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 (MR(TT_req)), either including (5+Y(LIN)) or excluding (5-Y(LIN)) a measured Y-intercept. Also, the average GEC (GEC(AVG)) based on all five submaximal stages, or the GEC based on the last submaximal stage (GEC(LAST)), were used as models to estimate the instantaneous MR(TT_req). The AnC was computed as the difference between the MR(TT_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-Y(LIN), GEC(AVG), and GEC(LAST) models, the 5+Y(LIN) model generated a MR(TT_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 (F(1.07,42) = 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+Y(LIN) and 5-Y(LIN), respectively (calculated from the regression equation), and 4.39 ± 0.28 and 4.38 ± 0.27 J⋅kg(–1)⋅m(–1) for GEC(AVG) and GEC(LAST), respectively (F(1.08,42) = 14.6, P < 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). 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+Y(LIN)) is likely to underestimate the MR(TT_req) and the GEC associated with the TT, and hence the AnC during maximal 4-min treadmill running.