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Cross-train for ultra-marathon success

100 miles is approximately the distance from the surface of the earth to the planet’s boundary, called suborbital space. This is also the distance run by ultra-marathon racers.

To be considered an ultra-marathon, the race must be longer than the traditional marathon distance of 42.195 kilometers (26.219 miles). Beyond that, ultra-marathons come in all shapes and sizes. Some are measured in distance such as 50 kilometers, 100 kilometers, 50 miles, or 100 miles. Others are measured in time, with the winner being the individual who runs the farthest distance in a given time (from 6 hours up to 10 days). Some occur on flat roads, whereas others occur on bumpy cross-country terrain. Some even include obstacle courses.

The International Association of Ultrarunners (IAU) is the organization that manages World Championships for various ultra-marathons ( ). One of the main objectives of this organization is to, “promote and develop long distance running worldwide.” Their goal is to bring ultra-marathon races around the world, which are governed by the rules and regulations of the International Association of Athletics Federation (IAFF).

Ultra-marathon running has grown in popularity, with the number of people completing an ultra-marathon estimated at ~70,000 per year (in 2013), up from ~3,000 in 1980 (Ultrarunning Magazine, 2014). The most popular ultra-marathon is the 50-kilometer race, with 51.5% of ultra-marathoners choosing this running distance. The majority of people running ultra-marathons are male (~70%) and between the ages of 30 to 49.

Properly training for an ultra-marathon is a process that takes more than a year, especially if you’re a first timer. Generally, people training for a marathon or ultra-marathon will run between 3 to 5 times (or more) per week, with weekly mileage increasing as the race approaches. Runners will often attempt one long run per week, heading towards but not approaching the full marathon distance. Research has found that people training for ultra-marathons run between 70 to 98 kilometers (43.5 to 60.9 miles) per week at training speeds of 10.3 to 10.7 kilometers (6.4 to 6.6 miles) per hour ( As many physiological adaptations need to occur to be prepared for running such long distances, it is likely that cross-training will enhance the body’s ability to complete the race. Research is still needed to determine the best training regimen to promote the optimal physiological changes for marathon and ultra-marathon racing.

Studies have shown that certain physiological factors are associated with improved performance in marathons and ultra-marathons. For example, lower body mass and body mass index as well as smaller upper arm girth are factors that are associated with shorter race finishing times ( Research has also shown that physiological factors such as maximal oxygen uptake (VO2 max), velocity at lactate threshold, running economy, and fractional utilization of VO2 max (i.e., the percentage of VO2 max at which the lactate threshold occurs) are good predictors of endurance running. In studies examining ultra-marathons specifically, success in completing races ranging from 84 to 150 kilometers is dependent on VO2 max, a high fractional utilization during the run, and peak treadmill speed (

Though these studies are elucidating in terms of what predicts race success, these studies were conducted on people who completed the race. To fully understand what predicts success in an ultra-marathon, you need to capture data from both finishers and non-finishers of the race.

Therefore, Drs. Philip Tan, Franki Tan, and Andrew Bosch at the Division of Exercise Science and Sports Medicine in the Department of Biology at the University of Cape Town in South Africa set out to determine what factors accurately predict completion of an ultra-marathon ( 26 individuals (23 men and 3 women) who completed the Craze Ultra-marathon in Singapore participated in the study. Runners were allowed 32 hours to complete this 161-kilometer (100 mile) race, which took place in late September on a relatively flat road. A variety of information about the participants’ body physiology and training routine were collected several weeks prior to the race.

On average, the mean race time was 27 hours and 36 minutes, with an average race pace of 6.0 kilometers per hour. Compared to non-finishers, finishers had a more intense training regimen, running farther for their longest training run and participating in more cross-training (i.e., training other than running). This type of training led to an improved physiological profile with finishers having lower lactate thresholds and increased velocities at lactate threshold. In essence, what determined success at completing an ultra-marathon (not surprisingly!) was fitness level prior to the race.

The authors suggest that, “Runners should not neglect the importance of the long runs and should incorporate cross-training to provide additional stimuli to the body while allowing the running muscles to recover from fatigue.”


Joyner, M. J., & Coyle, E. F. (2008). Endurance exercise performance: the physiology of champions. The Journal of physiology, 586(1), 35-44.

Knechtle, B., Rosemann, T., Knechtle, P., & Lepers, R. (2010). Predictor variables for a 100-km race time in male ultra-marathoners. Perceptual and motor skills, 111(3), 681-693.

Sjödin, B., & Jacobs, I. (1981). Onset of blood lactate accumulation and marathon running performance. International journal of sports medicine, 2(01), 23-26.

Tan, P. L., Tan, F. H., & Bosch, A. N. (2017). Assessment of Differences in the Anthropometric, Physiological and Training Characteristics of Finishers and Non-finishers in a Tropical 161-km Ultra-marathon. International Journal of Exercise Science, 10(3), 465-478.

Ultrarunnning Magazine (2014):


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