One of the important clinical features of asthma is the exercise intolerance due to an exacerbation.¹ Yet, to our knowledge, this end point has never been assessed in animal models of asthma. In a mouse model of chemical induced asthma we found early and late alterations in ventilatory function using unrestrained whole body plethysmography.^2–,⁴ Partly because this technique has been heavily criticised,⁵ we sought to provide another measure of functional impairment in asthma—namely, exercise endurance. This was done by a simple exercise test in which mice were forced to swim against a limited downwards current;⁶ if they stopped swimming the current pulled them under the water. Swimming endurance time is measured as a proxy of exercise tolerance. Task failure is defined as a period of 5 seconds under water.⁶

The protocol for sensitising and challenging mice was similar to that used previously,^2–,⁴ with small modifications. Male BALB/c mice (±20 g, 6 weeks old) received dermal applications of 20 µl …