Neural and muscular factors influence maximal power generation




Sleivert, Gordon Grant

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The purpose of this thesis was to investigate the role of selected neuromuscular factors thought to affect the generation of maximal power outputs in a complex multi-joint movement, using multiple muscles, contracting across multiple joints (cycle ergometry). The reliability of measurement for the neuromuscular variables was initially determined. There was a range of reliabilities, and this must be considered in the interpretation of both the cross-sectional and longitudinal studies. A cross-sectional study suggested that neural factors were not important in maximal power generation, but rather the amount of muscle, especially Type II muscle, seemed to differentiate those that could produce high power outputs and those that could not. Since there was no difference in the magnitude of relationship between either single or multi-joint strength, and multi-joint power, it was also suggested that the simulation of a power movement pattern (neural specificity) in a strength movement, would not influence power acquisition. A longitudinal study supported this since there was no difference in the rate of power acquisition between single and multi-joint strength training. Further, sprint training using an identical movement to that used in testing maximal power output, was not more effective than the strength training modalities in increasing power output, and the adaptations between these three training modes were similar. Likewise, sequencing of neurally specific sprint training after strength training does not cause greater power acquisition than sprint training alone. The muscle hypertrophy and strength or power improvements caused by training in these modes does not necessarily cause intrinsic improvements in muscle transferable to other movements using different modes of contraction (isokinetic strength). Thus some type of neural training effect seems to be evident. It does not involve increasing the activation of the muscle mass involved in a movement, but may involve plasticity of the motoneurones themselves (increased nerve conduction velocity) or a motor learning effect such that the co-ordination and synchronization of muscle and motor unit activation occurs more readily after training. In the long-term, this may be overridden by muscle adaptation since in the cross-sectional study no neural differences were noted.



Muscle strength, Muscle contraction, Neuromuscular transmission, Muscles