Sex Differences in Athletic Performance

The American College of Sports Medicine® (ACSM) has published an expert consensus statement, “The Biological Basis of Sex Differences in Athletic Performance,” which, as the title suggests, explores the current state of the field regarding sex-determined athletic differences between males and females.

In light of the ongoing public discussion about the inclusion of transgender athletes in cross-sex competition, the statement’s primary goal is to share the latest scientific knowledge and subject matter expertise on the issue; however, it does not make any policy recommendations, which are outside the scope of its purpose.

According to lead author Sandra Hunter, Ph.D., FACSM, “This statement emerges from the hard work of thought leaders who convened to discuss sex differences in athletic performance using a blend of research evidence and consensus of expert opinion.”

This consensus statement is the first in a series of three ACSM pronouncements on the topic of sex differences and transgender athletes. These are currently in development:

Paper 2: Clinical Care(health/performance) Issues of Transgender Athletes

The goal of this paper is to provide a systems-based approach for discussing the medical care of transgender athletes. The writing group will consider referencing the current International Olympic Committee guidance policy but will not provide an opinion regarding participation.

Paper 3: Call to Action on the Need for More Research

The goal of this paper is to identify the next steps needed to address research (or knowledge) gaps identified in papers #1 and #2.

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Resources

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Frequently Asked Questions

Abstract

Biological sex is a primary determinant of athletic performance because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes and sex hormones.

Adult men are typically stronger, more powerful, and faster than women of similar age and training status. Thus, for athletic events and sports relying on endurance, muscle strength, speed, and power, males typically outperform females by 10%–30% depending on the requirements of the event. These sex differences in performance emerge with the onset of puberty and coincide with the increase in endogenous sex steroid hormones, in particular testosterone in males, which increases 30-fold by adulthood, but remains low in females.

The primary goal of this consensus statement is to provide the latest scientific knowledge and mechanisms for the sex differences in athletic performance. This review highlights the differences in anatomy and physiology between males and females that are primary determinants of the sex differences in athletic performance and in response to exercise training, and the role of sex steroid hormones (particularly testosterone and estradiol). We also identify historical and nonphysiological factors that influence the sex differences in performance.

Finally, we identify gaps in the knowledge of sex differences in athletic performance and the underlying mechanisms, providing substantial opportunities for high-impact studies. A major step toward closing the knowledge gap is to include more and equitable numbers of women to that of men in mechanistic studies that determine any of the sex differences in response to an acute bout of exercise, exercise training, and athletic performance.
Our Goal

The primary goal of this consensus statement is to provide the latest scientific knowledge, mechanisms and subject matter expertise on the sex differences in athletic performance. Because this topic is an emerging, evolving and controversial cultural issue impacting athletic performance and competition, the statement intends to help inform the public dialogue with scientific research, assist with evidence-based solutions and contribute to an equitable and fair solution for all.

This statement does not claim or expect to answer all questions in regard to the issue and acknowledges that there are gaps in the data and further research is needed to address them.
What is an ACSM Pronouncement?

Pronouncements are official statements that reflect the position or stance of the American College of Sports Medicine on various topics. ACSM publishes five pronouncement types, each with its own protocols for development. All pronouncements undergo a rigorous approval, development and process. ACSM's Pronouncements are published in one of ACSM's official journals, and all are made freely available to the public.

ACSM pronouncements include Umbrella Reviews, Expert Consensus Statements, Contemporary Issues and Calls to Action. The Sex Differences and Athletic Performance pronouncement is considered an Expert Consensus Statement.
What is an ACSM Expert Consensus Statement?

ACSM Expert Consensus Statements are developed using a blend of research evidence and consensus of expert opinion. The document provides a mechanism by which the college can make an official comment in a timely and efficient manner on topics of high importance and/or with broad impact.
How will this statement benefit or contribute to the community?

The American College of Sports Medicine (ACSM) is committed to inclusive and safe physical activity, sport participation and competition for all. ACSM acknowledges the public dialogue regarding the inclusion of athletes who are transgender in physical activity and sport. Our role is to help inform public and scientific dialogue, assist with evidence-based solutions and contribute to an equitable and fair solution for all. We are committed to advancing the science on this important topic.

Understanding the latest science for the differences in performance between males and females, can inform policies of governing sports and athletic organizations on the inclusion of athletes who are transgender and/or have disorders (or differences) of sex development (DSD) within sex-based categories of competition.
What are the primary conclusions of the consensus statement?

The science shows that biological sex is a primary determinant of athletic performance and physical tasks because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes. The primary cause for the large sex difference in athletic performance is exposure to high levels of endogenous testosterone in boys at the onset of puberty (~12 years) that will rise ~20-30 fold in males during puberty and is 15 times higher in adult males than females by 18 years of age.

These sex differences in athletic performance emerge with the onset of puberty due to the anabolic effects of the endogenous sex steroid hormone, testosterone in males.

Adult men are stronger, more powerful, and faster than women of similar age and training status outperforming females by 10-30% in athletic events that require muscle power and/or aerobic capacity.
Does this statement represent an official ACSM policy position or recommendation for establishing policy on the matter of inclusion of athletes that are transgender?

This is not a policy statement or recommendation on the inclusion of athletes with DSDs or transgender athletes or how athletes should be categorized for recreational or competitive sports.

We do provide the scientific evidence for the differences in performance between biologic males and females primarily after the effects of puberty, and the basis for sex-based categories for many sports that can be used to guide policy decisions by policy makers.
Does the content of this consensus statement address athletes of all ages and competition levels?

This consensus statement focuses primarily on the sex differences of adult male and female athletes, with some information, although not a detailed and focused review, on children or youth.
Read Correction Note

The Consensus Statement Writing Group has corrected two errors identified in the original pronouncement published on Sept. 29. Both errors were found in the same statement in Box 1: Definitions.

Original Statement

Two percent of humans are intersex, harboring both male and female reproductive organs, and are reproductively fertile.

Corrected Statement

Differences/disorders of sex development (DSD) are rare conditions in which the development of chromosomal, gonadal, and anatomic sex is atypical (outside the binary of male/female).

Rationale for Corrections

This statement erroneously shared that “Two percent of humans are intersex..” The two percent figure represents the broadest range of conditions characterized by genital, reproductive, hormonal or sex chromosome differences, and includes many conditions that are not widely considered to be classified as DSD/intersex traits. The prevalence is much lower with narrower definitions of DSD/intersex. As a result, the two percent figure has been removed, the phrase corrected and the language is now consistent with the original corresponding sentence in the consensus statement itself (See page 19, under the heading “Hormonal Disorders (PCOS, DSD)”).

Additionally, the sentence incorrectly stated that individuals with DSD are “reproductively fertile.” Because some with DSD do experience infertility, the phrase was removed completely.

The Translational Journal of the American College of Sports Medicine will release an errata as soon as possible in order to ensure the published record is as accurate as possible.

Medicine & Science in Sports & Exercise will incorporate the corrected language into the final version of the consensus statement, which will appear in its December 2023 issue.