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The world of athletic performance is constantly evolving, and new disciplines emerge, challenging our understanding of human potential. Today, we dive into one such emerging sport, a fascinating blend of endurance and strength, that's capturing the attention of athletes and scientists alike. It's a sport that demands a unique combination of skills, and understanding its intricacies is key to both participation and performance.
This new frontier is often referred to as "hybrid sports" or "HX" sports, and at its core, it's a sport of sports. People are converging from diverse backgrounds like CrossFit, triathlon, running, trail running, and even obstacle course racing. Even athletes from disciplines like volleyball, surprisingly, are finding their way into this space, demonstrating its broad appeal and the varied skill sets it attracts.
A few years ago, a common approach in these hybrid events was simply to run a lot, focusing heavily on endurance. Many CrossFitters would participate, adding a bit more endurance training to their regimen. However, as triathletes began to enter the scene, their established aerobic base and structured training started to yield remarkable results, with many athletes breaking traditional time barriers.
The true emergence of the hybrid athlete, however, comes when someone possesses a strong foundation in endurance sports and then dedicates significant time to developing strength, motor skills, and mobility. This potent combination of capabilities creates a well-rounded, hybrid athlete capable of excelling in these multifaceted events. This is the genesis of what we see evolving today.
To understand this evolving landscape better, we turn to Dr. Jorge Gutiérrez Cellín, a doctor of health sciences and a professor and researcher at Francisco de Victoria University. His expertise in sports science provides a crucial lens through which to examine these new athletic demands and how the human body responds to them.
A key insight from Dr. Cellín is how traditional coaching often perpetuates specialization. A triathlon coach trains for triathlon, a CrossFit coach for CrossFit, and a running coach for running. Each offers valuable experience, but science is now stepping in to bridge these specialized perspectives and offer a more objective analysis.
This scientific approach is crucial, especially when looking at elite athletes. Dr. Cellín's research, for instance, involves measuring around 35 professional HX athletes, including four who are ranked in the top 15 globally. This cutting-edge work, some of which is still under review, is providing unprecedented insights into the physiological demands of these competitions.
For an athlete aiming to simply finish an HX event, the training structure is a critical consideration. These events are biomechanically unique and present a complex fatigue profile. The body is constantly being pushed through varied demands, from the leg-intensive ski erg to trunk engagement with sled pushes and pulls, followed by running.
This constant switching of demands means the cardiovascular system is under immense pressure. Imagine the heart and brain trying to process the signals from running, then pushing a heavy sled, then pulling it, then burpees, then rowing, and then carrying weights. It’s a physiological juggling act like no other.
Understanding these demands also helps identify potential red flags for new participants. As trainers and scientists, it’s vital to recognize when an athlete might not yet be ready for the unique stresses of HX. This proactive approach helps prevent injuries and ensures a positive introduction to the sport.
The individual behind this podcast, Rubén Espinosa, is a coach and the creator of this project, dedicated to exploring training, science, and health. His passion lies in understanding what makes us better, not just as athletes, but as individuals in all aspects of life. This episode aims to delve deep into the science behind HX.
Today, we have a truly gifted individual with us, someone with profound knowledge of what happens within the body during HX competitions. Dr. Jorge Gutiérrez Cellín is here to share insights that promise to be both surprising and incredibly informative for anyone interested in this sport.
Welcome, Jorge. It's a pleasure to have you. When we've shared snippets of HX or had athletes like Pelayo on, we've seen a range of reactions. Some are incredibly curious, asking how athletes achieve such rapid growth and performance. Others express outright rejection, labeling it simply "CrossFit in disguise" or "running in disguise."
Interestingly, many of the staunchest critics and skeptics of HX have been surprised by its rise. This is especially true considering recent news about the integration of HX with traditional triathlon to form a new discipline called "Hatlont." This collaboration signifies a growing recognition of HX's impact.
While there can be many interpretations of this partnership, a key takeaway is that HX has captured significant attention from both audiences and athletes, overshadowing many other disciplines. Its growing popularity certainly warrants a dedicated space for discussion, approached with the scientific rigor that Dr. Cellín exemplifies.
For those who might be unfamiliar, let's start with the basics. Jorge, can you explain what HX is and how it differs from CrossFit, for those who might think they're the same? This is a foundational question for understanding the sport.
You're absolutely right to ask that, Rubén. Many triathletes and endurance athletes initially viewed HX as just another fad. However, it has undeniably evolved from a trend into a clear and significant movement, demanding a step up in understanding and approach.
When we talk about HX, it's important to note that HX is a registered brand, not a sport in itself. It's similar to how "Ironman" is a brand that has a specific triathlon format. HX, as a brand, hosts a sport that combines running with functional workout exercises.
The format involves approximately 8.7 kilometers of running, spread across eight segments interspersed with eight specific workouts. These workouts include a 1000-meter ski erg, followed by a sled push with substantial weight – 200 kg for elite men and 150 kg for elite women.
After the sled push, athletes run another 1000 meters, then perform a sled pull with slightly less weight: 150 kg for men and 100 kg for women, over 50 meters. This is followed by another 1000-meter run, which can be particularly taxing due to the high recruitment of fast-twitch muscle fibers.
The next run segment leads into burpees, an exercise that demands maximum effort and often catches athletes off guard. Passing on the burpee segment too quickly can lead to significant fatigue, impacting subsequent runs. Following more burpees, there's a 1000-meter row.
After the row, it’s back to running, followed by a farmer's carry, where athletes carry heavy weights for 50 meters. Elite men carry 32 kg in each hand, and elite women carry 24 kg. This is then followed by lunges, with athletes carrying weight – 30 kg for men and 20 kg for women – while performing strict lunges.
Finally, to cap off the eight workouts, athletes face 100 wall balls. This exercise involves squatting and throwing a ball at a target at varying heights. For elite men, the ball weighs 9 kg, and for elite women, it's 6 kg. This combination makes HX incredibly demanding.
So, to summarize, you have eight running segments totaling 8.7 kilometers, interspersed with eight challenging workouts. This format is truly unique; no other sport in history shares these exact characteristics. This complexity is why it presents such a significant challenge for coaches, scientists, and athletes alike – figuring out how to train for it effectively.
It's a spectacular blend of cardiovascular work, metabolic conditioning, and demanding muscle fiber recruitment. Currently, there's very little research available on how to optimally train for HX, which is precisely where scientific inquiry, like that of Dr. Cellín's team, becomes so vital.
Before we delve into the training science of HX, I'm fascinated by your personal journey, Jorge. You’ve transitioned from being an athlete yourself, experienced the disillusions that can come with elite competition, and are now researching elite HX athletes. You're also incredibly generous in sharing your work. How did you arrive at this unique intersection of sports science and cutting-edge athletic performance?
I believe the key driving force throughout my journey has been passion. If there's one word that has consistently guided me, it's movement, exercise, and sport. I've often felt lost in life, but exercise has always been my compass, my reliable guide.
I’ve always been a skeptic, questioning authority figures, even professors, wondering if they might be misinformed. When I entered the physiology lab and saw my body’s real-time responses to various stimuli, it was a true awakening. From that moment, I was captivated by physiological research because it offers a direct connection to reality.
Alongside my academic pursuits, I've always prioritized training. I was an athlete competing in the 400 meters and 400-meter hurdles, even reaching high-performance training centers. While I achieved some success, like competing in national championships, that path eventually reached its natural conclusion.
A significant turning point was meeting someone with a visual impairment. My own athletic performance was plateauing, and I felt a calling to assist this individual. I saw it as an opportunity to embark on a new journey, one that would be meaningful and impactful.
My academic career led me to become a university professor at Francisco de Victoria University, where I'm encouraged to pursue my research passions. It was through my partner, Susan Alonso Domínguez, that I eventually discovered HX and the world of hybrid sports, which has, in turn, led me to where I am today.
What’s your opinion on why this sport has become so popular? As someone from an outdoor background, I understand the liberating feeling of running or cycling in nature. I never imagined that something as standardized as HX, where a competition in Bilbao or Hamburg is the same, would gain such traction.
While the social aspect, inherited from CrossFit’s tribal sense of belonging, is undeniable, there must be something more driving this incredible engagement. You've likely pondered this yourself; what do you believe is the core appeal?
I believe a significant factor, considering our evolutionary heritage, is that HX provides a functional format that the primate brain simply loves. It taps into our innate drive for varied physical challenges. My partner, Susan, and I often discuss this, and it's a conclusion we keep returning to.
This primal appeal stems from the diverse movements involved. You run, push, pull, drop to the ground for burpees, change planes of motion, and engage in isometric holds. You’re essentially mimicking ancestral behaviors like hunting and gathering, which creates a rich and engaging experience.
From a physiological perspective, HX can also serve as a functional health assessment. If you can complete an HX event, it suggests a high level of systemic functional health. You demonstrate the ability to push, pull, run, drop to the ground, and engage in cyclical activities like skiing and rowing.
The ski erg and rowing, for example, utilize opposing muscle chains. Rowing involves a flexion-based movement, while the ski erg emphasizes extension. This variety makes HX a remarkably comprehensive and engaging sport. It feels natural, and participants often describe a sense of peace and coherence.
Let’s shift our focus to what happens inside the body during an HX competition. When you, as a scientist, first began studying HX athletes in a laboratory setting, what was your initial impression? Coming from a speed-focused background like athletics, and with your understanding of endurance physiology, what did you observe?
[laughs] The initial impression was simply, "Wow." Developing a coherent and relevant battery of physiological tests is essential to answer research questions. Our first major question was straightforward: "What exactly is happening here?" Because there was so little existing data, we needed to describe the phenomenon first.
We designed a comprehensive physiological assessment to measure strength, cardiovascular capacity, metabolic markers, and more. Then, we’d measure athletes and relate these metrics to their competition performance. This involved bringing athletes into the lab for a battery of tests.
I've measured cyclists, runners, and athletes who specialize in specific energy systems. Endurance athletes excel aerobically but may show deficits in neuromuscular tests. Conversely, power athletes might excel in strength but struggle with aerobic capacity.
Then, we introduced these "hybrid" athletes into the lab. It was astonishing. Some could sustain incremental treadmill tests at 21 kilometers per hour, demonstrating incredible aerobic capacity. Simultaneously, in neuromuscular tests measuring maximal force, they were moving 300 kilograms.
The combination of that level of aerobic capacity and raw strength was truly remarkable. It led us to ask: what kind of athlete are we seeing here? Are they primarily CrossFitters who run, or triathletes who've become stronger, or something entirely new?
At this point, the sport is still very young and not yet fully mature. HX and other hybrid sports are essentially "sports of sports." The age demographic with the highest participation, typically between 30 and 40, suggests many are experienced athletes finding a second sporting life.
Athletes come from CrossFit, triathlon, road running, trail running, and obstacle course racing. Even a former volleyball player, a powerful athlete, is among the top competitors in Spain. These are incredibly interesting profiles.
A few years ago, breaking an hour in HX was considered a significant feat for elite men. Many participants were CrossFitters who had added some endurance. However, their body mass could be a limiting factor in a sport requiring sustained movement over distance.
Then, triathletes began to enter, bringing a massive volume of cardiovascular training developed over years. Strength adaptations, on the other hand, can be acquired more quickly. These triathletes started to excel, not only succeeding but also significantly lowering their times.
This highlighted a distinction: a more cardiovascularly focused athlete, with strong aerobic and metabolic systems, began to outperform those with a stronger background in pure strength sports. However, the ultimate hybrid athlete emerges when someone combines that endurance foundation with dedicated strength, mobility, and motor skill development.
These hybrid sports present a significant physiological challenge. Reaching the same level of performance can be achieved through various pathways, and individualization is key. Athletes with a strong endurance background will need to focus more on the workout components, increasing their strength levels to reduce the relative stress of the exercises.
Conversely, athletes coming from a strength background will face a longer learning curve in hybrid sports. The systemic, respiratory, and mitochondrial adaptations required for endurance take years to develop. We're talking about a 4 to 8-year adaptation period, similar to what's observed in the maturation of endurance athletes.
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Jorge, your specialty was the 400-meter hurdles. I remember your powerful legs and incredible speed. If we placed you, at your peak performance in that event, into an HX competition back then, what do you think would have happened?
Honestly, I probably would have died. [laughs] While I had some aerobic base, the sustained demands of HX would have been brutal. The 400-meter hurdles is a mixed event, but my training leaned heavily towards glycolytic power – producing energy quickly.
My physiology was geared towards explosive bursts, not the sustained aerobic output required for HX. Even a relatively short 10k run without specific training felt incredibly challenging for me. My mother's genetics likely gave me a mitochondrial advantage, but my training focus was different.
I was specializing in glycolytic pathways, measuring lactate production to assess power output. This is the energy system that allows for rapid bursts of power. If you push too hard, too fast in an HX event, you quickly enter that "poisoned" zone, disrupting your cellular balance.
My accelerator pedal was very sensitive. I would push it, and it would quickly lead to an anaerobic state, overwhelming my system. My first HX experience with my partner, Susan, was a stark example. I struggled immensely with the sled pushes, despite feeling I wasn't pushing that hard.
Afterward, my body's pH dropped, leading to metabolic acidosis, commonly known as lactic acid buildup. I couldn't run effectively, and the subsequent exercises, like burpees, felt impossibly difficult. This is the critical physiological difference for a pure sprinter in an HX event.
My body was efficient at clearing lactate and hydrogen ions from the bloodstream but not at re-oxidizing them within the muscle fibers. This is a key distinction from endurance training, which develops the pathways to efficiently utilize lactate for energy. Fast-twitch fibers are more glycolytic-dependent, while slow-twitch fibers rely more on mitochondrial energy production.
To put it in layman's terms, imagine your body as a car. Endurance athletes have a large, efficient engine designed for long journeys. Sprinters have a powerful, high-revving engine built for short bursts of speed. HX requires a blend of both, and if you only have the sprinter’s engine, you’ll quickly run out of fuel on a long race.
Let's try to answer the question of how to train for HX in a way that everyone can understand. We've established the competitive needs and the ideal athlete profile. But for the average person interested in HX, how should they structure their training?
The core principle is building a strong aerobic base, similar to training for a 10k race. I'd recommend at least three running sessions per week: one in Zone 2, below the first ventilatory threshold, to build endurance; a second session at a steady-state pace, below the second ventilatory threshold, for sustained effort; and a third session at a higher intensity, near VO2 max, to stimulate adaptations.
In terms of strength training, focus on fundamental movement patterns: pulling, pushing, squatting, and lunging. Improving functional mobility applied to these movements is crucial. If possible, incorporate sessions at an HX-specific gym or box to become familiar with the equipment like sleds and the overall competition environment.
The key is a combination of cardiovascular training and basic strength work that mimics the demands of the sport. This includes pushing, pulling, jumping, throwing, and running. It’s about building a robust and adaptable physiological system.
Now, turning the question around, as a health professional focused on prevention, what are the red flags you'd look for in someone to advise them that HX might not be suitable yet? In endurance sports, we often tell people when they're not ready. What are those indicators for you?
Firstly, an individual should be capable of completing a 10k run. This establishes a baseline level of running fitness. Beyond that, functional assessments are key. Can they perform a full squat with good range of motion? This is a significant indicator of mobility and core strength.
Another crucial functional assessment involves push and pull movements, and observing how they perform a burpee. HX demands a combination of pulling, pushing, jumping, and displacement. If someone struggles with basic functional movements or lacks adequate mobility, they may not be ready for the demands of HX.
If someone hasn't run a 10k, I'd strongly advise against attempting an HX event. They wouldn't enjoy it, and it would likely involve a lot of walking. While walking is fine, the full experience of HX is meant to be a comprehensive athletic challenge.
The wall ball exercise, for instance, can be a limiting factor if an athlete lacks proper squat mechanics. While modifications are sometimes allowed, a solid foundation in fundamental movements is essential. I’d encourage anyone considering HX to attend as a spectator first to understand the event's scale and intensity.
It's also important to distinguish between HX, the specific brand, and the broader category of hybrid sports. Many competitions share similar formats but operate under different names. These can sometimes offer a more accessible entry point.
For example, Deca involves shorter runs and more stations. Hybrid Day is similar to HX but has a longer history and may be more affordable. Hybrid Games lean more towards CrossFit with a surprise element. The key is finding a competition that aligns with your current fitness level.
As a health professional, you understand that injuries often result from a combination of factors like strength deficits, poor range of motion, or excessive fatigue combined with high intensity. Given the diverse movements in HX, do you foresee it becoming known for injuries, similar to how some perceive CrossFit?
It's possible, and we must differentiate between recreational and elite athletes. The recreational participants, who are the primary drivers of growth in this sport, may be more susceptible. Issues can arise from mobility limitations, leading to problems like lower back pain or sciatica, common in the core-intensive movements.
We also see injuries similar to those in runners, such as Achilles tendinopathy. However, among the elite athletes I've interacted with, severe upper body injuries are less common. The lumbar region seems to be a primary area of concern due to the significant hinge movements involved.
While the exercises are functional and not excessively high in load for elite athletes, the combination of fatigue and repetitive stress can be a factor. For example, 100 wall balls, even without significant weight, can lead to overload for a large segment of the population, especially if proper form breaks down.
The strain on the deltoids during the eccentric phase of the wall ball, or the impact on the ankles and hips during lunges, can also be problematic. The sled pushes, with prolonged posterior chain engagement in a tight ankle angle, followed by a plyometric running motion, present a complex challenge.
It's a valid concern that many participants might not have the necessary strength or mobility, leading to repetitive stress and potential injury. The key is ensuring athletes have a foundational level of fitness and are progressively introduced to the demands of the sport.
The profile of people drawn to HX is often highly educated about their bodies and well-prepared. Many invest in coaches, nutritionists, and physical therapists. This proactive approach to health likely mitigates injury risk.
The movements themselves are generally not overly complex, which reduces the risk of injury compared to highly technical skills. Furthermore, the emphasis on strength training inherently helps reduce injury rates, a factor often overlooked in pure endurance sports.
While fatigue can contribute to injuries, athletes in HX are typically engaging in strength training consistently. This builds a resilience that might be lacking in athletes who solely focus on endurance. The demands of HX, like pushing sleds or performing wall balls, necessitate a well-developed strength base.
Therefore, even amateur participants often arrive with a better strength foundation than a typical individual focused only on endurance. This foundational strength likely contributes to a lower injury incidence than one might expect. The exact best training method is still evolving, but the core principles are becoming clearer.
The science is crucial in understanding this evolving landscape. Instead of relying solely on individual experience, which can be subjective, scientific measurement provides objective data. This allows us to understand how athletes perform in real-time, not just based on anecdotal evidence.
For example, measuring an athlete's VO2 max, lactate thresholds, and neuromuscular capabilities provides a clearer picture of their physiological profile. This data helps us answer specific questions, like whether higher jump power correlates with better sled-pushing performance.
This scientific approach allows us to move beyond correlation and towards understanding causality. By meticulously measuring athletes and their performance, we can identify the physiological variables that truly determine success in HX. This objective data is invaluable for both athletes and coaches.
We're seeing incredible advancements in measurement tools, allowing for precise data collection. These sophisticated devices provide real-time insights into an athlete's physiological response during training and competition. This data is transforming how we understand and approach athletic performance.
The ability to collect and analyze such detailed data is transforming research. By studying elite athletes, we can perform a form of "reverse engineering," identifying the physiological characteristics that contribute to peak performance. This knowledge can then be applied to train future generations of athletes more effectively.
This data-driven approach is vital for understanding the nuances of HX. For instance, by analyzing pacing strategies in races, we can identify common patterns, such as athletes starting too fast. This empirical evidence helps inform more effective training and race-day execution.
The data reveals that professional athletes often start their runs at a very high pace, sometimes pushing too hard too early. While this might work for some with exceptional aerobic capacity, it can be detrimental for others, leading to early fatigue and impaired performance.
The research also highlights the significant impact of transitions, or "rock zones," on overall performance. These shorter running segments between workouts are crucial, and athletes who can maintain a strong pace here, even when fatigued, gain a significant advantage.
The data on pacing and transitions is critical for coaches. It allows them to tailor training programs to optimize performance across all segments of an HX event, rather than just focusing on one aspect. This holistic approach is essential for success in such a multifaceted sport.
The scientific method, with its emphasis on objective measurement and statistical analysis, is the key to unlocking the full potential of HX. It allows us to move beyond subjective opinions and gain a deeper, more accurate understanding of what it takes to excel.
This data-driven approach is not just for elite athletes. The intention is to eventually extend this research to the recreational level. By understanding the physiological demands and performance characteristics, we can create more effective and safer training protocols for a wider audience.
The journey from amateur to elite in HX is fascinating, and it’s built on a foundation of continuous learning and adaptation. Understanding the science behind the sport allows athletes and coaches to make informed decisions, optimize training, and ultimately, achieve their performance goals.
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