Inclusion Criteria:

• Clinical diagnosis of type 1 diabetes for at least 18 months (The diagnosis of type 1 diabetes is based on the investigator's judgment; C peptide level and antibody determinations are not needed.)
• HbA1c <10.0% (The DCA2000 will be used to assess eligibility.)
• Age 8.0 to <18.0 years
• Weight >39.5 kg at reinfusion centers and >46.0 kg at discard centers
• BMI >5th and <95th percentiles for age and gender
• Stable insulin regimen for at least 1 month and not anticipating a change prior to the subject's completion of the study (Stable is defined as no change in the overall insulin program, i.e., no change from SC injections to pump.)
• Insulin regimen involves use of an insulin pump
• Normal thyroid function (measured within the previous year)

Exclusion Criteria:

• A recent injury to body or limb, Addison's disease, muscular disorder, use of any medication or other significant medical disorder if that injury, medication or disease in the judgment of the investigator will affect the completion of the exercise protocol
• Asthma which has been medically treated within the last year
• Current use of glucocorticoid medication (by any route of administration)
• Current use of a beta blocker medication
• Use of pseudoephedrine 48 hours prior to visit (if used in the 48 hours prior to the scheduled visit, the visit will be deferred)
• Severe hypoglycemia resulting in seizure or loss of consciousness in the 2 weeks prior to a visit (if a severe episode occurs within 2 weeks prior to the scheduled visit, the visit will be deferred)
• Active infection (if at the time of the scheduled visit an infection is present, the visit will be deferred)
• Anticipating a significant change in exercise regimen between visits (i.e. starting or stopping an organized sport)