Prediction of walk-to-run transition using stride frequency: A test-retest reliability study

The transition from walking to running has previously been predicted to occur at a point where the stride frequency starts getting closer to the running attractor than to the walking attractor. The two behavioural attractors were considered to be represented by the freely chosen stride frequencies during unrestricted treadmill walking and running. The aim of the present study was to determine the relative and absolute test-retest reliability of the predicted walk-to-run transition stride frequency. Healthy individuals (n=25) performed walking and running on a treadmill in a day-to-day test-retest design. The two behavioral attractors were determined during walking and running at freely chosen velocities and stride frequencies. Subsequently, the walk-to-run transition stride frequency was predicted using camera recordings and a previously reported equation for prediction. The walk-to-run transition occurred at a velocity of 7.7±0.5kmh^-1 at day 1 as well as at day 2. Besides, the predicted walk-to-run transition stride frequencies were 69.7±3.3 strides min^-1 and 70.5±3.4 strides min^-1 on day 1 and day 2, respectively (p=0.08). A further comparison between the predicted walk-to-run transition stride frequencies at day 1 and day 2 showed an ICC_3,1 of 0.89, which indicated almost perfect relative reliability. The absolute reliability was reflected by a%-value of the standard error of the measurement (SEM%) of 1.6% and a%-value of the smallest real difference (SRD%) of 4.4%. In conclusion, the predicted walk-to-run transition stride frequency can be considered reliable across days.