Bi-exponential modeling derives novel parameters for the critical speed concept

Abstract

All-out exercise testing (AOT) has emerged as a method for quantifying critical speed (CS) and the curvature constant (D′). The AOT method was recently validated for shuttle running yet how that method compares with linear running is unknown. In the present study, we utilized a novel bi-exponential model that derives CS and D′ with additional new parameters from the AOT method. Fourteen male athletes (age = 21.6 ± 2.2 years; height = 177 ± 70 cm; weight = 83.0 ± 11.8 kg) completed a graded exercise test (GXT) to derive maximum oxygen uptake ((Formula presented.)) and the average speed between gas exchange threshold and (Formula presented.) (sΔ50%), a linear AOT, and two shuttle AOTs. Measurement agreement was determined using intraclass correlation coefficient (ICC α), typical error (TE), and coefficient of variation (CV). The y-asymptote (S0) of the speed-time curve (3.52 ± 0.66 m·sec−1) did not differ from sΔ50% (3.49 ± 0.41 m·sec−1) or CS (3.77 ± 0.56 m·sec−1) (P = 0.34). Strong agreement was observed for estimates of CS (ICC α = 0.92, TE = 0.18 m·sec−1, and CV = 5.7%) and D′ (ICC α = 0.94, TE = 16.0 m, CV = 7.6%) with significant (P < 0.01) correlations observed between (Formula presented.) and CS and between S0 and (Formula presented.) (r values of 0.74 and 0.84, respectively). The time constant of the decay in speed (τd) and the amplitude between maximal speed and S0 (Ad) emerged as unique metrics. The Ad and τd metrics may glean new insights for prescribing and interpreting high-intensity exercise using the AOT method.