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 (W_pot), forward kinetic (W_kinf) and the total center of mass (W_ext) work data obtained with this new method were compared with the reference data calculated from ground reaction force measurements. W_ext, W_pot and W_kinf 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 W_ext; r = 0.98, p < 0.05 for W_pot; r = 0.98, p < 0.05 for W_kinf). 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.