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PDM: Prediabetes (2013)

Citation:

van Dijk JW, Manders RJ, Tummers K, Bonomi AG, Stehouwer CD, Hartgens F, van Loon LJ. Both resistance- and endurance-type exercise reduce the prevalence of hyperglycaemia in individuals with impaired glucose tolerance and in insulin-treated and non-insulin-treated type 2 diabetic patients. Diabetologia. 2012; 55(5): 1,273-1,282.

PubMed ID: 22124605
 
Study Design:
Randomized Crossover Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate the impact of both resistance- and endurance-type exercise on daily blood glucose homeostasis. 24-hour glycemic control was assessed following a single bout of resistance-type exercise and endurance-type exercise in individuals with:

  • Impaired glucose tolerance (IGT)
  • Patients with type 2 diabetes treated with oral blood-glucose lowering medication (OGLM)
  • Patients with type 2 diabetes with exogenous insulin (INS).
Inclusion Criteria:
  • Male
  • IGT or type 2 diabetes
  • BMI higher than 40kg/m2.
Exclusion Criteria:
  • Female
  • BMI higher than 40kg/m2
  • Renal failure
  • Liver disease
  • Hypertension: BP higher than 160/100mm Hg
  • Myocardial infarction within last year
  • Stroke.
Description of Study Protocol:

Design

Randomized crossover experiment in which men were assigned to one of three groups based on their fasting blood glucose and medications taken.

Blinding Used

Not mentioned, implied with measurements.

Intervention 

  • Endurance-type exercise: In advance of study period, participants performed an incremental cycling test to determine their maximum workload capacity (Wmax). During the experimental period, participants completed 45 minutes of continuous cycling at 50% Wmax.
  • Resistance-type exercise: During experimental period, participants completed 45 minutes of resistance-type exercise (75% one repetition maximum)
  • Control: Experiment participants were seated for 45 minutes in a chair next to the cycle ergometer.

Statistical Analysis

  • Continuous Glucose Monitoring (CGM): Downloaded to personal computer using GlucoDay Software (V3.2.2)
  • Interventions: One-way repeated ANOVA, with intervention, group and intervention x group as within-subject factor, between-subject factor and interaction, respectively. When applicable, pairwise comparisons with Bonferroni correction were applied to locate differences between interventions and Scheffe's post-hoc test were applied to locate differences between groups. 
  • P<0.05 was considered significant
  • SPSS 15.0.1.1 software was used for analysis.
Data Collection Summary:

Timing of Measurements

Each participant participated in three intervention periods separated by at least four days. Each intervention period was three days during which the impact of a single session of exercise on subsequent 24-hour blood glucose homeostasis was assessed under free living conditions with the exception of diet.

Dependent Variables

Hyperglycemia was assessed using Continuous Glucose Monitoring.

Independent Variables

  • No exercise
  • Endurance exercise (cycling) was completed at 50% of Wmax
  • Resistance activity was completed using weights as a percentage of total body weight.

Control Variables

  • Diet during experimental period was the same for all participants; the diet followed ADA guidelines
  • Energy requirements were estimated using the Harris-Benedict equation with an activity factor of 1.4
  • Habitual physical activity was not changed; verified using triaxial accelerometer
  • For INS group, no changes to insulin regimen.

 

Description of Actual Data Sample:
  • Initial N: 45 men
    • 15 individuals with IGT
    • 15 type 2 diabetic patients treated with exogenous insulin (INS)
    • 15 type 2 diabetic patients treated with oral glucose-lowering medication (OGLM)
  • Attrition: 45 men
  • Age:
    • Individuals with impaired glucose tolerance (IGT): Mean age 61±2 years
    • Type 2 diabetic patients treated with oral blood-glucose lowering medication (OGLM): Mean age 60±1 years
    • Type 2 diabetic patients with exogenous insulin (INS): Mean age 61±1 years
  • Anthropometrics:
    • Participants were comparable on:
      • BMI
      • Blood pressure
    • Groups were significantly different on:
      • HgA1C
        • IGT: 6.1± 0.1
        • OGLM: 7.5±0.2
        • INS: 7.6±0.3
  • Location: Maastrict, The Netherlands.
Summary of Results:

Key Findings

  • Average 24-hour blood glucose concentrations were reduced from 7.4±0.2, 9.6±0.5 and 9.2±0.7mmol per L during the control experiment to 6.9±0.2, 8.6±0.4 and 8.1±0.5mmol per L (resistance-type exercise) and 6.8±0.2, 8.6±0.5 and 8.5±0.5mmol per L (endurance-type exercise) over the 24-hour period following a single bout of exercise in the IGT, OGLM and INS groups, respectively (P<0.001 for both treatments)
  • No significant differences were observed between the blood-glucose-lowering properties of resistance- and endurance-type exercise.

Average 24-hour Blood Glucose (mmol per L) in Control and Following Exercise

Variables IGT OGLM INS Statistical Significance of Group Difference
Control (no exercise)

7.4±0.2

9.6±0.5

 9.2±0.7  
Following resistance-type exercise 6.9±0.2 8.6±0.4 8.1±0.5 P<0.001
Following endurance-type exercise 6.8±0.2 8.6±0.5 8.5±0.5 P<0.001

Prevalence of Hyperglycemia in 24-hour Period in Control and Reduction Following Exercise

Variables

IGT

 OGLM INS Statistical Significance of Group Difference
Control 2:11±0:37 9:01±1:39 8:16±1:44  

Resistance-Type Exercise

(reduction of hyperglycemia per day, hours:minutes)

1:13±0:20

 6:32±1:21 5:16±1:27 P<0.001

Endurance-Type Exercise

(Reduction in hyperglycemia per day hours:minutes)

 1:19±0:33 6:32±1:46 5:21±1:37 P<0.001

Other Findings

  • The presence of hypoglycemia was not affected by exercise
  • Over the subsequent afternoon and evening following a single bout of resistance-type exercise, the prevalence of hyperglycemia tended to be lower when compared with control, but these observations did not reach statistical significance (P<0.08).

 

Author Conclusion:
  • Improvements in glycemic control following exercise training can be largely attributed to the cumulative effects of transient improvements glucose tolerance following each successive bout of exercise rather than to the structural adaptive response to prolonged exercise training
  • As medication was kept stable, diets were standardized and habitual physical activity was monitored, the effects of both types of exercise were occurred independent from changes in medication, diet and habitual physical activity
  • Given the equal impact of both types of exercise on daily glycemic control, endurance-type exercise sessions can be exchanged for resistance-type sessions without abating the positive impact of exercise on glycemic control
  • A more personalized exercise prescription, tailored to the needs and capabilities of the individual type 2 diabetic patient, is feasible.
Funding Source:
Government: The Netherlands Organisation for Health Research and Development
Reviewer Comments:
  • 100% attrition is impressive
  • Small number of subjects in groups
  • Only men were studied.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes