Theta burst stimulation (TBS) is a potent form of repetitive transcranial magnetic stimulation (rTMS). Standard 600-pulse intermittent theta burst stimulation (iTBS) can enhance the corticomotor excitability, whereas standard 600-pulse continuous theta burst stimulation (cTBS) can suppress the corticomotor excitability. Sham stimulation uses an extreme low stimulation intensity which will not influence with corticomotor excitability.

In the present study, real stimulation will be delivered in an intensity of 55% (low-intensity) or 70% (conventional intensity) individual resting motor threshold while sham stimulation will be delivered in an intensity of 20% (ineffective) individual resting motor threshold.

Low-intensity priming intermittent theta burst stimulation will use a session of 55% RMT cTBS followed by a session of 70% RMT iTBS. Both sessions will be applied to the ipsilesional primary motor cortex.

Theta burst stimulation (TBS) is a potent form of repetitive transcranial magnetic stimulation (rTMS). Standard 600-pulse intermittent theta burst stimulation (iTBS) can enhance the corticomotor excitability, whereas standard 600-pulse continuous theta burst stimulation (cTBS) can suppress the corticomotor excitability. Sham stimulation uses an extreme low stimulation intensity which will not influence with corticomotor excitability.

In the present study, real stimulation will be delivered in an intensity of 55% (low-intensity) or 70% (conventional intensity) individual resting motor threshold while sham stimulation will be delivered in an intensity of 20% (ineffective) individual resting motor threshold.

Conventional intensity priming intermittent theta burst stimulation will use a session of 70% RMT cTBS followed by a session of 70% RMT iTBS. Both sessions will be applied to the ipsilesional primary motor cortex.

A standard 600-pulse TBS [16] will be administrated using a MagPro X100 stimulator (MagVenture, Denmark) and a 65-mm figure-of-eight coil. The measurement of the motor hotspot and individual RMT will be in accordance with our established methodology [3, 9]. For patients with stroke, the intensity of real stimulation will be 55% or 70% RMT of the unaffected M1 [17], depending on their assigned condition. Sham stimulation will be delivered using the same coil with 20% RMT of the unaffected M1 [4, 6]. The priming and conditioning sessions will be delivered to the ipsilesional M1 sequentially. In line with previous works, the interval between them will be 10 minutes [2, 3]. For healthy adults, the stimulation will be applied exclusively to the non-dominant (right) M1.

Force data will be collected using a load cell (Force sensor ZNHM, Chino sensor, China). To assess maximal voluntary contraction (MVC) of the hand grip, three trials will be conducted using both paretic and nonparetic hands (or the dominant and non-dominant hands for healthy controls). Subsequently, separate tests will be performed to measure submaximal isometric force at 20% and 50% of the maximal voluntary force (MVF). Each trial will last for 20 seconds, with a 60-second intertrial interval to prevent fatigue. A total of 5 trials will be conducted for each level of muscle contraction. Muscle strength will be evaluated by calculating the mean force output, while the variability of force control will be assessed by calculating the coefficient of variation of force, i.e., the standard deviation of force/mean force output × 100%.

Force data will be collected using a load cell (Force sensor ZNHM, Chino sensor, China). To assess maximal voluntary contraction (MVC) of the hand grip, three trials will be conducted using both paretic and nonparetic hands (or the dominant and non-dominant hands for healthy controls). Subsequently, separate tests will be performed to measure submaximal isometric force at 20% and 50% of the maximal voluntary force (MVF). Each trial will last for 20 seconds, with a 60-second intertrial interval to prevent fatigue. A total of 5 trials will be conducted for each level of muscle contraction. Muscle strength will be evaluated by calculating the mean force output, while the variability of force control will be assessed by calculating the coefficient of variation of force, i.e., the standard deviation of force/mean force output × 100%.

Single pulses evoked an initial response in electroencephalogram, followed by a series of time- and phase-locked positive and negative deflections which could spread to the connected brain areas. The evoked potential is called transcranial magnetic stimulation-evoked potential.