دانلود رایگان مقاله انگلیسی مقایسه بین روش های مختلف تخمینی تولید انرژی بی هوازی - 2018 Frontiers

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 VO˙ 2-speed regression relationship was used to estimate the VO˙ 2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline VO˙ 2. 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 VO˙ 2 demand. An alternative method based on submaximal energy cost (EC, method 4) was also used to estimate VO˙ 2 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 VO˙ 2 demands and O2 deficits. The VO˙ 2 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.

DISCUSSION

The main findings of the current study were that the estimated supramaximal VO˙ 2 demand during a 600-m DS roller-skiing TT was 3% lower when a fixed value for baseline VO˙ 2 was included in the MAOD method (i.e., 4+Y, method 1) as compared to no inclusion of baseline VO˙ 2 (i.e., 4-Y, method 2) and the GE/EC methods (methods 3 and 4). The higher Y-intercept in the 4+Y vs. 4-Y method resulted in an 8% lower slope of the regression line. Although the estimated values of O2 deficit between the four methods were highly correlated (r = 0.86–0.99), the limits of agreements ranged from 5 to 21 mL·kg−1 and typical errors ranged from 1.9 to 6.0%, indicating that the different methods should not be used interchangeably. Moreover, since GE/EC was independent of speed, the O2 deficits estimated with the GE/EC methods using one submaximal stage vs. four stages were highly related (r = 0.98) and highly similar (bias of 1 mL·kg−1 ), as hypothesized. The MAOD method has been deemed valid for estimating the O2 deficit during isolated knee-extension exercise (Bangsbo et al., 1990). Nevertheless, there is currently no gold standard for estimating the O2 deficit during whole-body exercise and several different MAOD approaches have been used (Green and Dawson, 1993; Noordhof et al., 2010). One main discrepancy when using the MAOD method appears to be how the linear relationship between submaximal VO˙ 2 and speed is constructed. Inconsistencies in the literature relate to the duration, intensity and number of stages included in the modeling, as well as whether a continuous or discontinuous exercise protocol should be used (Green and Dawson, 1993, 1996; Noordhof et al., 2010). In the current study, a continuous 4 × 4-min protocol was employed incorporating relatively high exercise intensities (60–82% of VO˙ 2max). This was based on previous findings showing no differences in the estimated VO˙ 2 demand when using continuous vs. discontinuous protocols (Green and Dawson, 1996), or whether more than four stages are included in the linear regression (Bickham et al., 2002).