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 O2-speed regression relationship was used to estimate the O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline 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 O2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate 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 O2 demands and O2 deficits. The 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.
Highlights
In short-duration endurance events, such as middledistance running and sprint cross-country skiing, performance is related to the rate of aerobic energy supply and to anaerobic energy provision (Duffield et al, 2005; Losnegard et al, 2012)
The skiers completed the incremental test to exhaustion in 6.5 ± 1.2 min and reached a V O2max of 61.2 ± 7.1 mL·kg−1·min−1, a maximal ventilation rate of 157.3 ± 33.4 L·min−1, respiratory exchange ratio of 1.17 ± 0.05 and a maximal Heart rate (HR) of 202 (IQR = 197–206) beats·min−1
The main findings of the current study were that the estimated supramaximal V O2 demand during a 600-m DS roller-skiing time trial (TT) was 3% lower when a fixed value for baseline V O2 was included in the maximal accumulated oxygen (O2) deficit (MAOD) method (i.e., 4+Y, method 1) as compared to no inclusion of baseline V O2 (i.e., 4-Y, method 2) and the GE/energy cost (EC) methods
Summary
In short-duration endurance events, such as middledistance running and sprint cross-country skiing, performance is related to the rate of aerobic energy supply and to anaerobic energy provision (Duffield et al, 2005; Losnegard et al, 2012). This is the case, at least to some extent, during longer-duration endurance events performed over undulating terrains and at fluctuating intensities, since the oxygen uptake (V O2) demand will at times exceed the maximal oxygen uptake (V O2max) (Norman et al, 1989; Skiba et al, 2012). In addition to energy supply, the efficacy of converting metabolic energy to external work (i.e., gross efficiency, GE) is an important component of endurance performance (Joyner and Coyle, 2008)
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