Degradation of energy cost with fatigue induced by trail running: effect of distance

Eur J Appl Physiol. 2021 Jun;121(6):1665-1675. doi: 10.1007/s00421-021-04624-5. Epub 2021 Mar 5.


Purpose: The effect of trail running competitions on cost of running (Cr) remains unclear and no study has directly examined the effect of distances in similar conditions on Cr. Accordingly, the aims of this study were to (i) assess the effect of trail running races of 40-170 km on Cr and (ii) to assess whether the incline at which Cr is measured influences changes in Cr.

Methods: Twenty trail runners completed races of < 100 km (SHORT) and 26 trail runners completed races of > 100 km (LONG) on similar courses and environmental conditions. Oxygen uptake, respiratory exchange ratio, ventilation, and blood lactate were measured before and after the events on a treadmill with 0% (FLAT) and 15% incline (UH) and Cr was calculated.

Results: Cr increased significantly after SHORT but not LONG races. There was no clear relationship between changes in Cr and changes in ventilation or blood lactate. There was a significant correlation (r = 0.75, p < 0.01) between changes in FLAT and UH Cr, and the change in Cr was not affected by the incline at which Cr was measured.

Conclusion: The distance of the trail running race, but not the slope at which it is measured, influence the changes in Cr with fatigue. The mechanism by which Cr increases only in SHORT is not related to increased cost of breathing.

Keywords: Cost of running; Fatigue; Running economy; Trail running.

MeSH terms

  • Adult
  • Energy Metabolism / physiology
  • Female
  • Humans
  • Lactates / blood
  • Male
  • Muscle Fatigue / physiology*
  • Oxygen Consumption / physiology
  • Pulmonary Gas Exchange / physiology
  • Pulmonary Ventilation / physiology
  • Running / physiology*


  • Lactates