Power muscle stimulator

An electrical muscle stimulator is disclosed which provides unloaded isometric exercise of a pair of antagonist muscles associated with a rotatable limb, substantially without creating torque at the rotating joint. Further, a reduced pain stimulus signal is disclosed characterized in that it is continuous, biphasic and camel-back during a fundamental period thereof.

What is claimed is:

1. A method of isometrically stimulating muscles associated with a limb adapted to rotate at a joint, comprising:

substantially simultaneously:

(1) applying a first electrical stimulus to an agonist muscle associated with the limb to contract the agonist muscle whereby to tend to rotate the limb in one direction; and

(2) applying a second electrical stimulus to an antagonist muscle associated with the limb to contract the antagonist muscle whereby to tend to rotate the limb in another, opposite direction;

wherein the first and second electrical stimuli being effective to cause contraction of the respective muscles in an amount such that tendency of the limb to rotate in one direction is offset by a substantially equal tendency to rotate in the opposite direction whereby to isometrically stimulate the muscles substantially without creation of a net torque at the joint.

2. The method of claim 1, each of the first and second electrical stimuli having a characteristic waveshape, the characteristic waveshapes of the first and second stimuli being substantially identical.

3. The method of claim 1, the electrical stimuli each including a continuous biphasic segment which, during a fundamental period thereof, is camel-back having two portions having respective maximum amplitudes of a first polarity relative a reference separated by an intermediate portion having a maximum amplitude of a second polarity relative the reference.

4. The method of claim 1 further comprising:

generating an electrical signal having selected characteristics;

amplifying in a first channel the electrical signal to generate the first electrical stimulus for application to the agonist muscle; and

amplifying in a second channel the electrical signal to generate the second electrical stimulus for application to the antagonist muscle.

5. The method of claim 4 further comprising:

selecting at least some of the characteristics of the electrical signal.

6. The method of claim 4, generating the electrical signal including:

generating a selected, periodically repeating waveform signal;

generating a selected, periodically repeating profile signal; and

combining the waveform signal and the profile signal.

7. The method of claim 4, generating the electrical signal including generating a waveform signal including a stim segment and a variable length rest segment, the method further comprising selecting the length of the rest segment.

8. The method of claim 4, generating the electrical signal including generating a waveform signal including one of a plurality of selectable stim segments, the method further comprising selecting one of said stim segments.

9. The method of claim 8, at least some of the stim segments being continuous and biphasic.

10. The method of claim 9, at least one of the stim segments being continuous and biphasic, and, during a fundamental period thereof, camel-back having two portions having respective maximum amplitudes of a first polarity relative a reference separated by an intermediate portion having a maximum amplitude of a second polarity relative the reference.

11. The method of claim 10, the two portions having substantially identical durations and maximum amplitudes, the intermediate portion having a maximum amplitude equal, but of opposite polarity, to the maximum amplitude of either of the two portions, and a duration twice the duration of either of the two portions.

12. A method of reduced pain functional electrical muscle stimulation, comprising:

generating for application to a muscle a stim signal which is continuous and biphasic, and during a fundamental period thereof, camel-back having two portions having respective maximum amplitudes of a first polarity relative a reference separated by an intermediate portion having a maximum amplitude of a second polarity relative the reference, whereby to power contract the muscle without objectionable discomfort or pain.

13. The method of claim 12, the two portions having substantially identical durations and maximum amplitudes, the intermediate portion having a maximum amplitude equal, but of opposite polarity, to the maximum amplitude of either of the two portions, and a duration twice the duration of either of the two portions.

14. The method of claim 12, the stim signal having characteristics as follows: ##STR1## wherein R is a reference, t.sub.4 is the fundamental period of the stim signal, t.sub.1 is the duration of a first portion of the stim signal having a first polarity relative R and a maximum amplitude of Max A1, t.sub.2 is the period of a second portion of the stim signal having a second polarity relative R and a maximum amplitude of Max A2, t.sub.3 is the period of a third portion of the stim signal having the first polarity and a maximum amplitude of Max A1, and wherein t.sub.1 +t.sub.2 +t.sub.3 =t.sub.4 and t.sub.1 +t.sub.3 =t.sub.2.

15. The method of claim 14 wherein t.sub.1 =t.sub.3.

16. The method of claim 14 wherein the energy contained in the first portion plus the energy contained in the third portion is equal in magnitude to the energy contained in the second portion.

17. Apparatus for isometrically stimulating muscles associated with a limb adapted to rotate at a joint, comprising:

stimulator means for generating first and second electrical stimulus signals having respective characteristics;

channel means coupled to the stimulator means for substantially simultaneously applying the first and second electrical stimulus signals to respective agonist and antagonist muscles associated with the limb, the first electrical stimulus signal being effective to contract the agonist muscle whereby to tend to rotate the limb in one direction, the second electrical stimulus signal being effective to contract the antagonist muscle whereby to tend to rotate the limb in another, opposite direction, the first and second electrical stimulus signals being effective to cause contraction of the respective muscles in an amount such that tendency of the limb to rotate in one direction is offset by a substantially equal tendency to rotate in the opposite direction whereby to isometrically stimulate the muscles substantially without creation of a net torque at the joint.

18. The apparatus of claim 17, each of the first and second electrical stimulus signals having a characteristic waveshape, the characteristic waveshapes of the first and second electrical stimulus signals being substantially identical.

19. The apparatus of claim 17, the stimulator means including:

generator means for generating an electrical signal having selected characteristics;

first amplifier means coupled to the generator means for generating the first electrical stimulus signal and coupling same to the channel means for application to the agonist muscle; and

second amplifier means coupled to the generator means for generating the second electrical stimulus signals and coupling same to the channel means for application to the antagonist muscle.

20. The apparatus of claim 19, the channel means including:

first isolation means coupled to the first amplifier means for applying the first electrical stimulus signal to the agonist muscle; and

second isolation means coupled to the second amplifier means for applying the second electric stimulus signal to the antagonist muscle.

21. The apparatus of claim 19, the stimulator means further including:

means for selecting at least some of the characteristics of the electrical signal.

22. The apparatus of claim 19, the generator means including:

waveform generator means for generating a selected, periodically repeating waveform signal;

profile generator means for generating a selected, periodically repeating profile signal; and

means for combining the waveform signal and the profile signal whereby to generate the electrical signal.

23. The apparatus of claim 19, the generator means including:

means for generating a stim segment;

means for generating a variable length rest segment; and

means for selecting the length of the rest segment.

24. The apparatus of claim 19, the generator means including:

means for generating a plurality of stim segments; and

means for selecting one of the stim segments to be generated.

25. The apparatus of claim 19, the generator means including:

means for generating a stim segment, the stim segment being continuous and biphasic, and, during a fundamental period thereof, camel-back having two portions having respective maximum amplitudes of a first polarity relative a reference, separated by an intermediate portion having a maximum amplitude of a second polarity relative the reference.

26. The apparatus of claim 25, the two portions having substantially identical durations and maximum amplitudes, the intermediate portion having a maximum amplitude equal, but of opposite polarity, to the maximum amplitude of either of the two portions, and a duration twice the duration of either of the two portions.

27. An apparatus for functional electrical stimulation of muscle with reduced pain comprising:

means for generating a stim signal for application to a muscle; and

means for applying the stim signal to the muscle, the stim signal being continuous and biphasic, and, during a fundamental period thereof, camel-back having two portions having respective maximum amplitudes of a first polarity relative a reference, separated by an intermediate portion having a maximum amplitude of a second polarity relative the reference whereby to power contract the muscle without objectionable discomfort or pain.

28. The apparatus of claim 27, the two portions having substantially identical durations and maximum amplitudes, the intermediate portion having a maximum amplitude equal, but of opposite polarity, to the maximum amplitude of either of the two portions, and a duration twice the duration of either of the two portions.

29. The apparatus of claim 27, the stim signal having characteristics as follows: ##STR2## wherein R is a reference, t.sub.4 is the fundamental period of the stim signal, t.sub.1 is the duration of a first portion of the stim signal having a first polarity relative R and a maximum amplitude of Max A1, t.sub.2 is the period of a second portion of the stim signal having a second polarity relative R and a maximum amplitude of Max A2, t.sub.3 is the period of a third portion of the stim signal having the first polarity and a maximum amplitude of Max A1, and wherein t.sub.1 +t.sub.2 +t.sub.3 =t.sub.4 and t.sub.1 +t.sub.3 =t.sub.2.

30. The apparatus of claim 29 wherein t.sub.1 =t.sub.3.

31. The apparatus of claim 29 wherein the energy contained in the first portion plus the energy contained in the third portion is equal in magnitude to the energy contained in the second portion.

32. The apparatus of claim 27, the means for generating including:

first means for digitally generating a plurality of multi-bit outputs representing the stim signal;

second means coupled to the first means for producing an analog signal corresponding to the multi-bit outputs, the analog signal being proportional to the stim signal; and

amplifier means coupling the analog signal from the converter means to the means for applying whereby to amplify the analog signal to provide the stim signal.

33. A method of isometrically stimulating the biceps and triceps muscles of an arm, comprising:

substantially simultaneously:

(1) applying a first electrical stimulus to the biceps muscle to contract same whereby to tend to rotate the forearm in one direction relative the elbow; and

(2) applying a second electrical stimulus to the triceps muscle to contract same whereby to tend to rotate the forearm in another, opposite direction relative the elbow;

wherein the first and second electrical stimuli being effective to cause contraction of the respective muscles in an amount such that tendency of the forearm to rotate in one direction is offset by a substantially equal tendency to rotate in the opposite direction whereby to isometrically stimulate the muscles substantially without creation of a net torque at the elbow.

34. A method of isometrically stimulating the quadriceps and hamstring muscles of a leg, comprising:

substantially simultaneously:

(1) applying a first electrical stimulus to the quadriceps muscle to contract same whereby to tend to rotate the lower leg in one direction relative the knee; and

(2) applying a second electrical stimulus to the hamstring muscle to contract same whereby to tend to rotate the lower leg in another, opposite direction relative the knee;

wherein the first and second electrical stimuli being effective to cause contraction of the respective muscles in an amount such that tendency of the lower leg to rotate in one direction is offset by a substantially equal tendency to rotate in the opposite direction whereby to isometrically stimulate the muscles substantially without creation of a net torque at the knee.