Exercise in Child Health

Inclusion Criteria: Sickle Cell Disease * Tanner 1-5, corresponding approximately to ages 10-17 y/o * SCD diagnosis including all relevant genotypes * Determined to be in relatively good health as a patient with SCD with no complications from SCD that would render participation the study unadvisable * No evidence of other disease or disability that would impair participation in PA * Physician permission to perform CPET * BMI within the average range for age and condition Cystic Fibrosis * Confirmed diagnosis of CF based on either two CF-causing mutations and/or a sweat chloride concentration of \> 60 mmol/l after a positive newborn screening test or on two separate occasions * Tanner 1-5 corresponding approximately to ages 10-17 y/o as documented by a licensed independent provider at screening, or by a validated self-assessment tool * Determined to be in relatively good health as a patient with CF with no complications from CF that would render participation the study unadvisable as determined by a physician. Examples include history of submassive or massive hemoptysis or moderate to severe pulmonary hypertension. * BMI in the average range for age and condition * No evidence of other disease or disability that would impair participation in PA Comparison (Healthy control) * Tanner 1-5 corresponding approximately to ages 10-17 y/o * Determined to be in good health by pre-participation history and physical examination performed by primary care providers or PERC staff * BMI and PA participation (by history) in the average range for age * No evidence of disease or disability that would impair participation in PA Comparison (SARS-CoV-2) * Tanner 1-5 corresponding approximately to ages 10-17 y/o * Documented SARS-CoV-2 infection * Capable of doing exercise as determined by primary care providers or PERC a medical officer Exclusion Criteria: Sickle Cell Disease Treatment for substance or alcohol abuse * Requiring chronic monthly transfusions * Other conditions that preclude exercise such as neuromotor disease, heart disease, or any other condition that would prevent a child from participating in PA Cystic Fibrosis Treatment for substance or alcohol abuse * Other conditions that preclude exercise (such as neuromotor disease, heart disease, or any other condition that would prevent a child from participating in PA) * FEV1 \< 40% predicted based on Global Lung Index equations * Current infection with Burkholderia cenocepacia or Mycobacterium abscessus Comparison (Healthy control) Treatment for substance or alcohol abuse or chronic medication use • Determination by PERC staff of unsuitability for exercise Comparison (SARS-CoV-2) Treatment for substance or alcohol abuse or chronic medication use • Determination by PERC staff of unsuitability for exercise