Velocity-Dependent Transitions in Forward and Backward Running Mechanics in Female International Rugby Players

This study aimed to examine the relationship between spatiotemporal variables and velocity in forward and backward running and identify if, and where, distinct transitions in these relationships occur in female international representative rugby sevens athletes. Sixteen female international representative rugby sevens athletes completed forward and backward overground running from 40% to 100% of maximum velocity. Spatiotemporal variables were derived from ground embedded force plates and three-dimensional motion analysis. A segmented mixed modelling approach was used to model the relationship between spatiotemporal variables and running velocity. At velocities up to 5.95 and 3.27 m·s^-1 in forward and backward running, respectively, increases in ground contact distance, swing distance, and hence, stride length were observed. In forward running, our analyses revealed a distinct plateau in stride length at velocities above 5.95 m·s^-1, with a rapid rise in stride frequency thereafter. Backward running exhibited a similar, but distinct strategy at higher velocities; the increase in stride length became more conservative above 3.27 m·s^-1, whereas stride frequency became more prominent. Reductions in ground contact time and swing time accompanied the increase in stride frequency. Athletes displayed a greater reliance on increasing stride length at lower velocities, but its contribution declined as velocity increased. Thus, a change in strategy to that of increasing stride frequency was required. Forward running velocity may be enhanced by promoting rapid leg turnover during the swing-phases. Conversely, a focus on both force application during ground contact and rapid leg turnover during the swing-phases would appear best to enhance backward running velocity.