The Real Differences in Endurance Physiology Between Women and Men: From Substrate Utilization to Body Temperature—What the Evidence Can and Cannot Say

Setting the Boundaries of This Discussion

Sex-based physiological differences are a topic that easily polarizes: one side frames the differences as an inspirational myth of “women are born ultra-endurance,” while the other denies any differences outright. Science sits in the middle, full of “it depends.” This article compiles the differences where the current evidence is relatively solid, as well as the parts that are often over-extrapolated, and emphasizes that within-individual variation is often greater than the average difference between sexes—meaning group conclusions can rarely be applied directly to any specific individual.

Substrate Utilization: Women Do Tend Toward Higher Fat Oxidation

A relatively consistent finding is that at the same relative intensity during submaximal exercise, women tend to have higher fat oxidation and lower carbohydrate and protein utilization compared to men. The possible mechanism is related to the influence of estrogen on fat metabolism and intramuscular triglyceride utilization.

• What can be said: This is an average trend, relatively robust in studies that match relative intensity.
• What cannot be over-stated: This does not automatically mean “women are stronger at any ultra-long distance.” Performance is determined by too many factors (VO2max, lactate threshold, economy, pacing, body temperature, fueling strategy), and a single substrate difference cannot be linearly extrapolated to race outcomes. “The longer the distance, the stronger women get” is an oversimplified myth.

Muscle Fiber Types and Fatigue Resistance

Some studies indicate that women on average have a tendency toward a relatively higher proportion or larger relative area of type I (slow-twitch, fatigue-resistant) muscle fibers, and show better fatigue resistance in certain isometric/submaximal repetitive tasks; however, in maximal strength and explosive output, men are on average higher (related to differences in muscle cross-sectional area and total muscle mass). Key point: these are averages, and an individual athlete’s training status can substantially rewrite these differences.

Thermoregulation: Differences Exist but Are Context-Dependent

Women and men differ in thermoregulation (body surface area-to-mass ratio, sweat gland density and sweat onset, the influence of the hormonal cycle on baseline core temperature, etc.), but there is no simple answer to “who tolerates heat better”—it is highly dependent on the environment (dry heat vs. humid heat), body size, acclimatization status, and testing conditions. A more practically useful conclusion is that individualized heat acclimatization and hydration strategies matter more than sex-based generalizations.

A “Can Say / Should Be Cautious” Comparison Table

The Real Implications for Training

1. Training principles are broadly shared between sexes: Periodization, progressive overload, the value of strength for endurance, recovery management—these do not differ by sex.
2. Don’t use group differences to limit individuals: “Women tend toward fat oxidation” does not mean women shouldn’t train maximal strength and explosive power (as the previous strength series articles have explained, its value applies to both sexes).
3. Establish monitoring priorities specific to women: Energy availability, iron, bone, menstrual/hormonal status—these are not about “women being weaker,” but rather monitoring axes that deserve attention after being neglected in female sports science for too long.
4. Individualization beats sex-based generalizations: The recurring theme of this series—your individual data deserves more of your trust than group averages.

Why This Topic Matters

For a long time, sports science research has primarily used male subjects, directly extrapolating male data to females, causing issues specific to women (such as menstruation in REDs, the masking of signals by oral contraceptives, bone and iron) to be chronically underappreciated. The value of clarifying “real differences vs. myths” is not about ranking who is superior, but about ensuring female athletes receive evidence-based care that matches their physiology.

“The two least helpful sentences are ‘women are born more enduring’ and ‘sex makes no difference at all.’ The truth is: some differences are real but context-dependent, and the biggest problem is actually that we have studied women far too little. Rather than arguing over who is stronger, it’s better to do proper monitoring specific to women.” —A researcher in sex and exercise physiology

Related Reading

• Endurance Traits of Female Advantage: Research on Fat Oxidation Rate and Fatigue Resistance
• Training Physiology Differences Between Women and Men: Not Just Body Size, but Concepts of Metabolism and the Hormonal Cycle
• Sex Differences: Gender Differences in Endurance Sports Training and Scientific Approaches
• Sex Differences in Athletic Performance: Physiological Basis, Sources of Performance Gaps, and Training Implications