Kinematic and mechanical changes during a long half-marathon race: males and females at uphill/downhill slopes

BACKGROUND: The aim of this study was to compare the running kinematics and the spring mass model mechanics over an entire half-marathon race in male and female athletes on different slopes (- 7%, 0% and +7%). METHODS: 59 recreational runners (39 males and 20 females) participated in this study. Their running steps at own best self-selected speed were video recorded during a half-marathon (i.e. in ecological conditions): the kinematic variables (i.e. running speed, stride length and frequency, contact and flight time) were calculated, as well as the spring-mass characteristics (i.e. leg and vertical stiffness) of their running steps. RESULTS: Males were able to run with greater speeds and lengths compared to females (P < 0.001) but with lower flight times (P < 0.05), and they reached higher values of both leg and vertical stiffness (P < 0.001). During downhill running, step lengths were larger compared to the level and the uphill (+6%) whereas frequencies slightly decreased (-2%), and aerial times were the greatest ones (+17%). During uphill running, contact times were slightly higher compared to other conditions (+3%), and leg stiffness reached the lowest values (-8%). CONCLUSIONS: This study confirmed that there are important alterations in running steps in function of sex and surface slope. Importantly, the response to fatigue (i.e. alterations with the covered distance) does not alter these sex differences and is therefore independent of the sloped conditions.