Why Women May Have the Edge in Ultramarathons

When Rachel Entrekin crossed the finish line of the Cocodona 250 this year, she didn't just win the women's race. She won the whole thing. Outright. Beating every man on the course to become the first woman to claim the overall title at this 235-mile race through the Arizona desert, while setting a new course record in the process.

It's a result that stopped the ultrarunning world in its tracks. But for researchers studying extreme endurance performance, it wasn't entirely surprising. A growing body of evidence suggests that highly trained women don't just compete with men at ultra distances. Under the right conditions, they may actually outlast them.

What the Cocodona 250 Result Actually Signals

The Cocodona 250 is one of the most demanding events in the sport. Covering approximately 235 miles across Arizona's rugged trail systems, with significant elevation change and unrelenting desert heat, it tests nearly every physiological system a human body has. Finishing is an achievement. Winning overall is something else entirely.

Entrekin's victory didn't come from a single dominant day. It was built over hundreds of miles of sustained, smart effort, a performance that held together when others, many of them male competitors with strong 100-mile credentials, began to unravel. That pattern, a woman maintaining pace and form while men slow down, is showing up more frequently at the longest end of the sport.

It's also a reminder that if you're training for extreme distances, understanding how to handle prolonged heat exposure may be one of the most underrated variables in your preparation.

The Science Behind Physiological Durability

Researchers studying ultra-endurance performance have started using the term physiological durability to describe something specific: how well an athlete maintains their physical capabilities over extreme durations. Not just fitness, but resistance to the breakdown that accumulates over hours and days of continuous effort.

The emerging picture is striking. Studies examining performance degradation across long-duration events have found that highly trained women tend to show less decline in key metrics, including running economy, substrate utilization, and neuromuscular function, as events extend beyond 100 miles. Men, on average, show steeper performance curves over the same timeframes.

Several mechanisms appear to be at play. Women generally rely more heavily on fat oxidation as a primary fuel source during sustained aerobic effort, which becomes a meaningful advantage when glycogen stores are depleted and events stretch across multiple days. Hormonal profiles may also contribute to a more resilient inflammatory response, potentially reducing the acute muscle damage that accumulates during extreme efforts.

There's also evidence pointing to differences in pacing behavior. Research consistently shows that women tend to pace more evenly across long events, while men are more likely to go out faster and slow significantly in the back half. At 26.2 miles, that gap is manageable. At 235 miles, it can be race-defining.

Why the Performance Gap Narrows at Extreme Distances

The standard narrative about sex differences in endurance sport is straightforward: men are faster, they have more lean muscle mass, higher hemoglobin concentrations, and greater maximal oxygen uptake. At shorter distances, those advantages are real and significant. The performance gap between elite men and women sits at roughly 10 to 12 percent in events from 5K through the marathon.

But that gap shrinks as distance increases. Research analyzing finish-time differentials across race distances has found the gap narrows progressively past the marathon, and some studies suggest it may approach or reach parity at distances beyond 150 to 200 miles. Entrekin's result is one of the most visible real-world data points yet to support that model.

The reason isn't that women's aerobic capacity magically catches up. It's that the physiological traits men benefit from at shorter distances become less decisive, while the traits that favor women, fat-burning efficiency, durability under sustained metabolic stress, more conservative pacing, become increasingly important.

Think of it like a race between a sports car and a diesel truck. At 10 miles, the sports car wins easily. At 1,000 miles, you'd want to be in the diesel.

Nutrition as a Critical Variable

One area where the durability advantage for women may be most actionable is nutrition strategy. If women are genuinely better at oxidizing fat over long durations, that has direct implications for how you fuel across a multi-day race or a very long training block.

It doesn't mean ignoring carbohydrates. Carbohydrate fueling remains essential for high-intensity segments and for protecting cognitive function late in races. But it does suggest that female ultra runners may benefit from training their fat-burning systems more deliberately, particularly through longer fasted aerobic sessions and structured back-to-back long runs.

Protein intake also matters more than many athletes realize in the context of multi-day events. Muscle repair doesn't stop because you're still racing. If you're interested in the research on how protein timing and volume affect recovery during heavy training, the science on protein for muscle building and repair offers a useful framework even for endurance athletes.

Supplement quality is another variable that becomes particularly important when you're training at high volumes. Athletes pushing 80 to 120 miles per week are often supplementing heavily, and the risks of contaminated products are real. understanding supplement contamination risks should be part of every serious ultra runner's prep, not an afterthought.

What This Means for Training Structure

If physiological durability is a genuine advantage for highly trained women, it should show up in how you structure your training, not just your racing.

The most relevant application is the back-to-back long run. Running long on consecutive days, typically Saturday and Sunday in most training programs, has been a staple of ultra preparation for years. But research on durability suggests that women may respond particularly well to this format, building the kind of fat-adapted, fatigue-resistant fitness that pays dividends in the final third of a long race.

The key variables to manage are:

Duration over intensity: Back-to-back runs work best at a genuinely easy pace. The goal is cumulative time on feet, not speed.
Recovery between blocks: Easy days need to be genuinely easy. One common mistake is treating all non-hard days as moderate, which blunts the adaptation you're chasing.
Progressive overload across months: Durability is built slowly. Adding volume too quickly is the fastest way to break down the resilience you're trying to develop.
Simulating race conditions: Training on terrain, in temperatures, and at elevations similar to your target race is essential. If you're racing at altitude, knowing how altitude affects your physiology and pacing is a non-negotiable part of your prep.

For women targeting races beyond 100 miles, building a long base phase, potentially 16 to 24 weeks of steady volume before introducing race-specific intensity, appears to compound the natural durability advantages the research is pointing to.

Pacing Strategy Deserves More Attention

One of the clearest practical takeaways from both Entrekin's race and the underlying research is that pacing is not just a tactical decision. It's a physiological one.

Starting conservatively in a 200-plus-mile race isn't caution. It's efficiency. The athletes who try to bank time in the first 50 miles are making a metabolic withdrawal they'll pay back with interest somewhere around mile 150. The athletes who run within themselves early, trusting the durability they've built in training, tend to be the ones still moving strongly when others are walking or stopping entirely.

This is where female ultra runners may have a behavioral as well as physiological edge. The research on pacing consistency across long events consistently shows women executing more even splits. Whether that's driven by culture, coaching, physiology, or some combination of all three, the outcome is the same: less blowup risk, more resilience in the final stretch.

If you're currently building toward a fall ultra, the structural decisions you make now, how you balance volume, recovery, and race-specific simulation, will shape how durable you are on race day. What you do in the early training months matters far more than most athletes realize.

The Bigger Picture

Rachel Entrekin's win at the Cocodona 250 is a landmark result. It's the kind of performance that gets people talking, and rightly so. But it's most useful when it's understood not as an outlier, but as evidence of something that research has been quietly building the case for over several years.

At the very longest distances, the physiological playing field doesn't just level out. It may tilt. Women who train specifically for the demands of ultra-endurance, who build durability through smart volume, sound nutrition, and disciplined pacing, may find that the traits that limit them in shorter races become their greatest assets when the miles really start to stack up.

The sport is paying attention. The science is catching up. And the finish lines are starting to reflect both.