Reducing Exercise-induced Bronchoconstriction in Children With Asthma and Obesity
Reducing Exercise-induced Bronchoconstriction in Children With Asthma and Obesity
In obese children, excess fat exerts an increased mechanical burden on the respiratory
 system, particularly during exercise. It is unclear whether this burden reduces respiratory
 function and exercise tolerance and increases severity of exercise-induced
 bronchoconstriction in obese asthmatic children. The investigators propose that most of the
 respiratory effects in obese asthmatic children are the result of low lung volume breathing
 (i.e., reduced functional residual capacity). The first objective of this study is to
 investigate respiratory function, exercise tolerance, and exercise-induced
 bronchoconstriction in obese vs. nonobese asthmatic children. Guidelines from the American
 Thoracic Society strongly recommend interval warm-up exercise before planned exercise to
 reduce exercise-induced bronchoconstriction severity. However, no empirical data on the
 effects of interval warm-up exercise on exercise-induced bronchoconstriction severity are
 available in obese asthmatic children, where excess fat exerts such an unfavorable burden on
 the respiratory system, particularly during exercise. Thus, the second objective of this
 study is to investigate the effects of interval warm-up exercise on exercise-induced
 bronchoconstriction severity in obese and nonobese asthmatic children. Our approach will be
 to investigate exercise tolerance, respiratory function, and exercise-induced
 bronchoconstriction severity and the effects of (1) 8x30sec interval warm-up & (2)
 pretreatment with a bronchodilator compared with a no-treatment control on exercise-induced
 bronchoconstriction severity in 8-12 yr, prepubescent, obese and nonobese asthmatic children.

 [Aim 1]: To investigate respiratory function and exercise tolerance [Hypothesis]: Obesity in
 children with asthma will reduce respiratory function and exercise tolerance [Aim 2]: To
 investigate exercise-induced bronchoconstriction. [Hypothesis]: Obesity in children with
 asthma will increase exercise-induced bronchoconstriction severity as evidenced by a greater
 maximum % fall in forced expiratory volume in the first second after an exercise challenge
 test.

 [Aim 3]: To investigate the effects of interval warm-up exercise on exercise-induced
 bronchoconstriction severity. [Hypothesis]: Interval warm-up exercise will reduce
 exercise-induced bronchoconstriction severity after an exercise challenge test to a similar
 extent as bronchodilator and better than control, although to a greater extent in nonobese
 asthmatic children.
The investigators will enroll prepubescent, 8 - 12 yr old, obese (body mass index > 95th
 percentile; N=25) and nonobese (body mass between 16th and 84th percentile; N=25) children
 with mild asthma. The investigators will investigate the severity of exercise-induced
 bronchoconstriction during planned exercise performed 15 minutes after the following three
 conditions performed on separate days in a random order: (1) 8x30sec interval warm-up, (2)
 short-acting beta agonist or albuterol, & (3) control, in prepubescent, 8 - 12 yr old, obese
 and nonobese children with mild asthma. The investigators will also investigate differences
 in pulmonary function, exercise tolerance, and severity of exercise-induced
 bronchoconstriction between obese and nonobese children.

 The investigators will measure the following in all participants:

 1. Pulmonary function: spirometry, lung volumes, diffusing capacity of lung for carbon
 monoxide, maximum voluntary ventilation, maximal inspiratory and expiratory pressures,
 airway resistance, and expired nitric oxide

 2. Exercise tolerance during graded cycle ergometry: Gas exchange, ventilation, heart rate,
 blood pressure, pulse oximetry, electrocardiogram

 3. Ratings of perceived breathlessness and exercise induced bronchoconstriction in response
 to a 6 minute high-intensity exercise challenge after three conditions performed on
 three separate days:

 Three conditions that will precede the exercise challenge include:

 1. 8x30sec of interval warm-up 15min prior to exercise challenge: This includes eight 30sec
 bouts of high-intensity interval exercise at 85-95% of HRmax, with 45sec of recovery
 between.

 2. Two puffs of albuterol 15 min prior to exercise challenge

 3. Control: seated rest for 15min prior to exercise challenge
Inclusion Criteria:

 -  no history of smoking, no history or evidence of heart disease, no history of
 uncontrolled hypertension, no documented and/or diagnosed sleep disorders, no
 diagnosed diabetes, no metabolic disorders, no history of significant mental illness,
 no dietary restrictions, no serious health conditions, or no musculoskeletal
 abnormality that would preclude exercise.

 -  Normal weight children with a body mass index between the 16th and 84th percentile

 -  Obese children with a body mass index > 95th percentile but less than 170% above the
 95th percentile and less than an absolute body mass index of 40 kg·m2

 -  Pulmonary function criteria 1) forced vital capacity ≥ 80% predicted, 2) forced
 expiratory volume in the first second (FEV1) ≥ 75% predicted, and total lung capacity
 ≥ 80% predicted

 Exclusion Criteria:

 -  Children with significant diseases other than obesity and mild asthma will be
 excluded. A significant disease is defined as either a disease that in the opinion of
 the PI or medical consultant Dr. Craig Nakamura may put the participant at risk
 because of participation in the study or a disease that may influence the results of
 the study or the patient's ability to participate in the study.

 -  Children who cannot follow directions (e.g., eating before testing), adequately
 perform procedures (e.g., pulmonary function tests), or keep appointments (e.g., no
 shows for testing), will be excluded from study participation.

 -  Because the risk of severe exercise induced bronchoconstriction increases in children
 with moderate or severe obstructive airway disease, children with FEV1 < 75% predicted
 will be excluded from the study. Diagnosis of asthma (i.e., airway responsiveness with
 reversible obstruction) will be established by spirometry (i.e., improvement of FEV1
 of ≥8% after administration of bronchodilator).

 -  Children without reversible airway obstruction will also be excluded from the study.

 -  Children who have been hospitalized for an asthma exacerbation or who have taken oral
 glucocorticoids for asthma in the past year, and children who have been admitted to an
 intensive care unit or been intubated because of their asthma in the past five years,
 will be excluded to reduce the risk of exacerbation during the study.