空袋不能直立。
交感肾上腺系统不能维持直立位的脑灌注压。
The sympathoadrenal system is unable to maintain cerebral perfusion pressure in the upright posture.
这事经过如下：农忙时队长不叫我犁田，而是叫我去插秧，这样我的腰就不能经常直立。
It was so happened: during the rural busy season the team leader did not want me to plough instead he let me plant rice seedlings. Consequently I was unable to have my back straight very often.
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