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Hemoglobin is measured in every blood panel, a major determinant of athletic potential staring us right in the face.

Hemoglobin is a protein in red blood cells that carries oxygen to working muscles. It's a load-bearing pillar of athletic performance and aerobic development, influenced by genetics, iron levels, training history, altitude, and stress. Hemoglobin is so important that endurance sports have faced existential crises from athletes trying to hijack their physiologies through illegal, immoral performance-enhancing drugs like EPO, which stimulates red blood cell production and increases hemoglobin levels. 

A disturbing 2013 study in the PLOS One journal found that 4 weeks of EPO injections increased hemoglobin mass by 19.7%, which corresponded to a 6% improvement in 3k time trials with no training changes. That study was funded by the World Anti-Doping Association, which seems similar to the DARE program conducting a study on whether or not heroin feels good. Interestingly, that study also tried to optimize for iron levels to improve hemoglobin mass increases, having athletes take 100 mg of elemental iron a day (550% of the recommended daily value). Unethical, arguably evil use of EPO and blood doping has risked ruining Olympic endurance sports over the last 30 years, and it all gets back to that simple biomarker. Increased hemoglobin mass improves oxygen transport during exercise and thus has a profound impact on performance.

Cheating to raise hemoglobin mass is both vile and dangerous. But what if I told you that there are healthy, legal interventions that can improve hemoglobin mass? You can tell they are healthy because they often correspond with reduced stress and improved cardiovascular function-think optimizing iron intake, balancing stress, and living at altitude. You can tell they are legal because the interventions work over longer time horizons and only budge hemoglobin mass by a couple percent at most. It's the difference between feeling good after eating a serving of dark chocolate versus feeling good after snorting a bunch of cocaine. 

New Study on Heat Exposure and Hemoglobin Mass

A 2022 study in the Scandinavian Journal of Medicine and Science in Sports asked a fascinating question: how does heat training via heat suits affect hemoglobin mass in elite athletes? To evaluate the question, the study split 25 elite cross-country skiers into a heat group and a control group that were matched for intensity and duration of training. We're not just talking normal athletes, but national and international competitors at the pointy end of human performance. So any changes in hematological variables would be coming on top of relatively optimized physiologies.

Participants in both groups completed normal training in the AM. In the PM, the heat group did 50 minutes of low-intensity indoor cycling on a stationary bike 5 times a week for the 5-week intervention. But there was a very hot twist. They were wearing a "wool layer on both the upper and lower body, a wool hat, nylon rain jacket, down jacket, and nylon pants with poor evaporative capacity." While they followed the study instructions well, they fully ignored Nelly's instructions, because it got hot in there and they put on all their clothes. We need a follow-up study to test whether they do, in fact, want scrubs.

Despite the added double sessions in the heat, there was no difference between the groups in training duration or intensity across the 5 weeks. Now is the time when we take a step back to hypothesize what we think happens next. The participants' baseline attributes are relevant to your guesses. The heat group had a starting point hemoglobin of 16.1 g/dl and hematocrit of 45.7%, already very high (likely due to some combination of training and genetics). For comparison, in that dastardly EPO study, the end point for hemoglobin levels was 15.2 g/dl even after the 20% increase from undergoing the Armstrong protocol. Moving a pebble with a bulldozer is one thing. But this study was looking at moving a boulder with a finger flick. Could a flick of heat exposure with low-intensity training move that boulder?

The answer: a resounding yes. The boulder didn't move far, but it left an unmistakable trail, kind of like one of those mysterious moving rocks in Death Valley. And any movement of hematological variables through healthy means at this elite level of performance is a BIG FREAKING DEAL. 

Relative to the control group, the heat group's hematocrit increased by 1.58% and hemoglobin mass increased by 30 grams. While there was no change in the performance metrics tested, those blood changes should have beneficial impacts on performance and recovery over longer time horizons. 

So, Should I Just Hit the Sauna?

Here is where things get complicated, interesting, and frankly, a bit annoying. A 1997 study in the International Journal of Sports Medicine found no hemoglobin mass changes with 4 weeks of training in hot environments between 19 C and 32 C, with numerous studies over the years showing small or negligible changes. That is contrasted by a 2022 study in Medicine and Science in Sports and Exercise that found 2.4-2.6% increases in hemoglobin mass from training in a heat suit or heat chamber (see also this 2020 study in the journal Experimental Physiology and this 2019 study in Frontiers of Physiology showing hemoglobin mass increases from heat acclimation protocols). And now is where we have to start questioning the exact mechanism at play, which will help determine how you put these findings into practice.

One theory is that with heat exposure, the body increases plasma volume (the liquid content in the blood), reducing hematocrit (the percentage of red blood cells within a blood sample) through dilution. As the kidneys sense an offset, the body increases natural EPO production to raise hematocrit levels to baseline, but with a higher denominator from the increased plasma volume, thus increasing the numerator: red blood cells and total hemoglobin mass. In that formulation, even after the plasma volume goes down later, the body will be left with more hemoglobin mass to play with.

If the driver is just the plasma volume-hematocrit-hemoglobin mass pathway (for more, the "critmeter" theory is outlined in this 2003 conference paper), it shouldn't take heat suits or heat chambers to spur the adaptations. We should have seen them in the 1997 study, or other studies finding increased plasma volume from training interventions. Maybe it doesn't have to just be kinda hot, it needs to be REALLY hot. As the authors of the main 2022 study, we are looking at say: "The rate of EPO synthesis is mainly regulated by the hypoxiainducible factor (HIF) system, which, however, also has been shown to stabilize with increased heat shock protein expression." (Check out this 2005 research article in Physiological Genomics to go deep on the subject.) Heat shock proteins that incite the HIF system may require higher temperatures than normal training in warm ambient air.

Context and Implications of Heat Training

And that's just the tip of the iceberg (the hotberg?). A recent study on the topic of natural EPO synthesis made me concerned, and it has nothing to do with heat at all. Published online in November 2022 in the American Journal of Physiology, Endocrinology, and Metabolism, it found that post-exercise ingestion of exogenous ketones increased natural EPO production by 20% over a control group. While the mechanism is uncertain, it's possible that post-exercise ketones incite the HIF system, which may be part of the reason why it's reported that more than 60% of the Tour de France peloton takes them. 

I'm bringing up that preliminary study on ketones to illustrate why I'm such a proponent of heat for athletes probing the margins of performance physiology: studies seem to indicate that it's a natural, healthy way to increase hemoglobin mass and improve performance without probing the gray areas of what else incites the HIF system. Heat exposure has been practiced by some cultures for centuries, with plenty of positive impacts that have nothing to do with endurance performance (though based on the recent success of sauna-loving Norwegians, maybe there's a connection there too). 

There are tons of unanswered questions that will be addressed by future studies. How do these adaptations unfold over longer time horizons, as plasma volume stabilizes? Will it work with passive heat exposure, like the sauna or a hot bath? Could it be counterproductive in athletes with limitations on hemoglobin production, like those with low iron stores or naturally low genetic setpoints? Would it be less effective at altitude? Could there be hormonal impacts that reduce the efficacy over time, or prevent it from working in female athletes at all? That last question is the biggest, since all of the studies I have seen do not include female participants, likely because the menstrual cycle causes blood volume fluctuations beyond those seen from the interventions. 

Conclusion: So, How Much Heat Training Do I Need?

The longer I coach, the more I support year-round heat exposure because these study findings seem to be backed up in the training data for athletes Megan and I coach, even for performance in temperate conditions. I think there might also be a health benefit in winter, with increased blood volume assisting with healing and recovery at a time when blood volume can naturally contract by more than 10%. 

My very loose suggestion: talk to a doctor. After the doctor approves, consider a background heat stimulus year-round if you enjoy it (possibly conducted in a manner that can spur heat shock proteins, though always being safe). Examples include a sauna, hot bath, hot tub, or heat suit. Don't overdo it-heat is a major stress, and it can be dangerous. Please be careful.

I personally like to aim for 2 heat exposures a week, with one on my rest day and the other one whenever I have time, usually consisting of 15-25 minutes in the sauna or hot bath (getting out whenever my heart rate gets above 120, and being extra careful in hot baths since I seem more sensitive to them). A typical week when not doing specific heat training for a hot event might look like this:

The jury is still out on whether the hemoglobin mass increases from heat training seen in studies will apply to everyone (or anyone in the real world who isn't doing 50-minute bike sessions in their entire wardrobe). So most of all, consider this intervention if it's FUN, a way to add a bit more sweat to your day, and only if it's approved by your doctor, lawyer, family, and life insurance salesperson. 

There are some cool adaptations at the limits of our physiology. And the coolest part about heat: you may be able to explore some of those adaptations while soft pedaling in a couple layers of clothes, sitting on a wood bench, or taking a relaxing bath. 

 

 

Some victories are measured by finish times. Others are defined by the obstacles overcome simply to reach the starting line.

For American Paralympic swimmer Ali Truwit, completing the New York City Marathon represented far more than covering 26.2 miles. It was the culmination of an extraordinary journey of survival, resilience, and unwavering determination that began with a life-altering shark attack just two years earlier.

On a crisp November morning in 2025, Truwit crossed the iconic finish line wearing a carbon-fibre running blade, fulfilling a promise she had made while recovering in a hospital bed after losing her lower left leg. The emotional milestone marked another remarkable chapter in one of the most inspiring comeback stories in modern sport.

The road to that unforgettable finish began only days after Truwit celebrated a major personal achievement. In May 2023, she completed her first marathon in Copenhagen alongside her mother. Just ten days later, while enjoying a graduation trip to Turks and Caicos with former Yale swimming teammate Sophie Pilkinton, tragedy struck.

While the pair were snorkelling, a shark attacked Truwit, severely injuring her left leg. Displaying remarkable courage, the two swam approximately 55 metres back to their boat, where Pilkinton—then a medical student—quickly applied a tourniquet that stopped the bleeding and ultimately saved Truwit's life.

Doctors were forced to amputate her lower left leg on her 23rd birthday.

Even in the darkest moments of recovery, Truwit's determination never disappeared. Reflecting on having recently completed her first marathon, she joked with one of the first responders that at least she had managed to run a marathon before the attack. The responder's simple but powerful reply would remain with her throughout rehabilitation: "You'll run another one."

Those words became a source of hope during the long and demanding road back.

Only weeks after surgery, Truwit began learning to walk on a prosthetic limb before gradually returning to the swimming pool. The process was anything but straightforward. The water that had once been her sanctuary became a source of painful memories, yet she refused to allow fear to define her future.

Her relentless work ethic soon produced extraordinary results.

Less than 16 months after the attack, Truwit represented the United States at the Paris 2024 Paralympic Games, producing a sensational performance to claim both silver and bronze medals. Standing on the Paralympic podium was a powerful reminder of how far she had come in such a short period, and she dedicated those achievements to everyone who had helped save her life.

Still, another dream remained unfinished.

The New York City Marathon carried deep personal significance. It was not merely another endurance event but a symbolic return to the city where her life had changed forever. On November 2, 2025, she lined up in Staten Island accompanied by 13 family members and close friends, all proudly representing her nonprofit foundation, Stronger Than You Think. Among them was Pilkinton, the friend whose quick thinking had preserved her life on that unforgettable day in the Caribbean.

Together, they covered every mile of the marathon before celebrating an emotional finish that Truwit later described as being "over the moon."

Completing a marathon on a carbon-fibre running blade presents challenges far beyond those faced by able-bodied runners. The prosthetic demands greater strength from the hips, core, and remaining leg while requiring exceptional balance, coordination, and endurance. Truwit's preparation combined months of disciplined training, patience, and mental resilience as she effectively taught herself how to run again.

Her story extends well beyond medals and marathon finishes.

Inspired by her own recovery, Truwit founded Stronger Than You Think, a nonprofit organisation dedicated to helping individuals overcome physical and financial barriers following limb loss. Recognising that sports prosthetics can cost tens of thousands of dollars and are often not covered by insurance, the foundation provides financial assistance for prosthetic devices, supports water-safety education, and promotes opportunities within Paralympic sport.

The organisation has already helped provide more than 11 prosthetic limbs, delivered nearly $200,000 in direct support, and funded over 4,000 hours of water-safety lessons benefiting more than 700 young people.

Throughout her journey, Truwit has remained refreshingly honest about the emotional challenges that continue to accompany recovery. She has openly acknowledged that healing is an ongoing process and that grief can still come in waves. Rather than portraying an effortless comeback, she has demonstrated that resilience is built through persistence, even on the hardest days.

Her remarkable transformation resonates far beyond elite sport. While few people will ever experience the trauma she endured, countless runners and athletes understand the frustration of injury, disappointment, or rebuilding after adversity. Truwit's journey serves as a powerful reminder that recovery is rarely linear and that courage is often measured by the willingness to keep moving forward despite uncertainty.

Now looking ahead to the Los Angeles 2028 Paralympic Games, Truwit continues to redefine what is possible. She is no longer known simply as the swimmer who survived a shark attack. She has become a Paralympic medallist, marathon finisher, advocate, and symbol of resilience whose story continues to inspire athletes around the world.

Her journey proves that while life can change in an instant, so too can the strength of the human spirit. Sometimes the greatest triumph is not returning to the person you once were, but discovering someone even stronger than you ever imagined possible.

Sprint and hurdles superstar Sydney McLaughlin-Levrone has entered an exciting new chapter in her remarkable life, welcoming her first child with husband Andre Levrone. The four-time Olympic champion and women's 400m hurdles world record holder announced the birth of their daughter, Savannah Michelle Levrone, who was born on Sunday, July 12, 2026.

The couple shared the joyful news with an emotional message celebrating the arrival of their daughter and expressing gratitude to everyone who supported them throughout the pregnancy. Sydney described Savannah as "our blessing and our joy," while expressing excitement and faith for the future that lies ahead for their growing family.

The announcement marks a deeply personal milestone for one of the most accomplished athletes of her generation. Renowned for redefining the women's 400m hurdles through a succession of record-breaking performances, McLaughlin-Levrone now embraces a new role beyond the track as a mother.

The timing of the announcement adds another layer of significance. Just days earlier, Sydney reflected on the 10th anniversary of qualifying for her first Olympic Games at only 16 years old—a breakthrough that launched one of the most decorated careers in modern athletics. Ten years later, her journey has come full circle with another life-changing milestone, underscoring that her greatest moments continue to extend beyond sporting success.

The arrival of Savannah Michelle Levrone has been met with an outpouring of congratulations from athletes, fans, and the wider sporting community, who have celebrated the couple as they begin this new chapter together. As Sydney McLaughlin-Levrone steps into motherhood, the athletics world will undoubtedly continue to follow her inspiring journey—both on and off the track.

Ethiopia's Tsige Gebreselama produced one of the standout road running performances of the season on Sunday, storming to victory at the prestigious Boilermaker Road Race 15K in Utica, New York, with a sensational course record of 47:29.

From the opening kilometers, Gebreselama controlled the race with remarkable composure and precision, maintaining a relentless pace that ultimately erased the previous course record and secured one of the fastest performances ever recorded on the historic course. Her commanding display further reinforced her reputation as one of the world's leading road and distance runners.

The Ethiopian celebration continued as Melknat Wudu crossed the finish line in second place in 47:44, completing a dominant one-two finish for her country. Kenya's Priscah Cherono claimed third in 48:14 after a determined effort, rounding out a world-class podium in a race featuring some of the finest distance runners on the international circuit.

The battle behind the podium remained fiercely competitive. Kenya's Everlyn Kemboi finished fourth in 48:28, narrowly ahead of compatriot Selah Busienei, who clocked 48:31 for fifth. Ethiopia's Netsanet Desta and Alem Nigus Tsadik followed in sixth and seventh respectively, while Kenya's Mercy Cherono secured eighth place.

American athletes also delivered encouraging performances on home roads. Veteran Stephanie Bruce finished ninth in 50:40, with Jackie Gaughan completing the top ten in 51:02 to cap a strong showing for the host nation.

Boilermaker Road Race 15K – Women's Top 10 Results

1. Tsige Gebreselama (Ethiopia) – 47:29 (Course Record)

2. Melknat Wudu (Ethiopia) – 47:44

3. Priscah Cherono (Kenya) – 48:14

4. Everlyn Kemboi (Kenya) – 48:28

5. Selah Busienei (Kenya) – 48:31

6. Netsanet Desta (Ethiopia) – 48:46

7. Alem Nigus Tsadik (Ethiopia) – 48:48

8. Mercy Cherono (Kenya) – 50:23

9. Stephanie Bruce (United States) – 50:40

10. Jackie Gaughan (United States) – 51:02

The women's race combined exceptional depth with remarkable speed, as several athletes broke the 49-minute barrier in a contest that showcased the global strength of elite road running. Gebreselama's record-breaking run now stands as a new benchmark in the rich history of the Boilermaker 15K, adding another memorable chapter to one of the United States' most celebrated road races.

Kenya's Alex Matata delivered a sensational performance to claim the men's title at the prestigious Boilermaker Road Race 15K in Utica, New York, producing a dominant run that underlined his growing reputation as one of the world's finest road racers.

Matata surged to victory in an outstanding time of 42:24, mastering the demanding course with a display of strength, speed, and tactical brilliance. His commanding performance secured a memorable triumph in one of the United States' most celebrated road races, adding another significant international victory to his career.

Kenya's success was further highlighted by Kiprono Sitonik, who produced an equally impressive run to finish second in 42:53, completing a remarkable one-two finish for the East African nation. South Africa's Adam Lipschitz rounded out the podium after clocking 43:14 to claim third place following a determined effort.

The race featured a highly competitive international field, with American athletes Reid Buchanan and Hillary Bor finishing fourth and fifth respectively, while another Kenyan, Victor Shitsama, added to his country's strong showing by taking sixth place.

Matata's victory once again showcased Kenya's enduring strength in global road racing, as its athletes continued to dominate major international competitions through exceptional endurance, tactical awareness, and relentless finishing speed. His performance in Utica not only thrilled the spectators lining the streets but also reinforced the depth of Kenyan distance running on the world stage.

Men's Top 10 Results – Boilermaker Road Race 15K

1. Alex Matata (Kenya) – 42:24

2. Kiprono Sitonik (Kenya) – 42:53

3. Adam Lipschitz (South Africa) – 43:14

4. Reid Buchanan (United States) – 43:38

5. Hillary Bor (United States) – 43:40

6. Victor Shitsama (Kenya) – 44:02

7. Futsum Zienasellassie (United States) – 44:32

8. Charlie Sweeney (United States) – 44:37

9. Sam Lawler (United States) – 44:54

10. Tyler Berg (United States) – 45:08

With another major road racing title added to his résumé, Alex Matata continued his impressive 2026 campaign while reinforcing his status as one of the leading names on the international road racing circuit. The Boilermaker 15K once again delivered a high-quality contest, with athletes from across the globe producing memorable performances in one of the United States' most prestigious road races.

Eliud Kipchoge's remarkable World Tour continued on Brazilian soil as the Kenyan marathon icon completed the New Balance 42K Porto Alegre Marathon, crossing the finish line in 2:18:39 to place 12th overall during the second stop of his ambitious seven-continent global running tour.

Competing against a strong international field, the two-time Olympic marathon champion displayed the resilience and determination that have defined his legendary career. While the result was not among the victories that have made him one of the greatest marathon runners in history, Kipchoge once again demonstrated the unwavering commitment that continues to inspire athletes and fans across the globe.

Morocco's Zineddine Ouria claimed victory in a superb 2:08:49, with Kipchoge finishing 9 minutes and 50 seconds behind the race winner after navigating the demanding course in Porto Alegre.

Kipchoge began the race with controlled and confident pacing, reaching 5km in 15:34 before passing the halfway mark in 1:05:07. As the race entered its decisive stages, the pace gradually slowed, but the veteran marathoner pressed on with characteristic determination, completing the 42.195-kilometre challenge in 2:18:39.

For many, the story will be told through the finishing position. But for those who truly understand greatness, this journey is about far more than medals, records, or podium finishes. Kipchoge's World Tour is a celebration of the sport itself—an opportunity to connect with runners across every continent, inspire the next generation, and continue living by the philosophy that has become synonymous with his career: "No Human Is Limited."

The Brazilian appearance also carried added significance, coming shortly after Kipchoge was permanently honoured in Porto Alegre with his footprints unveiled at the entrance of Parque Harmonia—a lasting tribute to his extraordinary impact on distance running and his enduring legacy in the sport.

Once a champion. Forever an inspiration. Legends do not stop inspiring when the victories become fewer; they inspire because they never stop showing up. Through every stride, every finish line, and every challenge embraced, Kipchoge continues to prove that true greatness is measured not only by what an athlete wins, but by the lives they touch along the way.

With the second stop of his World Tour now complete, Kipchoge will turn his attention to the next chapter of his global adventure when he lines up at the Melbourne Marathon in Australia this October. Wherever he races, millions will once again follow the journey of a man whose legacy extends far beyond the stopwatch.