Growth and aging

Document Type



Human movement is the result of joint rotations. Muscles provide the "engine" for movement acting with a leverage or moment arm around joint axes of rotation. This leverage in combination with the external leverage provided by the environment has important implications for muscle length and shortening velocity, which, in turn, affects its capability to generate forces and transmit them to the skeleton. The main aim of this work was to gain a better understanding of how skeletal geometry and muscle leverage determine muscle function and movement. Ten children (Age: 9.2±1.3 years, Height: 1.36±0.04, Mass: 30.61±5.91) and 12 adults (Age: 27.4±2.6 years, Height: 1.75±0.10, Mass: 71.03±10.49) walked unshod on an instrumented treadmill (Bertec, OH, USA) at 80% of their preferred over-ground walking speed (0.66±0.81 and 1.07±0.13 ms-1, respectively) for a 10 min period. Reflective markers placed on the lower leg and foot provided lower body and Achilles tendon movement kinematics. Gait cycle events were determined from treadmill ground reaction force data and dependent variables were averaged over six consecutive walking steps for each participant. The results show that average moment arm showed a slight decreasing trend over the stance phase in both groups. The average external moment arm was larger in adults but the gear ratio was similar.