Exercise-induced asthma - a comparison between two modes of exercise stress.

Two types of treadmill exercise were performed by 10 asthmatics (mean age 32.4 +/- 8.9 years). One type of exercise was a steady state, submaximal effort lasting approximately 7 min. The other was a short, supramaximal effort designed to exhaust the subjects within 50 s. Ventilatory studies as well as gas exchange, arterial blood lactate (LA) and pH were measured pre- and post-exercise. The submaximal exercise caused the expected increase in Raw (19%) and a decrease in FEV1 (21%) and MMEF (20%) measured 10 min following exercise. In contrast, only the MMEF was reduced (26%) at 10 min after the short-exhaustive exercise. It was concluded that short (less than 1 min) and highly intense exercise challenge may cause a drastic fall in MMEF with no changes in FEV1.0 or Raw. It is postulated that the unequal ventilatory response to the two exercise modes is responsible for a greater respiratory heat loss during the long-submaximal exercise and consequently for the greater obstruction of the large airways. In addition the short-exhaustive exercise performed in this study may serve as a simple and accurate tool for detecting small airway obstruction as measured by the MMEF.