Respiratory muscle strength training (RMST) is a potential treatment option that has been shown to increase strength and ventilatory function in critically ill patients, patients on ventilators and patients with mild neuromuscular weakness. Currently researchers are examining the role of inspiratory muscle strength training (IMST) in pressure performance of ventilator dependent children with Pompe disease. However, normal pressure-flow-timing responses of lung function are not well-characterized in healthy children. The purpose of this study is to measure RMST-induced changes in respiratory function in healthy children. Children will undergo one session of lung function and strength testing. By studying healthy children's respiratory function, this study will also help to develop more efficient respiratory muscle training exercise prescriptions for children with neuromuscular weakness and impaired respiratory function.

The goals of this study are to collect and evaluate respiratory muscle strength training (RMST) induced changes in ventilatory function in healthy children. Children will undergo one session of pulmonary function and strength testing to quantify rate of inspiratory and expiratory pressure development and to determine whether inspiratory and expiratory pressure correlate to maximal respiratory pressures and forced pulmonary function tests. Currently normal pressure-flow-timing responses are not well-characterized in healthy children. The purpose of this study is to help develop more efficient RMST exercise prescriptions for ill children on ventilators and with neuromuscular weakness.

Participants in the study will refrain from caffeine products and exercise on the day of respiratory testing. In conjunction with respiratory testing, baseline and exertional blood pressure, heart and respiratory rate, and pulse oximetry will be monitored. Participants will complete tidal flow-volume assessments and forced expiratory maneuvers according to the AMerican Thoracic Society guidelines. Participants will undergo 5 sets of 10 maximal-effort breaths against standardized resistances (one set each at 0, 5, 10, 15, and 20 cm H20). Following each set, subjects will rate the load magnitude and their feelings of breathing discomfort using a 0-10 visual analog scale. Participants will also perform maximal inspiratory and expiratory pressure maneuvers. All tests will be separated by at least 2-3 minutes of rest.

Inclusion Criteria:

• Male or female subjects 4-16 years of age.
• Healthy subjects

Exclusion Criteria:

• Have primary pulmonary disease
• Have primary neuromuscular disease
• Have a connective tissue or autoimmune disease
• Have had a respiratory infection with in 15 days prior to study date
• Have acute aminoglycosides antibiotic therapy with in 15 days prior to study date
• Have acute corticosteroids with in 15 days prior to study date
• Have a need to use an inhaler routinely
• Have hepatic failure
• Have hematologic failure
• Have participated in other studies related to medications or exercise
• Have used tobacco products
• Have other precautions

Healthy Children