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Top trail runners mix running and walking on steep terrain, but even scientists aren't sure how we choose which is better

There was a time, in my younger days, when I thought I would never walk during a run. I abandoned that philosophy about two-thirds of the way up a mountain in Slovenia, where I was competing in the 2010 World Mountain Running Championships. The course climbed a little over 4,000 feet in 7.5 relentless miles. During one particularly steep section, I finally gave in and started to walk. To my surprise, I didn’t lose any ground to the runners around me. Lesson learned, and I’ve been less dogmatic ever since.

I’m not alone, though. Even among serious trail runners, there’s sometimes a tendency to keep running at all costs, according to Jackson Brill, a Salomon-sponsored trail runner and graduate student in Rodger Kram’s Locomotion Laboratory at the University of Colorado. But when the hills get steep enough, walking becomes inevitable—and the decision about when to switch back and forth between gaits is among the key tactical choices trail competitors have to make. As it happens, Brill and his colleagues have been researching this problem for several years, and a pair of recent studies offer some interesting new insights. The bottom line: “Our research,” Brill says with tongue in cheek, “gives people permission to walk if they want.”

Yes, It’s Running

To understand the transition between running and walking, you have to start with a simpler question: is there really any difference between them on the steepest slopes? Under normal circumstances, one of the key distinctions between the two gaits is that you always have at least one foot on the ground when you’re walking, whereas you leave the ground between each step when you’re running. But that rule of thumb breaks down on steep hills: even when you’re “running,” you never fully lose contact with the ground.

Not convinced? Take a look at this 2015 video of former Locomotion Lab researcher Wouter Hoogkamer running on the world’s steepest treadmill, which is jury-rigged to go all the way up to 45 degrees (i.e. a 100 percent grade). He looks to me like he’s running, but he always has one foot on the ground.

Kram and his team broke out this same treadmill, which has been used for a bunch of previous uphill running research, for a study published over the summer in the European Journal of Applied Physiology. Led by first author Clarissa Whiting, a former Penn track star, the researchers recruited ten elite trail runners and had them run or walk on level ground and with the treadmill set to 30 degrees. That’s steep: typical gym treadmills only go up to about nine degrees, and black diamond ski runs tend to be around 30 degrees.

Sure enough, even though the runners always had one foot on the ground, there were distinctive differences between uphill running and walking. One clue was the stride pattern: on the slope, cadence was 40 percent quicker for running than walking, and feet stayed on the ground for 40 percent less time—a similar pattern, though less pronounced, to what you’d see on level ground.

But the smoking gun came from an accelerometer clipped to the subjects’ waistbands, which measured the rise and fall of their center of mass. On level ground, walking produces two distinct acceleration peaks, one as you land and one as you push off. Running, in contrast, is a series of hops from one leg to the next, producing just one acceleration peak as you land and take off. The accelerometers found exactly the same patterns on the inclined treadmill, confirming that steep uphill running really is running, and not just some sort of bouncy fast-walk.

The Transition

That’s intellectually interesting, but in practice you’ll almost certainly be walking up any 30-degree hills you encounter. So in a separate study that’s currently under review (but available online as a preprint), Brill and Kram recruited another ten elite trail runners to run at zero, five, ten, and 15-degree slopes. The goal was to understand what prompts people to switch from a run to a walk or vice-versa, and determine whether our natural inclinations also correspond to the most efficient approach.

There’s been lots of research on the walk-run transition on level ground. At slow speeds, we burn less energy walking than running; at fast speeds, it’s the other way around. Scientists used to assume that the decision to switch from walking to running was simply a matter of sticking with the most efficient stride. But a series of studies since the 1990s have found that we actually tend to break into a run at slightly slower-than-expected speeds, when walking would actually be more energetically efficient.

There’s no consensus on why this happens, but one theory is that certain muscles in the calves or shin get fatigued or have trouble producing enough force during fast walking, so it’s more comfortable to run even if it costs a bit of extra energy. This makes intuitive sense: think about the feeling of walking so fast that you decide to break into a run. You switch because it’s uncomfortable, not because you’re out of breath.

Brill and Kram found that this pattern persisted at slopes up to ten degrees: the subjects switched from walking to running at a slower speed than the energetically optimal transition. But at the steepest slope of 15 degrees, the difference disappeared and they started running precisely when it became more efficient than walking. Once you’re going up a steep enough hill, it’s hard work regardless of whether you’re walking or running, so it appears that the desire to save energy and be as efficient as possible takes over.

Into the Wild

There’s another more subtle difference between level ground and steep uphills, Kram points out. On the flats, there’s not much ambiguity about whether you should walk or run. At any given speed, one feels right and the other feels wrong. In the mountains, on the other hand, there’s a pretty broad range of conditions where the decision is ambiguous. When you’re walking, you get the feeling that you’d probably be more comfortable running. And that may be true for a brief period of time after you switch, but pretty soon you get the sense that walking might have been more comfortable after all. There’s no stable equilibrium; you oscillate back and forth.

Another detail from Whiting’s study offers some possible insight on this. She attached electrodes to four different leg muscles in her subjects to compare muscle activation under the various testing conditions. The soleus, one of two main calf muscles, showed 36 percent less activity per stride during steep uphill running than during steep uphill walking, which is consistent with the idea that local muscle fatigue triggers the transition. You walk until your legs—and perhaps the calves in particular—get too uncomfortable. Then you start running, which initially feels better but eventually leaves you more out of breath, so you switch back to walking, and the cycle repeats.

For a competitive trail runner like Brill, it would be nice to take away some practical insights about when to switch. In his study, he also tested heart rate as a proxy for figuring out the most efficient transition point. While the heart rate values did correlate with energy consumption, there was too much individual variation to make it useful in the real world. Brill’s next study, when pandemic, fire, and other disruptions permit, will involve trail runners walking, running, or choosing their own mix of the two while climbing an actual mountain. The goal, after all, is to be as fast as possible, not as efficient as possible.

For now, Brill will stick to the approach he’s figured out through trial and error, relying on his intuition about which gait feels best at any given moment. He tries not to switch back and forth too frequently, sticking with each gait for at least 15 to 30 seconds. He doesn’t consult a heart-rate monitor. “It’s great that we’ve done all this research,” he says. “But when I hit the trail I pretty much throw it out the window.”

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Most Olympic marathoners spend their youth focused on running. They join track clubs, compete in national championships, and pursue the sport from an early age.

Julia Mayer’s journey was very different.

Today, Mayer is Austria’s marathon record holder, a multiple national record holder on the roads, and an Olympian. Yet for much of her athletic life, running was not her primary sport.

For 16 years, she played soccer.

Then she discovered something that would change her life.

“I noticed that I was really fast in the fun runs and that it was really, really fun,” Mayer said when reflecting on her transition from soccer to distance running.

What began as curiosity quickly became a passion. She eventually made the bold decision to leave soccer behind and focus entirely on running. It was a move that surprised many people around her, but Mayer believed she had found her true athletic calling.

The decision proved to be the right one.

Within a few years, Mayer developed into one of Europe’s top marathon runners. Her steady improvement carried her from local races to the international stage, where she began rewriting Austria’s record books.

She now holds Austrian records in the marathon, half marathon, and road 10K. Her marathon best of 2:26:08 established her as the fastest female marathoner in Austrian history. Her performances in the half marathon and 10K have further cemented her place among the country’s all-time great distance runners.

Her rise culminated with qualification for the 2024 Olympic Games in Paris.

Competing in the Olympic marathon represented the realization of a dream. On one of the most challenging marathon courses ever used for the Olympics, Mayer ran courageously against the strongest field in the world and finished 55th in her Olympic debut.

Behind the scenes, success has come through extraordinary dedication. During marathon preparation, Mayer trains twice a day and covers approximately 200 kilometers, or 124 miles, each week. The workload demands discipline, patience, and a deep commitment to continuous improvement. 

What makes her story especially inspiring is not simply the records or the Olympic appearance.

It is the fact that she found her greatest talent later than many elite runners.

In a sport where athletes are often identified at a young age, Mayer’s journey serves as a reminder that potential does not always reveal itself early. Sometimes it takes years of experience, a willingness to try something new, and the courage to follow a different path. 

The former soccer player who once chased a ball across a field is now chasing history on the roads of Europe.

And according to those closest to her, her best performances may still be ahead.

For runners of every age and ability, Julia Mayer’s story delivers a powerful lesson: it is never too late to discover what you are capable of.

From soccer player to Olympian, her journey proves that remarkable achievements can begin when least expected.

Megan Keith produced the performance of her career in Oslo on Thursday night, shattering one of Scotland’s longest-standing distance running records and cementing her place among Britain’s greatest female 3000m runners.

The 24-year-old clocked a sensational 8:28.35 over 3000m, breaking the Scottish outdoor record that had stood for nearly four decades. In doing so, Keith eclipsed the previous mark of 8:29.02, set by Scottish legend Yvonne Murray back in 1988, ending a record reign that had lasted 38 years.

Keith’s breakthrough run was more than just a national record. The performance also propelled her to third on the UK outdoor all-time list, placing her behind only two of Britain’s most celebrated distance runners — Paula Radcliffe, who leads the rankings with 8:22.20, and Laura Weightman, whose 8:26.07 remains the second-fastest outdoor mark by a British woman.

The significance of Keith’s achievement is amplified by the calibre of athletes she now joins in the record books. For decades, Murray’s mark stood as one of Scottish athletics’ most untouchable records, surviving generations of elite competitors. Keith has now succeeded where many outstanding runners have fallen short, announcing herself as one of the leading distance talents in British athletics.

Her time also compares favourably with the best performances produced indoors. Olympic medallist Laura Muir ran 8:26.41 indoors in Karlsruhe in 2017, underlining just how exceptional Keith’s outdoor effort in Oslo truly was.

The run continues a remarkable rise for the Scottish star, whose progression over recent seasons has transformed her from a promising prospect into a genuine force on the international stage. Running with confidence and composure against elite competition, Keith demonstrated both the speed and endurance required to challenge the very best in Europe and beyond.

With the World Championship season gathering momentum, Keith’s record-breaking display sends a powerful message. Not only has she etched her name into Scottish athletics history, but she has also established herself as a serious contender in one of the sport’s most competitive events.

In Oslo, Megan Keith did far more than break a record. She ended a 38-year wait, climbed into the upper echelon of British distance running, and delivered a performance that may prove to be a defining moment in her career.

British middle-distance talent Phoebe Gill took another significant step forward in her return to top form, producing a determined victory over 800 metres at the Meeting de Marseille in France on Wednesday.

Competing in challenging, wind-affected conditions, the 19-year-old demonstrated both resilience and composure as she held off a late charge from Switzerland's Veronica Vancardo to secure the win in 2:00.81. Vancardo finished just three hundredths of a second behind in 2:00.84, underlining the fiercely contested nature of the race.

While the margin of victory was narrow, the result represented another encouraging milestone for Gill as she continues to rebuild momentum following her injury setback. The young Briton showed impressive race awareness and strength in the closing stages, maintaining her advantage despite the difficult conditions that made fast running a challenge throughout the evening.

The Marseille triumph adds to a growing body of evidence that Gill is steadily progressing toward her best form. Earlier in her comeback campaign, she clocked 2:01.50 for 800m in Bydgoszcz before demonstrating her versatility with a strong 4:05.53 performance over 1500 metres at the BMC Grand Prix meeting in Trafford.

Those performances have highlighted not only her improving fitness but also her ability to compete across multiple distances as she carefully builds her season. The Marseille victory now provides further confirmation that the European junior star is moving in the right direction.

Gill emerged as one of Britain's most exciting middle-distance prospects through a series of breakthrough performances as a teenager, earning widespread recognition for her fearless racing style and remarkable maturity. Injury temporarily interrupted that upward trajectory, but her recent results suggest she is steadily rediscovering the form that made her one of the sport's brightest young talents.

With each race, the signs of progress become increasingly evident. Winning in difficult conditions and under pressure from a quality field is often a stronger indicator than a fast time alone, and Gill's latest success demonstrated exactly those qualities.

As the summer season gathers pace, the Marseille victory offers another confidence boost for the British teenager, whose return continues to gain momentum. If her recent progression is any indication, Gill could soon find herself back among the leading names on the European middle-distance circuit. 

The NCAA Track and Field Championships delivered a moment few could have predicted as Ja’Kobe Tharp produced one of the most astonishing performances in the history of sprint hurdling, rewriting the record books in spectacular fashion.

Competing in the opening round of the men’s 110-meter hurdles, the Auburn star stunned the athletics world by clocking an incredible 12.75 seconds, becoming the first athlete ever to break the 12.80-second barrier. In doing so, he eclipsed the long-standing world record of 12.80 set by Aries Merritt in 2012, a mark that had stood as one of the sport’s most revered achievements for more than a decade.

What makes Tharp’s breakthrough even more remarkable is the scale of his improvement. Entering the championships, the defending NCAA and U.S. champion had recorded a season-best of 13.05 seconds. Yet under the brightest spotlight, he unleashed a performance that exceeded every expectation, slicing an extraordinary 0.26 seconds from his personal best in a race that instantly became one of the greatest ever run.

The achievement sent shockwaves throughout the track and field community. While Tharp arrived in Eugene as one of the leading contenders for the NCAA title, few envisioned a performance capable of redefining the limits of the event. Instead, the American hurdler delivered a race for the ages, combining flawless technique, explosive speed, and impeccable rhythm from the first hurdle to the finish line.

The historic run not only secured his place in athletics history but also transformed the outlook of the championship. With the world record now in his possession, Tharp advances to the final as the overwhelming favorite, carrying momentum that could make an already unforgettable weekend even more extraordinary.

For years, the 12.80 barrier appeared untouchable. On a stunning day at the NCAA Championships, Ja’Kobe Tharp proved otherwise, producing the kind of performance that reminds fans why sport remains so unpredictable. In a matter of seconds, he turned a routine qualifying round into a landmark moment that will be remembered for generations.

The world record no one saw coming is now a reality—and Ja’Kobe Tharp is the man who changed history.

A new chapter in middle-distance running may have begun in Oslo after American teenager Cooper Lutkenhaus produced one of the most remarkable performances of the season, narrowly defeating reigning Olympic champion Emmanuel Wanyonyi in a thrilling men's 800m contest at the Diamond League meeting.

The 17-year-old sensation shocked a world-class field by crossing the finish line first in a race that came down to the smallest of margins. After an intense battle over the final metres, Lutkenhaus held off Wanyonyi by just one hundredth of a second, producing a dramatic finish that left the packed stadium in disbelief.

From the opening lap, the pace was relentless as the leading contenders positioned themselves for a fierce showdown. As the athletes entered the home straight, Wanyonyi appeared poised to unleash his trademark finishing kick. However, Lutkenhaus refused to be intimidated, matching the Olympic champion stride for stride before producing a perfectly timed lean at the line to secure a historic victory.

The result marks a breakthrough moment for the young American, who continues to establish himself as one of the brightest talents in global athletics. Defeating an Olympic champion at a Diamond League event is a feat many athletes spend entire careers pursuing, yet Lutkenhaus achieved it before reaching adulthood.

For Wanyonyi, the narrow defeat does little to diminish his status as one of the world's premier 800m runners. The Kenyan once again demonstrated his exceptional class and competitiveness, pushing the race to a world-class standard and forcing his young rival to deliver the performance of a lifetime.

Beyond the result itself, the race offered a glimpse into what could become one of the sport's most exciting rivalries in the years ahead. With established stars and emerging talents now pushing each other to new heights, the men's 800m continues to evolve into one of athletics' most captivating events.

On a memorable night in Oslo, the spotlight belonged to Cooper Lutkenhaus. At just 17 years old, he stood toe-to-toe with an Olympic champion and emerged victorious, announcing himself to the athletics world in spectacular fashion.