Stretching can cause systemic large local muscle shortening, the stasis of blood was "catch" back to the heart, and then greatly increase blood flow, improve blood circulation.

伸懒腰可惹起全身大局部肌肉的缩短，使瘀积的血液被“赶”回心脏，然后大大添加血流量，改善血液轮回。

youdao

The invention won't replace Raytheon's handiwork anytime soon, although Huynh notes that additional or more powerful sensors could theoretically catch real, muscle-bound sharks and not just their plastic counterparts.

ENGADGET: Liquidware team crafts laser tripwire that tweets intruder alerts, keeps fake sharks at bay (video)