Gas exchange kinetics in elite runners.

Oxygen uptake (VO[2]) kinetics measured in the frequency domain are known to be faster in subjects of greater aerobic fitness (Essfeld et al. 1987). Carbon dioxide output (VCO[2] ) kinetics have been shown to be delayed following 6 months sprint and strength training in footballers (Fukuoka et al 1997) and might also, therefore, be expected to differentiate subjects according to their aerobic fitness. The purpose of this study was to examine whether an established technique for measuring gas exchange kinetics could be applied as a test to differentiate between elite athletic groups. The subject groups selected for this study were 12 elite male sprinters (ST) and 12 elite male endurance runners (ET). A 300s pseudo random binary sequence (PRBS) exercise protocol was selected to investigate differences between ST and ET. Oxygen uptake (ml-min[-1]) and VCO[2] (ml-min[-1]) were measured on a breath-by-breath basis using a Marquette MGA 1100 respiratory mass spectrometer system. The test/retest reliability of the selected test procedure was examined by the limits of agreement technique. Ten healthy male subjects agreed to participate in the reliability study and all subjects completed 3 consecutive 300s PRBS cycles with 20 s work rate changes between 25 and 85 W on an electrically-braked cycle ergometer at a pedal cadence of 1 Hz. Fourier analysis was computed for frequencies 3.3, 6.7 and 10 mHz. The limits of agreement between test and retest were closer at each measured frequency of VO[2] kinetics than VCO[2] kinetics. The measurement error for VO[2] kinetics ranged from 18-35%, while VCO[2] kinetics displayed greater variability, ranging from 39 - 108%. The results of the reliability study suggest that, using the selected test procedure, VO[2] kinetics are more likely to detect physiological differences between ET and ST than VCO[2] kinetics.In the study of elite athletes, twelve elite male sprinters and twelve elite endurance runners completed the selected PRBS exercise test. Blood lactate concentrations taken pre and post testing remained below 2mM. Statistical analysis by two way ANOVA with repeated measures and tukey honest significant difference post hoc test showed significantly greater amplitude ratios for ET than ST at frequencies 6.7mHz (6.71 +/-1.09 and 5.47 +/-0.95 ml-min[-1]-W[-1]respectively) P<0.05) and 10 mHz (4.97 +/-0.98 and 3.56 +/-0.69 ml-min[-1]W[-1] respectively) (P<0.01) for VO[2] kinetics but not for VCO[2] kinetics. Significantly shorter phase shifts were observed for ET than ST at frequency 3.3mHz (-35.45 +/-4.31 and -41.26 +/-5.82 degrees respectively) (P<0.05) for VO[2] kinetics but not for VCO[2] kinetics, although a trend for faster VCO[2] kinetics was evident in ET. The findings of this study show that VO[2] kinetics and not VCO[2] kinetics, as measured by the selected PRBS test, differentiate between elite sprinters and endurance runners. This supports the further development of the VO[2] kinetics test as a practical measure to differentiate between sports groups.