Determination of both the time constant of vO and DeltavO/DeltaW from a single incremental exercise test: validation and repeatability.

• A single incremental cycle exercise test including a steady-state load, combined with respiratory gas exchange, was performed with the objective of determining the time constant (o2) and the amount of oxygen required at each load (o2/DeltaW) by using a novel equation. The protocol was validated using four exercise tests at different constant loads and conventionally fitted mono-exponential functions to determine o2, and interpolation of o2 versus load to determine o2/DeltaW. No significant differences were seen between the means of either o2 or o2/DeltaW determined with the two protocols. The correlation coefficient was 0·62 for o2 and 0·48 for o2/DeltaW. The absolute differences (2 SD) were 11·6 s for o2 and 1·1 ml min-1 W-1 for o2/DeltaW. The equations were compared in the same steady-state test and good agreement of o2 was obtained (R = 0·99). The 5-6-week repeatability (incremental test) was evaluated. No statistical differences were seen between the mean of the repeated tests. The difference between the tests (2 SD) were 20 s for o2 and 1·2 ml min-1 W-1 for o2/DeltaW. In conclusion, o2 and o2/DeltaW can be determined from a single incremental test. The validation showed an acceptable agreement, although the variations in absolute values were not negligible. This could partly be explained by the natural day-to-day variation and fluctuations in incoming raw data. The test-retest variation in absolute values was considerable, which must be taken into account when using o2 and o2/DeltaW for evaluation of aerobic function.

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MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

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