THE ANAEROBIC THRESHOLD IN CYSTIC-FIBROSIS - COMPARISON OF V-SLOPE METHOD, LACTATE TURN POINTS, AND CONCONI TEST

Physical exercise can improve sputum clearance in patients with cystic fibrosis (CF). To set up individual training protocols it is desirabl e to know the anaerobic threshold (AT). Established methods such as bl ood lactate measurements and ergometry can only be performed in specia lized centers. Conconi showed that the heart rate threshold (HRT), i.e ., the deflection point from the linear relationship between work load and heart rate, correlated significantly with the AT in healthy adult s. To assess the reliability of the HRT in CF, we performed ergometry in 32 CF patients (mean age, 21.0 +/- 5.5 years; mean Shwachman score, 77.8 +/- 12.0) according to the Conconi protocol. The HRT was compare d with the aerobic threshold (AeT) as determined by the V-slope method and with two turn points in the lactate performance curve (LTP1, LTP2 ). An HRT could be obtained in only 17 of the 32 patients (53%). In th ese 17 patients there was a significant correlation between HRT and th e other thresholds, but the absolute values for the AT differed consid erably: The mean HRT was 132% higher than the AeT according to Beaver, 107% higher than LTP1, and 19% higher than LTP2. Exercise protocols t hat rely solely on the HRT in CF will lead to excessive exertion durin g exercise training programs in these patients. According to these res ults the HRT of Conconi is not a suitable method to determine appropri ate exercise levels in GF training programs and might even be harmful in CF patients. These results also indicate the need to test the relia bility of a diagnostic procedure that has been developed only for heal thy people. (C) 1998 Wiley-Liss, Inc.