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The impact ultra-endurance events can have on your health

Viewer discretion is advised, ultra-endurance events are extremely difficult. So, train smart, not hard.

In light of the recent news of a Guinness World record attempt to complete 100 Ironmans in 100 days, let’s ask the question, “Are ultra-endurance events really all that healthy?” Before answering, or attempting to answer, it is worth acknowledging the positive impact endurance events have on one’s physical and mental health. But where is the line? When does something good impose a risk to health? Unfortunately, that may be dependent on the individual and there isn’t a general answer for all, but it is important to be wary of the risks and adopt a progressive approach to your training, racing and adventures.

(The man who is attempting this feat is Ryszard Kałaczyński from Witunia, Poland. Ultra-endurance feats are nothing new for him. In 2015 he completed 366 marathons in 366 days – a Guinness World Record.)

Related: A look at the Iron Cowboy’s record-breaking year

In an extensive review, recently published in Frontiers in Physiology (2020), researchers looked at the physiological impact ultramarathons have on participants. An ultramarathon is defined as being a running event greater than 50 kilometres or lasting longer than six hours. Thus, making the findings from this particular piece of literature interesting for triathletes that regularly participate in half and full Ironmans (four to seventeen hours to complete).

The characteristics of an ultra-endurance athlete on average

The stereotypical ultramarathoner is male, around 40 years of age, well educated and married. In this particular review, it was found that female ultramarathoners accounted for roughly 20 per cent of the total number of finishers. In comparison to marathoners, ultra athletes tend to be a bit older, complete larger training weeks and run slower. The biggest indicator of a runner transitioning into ultras is previous experience. For example, the number of long-distance races (half and full marathons) and personal best times for those events. Other important factors include the physical characteristics of an individual (body mass index) and training development. While more males participate in such events than females, and across shorter distances (5k to marathon) males have faster times (comparing world records), the difference between performance at the ultra distance is not as great between sexes and it decreases with age. Peak times for men and women occur between the age of 35-45. 

Related: Can we improve in endurance sports with age?

Ultra-endurance athletes are typically older in age (35 plus) and have years of endurance training under their belt. Photo: Steve Ashworth

Exercise-induced hyponatremia: Most common acute pathophysiological issue when completing ultra events

When it comes to endurance events, dehydration is always a possibility, and if it occurs, it can wreak havoc on your performance goals. To prevent dehydration, athletes compensate by drink large volumes of water. However, an overcompensation can be disastrous – even fatal. Delusional hyponatremia or exercised induced hyponatremia occurs when plasma sodium values drop below 135mmol/L. This can occur in endurance events, in particular in ultra events, when an athlete over drinks and is continuously sweating. Therefore increasing plasma volume and decreasing sodium content in plasma.

Related: Why are endurance sports so addicting?

This study came to inform ultra-endurance athletes and medical personnel about proper hydration protocols greater than marathons. Traditional guidelines advise that body mass losses beyond two per cent should be avoided during exercise. However, in prolonged exercise, this approach is not applicable as body mass loss does not reflect an equivalent loss of body water. 

Triathlon Magazine Canada Fuel station 2013 Ironman World Championship in Kona, Hawaii

Essentially, the perceived pressure some might feel to overhydrate is wrong and maybe more detrimental. Such a fluid overload may lead to hyponatremic encephalopathy which can be serious (low circulating potassium in body and brain). Symptoms of this are altered behaviour, seizures and edema (i.e. feet swelling). So, even on the simplest level, like water intake, ultra-endurance events can present numerous concerns. 


It is no secret that training for an endurance event exposes you to numerous musculoskeletal injuries, in particular overuse injuries. Such injuries will occur more often in beginners and after an extended time away from training.

Like shin splint and plantar fasciitis are a common overuse injury for runners.

During an event, 50 to 60 per cent will experience musculoskeletal problems. Due to the reliance on the lower limbs as the primary source of locomotion, the most common injuries occur around the knee and ankle joint. Common injuries are shin splints, patellofemoral syndrome and Achilles tendon inflammation. Like any event, these injures are often not due to the event itself, but due to the repetitive training that had to occur beforehand. On the other hand, acute injuries, like a twisted ankle may occur due to the terrain. 

Related: Four painful consequences of running in worn-out shoes

Thus, increasing the need for training literacy within the endurance community in how to train effectively – slow and methodical – always building upon what you have done beforehand. 

athlete's heart

While this may paint a depressing picture – “why would I want to do an ultramarathon or Ironman now?” There is some good news. Going for a long run, or completing an ultramarathon, enhances the physiologically adaptive mechanism of chondrocyte (cartilage cells) function via synthesis of supporting molecules, leading to the strengthening of joints, tendons and ligaments. So, with proper training, athletes can mitigate the negative effects of ultra events on their musculoskeletal system.

Other ‘problems’ and practical advice

Unfortunately, there are a whole host of negative consequences of doing ultra events. But there are also a whole host of positive benefits of doing these events if done properly. 

Here are some practical tips for those looking to do an ultra event:

  1. Build into training. Moving from the shorter distances to longer distances does not need to occur in a year. It is best practice to develop abilities at lower mileage before making a jump to longer events (if you wish to do so).
  2. Gain experience. Do half marathons and marathons. Build your endurance, speed and running efficiency.
  3. Train smart, not hard. Well, train hard, but also smart. Monitor your weekly mileage, resting heart rate and distribution of training load (hard vs easy).
  4. Consult with other athletes with more experience, coaches or medical professionals with a specialization/interest in endurance sports. 
  5. Mix training with different terrains – road, gravel, trail, adventures, flat and uphill. Have fun with it, endurance sports are pretty addicting and a lot more fun when not injured.