translation.en: They have two types of flight muscle: so-called power muscle, which is stretch-activated, which means that it activates itself and does not need to be controlled on a contraction-by-contraction basis by the nervous system.
translation.zh: 它们有两种用于航行的肌肉 所谓的力量型肌肉，这是舒张时激活的 这意味着它自己激活自己，并不需要被控制于 一个基于收缩的中枢神经系统