一前一后三个人轮换可以用英文表达为 "three people taking turns one after the other" 或者更简洁地说 "three people taking turns in a row." 如果是在特定场景下，比如运动或游戏中，你也可以具体说明，例如：

"In a relay race, three players take turns running one after the other."

或者

"The team members take turns operating the machine in a row."

这样的表达方式可以根据具体的上下文进行调整。