A Comparison between Different Methods of Estimating Anaerobic Energy Production

Abstract

Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise. Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7°) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O₂ deficit (MAOD) method the [Formula: see text]O₂-speed regression relationship was used to estimate the [Formula: see text]O₂ demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline [Formula: see text]O₂. The gross efficiency (GE) method (method 3) involved calculating metabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a [Formula: see text]O₂ demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate [Formula: see text]O₂ demand during the TT. Results: The GE/EC remained constant across the submaximal stages and the supramaximal TT was performed in 185 ± 24 s. The GE and EC methods produced identical [Formula: see text]O₂ demands and O₂ deficits. The [Formula: see text]O₂ demand was ~3% lower for the 4+Y method compared with the 4-Y and GE/EC methods, with corresponding O₂ deficits of 56 ± 10, 62 ± 10, and 63 ± 10 mL·kg^-1, respectively (P < 0.05 for 4+Y vs. 4-Y and GE/EC). The mean differences between the estimated O₂ deficits were -6 ± 5 mL·kg^-1 (4+Y vs. 4-Y, P < 0.05), -7 ± 1 mL·kg^-1 (4+Y vs. GE/EC, P < 0.05) and -1 ± 5 mL·kg^-1 (4-Y vs. GE/EC), with respective typical errors of 5.3, 1.9, and 6.0%. The mean difference between the O₂ deficit estimated with GE/EC based on the average of four submaximal stages compared with the last stage was 1 ± 2 mL·kg^-1, with a typical error of 3.2%. Conclusions: These findings demonstrate a disagreement in the O₂ deficits estimated using current methods. In addition, the findings suggest that a valid estimate of the O₂ deficit may be possible using data from only one submaximal stage in combination with the GE/EC method.

Keywords: anaerobic capacity; cross-country skiing; endurance exercise; energetics; oxygen deficit; oxygen demand; oxygen uptake.

Figure 1

(A) The linear relationship between mean ± SD treadmill speed and $\stackrel{.}{\text{V}}$O₂ during 4 × 4-min of submaximal diagonal roller-skiing at 7° using the Y-intercept (4+Y), together with the estimated $\stackrel{.}{\text{V}}$O₂ demand at the average speed attained during the 600-m time-trial (TT); (B) the same relationship without the use of a Y-intercept (4-Y); (C) the linear relationship between metabolic rate and power output for the same 4 × 4-min stages of submaximal diagonal skiing. The open square represents the supramaximal $\stackrel{.}{\text{V}}$O₂ demand estimated with the gross efficiency (GE) method. ^*Significant difference (P < 0.05) between the estimated supramaximal $\stackrel{.}{\text{V}}$O₂ demands using the 4+Y and GE methods.

Figure 2

Bland-Altman plots (left) and corresponding scatter plots (right) for the estimated O₂ deficits comparing three different methods: (A) 4+Y vs. 4-Y, (B) 4+Y vs. gross efficiency (GE [the average of four stages]), and (C) 4-Y vs. GE, where 4+Y and 4-Y represent the 4 × 4-min maximal accumulated O₂ deficit methods with the fixed baseline $\stackrel{.}{\text{V}}$O₂ as a Y-intercept either included (4+Y) or excluded (4-Y). Bland-Altman plots represent the mean difference in O₂ deficit (i.e., systematic bias) ± 95% (1.96 SD) limits of agreement (LOA) between the methods. Lines of identity are shown on the scatter plots by dashed lines.

Figure 3

Bland-Altman plots (left) and corresponding scatter plots (right) for the estimated O₂ deficits comparing three different methods: (A) gross efficiency (GE) as the average of the four submaximal stages vs. GE calculated from the last stage (GE_last), (B) 4+Y [$\stackrel{.}{\text{V}}$O₂] vs. 4+Y [MR], and (C) 4-Y [$\stackrel{.}{\text{V}}$O₂] vs. 4-Y [MR], where 4+Y and 4-Y represent the 4 × 4-min maximal accumulated O₂ deficit methods with the fixed baseline $\stackrel{.}{\text{V}}$O₂ as a Y-intercept either included (4+Y) or excluded (4-Y) and based on a linear regression between $\stackrel{.}{\text{V}}$O₂ and speed [$\stackrel{.}{\text{V}}$O₂], and metabolic rate and speed [MR]. Bland-Altman plots represent the mean difference in O₂ deficit (i.e., systematic bias) ± 95% (1.96 SD) limits of agreement (LOA) between the methods. Lines of identity are shown on the scatter plots by dashed lines.