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Contrary to what scientists once thought, even superficial cooling is enough to interfere with muscle oxygen supply.

The human body is an engine with efficiency similar to a car engine. In both cases, about three-quarters of the energy consumed is released as heat. That’s why it’s easy to heat the interior of a car: just blow some of that heat from the engine into the cabin. And it’s why endurance athletes worry a lot about getting too hot but mostly view cold as a minor annoyance rather than a fundamental limit on performance. If you’re pushing hard enough, you won’t be cold for long—right?

But new research published in the Journal of Applied Physiology suggests that cold really does diminish endurance performance. That’s contrary to what some previous research has found, but those earlier studies often involved volunteers who were ushered into a cold room and then immediately asked to exercise without waiting for their body temperatures to drop. In the new study, the volunteers got cold—and then stayed cold, no matter how hard they exercised. That’s a lesson that winter athletes will want to keep in mind next time they’re lingering in frosty air before a workout or a race.

The study was led by Phillip Wallace as part of his doctoral work in Stephen Cheung’s Environmental Ergonomics Laboratory at Brock University in Canada. Cheung is a serious cyclist whose lab has produced a bunch of interesting endurance-related research that I’ve written about previously on topics like heat, hydration, and self-talk. Cold research, on the other hand, usually focuses on safety-related topics like hypothermia and frostbite.

The new study compared cycling performance in four different conditions. In the control “thermoneutral” condition, the subjects sat in a temperature-controlled chamber set at 72 degrees Fahrenheit (22 Celsius) for 30 minutes. Then they started cycling with five minutes of warm-up at 100 watts before pedaling to exhaustion at 70 percent of VO2 max, which took on average just under 24 minutes. In the “cold shell” condition, the chamber was set to 32 degrees Fahrenheit (0 Celsius) and a wind speed of about one meter per second was added. Half an hour in these conditions was enough to significantly decrease skin temperature without dropping core temperature (as measured with a rectal thermometer) before starting the cycling test.

For the other two conditions, the subjects—ten men with an average age of 27—stayed in the 32-degree Fahrenheit chamber for long enough to drop their core temperatures by 0.9 or 1.8 degrees Fahrenheit (0.5 or 1.0 Celsius) before cycling, imposing mild hypothermia. Because of differences in body size, shape, and composition, people cool at different rates, but on average it took 116 minutes to reach the first threshold. For the second threshold, the average was 160 minutes, though three of the subjects didn’t cool all the way before hitting the maximum cooling time imposed by the research ethics board. During all the cooling trials, the subjects wore a T-shirt or cycling jersey and cycling shorts plus earmuffs, winter gloves, and a fleece blanket around their shoes—added warmth that turned out to be necessary during pilot testing.

There are a bunch of reasons you might expect endurance to suffer in the cold. Even with just a cold shell, your peripheral blood vessels will constrict, decreasing the flow of oxygen to your muscles. Cold also has more subtle effects on the chemistry of how oxygen is transported in the blood. And once you start shivering, you can burn a substantial amount of energy: in this study, the metabolic heat generated by the subjects doubled from the equivalent of about 10 percent of VO2 max in the thermoneutral condition to 20 percent in the hypothermic conditions. Shivering can also interfere with muscle contraction and coordination, and may even fatigue the muscles themselves.

Despite all these negatives, previous studies with similar cycling tests at 70 percent of VO2 max found that performance in 37 to 39 degrees Fahrenheit was either unaffected or even improved compared to moderate temperatures. Wallace’s results with pre-cooling were dramatically different, though. Time to exhaustion on the bike dropped from 23.8 to 16.2 minutes in the cold shell condition, 8.5 minutes in the first hypothermia condition, and 6.5 minutes in the second one. The results provide clear evidence that skin cooling alone is enough to reduce endurance by about 30 percent, and core cooling takes away another 30 to 40 percent.

It’s interesting to look at how the core temperatures evolved over the course of the time trials. Here’s a graph showing changes in temperature for thermoneutral (TN), cold shell (CS), and the two hypothermia (HYP) trials:

For both thermoneutral and cold shell, core temperature rises steadily through the time trial, as you expect from running a heat-generating engine to its limits. For the two hypothermia trials, on the other hand, the curve is almost flat, even though they’re cycling at exactly the same power output in all four trials. In fact, the core temperature even decreases during the first quarter of the trial, perhaps because warm blood is being pumped to peripheral muscles and cold blood is being shunted back to the core. The nuances of how heat is stored and moved around within the body are complex, but the upshot is that even cycling to exhaustion isn’t enough to warm you up if you’ve lingered for long enough in temperatures around the freezing mark.

One variable that’s hard to control is the mental effects of sitting around in a cold chamber for several hours. Physiology aside, you have to imagine that in those trials, the subjects just wanted to go home rather than ride a bike. As expected, their pre-ride motivation was lower, dropping from an average of three on a four-point scale in the thermoneutral trial to 2.5 and 2 in the hypothermia trials. Their initial perception of exertion when they started riding was also higher: 12 and 12.5 rather than 9.5 on the Borg scale, which measures exertion on a scale from 6 to 20. But by the end of the ride, the riders hit a max of 20 in all four conditions—so it’s not like they were unable or unwilling to push themselves.

The revelation that being really cold is bad for endurance may not seem that surprising. The most interesting distinction here, I think, is between exercising in the cold and being cold before you start exercising. One of my pathological neuroses as a runner is the fear of hearing the starting gun fire while I’m still wrestling to get my sweatpants off over my racing shoes. As a result, I often strip off my warm-ups well before the start even in sub-freezing temperatures. If there’s one idea I’ll take away from Wallace’s research, it’s that I need to invest in some tearaway pants.

Ethiopia’s Fotyеn Tesfay Haylu delivered one of the most remarkable women’s half-marathon performances ever seen on American soil on Sunday, powering to a commanding victory at the 2026 Buenos Aires Half Marathon in Argentina in 1:03:57.

Running with exceptional confidence and strength, Tesfay took control of the race and produced a superb solo performance to rewrite the event record. Her breathtaking run also carried historic significance, as she became the first woman to break the 64-minute barrier for the half marathon in the Americas, producing what is being celebrated as the fastest women’s half-marathon performance ever recorded on the continent.

The Ethiopian star was in a class of her own, crossing the finish line more than a minute clear of Turkey’s Nevin Can, who finished second in 1:05:06. Another Turkish athlete, Selin Can, completed the podium in third place with 1:05:11, as the leading trio all produced strong performances on the fast streets of Buenos Aires.

Kenya also featured prominently in the top positions, with Irene Jepchumba Kimais taking fourth in 1:06:04, followed by Sheila Chepkirui in fifth with 1:06:13. Magaret Akidor Ngathike finished sixth in 1:06:46, while fellow Kenyan Deborah Samum claimed seventh place in 1:08:32.

Brazil’s Nubia de Oliveira Silva was eighth in 1:11:13, while Argentina’s Sofia Luna and Dahyana Juarez rounded out the top 10 with times of 1:11:21 and 1:11:28, respectively.

Top 10 Women – 2026 Buenos Aires Half Marathon

1. Fotyеn Tesfay Haylu (Ethiopia) – 1:03:57

2. Nevin Can (Turkey) – 1:05:06

3. Selin Can (Turkey) – 1:05:11

4. Irene Jepchumba Kimais (Kenya) – 1:06:04

5. Sheila Chepkirui (Kenya) – 1:06:13

6. Magaret Akidor Ngathike (Kenya) – 1:06:46

7. Deborah Samum (Kenya) – 1:08:32

8. Nubia de Oliveira Silva (Brazil) – 1:11:13

9. Sofia Luna (Argentina) – 1:11:21

10. Dahyana Juarez (Argentina) – 1:11:28

For Tesfay, it was far more than a race victory. Her 1:03:57 performance was a statement of extraordinary quality, combining speed, endurance and remarkable solo running to produce a landmark result in Buenos Aires. In a race that will be remembered for years to come, the Ethiopian did not simply win—she redefined what was thought possible for women’s half-marathon running in the Americas.

Ethiopia’s Yomif Kejelcha produced one of the most extraordinary performances in road racing history on the streets of Buenos Aires, Argentina, reclaiming the half marathon world record with a sensational 56:51 performance at the 2026 Buenos Aires Half Marathon.

The former world record-holder delivered a breathtaking exhibition of speed and endurance to take 29 seconds off the previous pending mark of 57:20, set by Uganda’s Jacob Kiplimo and takes a huge chunk from his own former official world record. Kejelcha's new performance is pending the standard ratification procedures, but if officially ratified, it will return the world record to the Ethiopian star and mark another remarkable chapter in the evolution of the event. 

Kejelcha's achievement is particularly significant because the 57-minute barrier had already been broken before. Jacob Kiplimo had previously run under 57 minutes, clocking 56:42 that was not ratified demonstrating that the once-unthinkable barrier was possible. Kejelcha, however, has become the second man to run under 57-minute barrier who now returns to the top of the all-time rankings with another historic performance in Buenos Aires.

The Ethiopian's race was remarkable not only for the final time but also for the way he built his performance. He covered the opening five kilometres in 13:44 before reaching 10km in 27:18. Rather than slowing, Kejelcha accelerated through the middle stages, passing 15km in 40:39 and 20km in 54:02 as he continued to push the limits of elite road racing.

By the time he reached the finish line, Kejelcha had completed the race at an extraordinary average pace of approximately 2:42 per kilometre, producing one of the most astonishing sustained efforts ever witnessed in distance running. His stunning run sent a powerful message to the athletics world and further strengthened his status as one of the most formidable distance runners of his generation.

Behind the record-breaking champion, Ethiopia completed a dominant clean sweep of the men's podium. Tadese Worku Gebresilase claimed second place in 59:18, while Bereket Nega Batebo secured third in 1:00:17, giving Ethiopia a memorable one-two-three finish in the Argentine capital.

Kenya’s Jonathan Kipkoech Kamosong finished fourth in 1:00:20, followed by compatriot Simon Maywa in fifth with 1:00:55. Argentina’s Ignacio Erario gave the home supporters plenty to celebrate with an impressive sixth-place finish in 1:00:57, breaking the one-hour barrier in front of an enthusiastic local crowd.

Dillon Kipyeko of Kenya finished seventh in 1:01:07, with Robert Kiprop Koech eighth in 1:02:01. Mexico’s Julio Ortiz Ponce took ninth place in 1:03:17, while Colombia’s Jimmy Gómez completed the top 10 in 1:03:34.

The Buenos Aires Half Marathon will now take its place in the history books as the scene of a truly extraordinary breakthrough. For Kejelcha, this was more than just another victory. It was a spectacular return to the top, reclaiming a world record he had previously held and once again rewriting the limits of the half marathon.

The 56:51 performance remains pending ratification, but Yomif Kejelcha's run has already delivered one of the defining moments in the history of road racing.

Kenya delivered another commanding display of distance-running excellence at the Antrim Coast Half Marathon, with Isaia Lasoi leading a memorable Kenyan clean sweep of the men's podium in a race packed with world-class performances.

Lasoi emerged victorious after a thrilling battle at the front, crossing the finish line in a superb 58:26 setting a new course record. His winning performance underlined his strength and speed over the half-marathon distance, but he was made to work all the way by fellow Kenyan Daniel Mateiko, who finished just three seconds behind in 58:29 after an electrifying duel for the title.

The contest between the two leaders produced one of the standout moments of the race, with both athletes pushing deep into elite territory as they fought for victory. In the end, Lasoi found just enough to secure the win, while Mateiko's narrow defeat highlighted the remarkable depth and quality of Kenya's leading distance runners.

Vincent Kipkorir completed the Kenyan sweep, taking third place in 1:00:38 to ensure that all three places on the podium belonged to Kenyan athletes. Samwel Chebolei added further Kenyan strength to the results, finishing fourth in 1:01:01, while Amos Langat was also among the leading finishers.

The international field featured several prominent names. Australia's Jimmy Whelan produced a strong run, while Ethiopia's Yismaw Dillu featured among the front group. American marathon star Galen Rupp also delivered a notable performance, clocking 1:01:29 in another competitive outing for the experienced distance runner. Former world-class track and road athlete Edward Cheserek was also among the top finishers.

Lasoi's 58:26 victory, however, was the defining performance of the day. Together with Mateiko and Kipkorir, he gave Kenya a perfect podium and another emphatic reminder of the country's extraordinary strength in elite road running.

The Antrim Coast Half Marathon once again provided a fast, competitive stage for some of the world's finest distance runners, but when the decisive moments arrived, it was Kenya that owned the podium.

One of the most iconic milestones in the history of ultramarathon running is drawing closer, with entries for the historic 100th edition of the Comrades Marathon set to open on Tuesday, 25 August 2026.

The Comrades Marathon Association has officially announced a detailed entry process for the 2027 race, which will unfold in three stages and give runners around the world the opportunity to secure their place in what promises to be one of the most significant editions ever held of The Ultimate Human Race.

The announcement followed the official launch of the 2027 Comrades Marathon on Wednesday, 19 August, when the centenary campaign, “The Greatest Story Ever Run,” was unveiled alongside a special logo created exclusively for the landmark 100th edition.

The launch also revealed several major highlights for the Centenary Race. The historic event will take place on Sunday, 13 June 2027, and will be a Down Run, with 28,000 places available. The entry process will include a ballot, while the race will offer a record R8.919 million in prize money. Organisers have also set an ambitious goal of raising R10 million for the Amabeadibeadi charities, adding an important charitable dimension to the centenary celebrations. One of the defining moments of the launch was the unveiling of the special Centenary mark, created to commemorate this extraordinary milestone in the history of the race.

The entry process begins on 25 August at 10:00 a.m. SAST, when entries open for Green Number runners, Yellow Number runners and Amabeadibeadi charity entrants.

The next phase follows on 2 September at 10:00 a.m. SAST, when entries open for Comrades Marathon Association members. This window will remain open for 72 hours or until the available entry allocation is filled, with places offered on a strictly first-come, first-served basis.

For general entrants, the process will move to a ballot system. General entries open on 9 September at 10:00 a.m. SAST, with runners able to enter the ballot until it closes on 22 September at 4:30 p.m. SAST. The ballot draw is then scheduled to take place on 23 September.

Several other crucial dates will shape the road to the historic race. The substitution period will run from 15 to 31 March 2027, while 3 May 2027 is the final deadline for runners to submit their qualifying performances, seeding information and other required entry details.

To qualify for the 2027 Comrades Marathon, runners must complete a 42.2km marathon in under five hours between 15 June 2026 and 3 May 2027.

The journey will finally culminate on Sunday, 13 June 2027, when thousands of runners are expected to line up for the historic 100th edition of the Comrades Marathon.

The 2027 race will represent a remarkable moment for the legendary South African ultramarathon. For more than a century, the Comrades Marathon has captured the imagination of runners and spectators with its extraordinary test of endurance, determination and human spirit. Its centenary edition will celebrate the generations of athletes who have faced its demanding roads, conquered its challenges and helped build one of the world's most respected endurance events.

For runners dreaming of becoming part of this historic occasion, the road to Comrades 2027 is now clearly marked. From the opening of entries in August 2026 to race day in June 2027, every deadline will matter.

The Greatest Story Ever Run is preparing for its most historic chapter yet.

American sprint standout Sam Blaskowski is taking steps toward an international future with Poland after uncovering a powerful connection to his family's ancestral homeland.

The 23-year-old sprinter, who has established himself as one of the fastest Americans of his generation with a personal best of 9.89 seconds in the 100 metres, has begun the process of obtaining Polish citizenship with the aim of eventually representing Poland in international competition.

Blaskowski's connection to the country traces back through his great-grandparents, Franciszek and Julian Błaszkowski, who emigrated from Poland to the United States in 1905. Their journey more than a century ago has now opened an unexpected new chapter for their descendant, whose athletic ambitions could soon carry the Błaszkowski name back onto the international stage under Polish colours.

The sprinter has already received support from the Polish Athletics Association as he works through the citizenship and eligibility process. Should his transfer of allegiance be completed, Blaskowski could become a significant addition to Poland's sprint programme.

His credentials certainly make the prospect an exciting one. In addition to his sub-10-second speed over 100 metres, Blaskowski owns a personal best of 19.93 seconds in the 200 metres, demonstrating the kind of versatility that could prove valuable both individually and in Poland's 4x100m relay squad.

For Blaskowski, however, the move is about more than simply changing national colours. It represents an opportunity to reconnect with his family's heritage while pursuing his ambitions at the highest level of the sport.

With his sights set on becoming part of Poland's international sprint team and competing for relay medals, Blaskowski's journey from discovering his Polish roots to potentially representing the country of his ancestors could become one of the most fascinating allegiance stories in world athletics.

A century after Franciszek and Julian Błaszkowski left Poland for America, their family's story may now be coming full circle—this time at full sprint.