Although the effects of transcranial direct current stimulation (tDCS) on contralateral unimanual movement have been well reported, its effects on coordinated multi-limb movements remain unclear. Because multi-limb coordination is often performed in daily activities and sports, clarifying the effects of tDCS on multi-limb coordination may have valuable implications. However, considering the neural crosstalk involved in bimanual movements, including the transcallosal pathway and ipsilateral motor pathway, the extent of tDCS-induced improvement may differ between unimanual and bimanual movement. We examined how tDCS affects simultaneous bimanual maximal voluntary contraction by testing the effects of tDCS of bilateral primary motor cortex (M1) on unimanual and bimanual handgrip strength. Twenty-one right-handed healthy adults underwent three bilateral tDCS protocols (“RaLc,” with an anode on right M1 and a cathode on left M1, “RcLa,” with an anode on left M1 and a cathode on right M1, and “Sham”) in a randomized order. A 1.5 mA current was applied for 15 min during tDCS. Participants then performed maximal unimanual and bimanual handgrip tests. Bimanual handgrip force was higher in both hands in the RcLa condition than in the Sham condition. Similarly, unimanual handgrip force was higher in the RcLa condition than in the Sham condition. Stimulus responses were asymmetrical and were not observed in the RaLc condition. Our findings demonstrate that RcLa tDCS leads to neuromodulation that can produce greater unimanual and bimanual handgrip strength. This result provides basic evidence that tDCS may be useful in sports, particularly those involving bilateral coordination of upper limb movement.

中文翻译：

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双侧经颅直流电刺激对同时双手握力的影响

尽管经颅直流电刺激（tDCS）对侧单手运动的影响已有很好的报道，但其对多肢协调运动的影响尚不清楚。由于经常在日常活动和运动中执行多肢协调，因此澄清tDCS对多肢协调的影响可能会产生重要的影响。但是，考虑到涉及双向运动的神经串扰，包括跨call肌通路和同侧运动通路，tDCS引起的改善程度在单向运动和双向运动之间可能有所不同。我们通过测试双侧主要运动皮层（M1）的tDCS对单手和双手握力的影响，研究了tDCS如何同时影响双手的最大自主收缩。21名右撇子健康成年人接受了三种双边tDCS协议（“ RaLc”，阳极在M1的右侧，阴极在M1的左侧，“ RcLa”，阳极在M1的左侧，阴极在M1的右侧，“ Sham”）以随机顺序排列。在tDCS期间施加1.5 mA电流15分钟。然后，参与者进行了最大程度的单手和双手握力测试。在RcLa条件下，双手的握力要高于在Sham条件下的双手。同样，RcLa条件下的单手抓握力高于Sham条件下的单手抓握力。刺激反应是不对称的，在RaLc条件下未观察到。我们的发现表明，RcLa tDCS导致神经调节，可产生更大的单手和双手握力。这一结果提供了基本的证据，证明tDCS在体育运动中可能有用，