We have designed and built up a new piece of leg-extension equipment that minimizes the tibiofemoral shear joint load and suppresses the anterior cruciate ligament stress. This is achieved by a controlled radial displacement of the resistance pad along the lower-leg within the knee range of motion: for knee flexion angles greater than 40°, the pad is placed distally on the lower-leg; for knee flexion angles smaller than 40°, the pad is continuously moved proximally (up to 0.165 m from the knee joint) during kneeextension phase and distally during knee-flexion phase. The change in position of the resistance pad does not change the compressive component of the tibiofemoral joint load and the knee muscle torque. The resistance input lever of a commercial (Technogym S.p.a.) leg-extension machine was modified to include a longitudinal linear guide along which the resistance pad slides by means of a custom plate connection. The pad is moved by an asynchronous motor controlled with a custom-designed LabView algorithm. The maximum speed and acceleration of the pad, given by 5 m/s and 45 m/s2, respectively, were dimensioned to be consistent with almost all kinds of knee-extension exercise kinematics, including ballistic trials. A liner (angular) encoder senses the position of the pad (lever) with an accuracy of 1 mm (0.1 °). Some essential adjustments are built into the mechanical design of the device to optimize the pad displacement and give a comfortable fit to individuals of different sizes. This new electromechanical device was designed not only to be part of newly manufactured equipment, but also to be implemented in pre-existing leg-extension equipment with simple and inexpensive adaptations. In conclusion, this new device represents a next generation toll, powerful and reliable for early dynamic strengthening of knee extensor muscles in the first stages of rehabilitation following anterior cruciate ligament reconstruction.

A New Electromechanical Device for Minimization of the Knee Shear Joint Load in Leg Extension Equipment

FRANCESCHINI, Giordano;MASTRANDREA, FRANCESCO;CARNEVALI, VANESSA;BISCARINI, Andrea;
2010

Abstract

We have designed and built up a new piece of leg-extension equipment that minimizes the tibiofemoral shear joint load and suppresses the anterior cruciate ligament stress. This is achieved by a controlled radial displacement of the resistance pad along the lower-leg within the knee range of motion: for knee flexion angles greater than 40°, the pad is placed distally on the lower-leg; for knee flexion angles smaller than 40°, the pad is continuously moved proximally (up to 0.165 m from the knee joint) during kneeextension phase and distally during knee-flexion phase. The change in position of the resistance pad does not change the compressive component of the tibiofemoral joint load and the knee muscle torque. The resistance input lever of a commercial (Technogym S.p.a.) leg-extension machine was modified to include a longitudinal linear guide along which the resistance pad slides by means of a custom plate connection. The pad is moved by an asynchronous motor controlled with a custom-designed LabView algorithm. The maximum speed and acceleration of the pad, given by 5 m/s and 45 m/s2, respectively, were dimensioned to be consistent with almost all kinds of knee-extension exercise kinematics, including ballistic trials. A liner (angular) encoder senses the position of the pad (lever) with an accuracy of 1 mm (0.1 °). Some essential adjustments are built into the mechanical design of the device to optimize the pad displacement and give a comfortable fit to individuals of different sizes. This new electromechanical device was designed not only to be part of newly manufactured equipment, but also to be implemented in pre-existing leg-extension equipment with simple and inexpensive adaptations. In conclusion, this new device represents a next generation toll, powerful and reliable for early dynamic strengthening of knee extensor muscles in the first stages of rehabilitation following anterior cruciate ligament reconstruction.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/176354
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? ND
social impact