The aim of the present study was to investigate how the video speed of observed action affects the excitability of the primary motor cortex (M1), as assessed by the size of motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS). Twelve healthy subjects observed a video clip of a person catching a ball (Experiment 1: rapid movement) and another 12 healthy subjects observed a video clip of a person reaching to lift a ball (Experiment 2: slow movement task). We played each video at three different speeds (slow, normal and fast). The stimulus was given at two points of timing in each experiment. These stimulus points were locked to specific frames of the video rather than occurring at specific absolute times, for ease of comparison across different speeds. We recorded MEPs from the first dorsal interosseous muscle (FDI) and abductor digiti minimi muscle (ADM) of the right hand. MEPs were significantly different for different video speeds only in the rapid movement task. MEPs for the rapid movement task were higher when subjects observed an action played at slow speed than normal or fast speed condition. There was no significant change for the slow movement task. Video speed was effective only in the ADM. Moreover, MEPs in the ADM were significantly higher than in the FDI in a rapid movement task under the slow speed condition. Our findings suggest that the M1 becomes more excitable when subjects observe the video clip at the slow speed in a rapid movement, because they could recognize the elements of movement in others. Our results suggest the effects of manipulating the speed of the viewed task on the excitability of the M1 during passive observation differ depending on the type of movement task observed. It is likely that rehabilitation in the clinical setting will be more efficient if the video speed is changed to match the task’s characteristics.

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Continuous repetition of motor imagery leads to mental fatigue. This study aimed to examine whether fatigue caused by motor imagery training affects improvement in performance and the change in corticospinal excitability. The participants were divided into “physical practice training” and “motor imagery training” groups, and a visuomotor task (set at 50% of maximal voluntary contraction in participants) was performed to assess the training effect on fatigue. The measurements were recorded before and after training. Corticospinal excitability at rest was measured by transcranial magnetic stimulation according to the Neurophysiological Index. Subjective mental fatigue and muscle fatigue were assessed by using the visual analog scale and by measuring the pinch force, respectively. Additionally, the error area was evaluated and calculated at pre-, mid-, and post-terms after training, using a visuomotor task. After training, muscle fatigue, subjective mental fatigue, and decreased corticospinal excitability were noted in both of the groups. Moreover, the visuomotor task decreased the error area by training; however, there was no difference in the error area between the mid- and post-terms. In conclusion, motor imagery training resulted in central fatigue by continuous repetition, which influenced the improvement in performance in the same manner as physical practice training.

Purpose Previous evidence regarding the impact of exercise interventions on chemotherapy-induced peripheral neuropathy often focuses on lower limb functions, such as muscle strength and balance ability, while the effect on upper extremities remains unknown. We aimed to evaluate the e cacy of combined hand exercise intervention on upper extremity function, symptoms, and quality-of-life in patients with chemotherapy-induced peripheral neuropathy. Methods After screening 341 patients, 42 were randomly assigned to either the intervention (n=21) or control (n=21) groups.Participants were evaluated at baseline (T0), after one chemotherapy cycle (T1), and after two chemotherapy cycles (T2). The primary outcome was upper extremity function measured using the Michigan Hand Outcomes Questionnaire at T2. The intention-to-treat and as-treated populations were compared using a mixed-effect model. ResultsIn the intention-to-treat analysis, the decline in activities of daily living was signi cantly suppressed in the intervention group than in the control group at T2 (difference: 7.23; 95% con dence interval: 0.35, 14.10; P=0.0397). Similarly, in the as-treated analysis, the decline in activities of daily living was signi cantly suppressed in the intervention group than in the control group at T2 (difference: 13.09; 95% con dence interval: 5.68, 20.49; P=0.0008); and pain was also signi cantly improved in the intervention group than in the control group at T2 (difference: 13.21; 95% con dence interval: -22.91, -3.51; P=0.0083).Conclusion Performing a combined hand exercise intervention may prevent worsening in the activities of daily living using upper extremities in patients with chemotherapy-induced peripheral neuropathy.Trail registration number: UMIN000029389.