"比赛前量体重" can be translated into English as "weigh in before the competition" or "have a weight check before the match".
"Weigh in" is a common phrase used in sports contexts to refer to the process of measuring an athlete's weight before a competition, especially in sports like boxing, wrestling, or weightlifting where weight categories are important.
"Have a weight check" is a more straightforward way of saying the same thing, emphasizing the action of checking one's weight.
Both expressions are accurate and commonly used in English-speaking contexts.