BACKGROUND Foot dorsiflexion plays an essential role in both controlling balance and human gait. Electromyography (EMG) and sonomyography (SMG) can provide information on several aspects of muscle function. The aim was to establish the relationship between the EMG and SMG variables during isotonic contractions of foot dorsiflexors. METHODS Twenty-seven healthy young adults performed the foot ...

This study investigated whether the specific motor control strategy reported for eccentric muscle actions is dependent on muscle mechanical behavior. Motor evoked potentials, Hoffman reflex (H-reflex), fascicle length, pennation angle, and fascicle velocity of soleus muscle were compared between isometric and two eccentric conditions. Ten volunteers performed maximal plantarflexion trials in is...

In the present study, the in vivo force-length relations of the human soleus (SOL) and tibialis anterior (TA) muscles were estimated. Measurements were taken in six men at ankle angles from 30 degrees of dorsiflexion to 45 degrees of plantarflexion in steps of 15 degrees, and involved dynamometry, electrical stimulation, ultrasonography and magnetic resonance imaging (MRI). For each muscle and ...

Isometric muscle force attained during isometric contractions decreases after active shortening compared to that attained during purely isometric contractions. This phenomenon is called residual force depression. The aim of this study was to examine whether residual force depression occurs in human plantar flexors in both plantar flexed and dorsiflexed region. In addition, the magnitude of fasc...

The purpose of this study was to investigate if force enhancement (FE) in vivo is influenced by stretch-induced changes of muscle architecture. Therefore, 18 subjects performed maximum voluntary isometric (100 degree knee flexion angle) and isometric-eccentric-isometric stretch contractions (80 degrees-100 degrees; ω=60 degrees.s(-1)) whereby pennation angle and fascicle length of vastus latera...

Velocity-encoded phase-contrast magnetic resonance (MR) imaging techniques and a computer-controlled MR-compatible foot pedal device were used to investigate the medial gastrocnemius muscle and aponeurosis deformations during passive and active eccentric movements of the plantarflexors. Intrafascicular strain, measured as the ratio of strain in the fascicle segment at its insertion to strain at...

A fundamental feature of pennate muscles is that muscle fibers are oriented at an angle to the line of action and rotate as they shorten, becoming more oblique throughout a contraction. This change in fiber orientation (pennation angle) can amplify the shortening velocity of a fiber and increase output velocity of the muscle. The velocity advantage resulting from dynamic changes in pennation an...

The increase in passive torque during muscle stretching may constrain the range of motion of a joint. As passive torque can vary substantially among individuals, the present study examined whether the relative lengthening of the myotendinous structures of the medial gastrocnemius (MG) during passive stretching differs among individuals. Sixteen subjects performed passive stretching of the plant...