As someone who teaches at a journalism school, I often get grammar questions from friends and family. I am an editor, not a grammarian. But I am happy to help resolve these issues when I can.
That happened recently when a friend sent an email with a question regarding this sentence: “”Marathoners, we’ve got your backs on this one.” Her question: Should it be “back”?
My answer is yes. To my mind, the participants in a marathon make up a singular group, with one shared “back.” So I suggested going with that to indicate that the race’s organizers are supporting the overall community of runners.
That makes it different from this sentence: “The students shook their head.” In that sense, each student has a head. There’s no collective one.
For more grammar advice, check out Grammar Girl. She’s got your back.