And the harder you flex those opposing muscles, the more tension you'll have.
And the harder you flex those opposing muscles, the more tension you'll have.
这些反向肌肉群的力量越大，就会产生越强的身体紧张。
And the harder you flex those opposing muscles, the more tension you'll have.
这些反向肌肉群的力量越大，就会产生越强的身体紧张。