Individuals with asthma often limit exercise to avoid respiratory symptoms, thereby reducing their exercise capacity and potentially reducing their health-related quality of life.

In patients with moderate to severe asthma, the incremental step test (IST) provides excellent reliability and validity in assessing exercise capacity without ceiling or floor effects, according to a study published in Pulmonology.

The measurement properties of the IST in adults with asthma had not been previously investigated, although the test has proven reproducible and reliable in patients with COPD, bronchiectasis, acute lung diseases, and pulmonary hypertension, said the study authors. Therefore, researchers sought to investigate the measurement properties of the IST in 50 subjects with moderate to severe asthma recruited from a tertiary university hospital specializing in treating severe asthma.

All subjects performed 1 cardiopulmonary exercise test (CPET) and 2 ISTs in random sequences, with pulmonary gas exchange measured during all exercise tests. The researchers found that peak oxygen uptake (peak VO₂) levels were as follows: for the CPET, 27.6 ml/kg per minute; for the first IST, 22.3 ml/kg per minute; and for the second IST, 23.3 ml/kg per minute. The IST presented excellent reliability (intraclass correlation coefficient=0.93), very good measurement error (2.5%), and construct validity for peak VO₂ measurement compared with the CPET (P <.001) for assessing exercise capacity in subjects with moderate to severe asthma, with appropriate ceiling (10%) and floor (0%) effects.

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