The anaerobic threshold in cystic fibrosis: Comparison of V‐slope method, lactate turn points, and Conconi test

Abstract

Summary. Physical exercise can improve sputum clearance in patients with cystic fibrosis (CF). To set up individual training protocols it is desirable to know the anaerobic threshold (AT). Established methods such as blood lactate measurements and ergometry can only be performed in specialized 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 adults. 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 compared with the aerobic threshold (AeT) as determined by the V-slope method and with two turn points in the lactate performance curve (LTP 1 , LTP 2 ).An HRT could be obtained in only 17 of the 32 patients (53%). In these 17 patients there was a significant correlation between HRT and the other thresholds, but the absolute values for the AT differed considerably: The mean HRT was 132% higher than the AeT according to Beaver, 107% higher than LTP 1 , and 19% higher than LTP 2 . Exercise protocols that rely solely on the HRT in CF will lead to excessive exertion during exercise training programs in these patients. According to these results the HRT of Conconi is not a suitable method to determine appropriate exercise levels in CF training programs and might even be harmful in CF patients. These results also indicate the need to test the reliability of a diagnostic procedure that has been developed only for healthy people.

Symptoms, lactate and exercise limitation at peak cycle ergometry in adults with cystic fibrosis

“…However, there is little data concerning lactate accumulation during exercise in CF, although several small studies in subjects with milder disease have shown that lactate accumulation occurs [16][17][18][19]. There is very little information concerning symptom limitation during exercise in CF.…”

“…Several smaller studies have included lactate measurement in the assessment of peak exercise, and have shown that CF subjects do generate a rise in blood lactate on progressive exercise [16][17][18][19]. The present authors found raised lactate levels at peak exercise in CF patients across the full range of pulmonary disease severity, with those in the middle/ moderate group achieving very similar peak concentrations to controls.…”

Do responses to exercise training in cystic fibrosis depend on initial fitness level?

“…The VAT is a useful, reproducible method with which to determine aerobic fitness in healthy adults and children, as well as in CF, and especially for those who cannot perform a maximal incremental cycling test [24,25]. In healthy untrained people, the VAT occurs at intensities between 50-60% of V9O 2 ,peak and rarely surpasses 60% of V9O 2 ,peak [26].…”

Static Hyperinflation Is Associated With Decreased Peak Exercise Performance in Children With Cystic Fibrosis

“…11 Estimation of the anaerobic threshold by the V-slope method, which was used for some subjects, may have influenced breathing reserve index values at the anaerobic threshold, but not at W peak . 23 Our results show that breathing reserve index at W peak is a useful indicator of ventilatory limitation, even in younger children.…”