Running economy is a key determinant of endurance performance, and understanding the biomechanical factors that affect it is of great theoretical and applied interest. This study aimed to analyse how the ground-contact time and strike pattern used by competitive runners concurrently affect running economy.
Fourteen sub-elite male competitive distance runners completed a 6-min submaximal running trial at 14kmh?1 on an outdoor track using their habitual strike pattern (n=7 rearfoot strikers: average age, 25.3 years old (SD=2.4); average weight, 64.7kg (SD=5.6); average height, 175.3cm (SD=5.2); n=7 midfoot strikers: average age, 25.0 years old (SD=2.8); average weight, 69.6kg (SD=4.0); average height, 180.1cm (SD=5.1). During the run, the oxygen uptake and ground-contact time were measured.
Midfoot strikers showed a significantly shorter (p=0.015) mean contact time (0.228s (SD=0.009)) compared with rearfoot strikers (0.242s (SD=0.010)). Conversely, there was no significant difference (p>0.05) between the groups with respect to mean oxygen uptake (midfoot strikers: 48.4mlmin?1kg?1 (SD=5.3); rearfoot strikers: 49.8mlmin?1kg?1 (SD=6.4)). Linear modelling analysis showed that the effect of contact time on running economy was very similar in the two groups, with a 1ms longer contact time involving an approximately 0.51mlmin?1kg?1 lower oxygen uptake. In contrast, when controlling for contact time, midfoot striking involved an approximately 8.7mlmin?1kg?1 lower oxygen uptake compared with rearfoot striking.
When adjusting the foot�ground contact biomechanics of a runner with the aim of maximising running economy, a trade-off between a midfoot strike and a long contact time must be pursued.