Motor unit plasticity is currently incorporated into many professional and collegiate training regiments. Motor unit plasticity can be measured in many ways, the most important of which being neural firing frequency, EMG amplitude, muscle force output, pre-synaptic inhibition, and synchronization. Firing frequency is defined as the number of neuronal signals sent per second on one motoneuron. This frequency is measured in Hertz. Maximum firing frequency in humans typically ranges from 100–200 Hz. Studies incorporating electromyography have proven that adaptation mechanisms occurring as a result of resistance training can drastically increase the maximal firing frequency of a motoneuron. Firing frequency has been shown to
Vibration fatigue amplitude distribution is known. This distribution can be obtained from a time-history simply by counting cycles. To obtain it from the PSD another approach must be taken. Various vibration-fatigue methods estimate damage intensity based on moments of the PSD, which characterize the statistical properties of the random process. The formulas for calculating such estimate are empirical (with very few exceptions) and are based on numerous simulations of random processes with known PSD. As a consequence, the accuracy of those methods varies, depending on analyzed response spectra, material parameters and the method itself - some are more accurate than others. The