Daily Variation in Step Length of Trained Male Runners

Abstract

The purpose of this study was to quantify daily intra-individual variability in mean step length, a basic descriptor of the running pattern. Following 60 minutes of treadmill accommodation, nine trained male subjects (X age = 34.2yrs±7.2, × V̇O₂max = 57.0±4.8ml·kg·^-1·min^-1) performed daily (Mon-Fri) 6-minute treadmill runs at three submaximal speeds (2.68, 3.13 and 3.58m·s^-1) over a 4-week period. To minimize extraneous influences, subjects refrained from road racing and completed the 20 running sessions (5d·wk^-1·4 weeks for each speed) at the same time of day and in the same footwear. Treadmill velocity was calibrated for each 6-minute running bout and step length was determined during the last 2 minutes of each run. Results indicated that mean step length and coefficient of variation values were 0.984m and 2.50% at 2.68 m·s^-1, 1.124m and 2.22% at 3.13m·s^-1, and 1.254m and 2.26% at 3.58 m·s^-1. Reliability analyses indicated that the percentage of variation accounted for in step length across all speeds was high and improved very little as test number increased (range = 96% for two days vs 99% for five days). Taken together, these findings suggest that when testing conditions are controlled, within-subject variability in step length measures obtained at multiple submaximal running speeds is small in trained subjects and that criterion step length values can be obtained by averaging duplicate measurements.

Key words

Step length - submaximal running - reliability