experiments or data sharing, as well as establishing appropriate ranges of acceptable uncertainty. These findings are important for data sharing and multi-centre trials.