A little tougher approach is to tie yourself up to a stretchcord and swim to the other end.
一个比较有难度的练习方式是在腰上系上橡皮筋不停地游到尽头。
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"Thanks, thanks," said Monte Cristo, judging from the steward's utter prostration that he could not stretch the cord further without danger of breaking it.
Study Design. An experimental study to investigate the in vitro gene expression of neurotrophic factors and receptors in cultured rat spinal cord cells subjected to cyclic mechanical stretch forces.