Exercise-induced Blood Glucose Response in Patients With Type 2 Diabetes
Condition: Type 2 Diabetes Mellitus
MeSH terms: Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      Exercise is recommended for type 2 diabetes, which is a global health problem. However,
      during a moderate-intensity exercise training there is an unpredictable risk of hypoglycemia
      for patients with type 2 diabetes. Therefore, the investigators aim to explore trends in
      blood glucose levels in response to a 12-week moderate-intensity exercise training in
      patients with type 2 diabetes and to explore the predictors of post-exercise blood glucose
      (PEBG) and exercise-induced glucose response (EIGR). A descriptive and longitudinal design
      was conducted. Eligible type 2 diabetes patients were recruited from outpatient clinics of a
      medical center in Taiwan and invited to participate in a 12-week moderate-intensity
      exercise-training program. Each participant received 36 repeated measures of blood glucose
      during the exercise training program. Participants were randomly assigned to one of three
      exercise times (morning/afternoon/evening). Each exercise session was took place 1 to 2 hours
      after a meal. Capillary blood glucose levels were measured pre- and post-exercise. The EIGR
      was calculated from subtracting the PEBG from the before-exercise blood glucose (BEBG).
      Generalized estimating equation was used to examine the trends and predictors of PEBG and
      EIGR.
    

Detailed description: 
      A prospective and longitudinal design using purposive sampling was used. All eligible
      Taiwanese participants with T2DM at a medical centre were invited to participate in the
      exercise-training programme that included three sessions per week, 30 minutes per session for
      12 weeks (total 36 sessions). Each participant's exercise sessions were equally randomised
      into three times of day (morning/08:00-10:00, afternoon/14:00-16:00 evening/18:00-20:00)
      using permuted-block randomisation. Capillary blood glucose samples were obtained before and
      after each 30-minute moderate-intensity (60% VO2max) exercise session. The EIGR, described as
      the difference between BEBG and PEBG values, was calculated.

      Participants and setting: Participants with T2DM being seen at an outpatient clinic in a
      northern Taiwan medical centre were recruited by an endocrinology/metabolism physician.
      Participants, 40-60 years of age, diagnosed as having T2DM based on the criterion of the
      American Diabetes Association, and were being treated with oral antidiabetic medications only
      were eligible. Other inclusion criteria were (1) able to speak and understand Mandarin; (2)
      able to walk without assistance; (3) have no regular exercise habit; and (4) agree to join in
      a 12-week moderate-intensity exercise training after passing a graded exercise test (GXT),
      described below. Exclusion criteria included insulin therapy, a history of cancer, end-stage
      renal disease with dialysis, an inability to participate in exercise training due to comorbid
      neurological and musculoskeletal conditions, severe comorbidity or complications such as
      heart failure, autonomic neuropathy, and recent stroke within 6 months.

      Under an effect size of 0.2, thirty-six numbers of measurements with a correlation efficient
      of 0.32 among repeated measures, an expected power of 0.7 to 0.8, and an alpha of 0.05, the
      required sample size was between 12 and 14 based on repeat measures (within factors).
      Therefore, initially 52 T2DM patients were approached and seventeen eligible participants
      were invited by a research nurse to receive GXT. Fifteen passed the exercise test based on
      the guidelines of the American College of Sports Medicine (ACSM) for exercise testing. A
      second research nurse assessed the baseline characteristics (eg, self-reported demographics
      and lifestyle patterns, blood analyses and anthropometric measures) of the final 15
      participants. Participants were then invited to perform 36 exercise sessions (3 sessions/week
      for 12 weeks), which were randomly assigned to morning, afternoon, or evening using
      permuted-block randomization, except two dropped out after exercise test.

      Graded exercise test: The GXT was performed using a motorised treadmill (Trackmaster 400, JAS
      Fitness System, USA) for identification of maximum oxygen uptake (VO2max), maximum heart rate
      (HRmax) and the risk for potentially life-threatening cardiovascular disease (eg, myocardial
      infarction). GXT procedures followed a modified Balke protocol.20 Two observers (a
      medical/rehabilitation doctor and a research nurse) were involved with each patient
      throughout the GXT. The GXT was immediately stopped if the patient complained of exhaustion;
      reached maximum heart rate or VO2max, determined by the maximal amount of blood the heart
      pumps per minute (cardiac output) and the amount of oxygen utilised by the exercising muscles
      (arterial-venous oxygen difference); had a respiratory exchange ratio >1.15; developed
      symptoms such as chest pain, dyspnea, pallor, diaphoresis or dizziness; had systolic pressure
      greater than 250 mm Hg or diastolic pressure greater than 120 mm Hg; had a decrease in
      systolic pressure of more than 10 mm Hg compared to the systolic pressure at rest; or
      requested stopping the test.

      Ethical consideration: Institutional review board approval (TSGHIRB: 097-05-157) was obtained
      from Tri-Service General Hospital in Taiwan. All participants gave written informed consent
      when invited to join the study. Participants were assured that their participation was
      entirely voluntary and that they could withdraw at any time.

      Data analysis: Statistical analyses were performed by SPSS version 16.0 (SPSS Inc., Chicago,
      IL). Descriptive data are presented as mean/standard deviation (SD) and numbers/percentage
      (%). Before evaluating the trend of blood glucose response during the 12-week/36-session
      exercise-training programme, two variables including "training month (1st, 2nd and 3rd month
      of the training)" and "timing of exercise sessions (1st to 36th session of exercise)" were
      coded. With generalised estimating equations (GEE), the investigators examined the change
      patterns of BEBG, PEBG and EIGR over time during the training programme. The trend analyes of
      BEBG, PEBG and EIGR were adjusted for covariates (i.e, age, gender, baseline body mass index,
      VO2max, HgbA1c, antidiabetic medication (metformin, sulfonylureas or repaglinide) and
      exercise time of day (morning, afternoon or evening). When evaluating the predictors of EIGR
      and PEBG, univariable analysis was applied first and, following the multivariable analysis,
      incorporated with those significant covariates from univariable analysis. All of the
      statistical analyses were two-tailed and considered significant at p < .05.
    

Intervention name(s): a 12-week moderate-intensity exercise training
Intervention type(s): Behavioral
Intervention description(s): a 12-week, aerobic, moderate-intensity exercise training
Other intervention name(s): aerobic exercise training
Allocation: Randomized
Intervention model: Single Group Assignment
Intervention model description: Participants were randomly assigned to one of three exercise times (morning/08:00-10:00, afternoon/14:00-16:00 evening/18:00-20:00).
Training protocol: Treadmills were used for the aerobic exercise training. Participants received supervised exercise training three times per week on alternate days for 12 weeks at the medical centre.
All participants followed this training protocol and maintained their usual lifestyles. The duration of each training session was 30 minutes and took place 1 to 2 hours after a meal.
The intensity of the training was set at 60% VO2max (approximately equal to 72% HRmax) obtained from the GXT.
During each session of the 30-minute aerobic exercise training, the patient's heart rate was maintained at 72% of heart rate maximal on treadmill. Appropriate speed and grade were used to achieve the target heart rate being tracked by the heart rate monitor and to accurately control the required exercise intensity.
Masking: None (Open Label)
Primary purpose: Supportive Care
Keywords: exercise; blood glucose response; metabolic control; type 2 diabetes.