ZACH Insights / Sex differences in performance
The gap opens at puberty. Testosterone explains much of it.
Before puberty, girls and boys perform about the same. From puberty on, men are on average faster and stronger, by 10–30% depending on the event. This article follows the hormone behind most of that gap, what it changes in the body, and what it does not explain.
By Zacharias Razvi · Updated 14 November 2026 · 10 min read
The size of the gap
Ten to thirty percent, depending on the event.
A consensus statement for the American College of Sports Medicine, led by Sandra Hunter, summarises the research. Adult men are typically stronger, more powerful and faster than women of similar age and training. In events that rely on endurance, strength, speed and power, men outperform women by 10–30%, depending on what the event demands. 1
A review by Handelsman and colleagues, written for the debate on eligibility in women's sport, estimates the advantage at a minimum of 8–12%. 2 These are averages for groups. The ranges overlap, and many women outperform many men.
General education. The article explains physiology and research. It is not individual advice.
Model 1 · Puberty opens the gap
Hormone first, performance after.
Follow testosterone and performance from childhood to adulthood. Select a stage.
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No difference before puberty.
Before puberty there is no sex difference in circulating testosterone or in athletic performance. 2 On average, girls and boys of the same age perform at about the same level.
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Testosterone rises about 30-fold in boys.
At puberty the testes start producing about 30 times more testosterone than before. In girls it stays low. 1 2 The performance gap emerges at the same time.
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At least 15 times higher in men.
From then on, circulating testosterone in men exceeds that in women by at least 15 times at any age, and the two ranges do not overlap. 2 The gap in performance settles at 10–30%, depending on the event. 1
What testosterone changes
Muscle, strength and the blood's capacity to carry oxygen.
Handelsman and colleagues describe a reproducible dose-response relationship: the more circulating testosterone, the more muscle mass and strength, and the higher the haemoglobin, in both men and women. They conclude that these relationships largely account for the sex differences in muscle and haemoglobin. 2 Haemoglobin carries oxygen in the blood, so a higher level means more oxygen delivered per litre of blood pumped.
The ACSM statement describes the gap as the result of differences in anatomy and physiology that are set by the sex chromosomes and the sex hormones, and it also points to historical and non-physiological factors that affect the difference in performance. 1
Model 2 · From hormone to performance
Three routes from one hormone.
Select a route to see what it changes and which kind of event it affects most.
Testosterone increases muscle mass, strength and haemoglobin.
Where women often do better
Less fatigue in sustained contractions.
In a review of the research on fatigability, Hunter describes that women are usually less fatigable than men in sustained contractions at the same relative intensity, for example holding a set percentage of their maximum. The difference depends on the task: the type, intensity and speed of the contraction, the muscle and the conditions all change it. Proposed explanations include differences in muscle perfusion, metabolism and fibre type. 3
The review also points to a problem in the research itself. Many more men than women have been studied, which can hide the true size of differences in either direction. 3
Hormones that change through the month
The menstrual cycle has a trivial average effect.
- Who took part
- Women with regular cycles in 78 studies, pooled by McNulty and colleagues. 4
- What was compared
- Strength and endurance performance in the early follicular phase, the first days of the cycle, against the other phases.
- What they found
- Performance might be slightly lower in the early follicular phase, but the average effect was trivial, with a standardised difference of −0.06 (credible interval −0.16 to 0.04).
- What it cannot say
- How one woman responds. The result is an average across many small studies.
Injuries
Higher risk of knee ligament injury in some sports.
A meta-analysis by Montalvo and colleagues compared rates of anterior cruciate ligament (ACL) injury between female and male athletes per 10,000 exposures. In contact sports, female athletes had about three times the rate. In collision, limited-contact and non-contact sports, the differences were smaller and not statistically significant. 5
A wider angle at the knee, the Q angle, is often given as the explanation. It is a weak one on its own. Landing technique, neuromuscular control, the size of the notch in the thigh bone and hormones are all studied as contributing factors.
Data · ACL injury, female compared with male athletes
Incidence rate ratio by type of sport.
Contact 3.00. Non-contact 1.49. Limited contact 1.21. Collision 1.14.
A note on falling testosterone
A decline in one cohort, with open questions.
- Who took part
- 1,532 randomly selected men aged 45–79 in the Boston area, followed by Travison and colleagues from 1987 to 2004. 6
- What was compared
- Testosterone at three time points, separated from the effect of ageing itself.
- What they found
- A substantial decline in testosterone that was independent of age and was not explained by changes in smoking, obesity or other measured factors.
- What it cannot say
- What caused the decline, and whether it applies to younger men or to other countries. It is one cohort from one region.
What this article cannot tell you
The figures are averages for groups, mostly from studies of men. They say nothing about what one person can achieve, and they do not settle questions about eligibility in sport, which also involve fairness and inclusion. Questions about one's own hormone levels belong with a doctor.
Sources
Follow the evidence.
- Hunter SK, Angadi SS, Bhargava A, et al. The biological basis of sex differences in athletic performance: consensus statement for the American College of Sports Medicine. Medicine and Science in Sports and Exercise. 2023;55(12):2328–2360. PubMed record Supports: the 10–30% gap, its emergence at puberty, the 30-fold rise in testosterone and the anatomical factors.
- Handelsman DJ, Hirschberg AL, Bermon S. Circulating testosterone as the hormonal basis of sex differences in athletic performance. Endocrine Reviews. 2018;39(5):803–829. PubMed record Supports: no difference before puberty, the 30-fold and 15-fold ratios, the dose-response relationships with muscle, strength and haemoglobin, and the 8–12% advantage.
- Hunter SK. Sex differences in human fatigability: mechanisms and insight to physiological responses. Acta Physiologica. 2014;210(4):768–789. PubMed record Supports: lower fatigability in women in isometric tasks, its task dependence, the proposed mechanisms and the sex bias in research.
- McNulty KL, Elliott-Sale KJ, Dolan E, et al. The effects of menstrual cycle phase on exercise performance in eumenorrheic women: a systematic review and meta-analysis. Sports Medicine. 2020;50(10):1813–1827. PubMed record Supports: 78 studies and the trivial average effect in the early follicular phase.
- Montalvo AM, Schneider DK, Webster KE, et al. Anterior cruciate ligament injury risk in sport: a systematic review and meta-analysis of injury incidence by sex and sport classification. Journal of Athletic Training. 2019;54(5):472–482. PubMed record Supports: the incidence rate ratios by sport type.
- Travison TG, Araujo AB, O'Donnell AB, Kupelian V, McKinlay JB. A population-level decline in serum testosterone levels in American men. Journal of Clinical Endocrinology and Metabolism. 2007;92(1):196–202. PubMed record Supports: the cohort, the age-independent decline and that measured factors did not explain it.
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Where to go from here.
All Insights · Understanding strength · Cardiovascular fitness
General education, not a diagnosis or an individual treatment plan. Models are schematic unless a data source is stated beside the figure. Zacharias Razvi is a final-semester physiotherapy student and is not yet an authorised physiotherapist.