European journal of applied physiology
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Eur. J. Appl. Physiol. · Feb 2013
Randomized Controlled TrialThe effects of simulated obstructive apnea and hypopnea on arrhythmic potential in healthy subjects.
Preliminary evidence supports an association between OSA and cardiac dysrhythmias. Negative intrathoracic pressure, as occurring during OSA, may provoke cardiac dysrhythmias. Thus, we aimed to study the acute effects of simulated apnea and hypopnea on arrhythmic potential and measures of cardiac repolarization [QT(C) and T (peak) to T (end) intervals [TpTec]) in humans. ⋯ There were no significant changes of the QT(C) and TpTec intervals during central end-expiratory apnea. These data indicate that simulated obstructive apnea and hypopnea are associated with an increase of premature beats and prolongation of QT(C) and TpTec intervals. Therefore, negative intrathoracic pressure changes may be a contributory mechanism for the association between OSA and cardiac dysrhythmias.
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Eur. J. Appl. Physiol. · Feb 2013
Muscle gearing during isotonic and isokinetic movements in the ankle plantarflexors.
Muscle-tendon gearing is the ratio of the muscle-tendon unit velocity to the fascicle velocity and can be expressed as the product of the gearing within the muscle belly and the gearing due to tendon stretch. Previous studies have shown that gearing is variable and increases at higher velocities. Changes in the muscle activation levels and force development have been suggested to affect tendon gearing and thus muscle-tendon unit gearing. ⋯ The level of muscle-tendon unit gearing is largely determined by the belly gearing, but its variability is driven by changes in tendon gearing that in turn is a factor of the muscle activation and coordination. The belly thickness of the medial gastrocnemius decreased during contractions, but increased for the lateral gastrocnemius. It is likely that changes to the belly shape and 3-dimensional structure are important to the gearing of the muscle.