Maximal oxygen consumption and energy cost of running after a long-lasting running race: the 100 km of Sahara

Performance determinants, running energetics and spatiotemporal gait parameters during a treadmill ultramarathon

Purpose

The objective of this study was to investigate the changes in metabolic variables, running energetics and spatiotemporal gait parameters during an 80.5 km treadmill ultramarathon and establish which key predictive variables best determine ultramarathon performance.

Methods

Twelve participants (9 male and 3 female, age 34 ± 7 years, and maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max) 60.4 ± 5.8 ml·kg⁻¹·min⁻¹) completed an 80.5 km time trial on a motorised treadmill in the fastest possible time. Metabolic variables: oxygen consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂), carbon dioxide production (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙CO₂) and pulmonary ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E) were measured via indirect calorimetry every 16.1 km at a controlled speed of 8 km·h⁻¹ and used to calculate respiratory exchange ratio (RER), the energy cost of running (Cr) and fractional utilisation of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max (F). Spatiotemporal gait parameters: stride length (SL) and cadence (SPM) were calculated via tri-axial accelerometery.

Results

Trial completion time was 09:00:18 ± 01:14:07 (hh:mm:ss). There were significant increases in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂, Cr, F, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E and heart rate (HR) (p < 0.01); a significant decrease in RER (p < 0.01) and no change in SL and SPM (p > 0.05) across the measured timepoints. F and Cr accounted for 61% of the variance in elapsed finish time (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{{{\text{adj}}}}^{{2}}$$\end{document}Radj2 = 0.607, p < 0.01).

Conclusion

A treadmill ultramarathon elicits significant changes in metabolic variables, running energetics and spatiotemporal gait parameters. With F and Cr explaining 61% of variance in finish time. Therefore, those able to maintain a higher F, while adopting strategies to minimise an increase in Cr may be best placed to maximise ultramarathon performance.

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

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.

Changes in Running Economy During a 65-km Ultramarathon

Purpose: Running economy (RE), expressed as oxygen cost (O2 cost) and energy cost of running (Cr) is important in ultramarathon (UM) running as it can help predict race performance. Controversy remains if RE increases, decreases, or remains stable in UM running. We examined RE before, during, and after a 65-km UM. Methods: 15 male UM runners (mean age 45 ± 5.7 years) completed a standard exercise test (mean VO2max 48.8 ± 3.4 ml⋅kg-1⋅min-1) for determination of the individual testing speed (60% VO2max: mean speed 9.4 ± 0.7 km/h). This was followed by a 65-km UM (elevation ± 1093 m) consisting of three laps (each 21.7 km). Pre and post indirect calorimetry measurements at individual running speed on the treadmill at UM-specific slopes (average percentage of positive and negative elevation) at -3, +3%, and level grade were performed in randomized order on a motorized treadmill in the laboratory for calculation of RE. Additionally after each lap, testing at +3% took place. Results: The O2 cost, Cr, and RER increased significantly pre to post UM (p < 0.01). During the uphill running, a main effect of distance indicated a gradual, linear increase in O2 cost, F(2,28) = 5.81, p < 0.01,η p 2 = 0.29, and Cr, F(2,28) = 5.96, p = 0.01,η p 2 = 0.30. Conclusion: O2 cost and Cr increased significantly pre to post UM in all testing conditions as well as during the uphill testing throughout the UM. This is the first study to demonstrate a consistent increase in O2 cost and Cr among a range of different slopes, at individual running speeds and race-specific slopes giving further evidence that these measures of RE increase in UM running.

A simple method for assessing the energy cost of running during incremental tests

The energy cost of running (Cr) is classically determined from steady-state oxygen consumption (Vo2) at constant speed, divided by running speed. In the present study, Cr was determined during incremental treadmill tests in the course of the assessment of Vo(2max) and related parameters as follows. Assume that the running speed is increased by a constant amount (Deltav) at regular short intervals (T) and that, during each intensity transient below the gas exchange threshold, Vo2 increases exponentially, without time delay, toward the steady state. If Vo2 is averaged over homologous times within each speed step, neglecting the initial 10 s, the Vo2 difference between corresponding time values becomes constant and equal to the difference between the appropriate steady states. Thus Cr was obtained from the ratio of the difference between the Vo2 averages for any two homologous times, within subsequent periods, to the corresponding speed difference. Since in aerobic conditions, Cr on the treadmill is independent of the speed, and since Deltav and T were constant, the relationship between Vo2 and speed is described by straight lines, where the slope yields Cr above resting. This was indeed experimentally observed, the slopes of the linear regressions (R2 range: 0.78 to 0.97 n = 9 to 16) within the three time windows being essentially equal. In six subjects, the grand-average of Cr amounted to 0.177 +/- 0.011 ml O(2)/(kg.m) [3.70 +/- 0.23 J/(kg.m)]. This value is essentially equal to that obtained for the same subjects by applying the "classical" procedure [0.177 +/- 0.015 ml O2/(kg.m); 3.70 +/- 0.31 J/(kg.m)], so confirming the validity of the incremental approach for assessing the energy cost of treadmill running.