BACKGROUND: It is unclear whether mental simulation without actual muscle contraction associated with actual motion can increase the excitability of the spinal neural function. OBJECTIVE: To determine the best method for mental simulation without actual muscle contraction, we analyzed the F-wave of thenar muscles after stimulating the median nerve by motor imagery whilst holding the sensor of a pinch meter between the thumb and index finger and without holding the sensor. METHODS: Healthy volunteers (n = 11; mean age, 34 years) participated in this study after providing informed consent. We examined the F-wave of the left thenar muscles after stimulating the left median nerve at the wrist at rest and under holding and motor imagery conditions. For the motor imagery condition, the subjects were asked to establish 50% maximal voluntary contraction (MVC) of isometric contraction while holding the sensor between the thumb and index finger (motor imagery with the sensor condition) and without holding the sensor on another day (motor imagery without the sensor condition). RESULTS: The persistence and amplitude ratio of F/M during motor imagery with or without the sensor was better than that during relaxation. In particular, this ratio was significantly higher under the with sensor condition than under the without sensor condition. CONCLUSION: Movement preparation for a motor imagery task involving 50% MVC isometric contraction of the opponens pollicis is important.
To investigate the effect of physical therapy on F-wave characteristics in a patient with cerebrovascular disease, we tested the relationship between F-wave waveforms and the recovery of voluntary movement on the affected side. We measured F-waves of affected thenar muscles after stimulating the affected median nerve at the wrist in a left hemiplegia patient (female, 60 years old) with cerebrovascular disease. We analysed the F/M amplitude ratio and Fwave waveform values from 30 trials. F-wave waveform values were determined as follows. We calculated the correlation coefficient of each waveform and defined identifying F-waves as those with a correlation coefficient greater than 0.9. We determined the number of different wave forms from the number of identifying waveforms. F-waves were tested three times at 9, 52, and 70 months from sideration. The patient underwent physical therapy twice a week, with each session lasting 20 min. The F/M amplitude ratio gradually decreased and the number of F-wave waveform types gradually increased. Muscle tonus and voluntary movements of the affected arm gradually improved with physical therapy. In this patient with cerebrovascular disease, F-wave waveform values in her affected arm gradually increased as muscle tonus and voluntary movements of the arm improved.
BACKGROUND: No scientific basis exists for the effect of motor imagery with eyes open. OBJECTIVE: To investigate spinal neural function during motor imagery and at rest with eyes open or closed by analyzing F-waves generated by the left thenar muscles after left median nerve stimulation.
METHODS:Sixteen healthy volunteers performed motor imagery while achieving 50% maximal voluntary contraction by isometrically contracting the opponens pollicis muscle. For subjective comparisons after the test, patients were asked whether imaging was easier with eyes open or closed and were then asked to imagine the contraction while holding the sensor between thumb and index finger with eyes open or closed. RESULTS: Persistence during motor imagery under both visual conditions tended to increase compared with that at rest. F/M amplitude ratio was significantly higher during motor imagery under both visual parameters than at rest. Most subjects (14/16) found imaging easier with eyes open, but no relationship was found between F-wave data and subjective evaluations to determine the easier condition for motor imagery. CONCLUSION: Motor imagery with eyes open or closed increased the excitability of spinal neural output to the thenar muscles. However, subjective evaluation to determine the easier visual condition for motor imagery revealed insignificant results.
To study spinal neuron function during relaxation imagery, we analyzed F-waves of the left thenar muscles in 15 healthy subjects (9 males, 6 females; mean age, 27.9 ± 9.2 years) after stimulating the left median nerve at the wrist. Fwaves were recorded in a resting position and during and after a 1-min period of relaxation imagery; they were recorded immediately after and at 5, 10, and 15 min after the relaxation imagery period. Persistence, F/M amplitude ratio, and latency were analyzed from the recorded F-waves. No significant differences were observed in the abovementioned parameters obtained at rest, during, or after relaxation imagery (at any time points). However, the F/M amplitude ratio, as an index of spinal neuron excitability, was used to separate subjects into those with lower excitability, unchanged excitability, and higher excitability than the resting F/M ratios. In our subjective evaluation of the relaxation imagery methods, almost all subjects in the lower excitability group said they performed "relaxation imagery of the hand and thumb." In the higher excitability, almost all subjects said they performed "relaxation imagery of the whole body." These results indicate that a 1-min period of relaxation imagery does not change the excitability of spinal neurons in healthy subjects. However performing relaxation imagery focused on decreasing muscle tone in a specific area may decrease the excitability of spinal neurons.
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