2008, Number 4
Rev Invest Clin 2008; 60 (4)
VT/tI Relationship during steady-state exercise on a treadmill at the intensity close to second ventilatory threshold
Benito PJ, Calderón FJ, Peinado AB, Lorenzo I, Díaz V
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ABSTRACTIntroduction. Few works have approached the study of the tidal volumen/inspiratory time (VT/tI) relationship during long and constant load exercise in treadmill. The aim of the present study was to analyze the relationship VT/tI to an intensity corresponding to the mean point among the two ventilatory thresholds. Material and methods. Twenty-four males have participated, carrying out two tests in treadmill: 1) maximal incremental test and 2) a 30 minutes constant load test at the intensity corresponding to the mean point among the two ventilatory thresholds. The respiratory parameters, acid-base parameters and lactate concentration was analysed during the constant load test. Results. The breakpoint of relationship VT/tI during the maximum test was reached at VT 2,886 (465) mL, tI 0.57 (0.10) s and oxygen uptake (VO2) 4,606 (532.9) mL/min. During the effort at constant load the relationships VT/tI and tI/tTOT (inspiratory time/total time) were significantly lower to those corresponding to the breakpoint of Hering-Breuer (PHB). Although the lactate concentration was superior to 4 mmol/L, the parameters of the acid-base state stayed inside the limits that allowed to conclude the whole test. Conclusions. A value of the relationship VT/tI is adopted below the PHB, determinated with a maximum test, during an effort of 30 minutes at an intensity corresponding to the mean point among the two ventilatory thresholds. Both, carbon dioxide pressure end tidal values (Pet CO2) and the acid-base state, stay stable and below the values corresponding to the PHB.