Skipping vs Running Along Circular Paths: Which Is Better?

Abstract

1. INTRODUCTION Skipping, or bipedal gallop, is a bouncing asymmetrical gait, which cycle begins with the trailing foot strike, followed by the leading and a final, unsupported, ballistic phase(1). Unlike cursorial quadrupeds, humans occasionally or in specific conditions skip(2). Our research aims to investigate the potential advantages of skipping during asymmetric locomotor tasks, such as moving along circular paths. 2. METHODS Participants were asked to perform three trials along a circular path of radius 3 m: 1) Unilateral skipping with inner leading (Sk_I); 2) same with outer leading (Sk_O); 3) running (R). Auditive feedback was provided to maintain a constant stride frequency of 1.5 Hz. Ethics Committee approved the project. Metabolic baseline was obtained during 5’ upright standing before the trials, and subtracted from the average VO2 of the last minute of each trial (K5, Cosmed, Italy). The cost of transport (CT) was computed using the RER energetic equivalent(3). Speed was obtained by analysing videos (60 Hz). Vertical ground reaction forces were measured with instrumented insoles (Loadsol_pro, Novel, Germany)(4). Data were filtered (4th order zero-lag Butterworth LPF, 15 Hz cut-off). Gait events were identified using a 20N threshold. Duty factor (DF), peak vertical force and asymmetry indices were computed. 3. RESULTS The preliminary results are shown in table 1. The CT was averaged over a range of speed from 1.7 to 2.4 ms-1 (N=8). We have obtained kinetic data from a single subject so far. Therefore, DF and peak forces, averaged over 300 strides per condition, represent a within-subject stride variability. 4. DISCUSSION The CT was 25% higher in circular compared to linear running(5). Skipping did not show a similar trend, nor differences between inner and outer leading(6). Preliminary single-subject kinetic data indicate a trend toward a reduction of stance asymmetry in both skipping modes, compared to linear skipping. In running, the slightly increased DF of the outer foot, if confirmed, could underline a load-mitigating strategy that counteracts the increase of the outer peak GRF and the rise in force asymmetry during circular running. Although the metabolic cost remains high, skipping could present pros during asymmetric tasks like circular locomotion.