Introduction/Aims: The conventional recording of F waves from the vastus lateralis muscle (VL) may not accurately measure the F-wave amplitude, as the F-wave latency is short and overlaps with the M wave. However, the optimal stimulation site of the femoral nerve for recording M and F waves separately from the VL remains unclear. In this study we aimed to determine the optimal stimulation site of the femoral nerve to record M and F waves separately from the VL.

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Introduction/Aims Conventional recording of F‐waves from the vastus lateralis muscle causes severe pain in some subjects. Thus, we aimed to investigate the effects of the stimulation frequency on pain and F‐wave parameters when recording F‐waves from this muscle and to develop a method for recording F‐waves from the vastus lateralis muscle that causes minimal pain. Methods The subject's femoral nerve was electrically stimulated at 0.5 or 0.2 Hz 30 times, while F‐waves were recorded from the vastus lateralis muscle. Pain intensity was measured immediately using a visual analog scale. In addition, the visual analog scale, F‐wave persistence, F‐wave latency, and F/M amplitude ratio were compared between F‐wave recordings with 0.5‐Hz electrical stimulation and those with 0.2‐Hz electrical stimulation. Results Eleven healthy men participated in this study. The visual analog scale and F‐wave persistence decreased when electrical stimulation at 0.2 Hz was applied compared with electrical stimulation at 0.5 Hz. Discussion Electrical stimulation at 0.5 Hz increased pain due to temporal summation. However, electrical stimulation at 0.2 Hz did not cause temporal summation, suggesting reduced pain and excitability of the alpha motor neuron pool.

[Purpose] We investigated the effect of motor imagery of the non-trained hand on the excitability of spinal neural function. [Subjects and Methods] We enrolled 14 healthy subjects. First, we recorded the F-wave at rest with participants in the relaxed position. Next, they practiced correct left-hand thenar muscle activity at 30% of maximum voluntary contraction. Three minutes later, motor imagery of the left hand movement was performed, following which the F-wave was recorded again in the relaxed position. On a different day, the participants practiced left-hand thenar muscle activity again. Motor imagery of the right hand was performed in a similar manner to during left hand practice, and the F-wave was simultaneously recorded in the right-hand (non-trained hand) thenar muscle.[Results] Persistence was significantly increased by motor imagery. However, relative F-wave values did not differ between the trained and non-trained hands. [Conclusion] Motor imagery of the non-trained hand is effective as well as motor imagery of the trained hand.

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