The inter-subject range of variability in m.s.e. is high. For example, the subject with the highest m.s.e. was 9.8× more variable in this parameter than the subject with the lowest m.s.e. at 1.5 m s−1 (figure 1). The subject with the highest CV was 2.3× more variable than the subject with the lowest CV at 1.5 m s−1 (figure 1). The m.s.e. is not used as a common calculator of variability in gait studies, and thus we cannot directly compare magnitudes derived here to values measured for other gait parameters. However, the large inter-subject variation in m.s.e. and CV is striking given our relatively homogeneous cohort of healthy adults, who ranged from 21 to 44 years old with no pathology or pre-existing injuries and a low BMI. CV less than 5% in kinematic step parameters is considered low [1,12,33,41,46–49], and less than 3%  very low. Here, we found variability in the kinetic step-parameter of plantar pressure assessed by CV was less than 2.5% across all subjects.