Abstract
PurposeThe use of oxygen cost (dot{O}aero) parameters to predict endurance performance has recently been criticized. Instead, it is suggested that aerobic energy cost (dot{E}_{text{aero}}) provides greater validity; however, a comparison of these quantification methods has not previously been made.MethodsFifty-six male (n = 34) and female (n = 22) competitive adolescent (17 ± 1 years) middle-distance runners participated in a sub-maximal and maximal incremental treadmill test. Running economy (RE) was measured at the speed corresponding to lactate turnpoint, and the three speeds prior. Maximal oxygen uptake (dot{V}O2max), speed at dot{V}O2max and fraction of dot{V}O2max utilized across a range of intensities, and speeds from 0.8, 1.5 and 3 km races were also quantified. RE and fractional utilization were calculated in units of dot{O}aero and dot{E}aero.ResultsMultiple linear regression models demonstrated no discernible difference in the predictive capability of RE, fractional utilization and dot{V}O2max when expressed as dot{O}aero or dot{E}aero in both sexes. When plotted as a function of running speed, dot{O}aero displayed a stepwise decrease (F = 11.59, p < 0.001) whereas dot{E}aero exhibited a curvilinear response (F = 4.74, p = 0.015). Differences were also evident in the slopes plotted for %dot{V}O2max and %dot{E}aeromax against running speed (F = 5.38, p = 0.021).ConclusionsQuantifying aerobic determinants of performance in units of dot{E}aero provides no greater validity compared to dot{O}aero-based measurement. Although both dot{E}aero and dot{O}aero are sensitive to changes in speed, dot{E}aero provides the more valid reflection of the underlying metabolic cost of running. Physiologists should also be aware of the potential differences between expression of aerobic running intensity based upon %dot{V}O2max compared to %dot{E}aeromax.
Highlights
Distance running performance is largely dependent upon aerobic factors, including maximal oxygen uptake ( V O2max), running economy (RE) and the fraction of V O2max utilized over a given distance (Bassett and Howley 2000; Brandon 1995)
Allometric scaling revealed exponents that approximated three-quarters for V O2 at each speed [speed corresponding to their LTP (sLTP): b = 0.77, sLTP − 1 km h−1: b = 0.77, sLTP − 2 km h−1: b = 0.78, sLTP − 3 km h−1: b = 0.84] and V O2max [b = 0.74]
Similar to the study by Iaia et al (2009), the speeds selected in the present study represent the upper end of the range over which RE can be measured with high validity (≤ lactate turnpoint (LTP), RER < 1.0), whereas others have utilized a lower range of relative intensities (Fletcher et al 2009; Shaw et al 2014)
Summary
Distance running performance is largely dependent upon aerobic factors, including maximal oxygen uptake ( V O2max), running economy (RE) and the fraction of V O2max utilized over a given distance (Bassett and Howley 2000; Brandon 1995). It has recently been suggested that expressing physiological parameters in terms of aerobic energy cost ( Ė aero) provides greater validity for quantifying exercise intensity compared to traditional oxygen cost (Oaero)-based measurements (Beck et al 2018); these claims have not yet been fully examined with experimental data. Previous reports have confirmed that Ė aero provides a more sensitive measure of RE compared to Ȯ aero across range of intensities in highly trained runners (Fletcher et al 2009; Shaw et al 2014); this has not yet been established in lesser trained populations of runners, such as adolescents. Ė aero appears to provide a more reliable measurement of RE compared to Ȯ aero in high-performing adolescent runners (Blagrove et al 2017); validity-related issues associated with these measures have not previously been scrutinized in this age group
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