Are There Sex-Based Differences in Athletic Performance Before Puberty?

While sex-based differences in performance in children are smaller than in adults, they can mean the difference between a gold medal and no medal in sports.

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About the Author

Dr. Greg Brown is a professor of Exercise Science at the University of Nebraska at Kearney where he also serves as the Director of the LOPERs General Studies program. His primary teaching responsibilities are undergraduate and graduate courses in Exercise Physiology, but he has also taught courses in Introductory Anatomy & Physiology, Sports Nutrition, Research Methods, and Professional Development in Exercise Science. His research has evaluated the effects of nutritional supplements on the physiological response to exercise, the physiological responses to various types of exercise, effective teaching in the exercise science program, and sex-based differences in sports performance. He has authored or co-authored over 50 peer reviewed publications and serves as a peer-reviewer for over two dozen academic journals. He is a member of the American College of Sports Medicine (ACSM), the National Strength and Conditioning Association (NSCA), and the Association of American Educators (AAE). 

He and his wife (Amber) have two adult sons and one daughter-in-law. Sadly, both their cat and dog passed away in the past year. His hobbies include running, hunting, fishing, studying history, and watching movies. 

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In the current battle over women’s and girls’ rights to female-only sports, a commonly heard mantra is that there are no sex-based differences in sports performance before puberty. Those who make this claim often contend that if a male is put on puberty blockers before age 12 (or Tanner development stage 2; whichever comes first), he can compete fairly in the female category. But is this really true?Are there really no differences in athletic performance between boys and girls before the onset of puberty? Do puberty blockers administered to children really erase male sex-based athletic advantages? Below, I’ll try to provide answers to these questions.

Like many things currently being put forth in public discourse as settled science, the presence or absence of sex-based athletic differences before puberty is not an open and shut case. There are few databases of records for children’s competitive sports performance and there has been limited scholarly research evaluating sex-based differences in competitive sports performance before puberty. Currently, there are no consensus statements from professional organizations such as the North American Society for Pediatric Exercise Medicine (NASPEM), the National Strength & Conditioning Association (NSCA), the American College of Sports Medicine (ACSM), or the National Athletic Trainers’ Association (NATA) stating that there are, or are not, sex-based differences in athletic performance before puberty.

Below, I will cover the main reasons our data on pre-pubertal sex differences in athletic performance is relatively poor, and draw some preliminary conclusions based on the data we do have that indicates such differences are actually quite significant.