A run-through of some of the nasties you can encounter as an ultra-distance athlete and how you can try to avoid them

Injury and illness

You might think ultra runners suffer more injuries and potential illness than marathon runners, for example. Researchers writing in the International Journal of Sports Physiology & Performance looked specifically at whether this was the case in 1212 active ultra runners.

The team discovered that the most common chronic medical conditions were allergies/hay fever (25.1%) and exercise-induced asthma (13.0%). There was a low prevalence of serious medical issues.

In terms of training injuries, 64.6% of the ultra runners suffered from one that resulted in lost training days (average four).

However, these were not significant to lead to major time off work or school for example. Knee injuries were the most reported, while 5.5% suffered from stress fractures (with most involving the foot – 44.5%) of which there was a higher prevalence among women.

Interestingly it was also discovered that the ultra runners who suffered the most from injuries were younger and less experienced.

Kidney issues

Another issue that ultra marathoners can face is acute kidney injury (loss of kidney function). There are three stages to this condition and it’s largely the result of decreased kidney blood flow.

Researchers looked at the incidence of AKI in 26 runners participating in a 100km ultra in Taipei, Taiwan. It was discovered that 84.6% (22 runners) developed symptoms of AKI. Most exhibited those of stage one and none of stage three (stage three being the most severe).

Dehydration, improper fluid balance and urinary tract difficulties are key contributors to AKI in ultra marathoners. Further research has identified similar outcomes, with much also noting a return to near normal kidney function between stages and after completion of an ultra.

It would therefore appear that for the majority of ultra runners, AKI is something that may well be experienced but is unlikely to have long-term consequences for the majority. Remaining hydrated and taking on-board sufficient electrolytes will do much to reduce AKI.


Ensuring optimum sodium and fluid replenishment is crucial for ultra and stage races, however, it may not actually be a cure to cramping.

Researchers writing in Sports Medicine – Open discovered that runners with a prior history of cramping and muscle damage were more prone to suffering from these conditions compared to runners who did not have this specific history – and regardless of impaired sodium and fluid balance.

The research was conducted on runners in a 161km ultra and involved pre- and post-race blood tests and a post-race survey. Specifically, it was pointed out that those who suffered from cramping had higher levels of creatine kinase in their blood concentrations – which is an indicator of AKI.

So, although you may be optimally or near optimally hydrated and have taken on board sufficient electrolytes there’s still potential to suffer from cramping if you are so predisposed.


Hydration is a complex issue. Initially it’s advisable to try to work out how much fluid your body loses through sweat and where practical in the conditions that it will be subject to in the specific ultra/stage race you are preparing for and to consequentially implement a hydration strategy that reflects this.

You can do this quite simply by weighing yourself before a run and afterwards. The loss of body mass will approximate fluid losses.

Training in a heat chamber will provide you with an environment in which you can be more specific.

Hydration needs to be a constant process when competing in ultras and stage races – starting before, continuing throughout and after each stage, and the race where appropriate. Paradoxically it can be difficult to keep drinking during an ultra or stage race, but it goes without saying you must.

Writing in Research & Sports Medicine, sports scientists provide succinct advice for those considering hot weather ultras “… weight loss greater than 2% does not necessarily have adverse consequences on performance and use of sodium supplements or drinking beyond thirst is not required to maintain hydration during ultra-endurance events with high thermal stress.”

The research involved 381 starters in a 161km ultra marathon. However, in Nutrition Journal sports scientists did discover that finishers in another similar ultra exhibited a greater rate of fluid consumption and more closely met their energy replacement needs in comparison to non-finishers, although electrolyte consumption was broadly similar.