The question of whether women possess greater physical endurance than men is complex, defying a simple yes or no answer. Endurance is the ability to sustain a physical effort over time, and the comparison between sexes depends on the specific type, intensity, and duration of the effort. While men generally hold an advantage in short, high-power activities, the performance gap narrows significantly, or even reverses, as the physical challenge extends into hours or days. Biological differences in metabolism, muscle composition, and fatigue resistance explain these varying outcomes.
How Endurance is Measured
Scientists quantify physical endurance using several metrics that differentiate between the body’s maximum capacity and its sustainable work rate. Maximal oxygen consumption (\(\text{VO}_2\text{max}\)) is the most common measure of aerobic capacity, representing the maximum oxygen the body can utilize during intense exercise. Because men typically have greater muscle mass and higher hemoglobin concentrations, they generally exhibit a higher absolute \(\text{VO}_2\text{max}\), which contributes to performance differences over shorter distances.
A more practical measure of sustainable effort is the lactate threshold. This threshold represents the highest intensity of exercise an individual can maintain without a rapid accumulation of lactic acid. Athletes who can sustain a higher percentage of their \(\text{VO}_2\text{max}\) for a prolonged period are considered to have superior endurance.
Researchers also use time-to-exhaustion protocols, where a person exercises at a fixed, submaximal intensity until they can no longer continue. These tests range from dynamic activities like running to localized efforts like maintaining an isometric contraction. These methods highlight distinct physiological advantages related to either systemic aerobic fitness or localized muscle fatigue resistance.
Physiological Factors Influencing Sex Differences
Differences in endurance performance are driven by hormonal influence on fuel utilization and muscle fiber characteristics. Higher levels of estrogen in women play a significant role in altering metabolism during prolonged exercise. Estrogen promotes the oxidation of fat for fuel, which is an efficient energy source with vast reserves.
This enhanced fat oxidation capacity allows women to conserve glycogen stores in the muscles and liver. Since glycogen is the preferred fuel for high-intensity efforts, this glycogen-sparing effect provides a metabolic advantage that becomes more pronounced as exercise duration increases. This difference in substrate utilization means women are often more efficient at a given submaximal workload.
Women also tend to have a greater proportional area of Type I muscle fibers, or slow-twitch fibers. These fibers are highly oxidative and inherently more resistant to fatigue than the larger, powerful Type II (fast-twitch) fibers. This muscle composition contributes to greater overall fatigue resistance during prolonged, steady-state activities.
Performance in Ultra-Endurance Events
The metabolic and muscular advantages of women become most relevant in extreme, long-duration athletic events exceeding six hours. In traditional races like marathons, men consistently outperform women by 10 to 12% due to their higher absolute aerobic capacity (\(\text{VO}_2\text{max}\)) and greater muscle mass. However, in ultra-endurance sports, such as 100-mile or multi-day running events, this performance gap narrows substantially, sometimes shrinking to as little as 4%.
This diminishing gap is linked to the depletion of glycogen stores, which forces the body to rely on fat as the primary fuel source. The metabolic efficiency of fat oxidation, promoted by estrogen, allows female athletes to maintain their pace more consistently without “hitting the wall.” Studies show female ultra-runners often display more even pacing strategies and less performance drop-off in the later stages of a race.
In the most extreme long-distance events, such as those exceeding 195 miles, women have occasionally won the race outright, beating all male competitors. These instances highlight the potential for female physiology to excel when the challenge shifts from maximizing speed to maximizing sustained effort and resilience.
Localized Muscle Fatigue vs. Whole-Body Endurance
A distinction exists between whole-body aerobic endurance, which relies on the cardiopulmonary system, and localized muscular endurance, which relates to a specific muscle group’s fatigue resistance. When tested on single-joint, submaximal tasks, such as maintaining an isometric contraction, women frequently demonstrate greater resistance to fatigue than men. For example, women have maintained contractions in elbow flexors for a significantly longer absolute time in studies.
This localized fatigue resistance is often explained by differences in muscle size and strength. Because men have greater absolute strength, a fixed submaximal task requires a higher percentage of blood flow restriction in their larger muscles, which hastens fatigue. When the task is performed at a relative intensity, women’s smaller, fatigue-resistant Type I fibers, coupled with superior blood flow maintenance, allow them to sustain the effort longer.
Men maintain an advantage in activities where absolute strength and high \(\text{VO}_2\text{max}\) are the limiting factors. Conversely, women exhibit a greater capacity for sustained, low-intensity, or repetitive efforts, both systemically through metabolic advantage and locally through intrinsic muscle characteristics. The definition of “endurance” determines which sex demonstrates the superior capability.