ISSN:
1439-6327
Keywords:
Gas exchange
;
V-Slope
;
Exercise
;
O2 uptake
;
CO2 output
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (VE) to CO2 output (VCO2) rises, which coincides with changes of arterial partial pressure of carbon dioxide (P aCO2). Since P aCO2 changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO2,tc) RCP may be estimated by PCO2,tc measurement. Few available studies, however, have dealt with comparisons between PCO2,tc threshold (T AT) and lactic, ventilatory or gas exchange threshold (V AT), and the results have been conflicting. This study was designed to examine whether this threshold represents RCP rather than V AT. A group of 11 male athletes performed incremental excercise (25 W · min−1) on a cycle ergometer. The PCO2,tc at (44°C) was continuously measured. Gas exchange was computed breath-by-breath, and hyperaemized capillary blood for lactate concentration ([la−]b) and P aCO2 measurements was sampled each 2 min. The T AT was determined at the deflection point of PCO2,tc curve where PCO2,tc began to decrease continuously. The V AT and RCP were evaluated with VCO2 compared with oxygen uptake (VO2) and VE compared with the VCO2 method, respectively. The PCO2,tc correlated with P aCO2 and end-tidal PCO2. At T AT, power output [P, 294 (SD 40) W], VO2 [4.18 (SD 0.57)l · min−1] and [la−] [4.40 (SD 0.64) mmol · l−1] were significantly higher than those at V AT[P 242 (SD 26) W, VO2 3.56 (SD 0.53) l · min−1 and [la−]b 3.52 (SD 0.75), mmol · l−1 respectively], but close to those at RCP [P 289 (SD 37) W; VO2 3.97 (SD 0.43) l · min− and [la−]b 4.19 (SD 0.62) mmol · l−1, respectively]. Accordingly, linear correlation and regression analyses showed that P, VO2 and [la−]b at T AT were closer to those at RCP than at V AT. In conclusion, the T AT reflected the RCP rather than V AT during rapidly increasing incremental exercise.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00240412
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