Research design and statistics in biomechanics and motor control

Abstract

Biomechanics and motor control researchers measure how the body moves and interacts with its environment. The aim of this review paper is to consider some key issues in research methods in biomechanics and motor control. The review is organized into four sections: proposing, conducting, analysing and reporting research. In the first of these, we emphasize the importance of defining a worthy research question and of planning the study before its implementation to prevent later difficulties in the analysis and interpretation of data. In the second section, we cover selection of trial sizes and suggest that using three trials or more may be beneficial to provide more 'representative' and valid data. The third section on analysis of data concentrates on effect size statistics, qualitative and numerical trend analysis and cross-correlations. As sample sizes are often small, the use of effect size is recommended to support the results of statistical significance testing. In using cross-correlations, we recommend that scatterplots of one variable against the other, with the identified time lag included, be inspected to confirm that the linear relationship assumption underpinning this statistic is met and, if appropriate, that a linearity transformation be applied. Finally, we consider important information related to the issues above that should be included when reporting research. We recommend reporting checks or corrections for violations of underpinning assumptions, and the effect of these checks or corrections, to assist in advancing knowledge in biomechanics and motor control.

Information–movement coupling in developing cricketers under changing ecological practice constraints

“…Parametric assumptions were met, and each dependent variable (event initiation, bat height, step length, or angle) was compared between the bowler and machine condition using paired-samples t-tests, for both defence and drive shots. Additionally, effect size (r) was calculated to observe if significant effects were substantive, and to judge the relative magnitude and importance of each dependent variable (Mullineaux, Bartlett, & Bennett, 2001). Finally, Pearson's correlation coefficient was used to assess the relationship between backswing initiation and front foot movement.…”

Impaired microvascular endothelial function is restored by acute lower-limb exercise in post-surgical varicose vein patients

“…The acute effects of exercise on peak cutaneous flux responses in each group were assessed using mixed-model (group by time) ANOVAs for each position and drug, with paired-samples t-tests used to interpret significant interaction effects. Effect sizes (Cohen's d) were calculated for exerciseinduced changes in peak cutaneous flux responses, with 0.2, 0.5, and 0.8 representing small, medium, and large effects, respectively (Mullineaux et al, 2001). Statistical significance was set at P ≤ 0.05.…”

Three-dimensional angular kinematics of the lumbar spine and pelvis during running

“…Although useful for providing an indication of the amount of coordination between two angular rotations, position-time plots do not provide a suitable reflection of the pattern (i.e. linear versus non-linear relationship) of coordination (Mullineaux, Bartlett, & Bennett, 2001). For this purpose, the position of one angular rotation for the pelvis was plotted as a function of the position of its coplanar angular rotation for the lumbar spine.…”

“…Crosscorrelation analysis was therefore utilised to identify the time lag at which the peak correlation occurred between coplanar angular rotations. In order to improve the validity of cross-correlation analysis, it must be demonstrated that the assumption of linearity between the dependent variables is not violated (Mullineaux et al, 2001). Consequently, if cross-correlation analysis revealed the presence of a phase difference, then the angle-angle plot was re-calculated with the phase difference included for one of the angular rotations.…”