Faster O2 kinetics has been associated with a lower O2 deficit and greater tolerance to fatigue but it is unclear whether it is a determinant of endurance performance. This study investigated the relationships between VO2 kinetics parameters within constant load severe intensity swimming, and 400m swimming performance. Methods: Fourteen national level Portuguese swimmers (age 20.5 ± 3.0 yr.; mass 75.4 ± 12.4 kg) performed first a discontinuous incremental freestyle test (FS_EXT) and then two 7-min constant velocity freestyle swims (FS_CTA and FS_CTB), in a 50m pool, over a 10 day period. Cardiorespiratory analysis of expired air was performed in all three tests, which were each separated by at least 24h rest, using a breath by breath analyser (K4b2, Cosmed, Italy) and swimming snorkel (Aquatrainer, Cosmed, Italy). The discontinuous incremental test (FS_EXT, Roels et al., 2005) comprised 5 x 200 m swims with 30 s rest intervals. Speed was increased by 5-10% for each stage, the last of which was performed at maximal speed (vVO2max). Maximal oxygen uptake (VO2max) was taken as the highest 30 s VO2 average; the ventilatory threshold (VT) was established by the V-slope method, and the OBLA was determined from fingertip blood lactate concentration ([La], obtained between each 200m stage using a Lactate Pro analyser), in FS_EXT). The two 7-min constant velocity exercise bouts (FS_CTA and FS_CTB) were each performed at ?70% [= VT + 0.70 x (VO2max - VT)]. Performance was taken as official 400m completion time (T400) within a freestyle swimming competition that took place within one month of FS_EXT, FS_CTA and FS_CTB. The breath-by-breath data of FS_CTA and FS_CTB were 1-s interpolated, time-aligned and averaged. The parameters of the VO2 kinetics (td1, t1, A1, td2, t2, A2; i.e. time delay, time constant and amplitude of the primary phase and slow component, respectively) were modelled with two exponential functions. Results: t1 (15.8 ± 4.7 s) was significantly correlated with T400 (251.4 (Mean) ± 12.4 s (SD); r = 0.61; p = 0.02), absolute VO2max (4.2 ± 0.76 L.min-1; r = -0.66; p = 0.01) and vVO2max (1.46 ± 0.07 m s-1; r = -0.61; p = 0.02). None of the other measured VO2 kinetics parameters (td1: 12.2 ± 2.7 s; A1: 40.6 ±4.7 ml.kg-1.min-1; td2: 167 ± 67 s; t2: 115 ± 172.4 s; A2: 3.6 ± 2.5 ml.kg-1.min-1).were significantly correlated with T400. T400 was significantly correlated with absolute VO2max (r = -0.70, p = 0.01); and speed at both OBLA (1.34 ± 0.01 m.s-1; r = -0.88; p = 0.00) and VT (1.26 ± 0.08 m.s-1; r = -0.80; p = 0.00). Conclusion: The shorter time constant for the primary phase of the VO2 response in swimming (but not the amplitude of the slow component) appears to be associated with higher aerobic fitness and performance.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Published by The Norwegian School of Sport Sciences. All rights reserved.