to·nic·i·ty /toˈnɪsəti/
  強壯,肌肉彈性
  to·nic·i·ty /toˈnɪsətɪ/ 名詞
  張度,張力,強壯,緊張性
  To·nic·i·ty n. Physiol. The state of healthy tension or partial contraction of muscle fibers while at rest; tone; tonus.
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  tonicity
       n : the elastic tension of living muscles, arteries, etc. that
           facilitate response to stimuli; "the doctor tested my
           tonicity" [syn: tonus, tone] [ant: atonicity]