"比赛前量体重" can be translated into English as "weigh in before the competition" or "take a weight measurement before the match".
The first phrase, "weigh in before the competition," is more commonly used in sports contexts, especially in combat sports like boxing or wrestling, where athletes are required to meet a specific weight limit. The second phrase, "take a weight measurement before the match," is more literal and can be used in any context where weighing before an event is necessary.
For general use, "weigh in before the competition" is the preferred and more concise option.