Article

Tau(V) over dot O-2 at the onset of constant work rate (CWR) exercise is a variable of aerobic fitness that shortens with physical training and lengthens with cardiopulmonary disease. Determination of tau(V) over dot O-2 with sufficiently high confidence has typically required multiple exercise transitions limiting its clinical application. Objectives: To design a protocol to determine tau(V) over dot O-2 reliably but simply. Methods: On each of three days, five healthy men performed two CWR tests on a cycle ergometer below the metabolic threshold ((V) over dot O(2)theta) for blood lactate accumulation as determined by gas exchange measurements followed by an incremental work rate (IWR) test. Tau(V) over dot O-2 was determined (a) from the on-transit (on-tau(V) over dot
O-2) and off-transit (off-tau(V) over dot O-2) of six CWR tests both individually and superimposed, using non-linear regression with a monoexponential model, and (b) by geometric analysis of the IWR tests (ramp-tau(V) over dot O-2). Results: Group means (SD) were: (V) over dot O(2)MAX 3.84 (0.44) litres/min, (V) over dot O(2)theta 1.88 (0.23) litres/min, steady state exercise (V) over dot O-2 1.67 (0.07) litres/min, on-tau(V) over dot O-2 38.0 (5.3) seconds, off-tau(V) over dot O-2 39.0 (4.3) seconds, and ramp-tau(V) over dot O-2 60.8 (15.4) seconds. On-tau(V) over dot O-2 correlated with off-tau(V) over dot O-2 ( r = 0.87), (V) over dot O(2)MAX (r = 0.73), and (V) over dot O(2)theta (r = 0.89). The pooled mean tau(V) over dot O-2 from six superimposed tests agreed with the arithmetic grand mean of the six tests. Conclusions: The average of on-tau(V) over dot O-2 and off-tau(V) over dot O-2 fell within the 95% confidence interval of the pooled mean by the second test. Ramp-tau(V) over dot O-2 was longer and less reproducible. These findings support the use of both on- and off-transit data for the determination of tau(V) over dot O-2, an approach that reduces the number of transitions necessary for accurate determination of tau(V) over dot O-2, potentially enhancing its clinical application.

Langue : ANGLAIS

Tiré à part : OUI