Method and apparatus for measuring muscle fatigue

Apparatus for measuring muscle fatigue, in which electromyographic (EMG) signals from a muscle are measured to determine the fatigue level of the muscle, the apparatus comprising:

• input means (1) adapted to receive an EMG input signal x(t) from electrodes attached to the muscle to be analyzed and to sample said input signal to form a sequence of discrete signal values x.sub.i ;
• difference calculating means (S) for computing the difference .DELTA.x.sub.i between several pairs of successive sample values x.sub.i and x.sub.i.multidot.1 ;
• control logic means (3) for determining the sign of said difference .DELTA.x.sub.i and for providing the signals necessary for controlling the EMG measuring apparatus;
• first, second and third accumulator means (A1, B1, C) for selectively receiving, depending on the sign of the calculated difference .DELTA.x.sub.i, sampled values x.sub.i and said difference values .DELTA.x.sub.i ;
• dividing means (D1, E1) for computing separate sequences of quotients between values representative of the output from said third accumulator means and values representative of the output from one of said first and second accumulator means, respectively;
• statistical analyzing means (F,G) for obtaining for each of said sequences a single weighted quotient value representative of a number of said quotients;
• and
• multiplying means (H) for multiplying the obtained weighted values with each other in order to obtain an index indicative of fatigue during said time period in said muscle.