Simple method for measuring center of mass work during field running.
The purpose of this study was to propose and validate a new simple method for calculation of center of mass work during field running, in order to avoid the use of costly and inconvenient measurement devices. This method relies on spring-mass model and measurements of average horizontal velocity, and contact and flight times during running. Ten male, recreational subjects ran on a dynamometer treadmill at different velocities ranging from 2.22 to 4.44 m·s-1 during 4 min 30 s for each velocity. Twenty consecutive steps were analyzed after 3 min 30 s. The potential (Wpot), forward kinetic (Wkinf) and the total center of mass (Wext) work data obtained with this new method were compared with the reference data calculated from ground reaction force measurements. Wext, Wpot and Wkinf values calculated with the proposed method were respectively +3.39 ± 0.77% higher, -4.14 ± 0.72% lower and +7.34 ± 1.08% higher than values obtained by the reference method. Furthermore, significant linear regressions close to the identity line were obtained between the reference and the proposed method values of works (r = 0.99, p < 0.05 for Wext; r = 0.98, p < 0.05 for Wpot; r = 0.98, p < 0.05 for Wkinf). It was concluded that this new method could provide a good estimate of center of mass work in field running thanks to a few simple mechanical parameters.