It has been reported that insulin basal rate reduction initiated at exercise onset can reduce the hypoglycemic risk during exercise. However, another potentially more efficient strategy to prevent exercise-induced hypoglycemia could be to reduce insulin basal rate a certain time prior to exercise. The objective of this study will be to compare the efficacy of two strategies to prevent exercise-induced hypoglycemia during a 60-minute exercise at moderate intensity: 1) reduce insulin basal rate 40 minutes prior to exercise; 2) reduce insulin basal rate 90 minutes prior to exercise.

Inclusion Criteria:

1. Males and females ≥ 14 years of old.
2. Clinical diagnosis of type 1 diabetes for at least two years.
3. The subject will have been on insulin pump therapy for at least 3 months.
4. Last (less than 2 months) HbA1c ≤ 10%.

Exclusion Criteria:

1. Clinically significant microvascular complications: nephropathy (estimated glomerular filtration rate below 40 ml/min), neuropathy or severe proliferative retinopathy as judged by the investigator.
2. Recent (< 3 months) acute macrovascular event e.g. acute coronary syndrome or cardiac surgery.
3. Abnormal blood panel and/or anemia.
4. Ongoing pregnancy.
5. Severe hypoglycemic episode within two weeks of screening.
6. Other serious medical illness likely to interfere with study participation or with the ability to complete the exercise periods by the judgment of the investigator (e.g. orthopedic limitation).
7. Failure to comply with team's recommendations (e.g. not willing to change pump parameters, etc.).