In prolonged space flight, besides the obvious hazards of meteors, rocky debris, and radiation, astronauts will have to deal with muscle atrophy brought on by weightlessness; therefore, when they return to Earth, they face a protracted period of weight-training to rebuild their strength.
The underlined word atrophy, as used in the paragraph, most nearly means.
আপনি আমাকে যেকোনো প্রশ্ন করতে পারেন, যেমনঃ
Are you sure to start over?