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.