Relationship between energy cost and kinematics during the support phase of running

The present study was aimed to investigate effects of kinematics of the knee and hip joints on energy cost during supporting phase in different slope running. Twelve male middle- and long-distance runners were asked to run for three minutes on a treadmill at the speed of 13.5 km/h under three different slopes: incline, level, and decline. Sagittal plane kinematics, electromyography, respiratory gases, and the blood lactate levels were measured. Energy cost differed significantly between slopes, being the greatest in incline and the smallest in decline. The thigh angle at the lowest height of the body’s center of mass (LCoM) differed significantly between slopes, being the greatest in incline and the smallest in decline. Therefore, the thigh angle at LCoM may be one of key factors to determine energy cost during running. When the thigh inclined greater, the knee extensors may exert greater extension torque and consequently energy cost increases.