A motor unit-based model of muscle fatigue

Muscle fatigue is a temporary decline in the force and power capacity of skeletal muscle resulting from muscle activity. Because control of muscle is realized at the level of the motor unit (MU), it seems important to consider the physiological properties of motor units when attempting to understand and predict muscle fatigue. Therefore, we developed a phenomenological model of motor unit fatigue as a tractable means to predict muscle fatigue for a variety of tasks and to illustrate the individual contractile responses of MUs whose collective action determines the trajectory of changes in muscle force capacity during prolonged activity. An existing MU population model was used to simulate MU firing rates and isometric muscle forces and, to that model, we added fatigue-related changes in MU force, contraction time, and firing rate associated with sustained voluntary contractions. The model accurately estimated endurance times for sustained isometric contractions across a wide range of target levels. In addition, simulations were run for situations that have little experimental precedent to demonstrate the potential utility of the model to predict motor unit fatigue for more complicated, real-world applications. Moreover, the model provided insight into the complex orchestration of MU force contributions during fatigue, that would be unattainable with current experimental approaches

Does intra-party democracy affect levels of trust in parties? The cases of Belgium and Israel

© 2017 CCBY. Previous research has shown a steady decline of citizen's political trus and growing skepticism towards key institutions of representative democr acy. Political parties, which perform the crucial role of linking citizens to the political system, are in the eye of the storm: citizens are generally more distrusting towards parties than other social and political institutions. The relevant literature mentions that parties often implement intra-party democratization to remedy party distrust. This article examines whether democratic candidate selection processes actually affect party trust among voters. The analysis is based on the cases of Belgium and Israel, where politicians made a strong case for intra-party democracy in recent history. The results indicate that, while inclusive selectorates indeed increase trust levels, decentralization decreases trust towards parties in both countries.status: publishe