We investigated the influence of the imagined muscle contraction strengths on spinal motor neuron excitability in healthy volunteers. F‐wave was used for assessing spinal motor excitability. The F‐waves during motor imagery (MI) under 10, 30, 50, 70, and 100% maximal voluntary contractions (MVCs) were compared. Furthermore, we investigated changes of the F‐waves during motor imagery for 5 min. Motor imagery under 10, 30, 50, 70, and 100% maximal voluntary contractions can increase spinal motor neuron excitability. However, the imagined muscle contraction strengths were not involved in changes of spinal motor neuron excitability. Additionally, spinal motor neuron excitability after 5 min from onset of motor imagery returned to the rest level. Thus, in clinical use of motor imagery, slightly imagined muscle contraction strength is enough for facilitating spinal motor neuron excitability. Also, duration of motor imagery needs to be considered.
Part of the book: Neurological Physical Therapy
Motor imagery allows patients with difficulty in voluntary movements to mentally practice a target motor task. Numerous neurophysiological studies have investigated the mechanisms underlying the benefits of motor imagery, but many aspects remain unclear. Since both central and spinal neural function need to be leveraged to improve various motor functions, we have investigated motor imagery and spinal neural functions. Our previous research demonstrated a facilitation effect of motor imagery on spinal neural function and an immediate effect on muscle strength. Specifically, a mild imagined muscle contraction strength may be sufficient to enhance the excitability of spinal motor neurons. In addition, kinesthetic imagery or combined action observation and motor imagery may substantially enhance the excitability of spinal motor neurons. Also, keeping a position of the upper or lower extremities close to the desired movements leads to greater enhancement of the excitability of spinal motor neurons during motor imagery.
Part of the book: Physical Therapy