Anaerobic Capacity in Running: The Effect of Computational Method

Abstract

<i>Introduction</i>: To date, no study has compared anaerobic capacity (AnC) estimates computed with the maximal accumulated oxygen deficit (MAOD) method and the gross energy cost (GEC) method applied to treadmill running exercise.<br><br> <i>Purpose</i>: Four different models for estimating anaerobic energy supply during treadmill running exercise were compared.<br><br> <i>Methods</i>: Fifteen endurance-trained recreational athletes performed, after a 10-min warm-up, five 4-min stages at ∼55–80% of peak oxygen uptake, and a 4-min time trial (TT). Two linear speed-metabolic rate (MR) regression models were used to estimate the instantaneous required MR during the TT (MR<i>_{TT_req}</i>), either including (5+Y<i>_LIN</i>) or excluding (5-Y<i>_LIN</i>) a measured Y-intercept. Also, the average GEC (GEC<i>_AVG</i>) based on all five submaximal stages, or the GEC based on the last submaximal stage (GEC<i>_LAST</i>), were used as models to estimate the instantaneous MR<i>_{TT_req}</i>. The AnC was computed as the difference between the MR<i>_{TT_req}</i> and the aerobic MR integrated over time.<br><br> <i>Results</i>: The GEC remained constant at ∼4.39 ± 0.29 J⋅kg^–1⋅m^–1 across the five submaximal stages and the TT was performed at a speed of 4.7 ± 0.4 m⋅s^–1. Compared with the 5-Y<i>_LIN</i>, GEC<i>_AVG</i>, and GEC<i>_LAST</i> models, the 5+Y<i>_LIN</i> model generated a MR<i>_{TT_req}</i> that was ∼3.9% lower, with corresponding anaerobic capacities from the four models of 0.72 ± 0.20, 0.74 ± 0.16, 0.74 ± 0.15, and 0.54 ± 0.14 kJ⋅kg^–1, respectively (<i>F</i>_1.07,42 = 13.9, <i>P</i> = 0.002). The GEC values associated with the TT were 4.22 ± 0.27 and 4.37 ± 0.30 J⋅kg^–1⋅m^–1 for 5+Y<i>_LIN</i> and 5-Y<i>_LIN</i>, respectively (calculated from the regression equation), and 4.39 ± 0.28 and 4.38 ± 0.27 J⋅kg^–1⋅m^–1 for GEC<i>_AVG</i> and GEC<i>_LAST</i>, respectively (<i>F</i>_1.08,42 = 14.6, <i>P</i> < 0.001). The absolute typical errors in AnC ranged between 0.03 and 0.16 kJ⋅kg^–1 for the six pair-wise comparisons and the overall standard error of measurement (SEM) was 0.16 kJ⋅kg^–1.<br><br> <i>Conclusion</i>: These findings demonstrate a generally high disagreement in estimated anaerobic capacities between models and show that the inclusion of a measured Y-intercept in the linear regression (i.e., 5+Y<i>_LIN</i>) is likely to underestimate the MR<i>_{TT_req}</i> and the GEC associated with the TT, and hence the AnC during maximal 4-min treadmill running.