H. Nishizono et al., NONINVASIVE METHOD TO DETECT MOTOR UNIT CONTRACTILE PROPERTIES AND CONDUCTION-VELOCITY IN HUMAN VASTUS LATERALIS MUSCLE, Medical & biological engineering & computing, 33(4), 1995, pp. 558-562
The contractile properties and conduction velocity of motor units are
estimated by using surface array electrodes during voluntary isometric
contractions of the human vastus lateralis muscle. The subjects devel
op and maintain sufficient force to steadily discharge a given motor u
nit, assisted by visual feedback from an oscilloscope. The torque curv
e developed around the knee joint is triggered by an individual motor
unit and averaged. 31 motor units in five subects are studied. The twi
tch tension detected ranges from 3 to 27 m Nm with a mean of 12.3 m Nm
. The threshold force ranges from 1.88 to 10.12 Nm with a mean of 5.48
Nm, which is 3% of the maximal voluntary contraction. The rise time r
anges from 56 to 106 ms with a mean of 83 ms. The mean value of conduc
tion velocity is 4.64 m s(-1). The twitch tension is positively correl
ated to the threshold force (r = 0.839, p < 0.01), but has no relation
to the other parameters. It is concluded that the use of non-invasive
surface array electrodes provides the contractile properties of motor
units and muscle fibre conduction velocity during weak contractions.