Comment on 'The Influence of Running Velocity and Midsole Hardness on External Impact Forces in Heel-Toe-Running'.

Researchers not sufficiently sensitive to statistical power may interpret non-significant results as demonstrating that the conditions made no difference. Related issues include performer variability, sample size and effect size as they relate to experimental design. Examination of these factors suggests that caution must be exercised when interpreting the results of experimental data.