IE80580B1 - Muscle stimulator apparatus - Google Patents

Description

The present invention relates to a muscle stimulator apparatus. * I According to the present invention there is provided a muscle stimulator apparatus which in operation administers treatment in a plurality of phases each such phase comprising alternating muscle contraction and muscle relaxation periods consisting resectively of the presence and absence of pulse signals at a predetermined frequency, wherein in at least one phase, at the start of each muscle contraction period the on pulse width increases from zero to a maximum value over an initial plurality of pulses and at the end of each muscle contraction period the on pulse width decreases from said maximum value to zero over a final plurality of pulses, the on pulse width remaining substantially constant at said maximum value between said initial and final plurality of pulses, wherein over an initial plurality of muscle contraction periods at the start of the at least one phase the maximum value increases from an initial value to a constant value, and wherein the at least one treatment phase is preceded and followed by further treatment phases in each of which the maximum value of the on pulse width is constant for all muscle contraction periods.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a muscle stimulator apparatus, Figure 2 is a diagram illustrating the pulse width of treatment signals issued by the muscle stimulator apparatus of Figure 1 according to the embodiment of the invention, and Figure 3 is a diagram illustrating the variation in the pulse width of a portion of the treatment signal of Figure 2.

In a conventional muscle stimulatpr apparatus, Figure 1, a microprocessor 9 issues respective control signals 10 to a plurality of transducer circuits 8 which drive respective electrode pairs 7 connected to a patient (not shown). The characteristics of the treatment signals 6 applied to the patient by each pair of electrodes 7 is determined by the respective control signal 10 from the microprocessor 9.

The transducer circuits 8 include conventional variable amplitude circuitry so that the amplitude of the treatment signals 6 administered to the patient can be varied by the patient. The overall level of the treatment applied by each pair of electrodes 7 is therefore a product of the selected signal amplitude and the on/off duty cycle of the treatment signal as determined by the respective control signal 10j. This on/off duty cycle must be carefully controlled to prevent undue stress on muscles being treated.

Accordingly, in the present embodiment, the muscle stimulator apparatus is designed in operation to administer treatment signals in three distinct phases, Figure 2. In Figure 2 the horizontal axis is time and the vertical axis is pulse width.

In the first phase 11, which lasts approximately 5 minutes, the treatment signal 6 consists of alternate muscle contraction and muscle relaxation periods 12 and 13 respectively each of four seconds duration. During each four second muscle contraction period 12 the treatment signal 6 consists of 10Hz pulse signals whose on pulse width increases from zero to 230 microseconds (us) over the first 0.5 secs of treatment (i.e. over the first five or so pulses), then remains at 230us for the next three seconds, then reduces to zero over the final 0.5 secs. During the four second muscle relaxation period 13 no control signal is issued by the microprocessor 9.

In the second phase 14, lasting approximately 20 minutes, the treatment signal 6 likewise consists of alternate muscle contraction and muscle relaxation periods 15 and 16 respectively. Each muscle contraction period 15 lasts 5 secs and each muscle relaxation period 16 lasts 8 secs.

During each five second muscle contraction period 15 the treatment signal 6 consists of 50Hz pulse signals whose on pulse width increases from zero to a maximum 19 over the first 0.5 secs of treatment (i.e. over the first twenty-five or so pulses), then remains at the maximum for the next four seconds, then reduces to zero over the final 0.5 secs. As for the first phase, during each eight second muscle relaxation phase 16 no control signal is issued by the microprocessor 9.

However, in contrast to the first phase, where the maximum on pulse width is set at a constant 230us for each muscle contraction period 12, in the second phase the maximum on pulse width 19 for the muscle contraction periods 15 varies as a function of time as indicated in Figure 3. In particular, in this embodiment the maximum pulse width 19 for each muscle contraction period 15 begins at lOOus for the first such period 15 and widens to 230us over the initial 5 to 6 such periods of phase 2. This pulse width widening is therefore spread over the first 1.5 minutes of the second phase and for the remaining 18.5 minutes of the second phase the maximum pulse width remains at 230us.

The third phase 17 lasts approximately five minutes and has alternating contraction and relaxation periods 12, 13 respectively having the same parameters as the first phase.

Claims (2)

1. A muscle stimulator apparatus which in operation 5 administers treatment in a plurality of phases each such phase comprising alternating muscle contraction and muscle relaxation periods consisting resectively of the presence and absence of pulse signals at a predetermined frequency, wherein in at least one phase, at the start of each muscle 10 contraction period the on pulse width increases from zero to a maximum value over an initial plurality of pulses and at the end of each muscle contraction period the on pulse width decreases from said maximum value to zero over a final plurality of pulses, the on pulse width remaining 15 substantially constant at said maximum value between said initial and final plurality of pulses, wherein over an initial plurality of muscle contraction periods at the start of the at least one phase the maximum value increases from an initial value to a constant value, and wherein the at least 20 one treatment phase is preceded and followed by further treatment phases in each of which the maximum value of the on pulse width is constant for all muscle contraction periods. _ 25

2. A muscle stimulator apparatus substantially as described with reference to the accompanying drawings.