The Calculation of the Uphill Energy Cost of Running from the Level Energy Cost of Running in a Heterogeneous Group of Mountain Ultra Endurance Runners

Abstract

Ultra-endurance mountain running has become extremely popular in recent years, and the energy cost is one of the factors that influence the final performance. The aim of this study was to determine if the energy cost of uphill running (uphill Cr) can be calculated from level Cr (Energy cost of running in mLO2.kg -1 .mn -1 ) in a heterogeneous group of mountain ultra-endurance runners using the di Prampero equation, and if fatigue could change this relationship. Twenty-four male ultra-trail runners ran on a level and uphill (10%) treadmill at 60% of velocity at V O2max (velocity at V O2 max in m.s -1 ) before and after a mountain ultra-marathon (MUM).The mean performance on the MUM was 728 ± 117 minutes. Positive and strong correlations were found between level and uphill Cr pre-MUM (r = 0.84, P < 0.001) and post-MUM (r = 0.86, P < 0.001), in mLO2.kg -1 .mn -1 . This study demonstrated that level and uphill Crs are related in a heterogeneous group of mountain runners. However, the differences observed between theoretical and real uphill Crs (7.9 and 8.5% pre and post-MUM) demonstrated that an uphill Cr measurement is necessary to predict the performance of high level runners.Keywords: Uphill Running, Energy Cost of Running, Endurance Mountain Runners BackgroundThe energy cost of running on level and on positive gradients has been extensively investigated (1, 2), and the place of Cr among ultra-endurance performance factors is still debated (3, 4). According to (2) and (5) (2016) demonstrated that this statistical relationship could hide individual variations with a significant impact on the performance during mountain races (6) in a homogeneous group of high level mountain endurance runners. Indeed, it was found that uphill Crs at 25% and 12.5% grades (respectively Cr 25% and Cr 12.5% ) were associated with each other (r = 0.78, P < 0.01) whereas level Cr was not associated with either Cr 25% or Cr 12.5% (r = 0.09 and r = 0.10). The fact that some runners have an inferior (greater) Cr in level running and a superior (lower) Cr in uphill running can be related to muscular and mechanical factors and other individual characteristics (7,8). However, this absence of relationship was observed in a smaller group of runners (n = 10).The aim of the present study was to determine if level and uphill Crs are correlated in a heterogeneous population of mountain runners, and if this relationship is strong enough to calculate uphill Cr from level Cr with di Prampero equation. We hypothesized that level and uphill Crs were correlated in this type of population and we evaluated the differences between the real and the calculated uphill Cr. Methods ParticipantsA total number of 24 healthy male and experienced mountain runners participated in this study (mean ± SD: age 41.7 ± 9.5 years, height 1.77 ± 0.04 m, mass 71.7 ± 5.5 kg, Body Mass Index 22.9 ± 1.3 kg.m -2 , V O 2 max 4.64 ± 0.36 m.s -1 ). Subjects were recruited on a voluntary basis. They had to be classified by the International Trail Running Association, with at...

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