Effects of inspired air conditions on catecholamine response to exercise in asthma

[Physical fitness in children with asthma]

The exercise limitation in a child with asthma is the result of several factors: the lack of ventilatory reserve, muscle deconditioning, and cardiac limitation. The severity of the airway obstruction is a major determinant of physical fitness. Aerobic and anaerobic fitness are equally affected. Both types of fitness can be improved by specific training programs.

Exercise-induced bronchoconstriction in adults with asthma--comparison between running and cycling and between cycling at different air conditions

The bronchial response to cycling and running was compared in six adult asthmatic persons. The effects of different air conditions during cycling regarding the induction of bronchoconstriction was studied. The exercise consisted of 6 minutes' work at an intensity of 80-85% of maximal heart rate. Heart rate, oxygen consumption and ventilation were measured to check that the exercise level was the same in all tests. Peak expiratory flow (PEF) was used to test for bronchoconstriction. Bicycling and treadmill running were performed under indoor conditions and bicycling while breathing cold, dry air (-18 degrees C) and room-tempered humid air (60% RH), respectively. No difference in bronchoconstriction was found between cycling and running under indoor conditions. However, bicycling exercise with inhalation of cold dry air provoked more bronchoconstriction than when inhalating humid air (PEF reductions of 19.4+/-6% and 6.1+/-2%, respectively). No differences were found between the exercise modes in heart rate, oxygen consumption, ventilation per minute, respiratory rate, carbon dioxide elimination or subjective ratings of perceived exertion and breathlessness. It is concluded that it is not the type of exercise, but the ventilation demand and humidity of the inspired air that are the main determinants of the occurrence and degree of bronchoconstriction.

Exercise-induced asthma in children: a comparative study of free and treadmill running

BACKGROUND

Exercise is one of the most common precipitating factors of acute asthmatic crises in childhood. Although it has been described as more frequent among children, this is probably due to their more abundant physical activity. Nevertheless, it also occurs at other ages.

OBJECTIVE

The aim of this study is to assess possible differences in postexercise spirometry after treadmill and free running provocation tests.

METHODS

We compared the results obtained in a treadmill test performed by 30 asthmatic children and 30 healthy children with the results obtained with these same children in a free running test, keeping similar environmental conditions (temperature and humidity), exercise intensity (assessed by heart rate), and airway status at the time of the test.

RESULTS

Seventy-three percent of the patients had positive treadmill tests and 63.3% had positive free running tests. For the spirometric parameters studied, there were no significant differences in the percent decrease in postexercise performance after either of the provocation tests. For FEV1, which is the most sensitive diagnostic parameter, the sensitivity was 53.3% in treadmill running and 56.7% in free running, with a specificity of 100% in both tests.

CONCLUSIONS

If environmental conditions, exercise intensity, and airway status are controlled at the time of the test, treadmill and free running can be used indistinctly as asthma-inducing exercises.

Wingate test performance in children with asthma: aerobic or anaerobic limitation?

To investigate the anaerobic capacity in children with bronchial asthma, eight male children with atopic asthma (age: 12 +/- 1.7 yr) and seven healthy control subjects (age: 12 +/- 1 yr) performed a 30-s all-out exercise test: the Wingate anaerobic test (WanT). Post-exercise plasma epinephrine (E), norepinephrine (NE), venous blood lactate (La), and blood pH levels were determined. Peak power (Ppeak), mean power (Pm), and total energy expenditure (Wtot) during the WanT were assessed. The relative importance of aerobic (WO2) and anaerobic (Wana) energy release during the WanT was also evaluated. In comparison with control subjects, the children with asthma exhibited lower Ppeak (W.kg-1): 6 +/- 1.14 vs 7.3 +/- 0.5, P < 0.05; lower Pm (W.kg-1): 4.7 +/- 0.8 vs 5.9 +/- 0.5, P < 0.05; and lower Wtot (Jg-1): 140.3 +/- 25 vs 176.9 +/- 19, P < 0.05. The relative contribution of WO2 (26%) and Wana (74%) to the Wtot was identical in both groups. Blood lactate and pH kinetics revealed significantly lower La values and less acidosis in the asthmatic group (P < 0.001). Lastly, E (pg.ml-1) concentrations were lower in the asthmatic group: 274.96 +/- 84.58 vs 901.28 +/- 604.76, P < 0.05. These results suggest a reduced anaerobic capacity in children with asthma. A diminished adrenergic response to exhausting exercise, leading to a decreased anaerobic glycolysis, could partly account for this phenomenon.