Unexpected Fascicle Length Changes In Denervated Feline Soleus Muscle During Stance Phase Of Walking.

After surgical repair of traumatically severed peripheral nerves, associated muscles are paralyzed for weeks. Little is known about fascicle length changes in paralyzed muscles during locomotion. The aim of this study was to investigate to what extent, if any, muscle fascicles of denervated feline soleus (SO) change length during stance of walking when intact SO synergists are actively contracting.

Basis for the Induction of Tissue-Level Phase-2 Reentry as a Repolarization Disorder in the Brugada Syndrome.

Aims: Human action potentials in the Brugada syndrome have been characterized by delayed or even complete loss of dome formation, especially in the right ventricular epicardial layers. Such a repolarization pattern is believed to trigger phase-2 reentry (P2R); however, little is known about the conditions necessary for its initiation. This study aims to determine the specific mechanisms that facilitate P2R induction in Brugada-affected cardiac tissue in humans.

Hypohydration and Human Performance: Impact of Environment and Physiological Mechanisms.

Body water losses of >2 % of body mass are defined as hypohydration and can occur from sweat loss and/or diuresis from both cold and altitude exposure. Hypohydration elicits intracellular and extracellular water loss proportionate to water and solute deficits. Iso-osmotic hypovolemia (from cold and high-altitude exposure) results in greater plasma loss for a given water deficit than hypertonic hypovolemia from sweat loss.

Carbohydrate ingestion but not mouth rinse maintains sustained attention when fasted.

Unlabelled: Carbohydrate (CHO) receptors in the mouth signal brain areas involved in cognitive tasks relying upon motivation and task persistence; however, the minimal CHO dose that improves mental activity is unclear.

Purpose: To determine if CHO (via ingestion or oral rinse) influences sustained attention without eliciting glycemic responses when in a fasted state.

Methods: Study A: Six healthy adults completed five treatment trials, ingesting 0-6% CHO solutions to evaluate glycemic response.

The visual encoding of tool-object affordances.

The perception of tool-object pairs involves understanding their action-relationships (affordances). Here, we sought to evaluate how an observer visually encodes tool-object affordances. Eye-movements were recorded as right-handed participants freely viewed static, right-handed, egocentric tool-object images across three contexts: correct (e.

Accurate stepping on a narrow path: mechanics, EMG, and motor cortex activity in the cat.

How do cats manage to walk so graciously on top of narrow fences or windowsills high above the ground while apparently exerting little effort? In this study we investigated cat full-body mechanics and the activity of limb muscles and motor cortex during walking along a narrow 5-cm path on the ground. We tested the hypotheses that during narrow walking 1) lateral stability would be lower because of the decreased base-of-support area and 2) the motor cortex activity would increase stride-related modulation because of imposed demands on lateral stability and paw placement accuracy. We measured medio-lateral and rostro-caudal dynamic stability derived from the extrapolated center of mass position with respect to the boundaries of the support area.

Reliability of Visual and Somatosensory Feedback in Skilled Movement: The Role of the Cerebellum.

The integration of vision and somatosensation is required to allow for accurate motor behavior. While both sensory systems contribute to an understanding of the state of the body through continuous updating and estimation, how the brain processes unreliable sensory information remains to be fully understood in the context of complex action. Using functional brain imaging, we sought to understand the role of the cerebellum in weighting visual and somatosensory feedback by selectively reducing the reliability of each sense individually during a tool use task.

Consensus recommendations on training and competing in the heat.

Exercising in the heat induces thermoregulatory and other physiological strain that can lead to impairments in endurance exercise capacity. The purpose of this consensus statement is to provide up-to-date recommendations to optimise performance during sporting activities undertaken in hot ambient conditions. The most important intervention one can adopt to reduce physiological strain and optimise performance is to heat acclimatise.

INSECT FLIGHT. Luminance-dependent visual processing enables moth flight in low light.

Animals must operate under an enormous range of light intensities. Nocturnal and twilight flying insects are hypothesized to compensate for dim conditions by integrating light over longer times. This slowing of visual processing would increase light sensitivity but should also reduce movement response times.

Distinctive laterality of neural networks supporting action understanding in left- and right-handed individuals: An EEG coherence study.

Prior work has demonstrated that perspective and handedness of observed actions can affect action understanding differently in right and left-handed persons, suggesting potential differences in the neural networks underlying action understanding between right and left-handed individuals. We sought to evaluate potential differences in these neural networks using electroencephalography (EEG). Right- and left-handed participants observed images of tool-use actions from egocentric and allocentric perspectives, with right- and left-handed actors performing the actions.

3D anatomy and deformation of the seated buttocks.

Aim: To describe the 3D anatomy and deformation of the buttocks during sitting.

Materials And Methods: The buttocks of 4 able-bodied individuals and 3 individuals with spinal cord injury were scanned sitting in a FONAR Upright MRI. T1-weighted Fast Spin Echo scans were collected with the individuals seated on a custom wheelchair cushion to unload the ischial tuberosities (ITs) and seated on a 3 inch foam cushion.

Activation of p38 in C2C12 myotubes following ATP depletion depends on extracellular glucose.

Muscle cells adjust their glucose metabolism in response to myriad stimuli, and particular attention has been paid to glucose metabolism after contraction, ATP depletion, and insulin stimulation. Each of these requires translocation of GLUT4 to the cell membrane, and may require activation of glucose transporters by p38. In contrast, AICAR stimulates glucose transport without activation of p38, suggesting that p38 activation may be an indirect consequence of accelerated glucose transport or metabolism.

N-terminal and C-terminal domains of calmodulin mediate FADD and TRADD interaction.

FADD (Fas-associated death domain) and TRADD (Tumor Necrosis Factor Receptor 1-associated death domain) proteins are important regulators of cell fate in mammalian cells. They are both involved in death receptors mediated signaling pathways and have been linked to the Toll-like receptor family and innate immunity. Here we identify and characterize by database search analysis, mutagenesis and calmodulin (CaM) pull-down assays a calcium-dependent CaM binding site in the α-helices 1-2 of TRADD death domain.

Symmetrical kinematics does not imply symmetrical kinetics in people with transtibial amputation using cycling model.

People with amputation move asymmetrically with regard to kinematics (joint angles) and kinetics (joint forces and moments). Clinicians have traditionally sought to minimize kinematic asymmetries, assuming kinetic asymmetries would also be minimized. A cycling model evaluated locomotor asymmetries.

Locomotor control of limb force switches from minimal intervention principle in early adaptation to noise reduction in late adaptation.

During movement, errors are typically corrected only if they hinder performance. Preferential correction of task-relevant deviations is described by the minimal intervention principle but has not been demonstrated in the joints during locomotor adaptation. We studied hopping as a tractable model of locomotor adaptation of the joints within the context of a limb-force-specific task space.

Task-dependent inhibition of slow-twitch soleus and excitation of fast-twitch gastrocnemius do not require high movement speed and velocity-dependent sensory feedback.

Although individual heads of triceps surae, soleus (SO) and medial gastrocnemius (MG) muscles, are often considered close functional synergists, previous studies have shown distinct activity patterns between them in some motor behaviors. The goal of this study was to test two hypotheses explaining inhibition of slow SO with respect to fast MG: (1) inhibition occurs at high movement velocities and mediated by velocity-dependent sensory feedback and (2) inhibition depends on the ankle-knee joint moment combination and does not require high movement velocities. The hypotheses were tested by comparing the SO EMG/MG EMG ratio during fast and slow motor behaviors (cat paw shake responses vs.

The regulation of limb stiffness in the context of locomotor tasks.

Locomotion on ramped surfaces requires modulation of both pattern generating circuits and limb stiffness. In order to meet the mechanical demands of locomotion under these conditions, muscular activation patterns must correspond to the appropriate functions, whether the muscles are serving as force generators or brakes. Limb stiffness is a critical mechanical property that determines how the body interacts with the environment, and is regulated by both intrinsic and neural mechanisms.

A single bout of resistance exercise can enhance episodic memory performance.

Acute aerobic exercise can be beneficial to episodic memory. This benefit may occur because exercise produces a similar physiological response as physical stressors. When administered during consolidation, acute stress, both physical and psychological, consistently enhances episodic memory, particularly memory for emotional materials.

Individuals with transtibial limb loss use interlimb force asymmetries to maintain multi-directional reactive balance control.

Background: Deficits in balance control are one of the most common and serious mobility challenges facing individuals with lower limb loss. Yet, dynamic postural balance control among individuals with lower limb loss remains poorly understood. Here we examined the kinematics and kinetics of dynamic balance in individuals with unilateral transtibial limb loss.

Impact of skin temperature and hydration on plasma volume responses during exercise.

Heat stress and hydration may both alter plasma volume (PV) responses during acute exercise; potential interactions have not been fully studied. The purpose of this study was to determine the effect of graded elevations in skin temperature (Tsk) on PV changes during steady-state exercise under conditions of euhydration (EU) and hypohydration (HYPO, -4% of body mass). Thirty-two men (22 ± 4 yr) were divided into four cohorts (n = 8 each) and completed EU and HYPO trials in one environment [ambient temperature (Ta) 10, 20, 30, and 40°C].