Introduction Recent theoretical studies indicate that during leg extension exercises the tibiofemoral shear forces and the ACL strain-forces can be externally modulated. These modulations can be obtained by a controlled displacement of the application point of the resistance force along the lower-leg during the knee flexion/extension (Biscarini, 2008), or through an external compressive force applied on the knee joint (Fleming et al., 2007). Methods We have designed and developed two innovative leg extension prototypes which integrate these functions. In the first prototype, the resistance lever of a standard leg-extension equipment was replaced by a linear guide along with the resistance pad can slide. The pad movement along the guide is generated by an electric motor controlled by an angular encoder placed on the rotation axis of the equipment, and a linear encoder installed along the linear guide. A feedback control algorithm was developed to provide an accurate and fast dynamic control of the pad positioning. In the second prototype, a foot platform was inserted at the distal side of the resistance lever to exert a controlled axial compression on the lower limb during the exercise. Two protocols for surface EMG and imaging techniques measurement were designed to assess and compare the levels of hamstring co-contraction (which is known to represent a protective factor for the ACL) and the anterior tibial translation (which is proportional to the ACL strain-force), during the exercise with these two new prototypes and the standard equipment, at different levels of external resistances. Each trial was also repeated encouraging the subjects to intentionally enhance hamstring co-activation during the exercise. Results EMG data collected on seventeen healthy subjects indicate that hamstring co-activation is not influenced by pad movement and axial compression. However, the hamstring co-activation was increased from two to four times when the subjects were encouraged to intentionally co-contract the knee flexor muscles during the leg extension exercise. Discussion Intentional hamstring co-contraction in leg extension exercises can be an effective strategy for ACL protection and tibiofemoral joint stability in ACL deficient patients, and in rehabilitation programs after cruciate ligament reconstruction. Further investigations with imaging techniques will definitely asses the effectiveness of the two prototypes. References Biscarini (2008). Medical Engineering & Physics 30(8), 1032-1041 Fleming et al. (2003). Am J Sports Med 31(5), 701-707
Innovative technologies for knee rehabilitation in subjects with anterior cruciate ligament injuries.
BENVENUTI, Paolo;
2013-01-01
Abstract
Introduction Recent theoretical studies indicate that during leg extension exercises the tibiofemoral shear forces and the ACL strain-forces can be externally modulated. These modulations can be obtained by a controlled displacement of the application point of the resistance force along the lower-leg during the knee flexion/extension (Biscarini, 2008), or through an external compressive force applied on the knee joint (Fleming et al., 2007). Methods We have designed and developed two innovative leg extension prototypes which integrate these functions. In the first prototype, the resistance lever of a standard leg-extension equipment was replaced by a linear guide along with the resistance pad can slide. The pad movement along the guide is generated by an electric motor controlled by an angular encoder placed on the rotation axis of the equipment, and a linear encoder installed along the linear guide. A feedback control algorithm was developed to provide an accurate and fast dynamic control of the pad positioning. In the second prototype, a foot platform was inserted at the distal side of the resistance lever to exert a controlled axial compression on the lower limb during the exercise. Two protocols for surface EMG and imaging techniques measurement were designed to assess and compare the levels of hamstring co-contraction (which is known to represent a protective factor for the ACL) and the anterior tibial translation (which is proportional to the ACL strain-force), during the exercise with these two new prototypes and the standard equipment, at different levels of external resistances. Each trial was also repeated encouraging the subjects to intentionally enhance hamstring co-activation during the exercise. Results EMG data collected on seventeen healthy subjects indicate that hamstring co-activation is not influenced by pad movement and axial compression. However, the hamstring co-activation was increased from two to four times when the subjects were encouraged to intentionally co-contract the knee flexor muscles during the leg extension exercise. Discussion Intentional hamstring co-contraction in leg extension exercises can be an effective strategy for ACL protection and tibiofemoral joint stability in ACL deficient patients, and in rehabilitation programs after cruciate ligament reconstruction. Further investigations with imaging techniques will definitely asses the effectiveness of the two prototypes. References Biscarini (2008). Medical Engineering & Physics 30(8), 1032-1041 Fleming et al. (2003). Am J Sports Med 31(5), 701-707
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