Comparison between different methods of analysis of slow component of oxygen uptake: A view in severe exercise domain

Abstract

The objective of the present study was to compare in severe exercise domain, different techniques used for measuring the amplitude of the slow component (SC) of oxygen uptake kinetics. Ten trained cyclists, male (age: 25 ± 3.6 years, body mass: 67.2 ± 4.5 kg, height: 174.8 ± 6.5 cm and V̇O2max: 62.4 ± 3.1 mL.kg-1.min -1), performed two identical bouts transitions at constant load [mean ± SD (intensity 75%Δ: 75% of the difference between the V̇O2 lactate threshold and the V̇O2max)] in different days. The SC was calculated from different methods: (1) bi-exponential model [V̇O2(t) = V̇O2base + A1 (1 - e-(t-TA1/τ1)) + A2 (1 - e-(t-TA2/τ2))], (2) predetermined intervals (ΔV̇O2 6-2: difference between the second min V̇O2 and the end V̇O2; ΔV̇O2 6-3: difference between the third min V̇O 2 and the end V̇O2) and (3) difference between the end V̇O2 and the value obtained from a mono-exponential adjustment of the "primary component" (predetermined time of 120 s) (SC 6-"PC"). All the methods were compared among themselves. The results showed a significant underestimation of the SC obtained by method of predetermined intervals (ΔV̇O2 6-2: 432 ± 126 ml.min-1 and ΔV̇O2 6-3: 279 ± 88 ml.min-1) when compared with bi-exponential model (676 ± 136 ml.min-1) and SC6-"PC" [(719 ± 265 ml.min-1 (p < 0.05)]. There was not significant difference among the other comparison. The results suggest that the use of predetermined time may underestimate the SC when compared with bi-exponential model and SC 6-"PC".