A runner can lose a lot of advantage by even glancing back to see how far behind the others are.
一个赛跑运动员甚至回头看一眼后面的运动员还有多远，就可能失去很多优势。
I walked up the path, glancing at the windows to see if anyone was looking for me.
我一面在路上走着，一面注意着陆窗户，看看是否有人在找我。
He thought he heard someone following him, and glancing round. He caught sight of a dark figure in the shadows.
他觉得有人在跟踪他，便向周围扫了一眼，发现阴暗处有一个黑影。
