In the days that followed, there came vigils and funerals and uncountable private decisions that felt like tests of mind and muscle: Fight or flight?

The destructive effects of spaceflight on skeletal muscle, despite in-flight exercise, pose significant safety risk for future manned missions to Mars.

The moth's flight muscle grows and flight capacity increases as its ovary develops, but its flight muscle degenerates and flight capacity decreases after the moth begins laying eggs.