'Whip from the hip': thigh angular motion, ground contact mechanics, and running speed

During high-speed running, lower limb vertical velocity at touchdown has been cited as a critical factor needed to generate large vertical forces. Additionally, greater leg angular velocity has also been correlated with increased running speeds. However, the association between these factors has not been comprehensively investigated across faster running speeds. Therefore, this investigation aimed to evaluate the relationship between running speed, thigh angular motion and vertical force determinants. It was hypothesized that thigh angular velocity would demonstrate a positive linear relationship with both running speed and lower limb vertical velocity at touchdown. A total of 40 subjects (20 males, 20 females) from various athletic backgrounds volunteered and completed 40 m running trials across a range of sub-maximal and maximal running speeds during one test session. Linear and angular kinematic data were collected from 31-39 m. The results supported the hypotheses, as across all subjects and trials (range of speeds: 3.1-10.0 m s^-1), measures of thigh angular velocity demonstrated a strong positive linear correlation to speed (all R²>0.70, P<0.0001) and lower limb vertical velocity at touchdown (all R²=0.75, P<0.001). These findings suggest thigh angular velocity is strongly related to running speed and lower limb impact kinematics associated with vertical force application.