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 VO2max: 62.4 ± 3.1 mL.kg¹.min¹), performed two identical bouts transitions at constant load [mean ± SD (intensity 75%delta: 75% of the difference between the VO2 lactate threshold and the VO2max)] in different days. The SC was calculated from different methods: (1) bi-exponential model [VO2(t) = VO2base + A1 (1 e(tTA1/t1)) + A2 (1 e(tTA2/t2))], (2) predetermined intervals (deltaVO262: difference between the second min VO2 and the end VO2; deltaVO263: difference between the third min VO2 and the end VO2) and (3) difference between the end VO2 and the value obtained from a mono-exponential adjustment of the "primary component" (predetermined time of 120 s) (SC6"PC"). All the methods were compared among themselves. The results showed a significant underestimation of the SC obtained by method of predetermined intervals (deltaVO262: 432 ± 126 ml.min¹ and deltaVO26-3: 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 SC6"PC".
Kinetics; Oxygen uptake; Cyclists; Lactate; Bi-exponential model
