Brazilian Journal of Physical Therapy
Print version ISSN 1413-3555
PITHON, KR et al. Comparison of cardiorespiratory responses between constant and incremental load exercises below, above and at the ventilatory anaerobic threshold. Rev. bras. fisioter. [online]. 2006, vol.10, n.2, pp. 163-169. ISSN 1413-3555. http://dx.doi.org/10.1590/S1413-35552006000200005.
OBJECTIVE: To apply different analytical methodologies to data from continuous ramp tests (CRT) and discontinuous step tests (DST), and compare responses from cardiorespiratory parameters. METHOD: Eight men performed spirometric tests on an electrically braked cycle ergometer: CRT increasing from 20 to 25 W.min-1 and DST in 15-min steps, each based on the ventilatory anaerobic threshold (VAT) for CRT. Step 1 was 70% VAT; step 2, 100% VAT; and step 3, 130% VAT. VAT was determined as loss of parallelism between O2 uptake (VO2) and CO2 output (VCO2). Heart rate (HR, bpm), VCO2, VO2 (ml.min-1), VO2 (ml.kg.min-1) and ventilation (VE L.min-1) values for CRT were obtained as moving averages of eight breath-to-breath respiratory cycles, using linear regression. For DST, means were applied from the third to fifteenth minute of the steps. Statistical comparisons utilized the Kolmogorov-Smirnov test, ANOVA, post-hoc Tukey-Kramer test and linear regression, with significance limit of p<0.05. RESULTS: At peak exercise, there was a statistically significant difference between breath-to-breath and other methodologies. Comparing protocols: VO2, VCO2 and VE gave similar results for VAT and step 1 (p>0.05), but VO2 was different between VAT and all steps (p<0.05). HR was different between VAT and step 3 (p<0.05). There were significant differences between the three steps (p<0.05). CONCLUSIONS: The results indicate that linear regression was effective for estimating cardiorespiratory parameters. Regarding the protocols, it was found that, to obtain cardiorespiratory responses in DST that were similar to VAT from CRT, the power had to be decreased by 30%.
Keywords : ventilatory anaerobic threshold; physical exercise; discontinuous step test; continuous ramp test; heart rate.