Physiological Characteristics of Female Ultramarathon Runners: Research on How the Gender Gap Narrows with Distance

Based on the Journal of Applied Physiology, Medicine & Science in Sports & Exercise, Sports Medicine, British Journal of Sports Medicine, and other international peer-reviewed journals, this article provides an in-depth analysis of the scientific evidence on “female ultramarathon running and the sex gap” within the field of female exercise physiology. It also integrates Taiwan’s local climate, race, and sports culture contexts to offer evidence-based training and health strategies.

Within the scope of female exercise physiology, “female ultramarathon running and the sex gap” is a topic that carries both academic depth and practical value, yet has long been misunderstood or overlooked. The knowledge accumulated in sports science over the past few decades has largely been based on studies of healthy adult males, meaning that many of the unique physiological characteristics and needs of female exercise physiology have only received systematic attention and research in recent years. In fact, adolescents, females, and special populations (such as the elderly, pregnant and postpartum women, and those with chronic illnesses) differ fundamentally from the “standard young male athlete” in terms of physiological structure, hormonal environment, developmental stage, and health context. Directly applying adult male training principles and physiological data to these groups can, at best, diminish effectiveness and, at worst, cause health damage. This is precisely why understanding “female ultramarathon running and the sex gap” is so important—it allows us to move beyond the myth of a “one-size-fits-all” approach and provide scientific guidance that truly aligns with the physiology and needs of different populations. As Taiwan moves toward an aged society, gender equality awareness rises, and youth sports participation becomes increasingly common, the local applicability of female exercise physiology is particularly prominent. This article will take you from the physiological mechanisms at the cellular and systemic levels, through empirical research in top international journals, the quantitative relationship between dose and effect, and differences in responses across populations, to directly actionable training applications and Taiwan’s local context. Finally, it will debunk long-circulated myths, ensuring your understanding of “female ultramarathon running and the sex gap” is truly built on science rather than hearsay or outdated stereotypes.

Academic Research Review

Regarding the scientific exploration of “female ultramarathon running and the sex gap,” the field of female exercise physiology has accumulated rigorous and rich evidence in recent years. Below are several representative studies selected for their value in methodological design, study populations, and strength of conclusions, which together form our current understanding:

1. Tiller et al. (2021). A Sports Medicine review of sex differences in ultra-endurance exercise, systematically organizing evidence of women’s relative advantages at extremely long distances.

2. Bam et al. (1997). The renowned South African ultramarathon study published in Medicine & Science in Sports & Exercise, observing the phenomenon of women narrowing or even surpassing the gap at ultra-long distances.

3. Waldvogel et al. (2019). Published in the International Journal of Environmental Research and Public Health, analyzing the relationship between the sex gap in ultramarathon performance and distance.

4. Deaner et al. (2015). Published in PLOS ONE, examining participation rates and physiological factors behind the sex gap in endurance performance.

Taken together, these studies show that the scientific picture of “female ultramarathon running and the sex gap” has deepened with advances in research methods and a growing awareness of “population specificity.” Early studies often interpreted data from adolescents, females, or special populations directly within the framework of adult males, overlooking the fundamental differences brought by developmental stage, hormonal cycles, aging processes, or disease context. In contrast, recent high-quality research increasingly emphasizes research methods “tailored to specific populations”—analyzing adolescents by biological maturity rather than chronological age, incorporating menstrual cycle and energy availability as control variables in female studies, and conducting stratified assessments of resistance training and cardiovascular risk in older adults. This methodological evolution allows us to progress from “treating differences as noise” to “treating differences as the core of research.” It is worth noting that this field still faces several challenges: the number of studies on females and special populations remains relatively low compared to males, sample sizes are often limited; longitudinal tracking (especially long-term development in adolescents) is costly; and ethical considerations prevent certain interventions from being conducted in vulnerable populations. Therefore, when interpreting conclusions, we must both value the population-specific insights these studies reveal and remain mindful of the level of evidence and scope of applicability—a conclusion drawn from a specific age, sex, or health status group may not necessarily be extrapolated to other groups. It is this dual caution regarding population differences and evidence quality that forms the foundation for the scientific application of female exercise physiology and is the consistent stance of this article.

Core Mechanisms

In standard marathons and middle-to-short distances, men hold an advantage due to higher maximal oxygen uptake, greater muscle mass, and higher absolute speed, with the gap between the best male and female performances being approximately 10% to 12%. However, a fascinating phenomenon is that as race distance extends to ultramarathon distances (especially over 100 km), the sex gap in performance gradually narrows, and in some extreme ultra-long races, there have even been individual cases of women approaching or surpassing top men. Several physiological bases underlie this. First, fat oxidation: women burn a higher proportion of fat during exercise and spare glycogen more efficiently. In ultra-long durations where fuel sustainability becomes a critical limiting factor, this metabolic characteristic turns into an advantage, helping delay glycogen depletion and hitting the wall. Second, fatigue resistance: women have a higher proportion of fatigue-resistant slow-twitch muscle fibers, and lower absolute strength results in less intramuscular blood flow occlusion, allowing them to better maintain output during prolonged submaximal contractions. Third, pacing and strategy: studies have observed that women tend to pace more evenly in ultramarathons, with fewer instances of starting too fast and then collapsing, and this pacing stability is extremely valuable over ultra-long distances. Fourth, there are possible differences in muscle damage and recovery. Of course, caution is needed in interpretation: the number of female participants in elite ultramarathons is far smaller than males, and the small sample size limits the statistical significance of “individual cases of surpassing.” The physiological advantage is a “relative narrowing of the gap” rather than a complete reversal. However, the important value of these findings lies in challenging the stereotype that “female endurance is inherently inferior” and revealing unique physiological characteristics that female athletes can leverage. For Taiwan’s increasingly thriving ultramarathon and ultra-distance cycling community, this means that female athletes possess innate conditions worth capitalizing on in the most demanding ultra-long challenges.

To truly understand “female ultramarathon running and the sex gap,” one must return to the unique physiological context of female exercise physiology: how the developing body, fluctuating hormones, aging systems, or disease effects alter exercise responses at the cellular, tissue, and systemic levels. The table below organizes the key points of action for this topic across different physiological levels, helping you build a complete mechanistic picture:

| Physiological Level | Key Mechanisms | Implications for Training and Health |

|—|—|—|

| Endocrine/Hormonal | Population differences in sex hormones, growth and metabolic hormones | Affects adaptation direction, energy regulation, and reproductive/skeletal health |

| Bone and Muscle | Bone mass accumulation/loss, muscle fiber composition and protein synthesis | Determines bone density, strength development, and injury risk |

| Cardiovascular and Metabolic | Population-specific characteristics of cardiac remodeling, oxygen uptake, and substrate utilization | Affects endurance performance, recovery, and long-term health |

| Neural and Psychological | Neuromuscular control, motivation, and psychosocial needs | Determines skill development, injury prevention, and sustained participation |

Special emphasis should be placed on the two dimensions of “developmental stage” and “individual differences.” The same intervention may produce vastly different or even opposite effects depending on maturity, age, sex, hormonal status, or health conditions—this is precisely where female exercise physiology is most susceptible to being misled by oversimplified recommendations. For adolescents, for example, the effects, risks, and optimal timing of a training stimulus differ before and after PHV; for females, energy availability and menstrual function are key regulators behind many physiological responses; for older adults, anabolic resistance and the rate of decline make the meaning of “stimulus intensity” different from that in younger people. “Female ultramarathon running and the sex gap” deserves in-depth exploration precisely because it can specifically influence certain key aspects of female exercise physiology. The more thoroughly you understand the mechanisms, the better you can judge “for whom, at what stage, what to do, and how much,” rather than blindly applying unsuitable general rules. This ability to adjust according to population and individual context is precisely the dividing line between those who understand female exercise physiology and those who train blindly.

Dose-Response Relationship

In female exercise physiology, “dose determines effect” is a core principle, but this dose often needs to be recalibrated for population-specific characteristics. Stimuli that are too low fail to reach the adaptation threshold and produce no benefit; loads that are too high may exceed the compensatory capacity of vulnerable populations, causing injury, developmental disruption, or health damage. The table below summarizes the dose-response correspondence for “female ultramarathon and sex differences,” serving as the most important quantitative reference when designing training and health plans for specific populations:

Dose / Condition	Physiological State	Effects and Key Points
Marathon distance	Men lead by approximately 10–12%	Dominated by absolute speed and VO₂max
50–100 km	Gap begins to narrow	Fat oxidation and fatigue resistance become apparent
>100 km ultramarathon	Smallest gap	Combined effect of stable pacing + metabolic advantages
Pacing strategy	Women are more even	Reduces late-race collapse; advantageous at ultra-long distances

As shown in the table above, the dose-response relationship in female exercise physiology often presents as a threshold-type or inverted U-shaped curve: before reaching the effective dose, benefits increase with dose; but beyond a certain critical point, not only are there no additional benefits, but risks and costs rise sharply—this is especially critical for vulnerable populations (developing adolescents, women prone to energy imbalance, and older adults with diminished compensatory capacity). This means that “finding the optimal dose for the specific population and individual” matters far more than “blindly pursuing more and stronger.” In practical application, it is recommended to continuously monitor responses using objective indicators (such as performance, recovery, health markers, and subjective feelings) and calibrate according to population characteristics and individual data. Remember: the group average in research reports is a starting point, not an endpoint; each person’s maturity, hormonal status, health background, and genetics will cause the optimal dose to shift individually. Only by calibrating with your own data and professional assessment can group science be safely translated into an individual prescription.

Differences Across Populations

The impact of “female ultramarathon and sex differences” is not equal for everyone. Age and maturity, sex, training status, hormonal state, health conditions, and genetic background all significantly modulate individual response magnitude. Ignoring these differences and applying a one-size-fits-all recommendation is one of the most common and dangerous errors in the application of female exercise physiology.

Population Dimension	Response Characteristics	Practical Recommendations
Beginners vs. advanced athletes	Advanced athletes have mature adaptations and better tolerance but smaller marginal gains	Beginners should progress conservatively, building a foundation before increasing load
Men vs. women	Differences in hormones, body composition, bone, and metabolic characteristics	Women need individualized assessment of energy, iron, and bone health
Young vs. older	Older individuals recover more slowly, have anabolic resistance, and accelerated decline	Older adults need sufficient stimulus intensity but longer recovery and screening
Developmental stage	Maturity influences adaptation direction, risk, and timing	Arrange training based on biological maturity rather than chronological age

Regarding specific population considerations for this topic: the female ultramarathon advantage is a group trend with large individual variation; the number of elite female participants is small, so the statistical significance of individual cases surpassing expectations should be interpreted cautiously.

When interpreting individual differences, one must also be wary of a statistical trap: research reports mostly present “group average responses,” but beneath the average often lies enormous individual variability. In the same intervention, some may be strong responders while others barely respond. This is why even when a study shows “average effectiveness,” you still need to combine professional assessment and your own response to confirm applicability. Taking common athletic populations in Taiwan as an example—whether it’s adolescents burdened with heavy academic workloads, women balancing family and training, or middle-aged and older adults pursuing healthy aging—correctly understanding the physiological characteristics of your own population group is the only way to avoid the ineffective or even harmful consequences of “copying someone else’s training plan.” After understanding population differences, you will realize: truly professional female exercise physiology advice is always an individualized prescription that “varies by person and by stage,” never a one-size-fits-all slogan.

Practical Training Applications

Theory must ultimately translate into actual training and health practices. Below is a practical framework for converting “female ultramarathon and sex differences” into concrete applications:

• Population matching: All training and health recommendations must first ask, “Is this appropriate for this population?”—adolescents prioritize development and protection, women prioritize energy and bone health, and older adults prioritize safety and functional maintenance; the starting points differ for each.

• Progression and monitoring: Progress gradually from an appropriate starting point, continuously monitoring responses with objective indicators (performance, recovery, health markers) and subjective feelings, dynamically adjusting based on individual conditions.

• Health over performance: For vulnerable populations, long-term health (development, bone, endocrine, cardiovascular) always takes precedence over short-term performance; never sacrifice health for temporary numbers.

• Holistic context: Training is only one piece of the puzzle; sleep, nutrition (especially energy availability), recovery, psychological and social support are equally critical—no single intervention can compensate for overall imbalance.

• Professional collaboration: When dealing with growing adolescents, female-specific health issues, or older adults and those with chronic conditions, seeking collaborative assessment from coaches, medical professionals, nutritionists, and psychologists in a timely manner is the safeguard for safety and effectiveness.

As an example of practical planning, when designing a program, one should first clarify the population characteristics and health context of the individual, then set reasonable goals, doses, and monitoring indicators accordingly. The most common mistake people make is directly applying practices seen on social media or in elite adult athletes to adolescents, women, or older adults, ignoring the underlying physiological differences—this is precisely what female exercise physiology strives to avoid. Daily training and life itself serve as the best laboratory for observing population and individual responses and building personalized data.

It is recommended to integrate training logs with health monitoring, recording key indicators (such as growth and injuries in adolescents, menstrual and iron status in women, strength and recovery in older adults) alongside training content and physical responses. After weeks to months of accumulation, the value of this personalized database will far exceed any general guideline. Furthermore, don’t overlook the often-underestimated component of “recovery and long-term development”—for vulnerable populations, over-pursuing short-term progress at the expense of recovery and health often leads to injury, burnout, or health problems, ultimately stalling the engine of long-term progress. Treat population matching and health priority as core training principles with genuine seriousness, and both your results and safety will be markedly different.

Local Applications in Taiwan

Taiwan’s unique climate, terrain, social structure, and sports culture add distinctive local color to the application of “female ultramarathon and sex differences.” Climatologically, hot and humid summers and cold and damp winters pose additional challenges for different populations (especially adolescents and older adults with different thermoregulatory capacities); topographically, the extreme elevation gain from sea level to Wuling at 3,275 meters provides a rich training environment; socially, Taiwan is entering an aged society, faces heavy academic pressure, and has rising gender equality awareness—all of which profoundly affect the exercise circumstances of various populations.

Taking local contexts as examples: adolescent athletes often face dual pressures from academics and training, lacking systematic recovery and long-term development planning; female sports enthusiasts face insufficient attention to energy availability, iron, bone health, and female-specific health issues; older adults need friendly, safe environments and communities that accommodate different abilities. Leveraging Taiwan’s dense convenience store supply points, diverse cycling and running routes, and growing sports communities, while designing population-appropriate activities (such as multi-sport development for adolescents, women-friendly gear and environments, and group rides for older adults), is the way to truly implement female exercise physiology science for every sports enthusiast in Taiwan, promoting health and sports participation for all.

Common Myth-Busting

Myth: “Women running ultramarathons are definitely much slower than men.” As distance increases, the sex gap narrows significantly; women have advantages in fat oxidation, fatigue resistance, and pacing stability; at the most extreme ultra-long distances, the sex gap may narrow substantially.

This type of myth spreads widely often because it “sounds reasonable,” is easy to pass along by word of mouth, or stems from inappropriately applying adult male concepts to other populations. Yet the value of science lies precisely in testing intuition with rigorous evidence: many seemingly self-evident notions fail to hold up under rigorous research on specific populations. The field of female exercise physiology is especially rife with outdated stereotypes and oversimplified claims that compress complex population differences, developmental stages, and individual variability into a single slogan. The next time you hear a categorical exercise recommendation aimed at adolescents, women, or special populations, it’s worth asking: “What is the level of evidence for this claim? Was it studied in this population? Or is it a conclusion from another group being directly applied here?” Cultivating this evidence-based, population-specific critical thinking is more valuable than memorizing any single conclusion, and it is a key step toward making female exercise physiology more scientific and preventing harm.

Conclusion

“Women’s Ultramarathon and the Gender Gap” is a topic in female exercise physiology that combines both theoretical depth and practical value. As can be seen from the international journal evidence reviewed in this article, adolescents, women, and special populations have unique physiological characteristics and needs—they are by no means “scaled-down” or “special-case” versions of adult men. Understanding and respecting these differences is precisely the starting point for scientific, individualized training. The key lies in grasping the mechanisms, calibrating the dosage, adjusting according to population and individual, and always prioritizing long-term health over short-term performance. For sports enthusiasts in Taiwan, while mastering scientific principles, it is equally important to integrate local climate, environmental, and social contexts, transforming general principles into prescriptions suited to one’s own population and individual needs. May every adolescent, woman, and older adult who sweats through exercise on their growth journey and at every stage of life safely, healthily, and sustainably enjoy the joy and benefits of sport through the wisdom of female exercise physiology. The value of sport has never been limited by age, gender, or circumstance—let science become a force that benefits everyone.

Related Reading

• The Impact of Media Coverage on Women’s Sports: A Study on Gender Equality in Sports Media
• The Benefits of Resistance Training for Women: A Study Comparing Differences and Mechanisms with Men
• Sex Differences in Heat Adaptation: A Study on Sweat Rate and Core Temperature Regulation
• Sex Differences in Cardiac Adaptation: An Echocardiographic Study on Sex-Specific Athlete’s Heart