Ultra-Endurance vs Conventional Endurance

Ultra-Endurance vs Conventional Endurance at Ultraverse Supplements

Ultra-Endurance vs Conventional Endurance – Differences, Similarities, and Differences Between Similarities

There’s a lot of similarities between ultra-endurance and conventional endurance sports*. In fact, there might be more similarities than there are differences.  However, many of the similarities are…different.  Confused? 

Simply put, many of the physiological and psychological considerations that come into play in conventional endurance are similar to those in ultra-endurance.  However, when it comes to ultra-endurance training and competition, often, they’re multiplied, sometimes exponentially.  The purpose of this blog is to highlight the similarities and differences between ultra-endurance and conventional endurance.  I do not go into detail on how to best handle each of these unique challenges.  The reason being that each of these strategies likely warrants an entire blog – calm down, we are working on it!

*Just so we are all on the same page – ultra-endurance sports are sports that typically last over 6 hours.  Such sports include ultra-running, cross-country skiing, FKT attempts, Ironman traithlons, long-distance cycling, and others.

Things That Are Just Plain Different

These longer events rely more on adequate exercise management and long term preparation, optimal rate of movement, sufficient nutrition to accommodate environmental stressors, and psychologic toughness (Zaryski & Smith, 2005).”


Ultra-endurance events are typically defined as those that last more than 6 hours, but can last days.  In fact, there’s really no limit to how long they can be in terms of mileage or duration.  In comparison, the average marathon finishing time in the U.S. is about 4 hours.  With increased time in competition comes the need for increased time in training. 

Compared to marathoners, ultra-marathoners spend more time training while also covering more mileage (O’Loughlin et al., 2019).  As race length increases, so does time invested in training.  This increased workload is necessary as ultra-athletes have been shown to achieve superior race times with additional training volume (Knechtle & Nikolaidis, 2018).


The increased training time and mileage are partially offset by decreased intensity.  In other words, ultra-athletes train at lower relative intensities than do conventional endurance athletes (Knoth et al., 2012).  The longer an event or training session, the lower the relative intensity.  Additionally, many coaches agree that lower intensity in competition should equal lower average intensity in training, often with increased duration taking its place.  This results in key physiological and psychological influences to consider.


As a result of decreased intensity in training and competition, ultra-endurance sports are primarily aerobic in nature.  Many would argue (I wouldn’t disagree) that some high-intensity and anaerobic work is still worthwhile and beneficial.  However, most would agree that the optimal amount of high-intensity is significantly less in ultra-endurance sports when compared to conventional endurance training.  This varies to a certain degree depending on the ultra-event one is taking part in and training for.


Being primarily aerobic in nature means that ultra-endurance sports require a higher percentage of calories to come from fat for energy. Since it has long been established that the most efficient (I said efficient, not abundant) energy source is carbohydrate, optimal fat utilization is an essential physiological attribute for optimal performance.   Significantly increased amounts of muscular breakdown is another dilemma that ultra-athletes are presented with (Nikolaidis et al., 2018).  When duration increases, so do muscle catabolism and the use of protein as a fuel source.  An increased caloric deficit further exacerbates this problem.

Race Fuel


Most conventional endurance distances require little to no caloric intake during training and competition. Even when it comes to the marathon distance, a well-prepared, athlete can often get by with minimal caloric intake during the event without repercussion. On the other hand, ultra-athletes must ingest calories in the form of carbohydrates to prevent glycogen and carbohydrate depletion.  While ketogenic athletes can get by with significantly fewer calories from carbohydrates because of improved fat adaptation, the vast majority of athletes require increased intake to avoid “hitting the wall.”  As to whether or not the ketogenic diet leads to improved endurance performance, it is less clear. See my “Trending Diets” blog to learn more about the keto diet as it applies to endurance and ultra-endurance performance.

As distance and duration extend, so does the need for additional calories, not only from carbohydrates but also from the other macronutrients – protein and fat. Protein ingestion is critical for preventing muscles from being broken down as a fuel source, a process that manifests with long exercise duration. For this reason, as racing and training becomes increasingly long, you start to see more “real foods” as a source of fuel, as opposed to traditional gels, carbohydrate drinks, and the like. Many choose to consume real food as their primary energy source in multi-day events, using gels and sugary beverages to a far lesser degree or to fill the gaps between aid stations. 

When duration increases, pace and intensity decrease, and when pace and intensity decrease, the body’s ability to digest real food improves. Real food can prevent taste fatigue and is more macronutrient and micronutrient diverse.  Whether eating real food or race food, the degree of caloric insufficiency is directly correlated with diminished performance in ultra-distance competition (Williamson, 2016). 


Although it could be argued that conventional endurance athletes experience GI issues as well, the scale of such isn’t even in the same ballpark.   Any veteran of ultra-distance competition has likely experienced their fair share of GI distress.  This is an unfortunate side effect of consuming large amounts of calories during activity.  During activity, blood is drawn away from the stomach to fuel working muscles, impairing digestion.  The higher the intensity, the more blood is required for working muscles, making digestion increasingly difficult.

The most frequently experienced symptom is nausea, which is reported by up to 90% of non-finishers (Stuempfle & Hoffman, 2015).  Although a high number of finishers experience GI issues as well, digestive issues are one of the primary reasons non-finishers give for quitting during competition (Hoffman & Fogard, 2011).  Research also indicates that athletes who cover less mileage in training are more likely to experience nausea when it comes to race time (Glace et al., 2002).  Other symptoms, such as diarrhea, vomiting, and gastrointestinal bleeding, are not uncommon.

Prevention seems to depend on the individual, distance, intensity, weather, and circumstance.  Often, easily digested carbs like gels and drinks can speed up digestion and prevent GI distress.  On the other hand, the same strategies can lead to taste fatigue and, as a result, nausea.  When nauseous, increasing the intake of fat is sometimes effective (Stuempfle et al., 2013).  For others, especially in longer/lower intensity events, eating what they enjoy most has proven to be an effective strategy.


Although not an issue in shorter ultra-events, many events present with the wonderful opportunity for sleep deprivation. 

This problem is unique to lengthier ultra-endurance events and presents many challenges, including cognitive impairment.

The strategic management of sleep in the form of “sleep banking” has proven to be beneficial for athletes (Poussel et al., 2015).  Additionally, results indicate that the less an athlete sleeps during an event, the better an athlete typically performs in regards to finishing time (Van Helder and Radoki, 1989).  This should not be mistaken for advice to avoid sleep.


Often a direct result of sleep deprivation combined with strenuous exercise, cognitive impairment becomes a serious issue during lengthier efforts.  In events lasting longer than 24 hrs, participants often experience decreased motivation and impaired reaction and response time (Hurdiel et al., 2015).  As cognition further deteriorates, hallucinations can occur.  We’ve all heard (or experienced) plenty of wild hallucination stories!  It’s essential to stay mentally sharp during extended efforts if possible, not only for performance but also for personal safety.

SIMILARITIES…that are different

Hydration is keyHYDRATION

No matter the duration, distance, intensity, or sport, hydration is vital. One simply cannot perform at their optimal potential if they are not adequately hydrated. We all know this. It does seem, however, that ultra-endurance sports present with additional hydration-related complications. The two main complications being hyponatremia and hypernatremia. Hyponatremia is an abnormally low concentration of sodium in the blood. Hypernatremia is, you guessed it, an abnormally high concentration of sodium in the blood.

Interestingly, evidence has shown that ultra-athletes have similar hyponatremia incidences to that of marathon runners yet are three times as likely to develop hypernatremia (Krabak et al., 2017). On the other hand, the athletes who most commonly develop symptomatic hyponatremia are those that go beyond the marathon distance (Montain et al., 2001). I know, that’s a lot of hypos and hypers. Basically, ultra-athletes are at greater risk when it comes to both conditions compared to conventional athletes. They’re significantly more likely to suffer from hypernatremia (high sodium) and typically develop more severe cases of hyponatremia (low sodium).


By now, you probably have an idea where this is going…yep, studies show that ultra-athletes are more likely to suffer from infection than athletes competing at shorter distances (Castell et al., 1996).  Biomarkers taken after ultra-events show significantly affected values leading to impaired immune function.

The concentration of glutamine is significantly reduced during prolonged exercise, negatively impacting immunity (Castell & Newsholme, 1997).  Therefore, glutamine ingestion following endurance exercise has proven effective (Castell & Newsholme, 2011).  Immediate carbohydrate ingestion following prolonged exercise is another effective strategy (Peake et al., 2016).  In summary, adequate rest, solid nutrition, and a practical supplement regimen are critical in preventing a compromised immune system.

Injured Runner


Injuries are part of any sport, and overuse injuries are particularly high in endurance sports.  However, evidence suggests that overuse injuries are even more prevalent in ultra-endurance sports (Malliaropoulos et al., 2015).  This seems reasonable as training time and distance are typically increased.  There is also an increased amount of injuries suffered during competition. One study found 50-60% of participants suffered musculoskeletal injuries during lengthier ultra-marathons (Knechtle & Nikolaidis, 2018).

Injuries are more prevalent in both training and racing, especially in higher impact ultra-sports, such as ultra-running.   Proper recovery techniques, injury prevention exercises, high-quality nutrition, adequate sleep, and the ability to recognize the onset of injury are just a few of the critical principles for any sustainable ultra-athlete.


Cortisol, “the stress” hormone, can wreak havoc on an athlete if not held in check. While absolutely necessary and beneficial for optimal performance, when cortisol becomes chronically elevated, performance, and health in general, are sure to suffer. Many studies have effectively examined the impact that endurance exercise has on cortisol, most of them focusing on conventional endurance. Endurance athletes seem to be particularly susceptible to chronically elevated cortisol levels, even outside of training and racing (Skoluda et al., 2012).

Ultra-endurance events likely amplify the effect on cortisol and other hormones, and this effect seems largely influenced by the length of the race (Knechtle & Nikolaidis, 2018). In summary, cortisol is more likely to remain elevated as time in training and competition increases, putting ultra-athletes at higher risk.  If you would like to know more about the importance of cortisol in endurance and ultra-endurance sport, see my blog on cortisol.


The impact that an ultra-event has on the organs is one of those topics that could easily be its own blog.  Actually, it could be a blog for every organ.  Just know that the familiar pattern of “the longer and more exhaustive the effort, the greater the impact” seems to be true when it comes to your organs as well.  Several studies have taken various biomarkers pre, during, and post-race to assess the impact ultra-distance exercise has on the organs.  The most affected organs seem to be the kidney and the liver. Liver complications seem to be an issue mostly in very long, low-intensity efforts (Shin et al., 2016).

Some studies have suggested that up to 50% of ultra-runners suffer from acute kidney damage during an event (Lipman et al., 2017).  The common practice of taking NSAIDs further harms renal function.  Taking NSAIDs is well documented as being a DANGEROUS practice when it comes to extended duration exercise. 

Organ function will fully recuperate with rest and recovery in the vast majority of cases.  However, there are cases where permanent damage has been observed, typically due to ill-advised practices.  It’s important to stay adequately hydrated and avoid substances that have been shown to exacerbate the problem.


Although muscles could technically be considered organs, muscle damage warrants its own section.  Ultra-endurance athletes, and in particular, ultra-runners, are prone to very high levels of muscle damage.  The extent of damage is directly correlated to duration and intensity.  Creatine-kinase (CK) is a useful marker for measuring muscle damage, and measurements as high as 100,000 – 200,000 U/L (depending on length) have been observed (Knechtle & Nikolaidis, 2018).  To put that into perspective, a normal range for CK is below 198 U/L.  Do the math.  That’s a lot of damage.

High training volumes have shown to be beneficial in reducing the extent of muscle damage during an event (Hoffman et al., 2017).  Studies have also demonstrated that BCAA ingestion during prolonged exercise reduces CK and, therefore, muscle damage (Coombes & McNaughton, 2000).  There’s obviously no way to avoid muscle damage during an ultra-event or even in exhaustive training efforts.  It’s just part of it.  These exhaustive efforts are required for optimal performance and preventing excessive muscle damage during the event.  

Optimal nutrition, training, and supplementation are critical factors for reducing muscle damage in training and competition.


There are too many different biomarkers impacted by ultra-endurance sport to go into any sort of detail.  Some include pronounced changes in bilirubin, white blood cell count, myoglobin, and antioxidant status (Jastrzębski et al., 2016).  These are just a few examples, but the list goes on and on and includes numerous hormonal biomarkers.  These, too, seem very much influenced by prolonged exercise.  The vast majority of the time, these changes are considered relatively harmless and typically return to normal with adequate rest and recovery (Bird et al., 2014).

BONE IMPACT– Studies suggest ultra-athletes put a significant amount of stress on their bones as distance and duration increase (Sansoni et al., 2017).  If not remedied with adequate nutrition, this stress could lead to losses in bone density.  Ultra-distance athletes, especially those who are post-menopausal women, need to pay special attention to bone health.  

Things that are the exact same


Immediate recovery doesn’t change with extended durations.  The 30-minute window of opportunity to replenish glycogen is still the same.  One actually doesn’t need more macronutrients in this 30-minute window after a 6-hour training session compared to a 2-hour training session.  Instead, the additional caloric deficit should be accounted for DURING activity. For more information on optimal endurance recovery see this blog.

Therefore, immediate ingestion of a 3:1 to 4:1 carbohydrate/protein drink at 1 to 1.2 grams of carbohydrate/kg is still the gold standard for immediate post-exercise recovery, ultra-endurance, or otherwise.  The numbers don’t change!

Now, obviously, these are numbers created for the traditional carbohydrate-fueled athlete.  A ketogenic athlete might need to do this differently depending on how many carbs they can consume and stay in ketosis.  This has a tendency to vary significantly between individuals, as does the stringency of ketogenic diets.  A ketogenic or LCHF athlete might abstain from post-exercise carbohydrates altogether, depending on their particular needs.  There are various dietary strategies used to manipulate fat-adaptation, all of which seem to have potential drawbacks.

Wrap up

Wow, that was a lot.  One thing is for sure, I forgot something.  As you can see, there are many considerations to take into account when comparing ultra-endurance to conventional endurance.  It may seem overwhelming, but you don’t have to memorize all this stuff.  Just be aware of the issues unique to ultra-running and other ultra-endurance sports and know that even the similar issues are typically amplified during ultra-distance competition and training.

Set yourself up for success, and listen to your body.  Learning as you go is part of the ride!  Good luck, fellow endurance weirdos.  I wish you the best in the pursuit of whatever goal you may be chasing.


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