Purpose: The aim of the study was to analyze the general kinematics of the cycle, leveling of the center of mass and inverted pendulum model in school-age children when they walk at three different auto-selected speeds. Methods: The kinematics of walking cycle, angular actions that contribute to reducing the vertical displacement of body center of mass (pelvis, hip, knee and ankle) and pendulumlike determining variables (mechanical work, pendulum-like recovery and congruity percentage), were analyzed in children for three different self-selected speeds. Differences for each variable with the speed were tested by ANOVA with Bonferroni post-hoc analysis. Omega squared (omega 2) was calculated for the values of the effect sizes. Results: None of the angular variables associated with the leveling of the vertical trajectory of body center of mass changed. Likewise, recovery and congruity percentage presented values similar to those obtained in previous studies and did not show significant changes with the speeds. Conclusions: Nevertheless, changes in horizontal mechanical work and cycle phases, indicate that at some point during the cycle the mechanical energy transfer may have been affected for speed changes. Our results warn about the implication that small changes in the speed during functional evaluations of gait in children may have.