DM: Physical Activity (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To establish whether the glycemic control achieved in exercise-trained adolescents with type 1 diabetes mellitus is dependent on the quality of glycemic control prior to the initiation of exercise training.
Inclusion Criteria:
Adolescents with type 1 diabetes.
Exclusion Criteria:
Free of diabetic complications that would have prevented them from participating in a training program.
Description of Study Protocol:


Patients were selected from population treated by one of the researchers.  Patients were regularly attending Princess Margaret Hospital Diabetic Clinic.


Randomized Controlled Trial. 

Blinding used (if applicable)

Not used - lab tests.

Intervention (if applicable)

Randomized to groups with either lower or higher than 9% HbA1c and submitted to 12 weeks of supervised training and 12 weeks of unsupervised training.

Statistical Analysis

Results analyzed using paired Friedman nonparametric test.  Similar conclusions reached when data were submitted to ANOVA with repeated measures.

Data Collection Summary:

Timing of Measurements

All patients tested before exercise program, following 12 weeks of supervised training, and after an additional 12 weeks of unsupervised training.

Dependent Variables

  • Body composition measured through skinfold measurements
  • Height, weight, BMI
  • Aerobic capacity measured through Aerobic Power Index submaximal test
  • HbA1c determined by agglutination inhibition immunoassay

Independent Variables

  • Training protocol
  • Subjects instructed to follow normal diet and keep records

Control Variables


Description of Actual Data Sample:

Initial N: 24 adolescents, 12 per group, 12 females

Attrition (final N):  24 assumed; any dropouts not discussed

Age:  mean age 14.0 +/- 1.2 years

Ethnicity:  not mentioned

Other relevant demographics

Anthropometrics:  subjects were of similar socio-economic backgrounds 

Location:  Australia


Summary of Results:


  Pretraining (0 weeks) Supervised Training  (12 weeks)

Unsupervised Training (12 weeks)

Height - Trained (cm) 159.5 +/- 2.9 160.3 +/- 2.8 161.1 +/- 2.9

Height - Control (cm)

157.6 +/- 3.5

158.7 +/- 3.4

159.4 +/- 3.3

Skinfold Scores - Trained (mm)

123 +/- 11 119 +/- 12 125 +/- 13
Skinfold Scores - Control (mm) 100 +/- 9 103 +/- 13 100 +/- 10
Body Mass - Trained (kg) 55.4 +/- 3.7 57.0 +/- 3.6 57.5 +/- 3.7
Body Mass - Control (kg) 48.8 +/- 3.8 50.6 +/- 3.5 51.3 +/- 3.4
BMI - Trained 21.4 +/- 2.5 21.9 +/- 2.4 21.9 +/- 2.6

BMI - Control

19.4 +/- 2.4

19.9 +/- 2.2

20.0 +/- 2.0

Other Findings

12 weeks of supervised training caused a 17% rise in the patients' aerobic capacity which during the following period of unsupervised training decreased to pre-training levels (p < 0.05), thus suggesting a poor compliance with unsupervised training. 

The aerobic capacity of patients in the untrained control group remained stable for the duration of the study (p < 0.05).

In both poorly-controlled and well-controlled diabetic patients, HbA1c did not change in response to 12 weeks of supervised exercise training and remained stable during weeks of unsupervised training (p < 0.05).

In both untrained control groups, HbA1c remained at constant levels for the duration of the study (p < 0.05).

Author Conclusion:
The average levels of HbA1c in poorly and well controlled diabetic patients were not affected by training, a finding indicating that irrespective of the quality of glycemia prior to exercise training, glycemic control in adolescents with type 1 diabetes mellitus does not improve in response to exercise training alone.
Funding Source:
Reviewer Comments:
Subject selection methods may have led to bias.  Small number of subjects per group - final N not discussed.  Authors note that lack of improvement in glycemic control may be due to increased carbohydrate intake but food records were not analyzed.
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? ???
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? ???
  4.1. Were follow-up methods described and the same for all groups? No
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  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? N/A
  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? Yes
  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? No
  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? ???
  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)? ???
  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? No
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? Yes
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