Prediction of summation in incompletely fused tetanic contractions of rat muscle

Dynamic changes of twitchlike responses to successive stimuli studied by decomposition of motor unit tetanic contractions in rat medial gastrocnemius

“…When the force curve developed by (i Ϫ 1) pulses is mathematically subtracted from that developed by i pulses, the ith supplement of force (the ith contraction) is calculated. It was shown that these contractions had twitchlike forms (MacIntosh et al 2007;Raikova et al 2008;Stein and Parmiggiani 1981). For an analytical description of these twitch-form curves, a six-parameter analytical function was proposed and tested in several series of experiments to prove its ability to describe precisely all twitch forms .…”

“…In general, successive MU action potentials recorded in a muscle are quite stable in amplitude and shape (Mambrito and De Luca 1983;Stålberg 2003), although small changes in duration and amplitude of MU action potentials, related to a decrease in muscle fiber conduction velocity, were also reported during 30 s of voluntary activity (Farina and Falla 2007). Contrary to this, the twitchlike responses to successive motoneuronal action potentials within a tetanic contraction are highly variable, as reported in several studies on cat Parmiggiani 1979, 1981) and rat (MacIntosh et al 2007) muscles. These studies have shown that the amplitude of a single muscle twitch may be significantly smaller than a twitchlike response to one of the stimuli within a train.…”

Model-generated decomposition of unfused tetani of motor units evoked by random stimulation

“…The area under the twitch force curve can be considered as a mechanical quantity caused by application of a pulse (MacIntosh et al, 2007). In view of classical mechanics, the FTA reflects the potential to develop changes in the momentum of an object on which a force acts for a given time (Enoka, 2002, p. 91).…”

“…Individual responses (twitches) to successive action potentials were extracted and analyzed using a method used by Stein and Parmiggiani (1979, 1981), and MacIntosh et al (2007. MUs were stimulated with progressively increasing number of pulses and the successive twitches were calculated as the difference between the contractile response to n+1 pulses and the response to n pulses (Raikova et al, 2007b).…”

Experimentally verified mathematical approach for the prediction of force developed by motor units at variable frequency stimulation patterns

“…During voluntary muscle activity, MUs generate unfused tetanic contractions (Grimby et al, 1979;Hennig and Lømo, 1987;Nordstrom et al, 1989;De Luca and Erim, 1994). It has been shown (by subtraction of successive force curves of contractions evoked by a progressively increasing number of pulses) that the tetanic force represents the sum of the forces of individual twitches Parmiggiani, 1979, 1981;MacIntosh et al, 2007;Raikova et al, 2008). These twitches have bell-shaped forms, but their parameters (amplitudes, contraction and relaxation times) are variable.…”