Suspending Basal Insulin Levels for Exercise in Adults With Type 1 Diabetes
Condition: Type1 Diabetes Mellitus; Physical Activity; Hypoglycemia
MeSH terms: Diabetes Mellitus; Diabetes Mellitus, Type 1; Hypoglycemia
Study type: Observational

Summary: 
      The purpose of the study is to determine the effects of insulin suspension at start of
      exercise in individuals with type 1 diabetes. A total of 3 sessions will be required for this
      project. The first will be a familiarization session that requires completed informed
      consent, anthropometric measurements (height, weight, body fat percentage), questionnaires,
      and a test of maximal aerobic fitness. The remaining 2 sessions will be steady-state aerobic
      exercise as well as circuit exercise.
    

Detailed description: 
      Written informed consent will be collected on the first day during the familiarization
      session from all individuals that wish to participate. A researcher will provide a brief
      explanation on how the continuous glucose monitor (CGM) works (Medtronic Inc., Canada) during
      the first visit to the laboratory. They will also describe how the CGM sensor insertion
      process will occur for those participants who have not worn one in the past. The participant
      will clean and sanitize the area and insert the CGM superficially in the skin themselves and
      connect the transmitter device to the sensor. The CGM will be worn for a total of 7 days and
      then removed by the participant and returned to the researcher to be downloaded. The sports
      armband will also be placed on the left upper arm and be worn continuously for 7 days. The
      principal student investigator (PSI) or principal investigator (PI) will provide all
      participants with information about the sports armband and place it on the skin immediately
      following. This device simply sits on the surface of the skin, but has a specific placement
      and activation and must be applied by the PSI or PI. Finally, during exercise visits, the
      Zephyr bioharness will be connected just below chest level and around the rib cage. This
      device is sits on top of the skin simply like an elastic band around the rib cage. The
      bioharness will only be worn during exercise visits and disconnected at the end of each
      activity.

      Blood glucose levels will be monitored frequently during exercise using a Contour Link
      glucometer (Bayer, Canada). Participants will use personal lancing device for finger pokes,
      but the investigators will provide the glucometer and test strips. Each blood sugar check
      will be recorded in the data binder along with carbohydrate intake, any changes in basal rate
      or pump settings, and food intake. If blood glucose levels reach 3.9 mmol/L or less,
      participants will be asked to stop activity immediately and consume fast-acting carbohydrates
      (i.e. Dextrose tablets (Dex4, USA)). 15-minutes after ingestion of carbohydrates, blood
      glucose will be tested again before allowing the individual to return to activity safely. On
      the last day of testing, participants will be asked to return the CGM, sports armband, and
      bioharness to the research team. The data will later be uploaded and analyzed.

      Patients will undergo a fitness assessment (maximal aerobic capacity) during visit 1 and
      perform 40-minutes of continuous (treadmill jogging) and 40-minutes of intermittent
      (calisthenics) high-intensity type exercises (visit 2 and 3). Upon entry to the laboratory,
      participants will be asked to check blood glucose levels using the glucometer provided. The
      first exercise session will consist of a 40-minute treadmill walk/jog at ~40-50% of VO2max.
      The second exercise session will include various aerobic and anaerobic activities including
      push-ups, plank, jumping jacks, high knees, etc. Regular finger capillary blood samples will
      be collected every 10-minutes during exercise. Once the exercise session is complete,
      participants will be asked to remain in the laboratory for 30-minutes for additional blood
      glucose measurements and to ensure hypoglycemic episodes do not occur post-exercise.
      Participants will be given the contour link glucometer to monitor glucose levels throughout
      the evening and night.
    

Observational model: Case-Crossover
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Participants were recruited by random sampling as well as an email blast using previous
        studies that involved individuals with type 1 diabetes on insulin pump therapy and
        regularly active. The previous research project at York University had the same inclusion
        criteria, so that email list will be used to contact those individuals for this study as
        well.