Anaerobic Capacity in Running: The Effect of Computational Method

Introduction: 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. Purpose: Four different models for estimating anaerobic energy supply during treadmill running exercise were compared. Methods: 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 (MRTT_req), either including (5+YLIN) or excluding (5-YLIN) a measured Y-intercept. Also, the average GEC (GECAVG) based on all five submaximal stages, or the GEC based on the last submaximal stage (GECLAST), were used as models to estimate the instantaneous MRTT_req. The AnC was computed as the difference between the MRTT_req and the aerobic MR integrated over time. Results: 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-YLIN, GECAVG, and GECLAST models, the 5+YLIN model generated a MRTT_req 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 (F1.07,42 = 13.9, P = 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+YLIN and 5-YLIN, respectively (calculated from the regression equation), and 4.39 ± 0.28 and 4.38 ± 0.27 J⋅kg–1⋅m–1 for GECAVG and GECLAST, respectively (F1.08,42 = 14.6, P –1 for the six pair-wise comparisons and the overall standard error of measurement (SEM) was 0.16 kJ⋅kg–1. Conclusion: 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+YLIN) is likely to underestimate the MRTT_req and the GEC associated with the TT, and hence the AnC during maximal 4-min treadmill running