In explosive movements involving the lower extremity elastic recoil and transportation of power from knee to ankle via m. gastrocnemius allow power output about the ankle to reach values over and above the maximum power output of the plantar flexors. The object of this study was to estimate the relative power and work contributions of these two mechanisms for the push-off phase in one-legged ju...

This study focuses on neuromuscular mechanisms behind ankle torque and EMG variability during a maintained isometric plantar flexion contraction. Experimentally obtained torque standard deviation (SD) and soleus, medial gastrocnemius, and lateral gastrocnemius EMG envelope mean and SD increased with mean torque for a wide range of torque levels. Computer simulations were performed on a biophysi...

While previous studies have shown that muscle stretching suppresses monosynaptic spinal reflex excitability in stretched muscles, its effects on non-stretched muscles is still largely unknown. The purpose of this study was to examine the effects of muscle stretching on monosynaptic spinal reflex in non-stretched muscles. Ten healthy male subjects participated in this study. Muscle stretching of...

We used computer simulations to study the dendritic spatial distribution of low voltage-activated L-type calcium (Ca(V)1.3 type) channels, which mediate hysteretic persistent inward current (PIC) in spinal motoneurons. This study was prompted by the growing experimental evidence of the functional interactions between synaptic inputs and active conductances over the motoneuron dendritic tree. A ...

Activation of skeletal muscle twice in quick succession results in nonlinear force summation (i.e., doublet potentiation). The force contributed by a second activation is typically of augmented amplitude, longer in duration, and generated at a greater rate. The purpose of this study was to examine force summation in a muscle attached to a compliant tendon, where considerable internal shortening...

Percutaneous electrical stimulation over tibialis anterior and triceps surae was performed in 14 patients with traumatic spinal cord injury (SCI) to look for evidence that 'extra contractions' can develop, beyond those due to activation of the motor axons beneath the stimulating electrodes. Criteria for the extra contractions included marked asymmetry of force with respect to stimulation, progr...

This study aimed to examine the effects of application of kinaesthetic tapes on plantarflexor muscle performance. We hypothesised that taping of the triceps surae muscle would improve plantarflexor muscle strength and endurance with no significant effect on drop jump performance. Using a repeated-measures design, all performance measures were obtained in 24 volunteers on two separate occasions:...

BACKGROUND AND PURPOSE Intensive eccentric exercise can cause muscle damage. We simulated an animal model of isokinetic eccentric exercise by repetitively stretching stimulated triceps surae muscle-tendon units to determine if such exercise affects the mechanical properties of the unit within its physiologic excursion. METHODS Biomechanical parameters of the muscle-tendon unit were monitored ...

Among the mechanisms that may result in modulation of the stretch reflex by the recent history of muscle contraction is the history dependence observed under some conditions in the response properties of muscle spindles. The present study was designed to test one report that in successive trials of muscle stretch-release, spindle afferent firing during stretch, i.e., the dynamic response shows ...

The influence of motoneuron pool properties on the stability of the stretch reflex at the ankle in subjects with spinal cord injury was tested using a comprehensive model of the reflex pathway. This model included the passive and active components of the triceps surae muscles, muscle spindles, neural transport delays, limb mechanical properties, and a lumped parameter model of the motoneuron po...