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John H. Lawrence III and T. Richard Nichols

Muscle actions are often defined within a single anatomical reference plane. Yet animals must control posture and movement within a three-dimensional (3-D) environment, responding to a 3-D array of perturbing forces. Based on information gained regarding the 3-D muscle mechanics at the cat ankle joint complex (companion paper), we decided to study how alterations in the 3-D AJC orientation might affect ankle joint postural control. We used a 6 degree-of-freedom force-moment sensor to assess the affect of ankle joint orientation on the 3-D isometric joint torques evoked by electrical stimulation of muscles crossing the ankle joint complex (AJC) in the deeply anesthetized cat. An orthogonal axis system was established at the designated ankle rotation center, such that pitch (flexion-extension), yaw (abduction-adduction), and roll (inversion-eversion) axis torques were calculated. Experimental results suggest that both the magnitude and sign of extra-sagittal torques from the gastrocnemius muscles are joint angle dependent. Also, the hind limb levering system stabilizes the AJC against large yaw and roll rotations away from the control position.

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John H. Lawrence III and T. Richard Nichols

Muscle actions are often defined with respect to a single anatomical reference plane based on a “predominant” functional activity. Yet animals must control posture and movement within a three-dimensional (3-D) environment, exerting control over more than one reference plane when responding to a 3-D array of perturbing forces. Consequently, enhanced knowledge concerning the 3-D torque capabilities of certain appendicular muscles might provide for greater understanding of the biomechanical basis for motor control. We propose that the cat postural control mechanism utilizes the inherent 3-D mechanical actions of ankle flexors and extensors to maintain extra-saggital joint stiffness. We used a 6 degree-of-freedom force-moment sensor to assess the effect of ankle joint orientation on the 3-D nature of isometric joint torques evoked by electrical stimulation of muscles crossing the AJC in the deeply anesthetized cat. An orthogonal axis system was established at the designated ankle rotation center, such that pitch (defining flexion-extension), yaw (abduction-adduction), and roll (inversion-eversion) axis torques were calculated. Experimental results show that the classical cat ankle flexor and extensors evoke large extra-sagittal torques as well. Also, the hind limb levering system stabilizes the AJC against large yaw and roll rotations away from the control position.

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Rebecca L. Krupenevich, William H. Clark, Gregory S. Sawicki and Jason R. Franz

Compared with young adults, older adults often display a characteristic reduction in propulsive power at the ankle during the push-off phase of walking. 1 , 2 Although colloquially described in the biomechanics literature as a product of ankle joint velocity and net joint moment, ankle power

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Roel De Ridder, Tine Willems, Jos Vanrenterghem, Ruth Verrelst, Cedric De Blaiser and Philip Roosen

) increases the vulnerability to excessive inversion. 14 Furthermore, individuals with CAI have been reported to land with a more inverted ankle joint, which has been suggested to create a vulnerable situation. 15 Based on this premise, the effect of taping during the preparatory phase on the ankle joint

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Kentaro Chino and Hideyuki Takahashi

independent of muscle mass. We previously assessed muscle stiffness of the medial gastrocnemius by shear wave elastography, and examined sex-related differences in the muscle stiffness and passive ankle joint stiffness. 8 Significantly greater ankle joint stiffness in men than in women was not found at 30

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William H. Clark and Jason R. Franz

The triceps surae muscle–tendon units are important in governing walking performance, acting to regulate mechanical behavior of the ankle joint through the interaction between active muscle and passive elastic structures. 1 – 3 Ankle joint quasi-stiffness (k A ), the slope of the relation between

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M. Spencer Cain, Kyeongtak Song, J. Troy Blackburn, Kimmery Migel and Erik A. Wikstrom

Key Points ▸ Plantar flexor musculotendinous stiffness does not improve in chronic ankle instability patients following joint mobilization. ▸ Ankle joint mobilizations improve fibularis musculotendinous stiffness in those with chronic ankle instability. ▸ Improved musculotendinous stiffness may

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Erik A. Wikstrom, Sajad Bagherian, Gary Allen and Kyeongtak Song

measure of neuromuscular control which plays an important role in dynamic joint stability. 2 , 4 Multiple treatment approaches are available for patients with CAI and recent research has highlighted the benefits of manual therapy techniques such as ankle joint mobilizations at improving dorsiflexion

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Gabrielle Stubblefield, Jeffrey Tilly and Kathy Liu

suffered an ankle sprain within 6 months of testing. After baseline ankle joint laxity profiles were recorded, the sports medicine staff reported to the research team any participants that suffered a LAS during their respective seasons. Of the 89 athletes, six were diagnosed with an acute LAS (see Table  1

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Erik A. Wikstrom, Sajad Bagherian, Nicole B. Cordero and Kyeongtak Song

approaches are available for treating those with CAI. 5 Recent research has highlighted the benefits of manual therapy techniques such as ankle joint mobilizations at improving a number of clinician-oriented outcomes such as dorsiflexion range of motion and postural control. 6 – 9 However, the effects of