The Effect of Increasing Step Frequency on Running Economy in Female Runners

Abstract

Running economy (RE) is the steady-state VO2 for a given sub-maximal running velocity and when runners are of similar ability (ie, have similar VO2max values), it has been shown to account for up to 65% of the variability in performance time. Step frequency (SF) training as a means to minimize the oxygen cost of running and therefore, improve RE has not yet been investigated. PURPOSE: To determine whether a short training program (15 min for 10 days) to increase step frequency (SF) to 180 steps per min would elicit improvements in RE. METHODS: Female subjects were recruited from local races and track clubs and were required to have a 5 km personal record time between 17 and 22 min, within the past year. Subjects were screened for SF; runners with SFs ≥ 176 steps per min were excluded from the study. Each runner reported to the laboratory for 12 consecutive days and completed two RE tests (Day 1 & 12), followed by a VO2max test (Day 1 only), and completed a 10 d training program to increase SF (Days 2-11). The RE tests were conducted at two running velocities: 201 and 228 m·min-1 and two different SFs: preferred SF (PSF) and 180 steps per min. Each runner ran for five minutes at each speed and RE was calculated as the mean steady-state VO2 between the 4th and 5th minute. A 5-min recovery was given between each velocity and between each test. The training program consisted of running at 180 steps per min for 15 min at a self-selected velocity between 201 and 228 m·min-1. A metronome was used to help subjects maintain the altered SF and SF was monitored using a footswitch and a BIOPAC MP100 Data Acquisition System. A repeated measures ANOVA was used to test for differences and significance was established at the p<0.05 level. RESULTS: Oxygen consumption was lower at each testing velocity and SF condition following the 10-day training program. While not statistically significant, the average drop in VO2 across both speeds and SF conditions was 3.0%. At the PSF condition, these lower oxygen consumptions were achieved at significantly greater SFs (p<0.05) and significantly lower heart rates (p<0.05). On average across the two speeds, HR was 4.0% lower and SF was 4.0% higher. CONCLUSIONS: The results from this study suggest that the short training program to increase SF lowered oxygen consumption and therefore, improved RE in well-trained female runners.