Comparison of Level and Graded Treadmill Tests to Evaluate Endurance Mountain Runners

Abstract

Mountain endurance running has increased in popularity in recent years. Thus the aim of the present study was to determine if maximal oxygen uptake (VO2max) and energy cost of running (Cr) measured during level and uphill running are associated. Ten high level male endurance mountain runners performed three maximal oxygen uptake tests at three slope conditions (0, 12.5 and 25%). Metabolic data, step frequency (SF) and step length (SL) were recorded. No significant differences were found in VO2max (63.29 (±3.84), 63.97 (±3.54) and 63.70 (±3.58) mlO2/kg(-1)/min(-1)) or associated metabolic data at 0, 12.5 and 25% slope respectively. High intra-individual correlations were found between metabolic data measured in the three conditions. The energy cost of running was significantly different between slopes (0.192 (±0.01), 0.350 (±0.029) and 0.516 (±0.035) mlO2/kg(-1)/min(-1), p < 0.01), 0, 12.5 and 25% respectively. However, Cr0% was not correlated with either Cr25% or Cr12.5% (rs = 0.09 and rs = 0.10), in contrast, Cr25% and Cr12.5% were correlated (rs = 0.78). Step length was positively correlated with speed under the three slope conditions. Step frequency was significantly lower at 25 compared to 12.5 and 0% slope. We found that the maximum aerobic power did not differ between level and graded treadmill tests. However, the increase in Cr on the inclined versus level conditions varied between subjects. None of the measured anthropometric or kinematic variables could explain the higher increase in Cr of some subjects when running uphill. Thus, a short graded (5min at 12.5%) running test should be performed at a submaximal velocity (around 40% of level vVO2max) to enhance understanding of an endurance runner's uphill capability. Key pointsIn elite endurance mountain runners, there is no difference in VO2max values between level and uphill running.In a homogeneous group of mountain runners, uphill Cr is not associated with level Cr.To assess performance potential of endurance mountain runners, a standardized uphill running protocol should be performed.

Keywords: VO2max; energy cost of running; step frequency; uphill running.

Figure 1.

A. Energy cost of running (Cr, mlO₂ .kg^-1.m^-1) measured at five velocities at the Ventilatory Threshold at the three conditions of slope. Significant differences, p < 0.01, have been observed between 0, 12.5 and 25%. There was a speed effect only at 25%, p < 0.05 and no differences observed between the five speeds at 0 and 12.5%. B. Step Frequency (SF, Hz, step.s^-1) measured at five velocities at the Ventilatory Threshold at three conditions of slope. SF increased with speed at 0 and 25% grade and SF at 25% was significantly lower than that observed at 12.5% and 0%, p < 0.05. C. Step length (SL, m) measured at five velocities at the Ventilatory Threshold at the three conditions of slope. (SL significantly increased with speed in each condition and SL at 25% was significantly lower compared to SL at 12.5% (p < 0.01) and SL at 0% (p < 0.01) in the same way, SL at 12.5% was significantly lower than SL at 0% (p < 0.05)). Energy Cost of Running, Step Frequency and Step Length measured at five velocities at the Ventilatory Threshold under the three slopes conditions.