The ERGYS Rehabilitation System uses computerized functional electrical stimulation (CFES) to allow persons with little or no voluntary leg movement (e.g., SCI) to actively pedal a stationary leg-cycle ergometer. Computer generated, low-level electrical pulses transmitted through surface electrodes cause coordinated contractions of the large muscles of the legs. Sensors located in the ERGYS provide continuous feedback to a computer which controls the sequence of muscle contractions as well as the resistance to pedaling. The result is smooth and natural pedaling, with the rider’s leg muscles supplying the power. The benefits to this therapy include the prevention of muscle disuse atrophy, relaxation of muscle spasms, improved circulation, and increased range of motion. Clinical studies have also documented improvements to the cardiovascular system as well as other systemic benefits.
SPECIFICATIONS
Number of Stimulus Channels: 6. Maximum stimulus intensity for each channel is independently programmable
Output Waveforms: Selectable biphasic waveshapes
ERGYS1/REGYS compatible waveform
Amplitude : 0 - 140 milliamps, constant current*
Instantaneous stimulus levels set by closed-loop control algorithm
Pulse Duration: Selectable: 400 - 1000 microseconds
Phase Duration: Selectable: 200 - 500 microseconds
Repetition Rate: 30, 40, 50, 60 pulses per second
Power Requirements: 115 Volts AC, 60 Hz (220/240 VAC, 50/60 Hz optional)
Dimensions (seat upright): 84" x 36" x 48" (213 cm x 91 cm x 122 cm)
Dimensions (seat reclined): 106" x 36" x 48" (269 cm x 91 cm x 122 cm)
Weight: 235 lbs. (107 kg)
How the ERGYS Works: An Automobile Analogy
When discussing the technical details of the ERGYS with riders and clinicians, our favorite analogy at Therapeutic Alliances is one of a six-cylinder automobile with the cruise control set at 50 miles per hour. In the case of the ERGYS, the analog of miles per hour is revolutions per minute (RPM) of pedaling, and the 6 cylinders of the car can be thought of as the quadriceps, hamstrings, and gluteal muscles of the rider’s legs. It follows in our analogy that the ERGYS "spark plugs" are the electrodes placed over the motor nerves of the muscles. In an automobile, the source of power is the combustion of a mixture of air and gasoline. The ERGYS equivalent of combustion is the electrochemical reaction that takes place when the muscle nerve is electrically stimulated via a surface electrode.
The ERGYS sequences its electrical stimulus much like an automobile fires its spark plugs. The automobile sequence is timed so that the linear travel of the pistons in the cylinders is smoothly converted to the circular motion of the drive train shaft, and, ultimately, to the rotation of the tires. Each piston is restrained by a cylinder wall so that the movement of the piston is restricted to a direction that will contribute to the turning of the crank shaft. With the ERGYS, the Leg Restraints can be thought of as the cylinder walls. The Leg Restraints help to ensure that the force generated by the muscle contractions is transferred to the pedal crank and not lost through a "wobbling" of the legs at the hip and knee joints. As with any piston-cylinder combination, the truer the motion, the more efficient the transfer of power.
Our bodies tend to naturally convert muscle contractions into the circular motion necessary to accomplish tasks such as pedaling a bicycle. The ERGYS computer sequences the contractions of the quadriceps, hamstrings, and gluteal muscles in an order that allows for the hip, knee, and ankle joints to combine to create the repetitive circular motion of pedaling.
Sensors in the ERGYS perform a variety of measurements that govern a session. One sensor is used to track the angular position of the pedal crank, and hence the position of the legs. This position is used by the ERGYS computer to select the muscle to be stimulated. The intensity of the stimulus is dictated by the pedaling rate, which the ERGYS computes by measuring the change in pedal position over a fixed unit of time. Rates below 50 RPM will call for the ERGYS to increase the stimulus level. Conversely, rates above 50 RPM will cause the ERGYS to lower the stimulus level. In this way, the "closed-loop" control of the ERGYS is similar to the cruise control of a car. The ERGYS will continuously raise and lower the stimulus intensity to keep the rider at 50 RPM, much like a cruise control will meter the flow of gasoline to maintain a preset speed.
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