PDM: Prediabetes (2013)


Burtscher M, Gatterer H, Kunczicky H, Brandstatter E, Ulmer H. Supervised exercise in patients with impaired fasting glucose: Impact on exercise capacity. Clin J. Sport Med. 2009; 19 (5): 394-398.

PubMed ID: 19741312
Study Design:
Randomized Controlled Trial
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Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The main goal of this study was to compare the effects of counseling alone with that of additional participation in supervised training courses on exercise capacity in patients with impaired fasting glucose.

Inclusion Criteria:

Subjects had to be between 40 and 65 years of age with impaired fasting glucose (defined as fasting plasma glucose concentration of 100-125mg/dL).

Exclusion Criteria:

Subjects were excluded if they were diagnosed with diabetes, the presence of chronic disease rendering a three-year survival unlikely, and cardiopulmonary or musculoskeletal diseases not compatible with the exercise program.

Description of Study Protocol:


Subjects were recruited from a high risk population (overweight (BMI >25kg/m2) or those with first-degree relatives with Type 2 DM) by 10 family physicians in the western part of Austria.


Randomized, controlled intervention trial using a nested cohort approach. 

Blinding used

Not applicable


Participants were randomly assigned into either the counseling alone group or the counseling and supervised exercise group. Both groups were instructed on lifestyle changes to help prevent DM (including dietary goals/eating habits) and increasing physical activity aiming for 30 minutes of activity daily. One group was offered a supervised, progressive, individually tailored aerobic exercise program for one hour twice weekly.

Statistical Analysis

  • Changes between groups were analyzed with a two-way analysis of variance for repeated measurements (group and time)
  • Differences within groups was analyzed with post hoc paired t-tests with Bonferroni correction
  • Correlation analysis was performed to analyze the relationship between changes of performance and training parameters (total time, intensity, frequency)
  • P-values of <0.05 were considered significant.
Data Collection Summary:

Timing of Measurements

All measurements were taken at baseline, before the study began, and after the 12-month intervention program.

Dependent Variables

  • Changes in the level of exercise capacity: Exercise testing was performed on a cycle ergometer beginning with a workload of 25 watts and increased by 25 watts every two minutes until exhaustion (with pedal rate maintained at 70-80rpm). Exercise capacity was expressed in power output and in metabolic equivalents according to ACSM formulas.
  • Body mass: Height and weight were measured with standard calibrated devices. BMI calculated as weight (kg) / height (m2).
  • Body fat: Measured with bioelectrical impedance analysis (BIA)
  • Fasting blood glucose
  • Total cholesterol and HDL was also measured.

Independent Variables

The intervention was the one hour twice weekly individually tailored exercise program. Aerobic work was performed at an intensity corresponding to a blood lactate level of 2-3mMol/L which was determined based on each individual's initial exercise test. Strength training was also incorporated for most individuals. 

Control Variables

  • Nutritional intake was recorded for the counseling and supervised exercise group for one-week periods at the beginning and end of the study period
  • All patients kept a log book of their physical activity.
Description of Actual Data Sample:
  • Initial N: 131 eligible patients (n=68 to the counseling group, n=63 to counseling and exercise group) were initially recruited, however, after month 12, the study had to be terminated (due to financial issues). At that time, only 18 patients had completed the counseling plus supervised exercise group.
  • Attrition (final N): The initial 18 subjects who completed the exercise intervention were compared to 18 patients from the counseling alone group matched for age and gender using a nested-cohort approach. 
  • Age:
    • Counseling and exercise group: 59.1 (7.8) years
    • Counseling alone group: 55.8 (5.5) years
  • Ethnicity: Not specified
  • Other relevant demographics:
    • Each group consisted of eight males and 10 females
    • All subjects were overweight, had a mild degree of IFG and low exercise capacity
  • Anthropometrics:
    • BMI was significantly different between the groups at baseline: 30.6 (4.1) kg/m2 for the counseling and exercise group vs. 27.3 (3.8) kg/m2 for the counseling alone group (P=0.03).
    • No significant differences at baseline between groups on anthropometric data, blood values, exercise capacity, and exercise responses. 
  • Location: Western Austria.
Summary of Results:

Key Findings

  • After the 12-month intervention, both groups had lower FBG
  • Mean values of total cholesterol and HDL did not change within or between groups
  • The percent of body fat did not change within or between groups, however, a small but significant decrease of body weight and BMI was observed only in the supervised exercise group.

Results of Pre- and Re-tests of Both Groups

  Counseling and Exercise Counseling Alone  
  Pretest   Retest     Pretest   Retest     ANOVA
  N Mean (±SD) N Mean (±SD) % Change N P-value N Mean (±SD) % change P-value
Body Mass (kg)  18 86.9 (13.5) 18 84.3(11.5)* -3.0 18 79.4(12.3) 18 80.2(12.0) +1.0 0.03
BMI (kg/m2)  18 30.6(4.1) 18 29.7(3.6)* -2.9 18 27.3(3.8)** 18 27.6(3.9) +1.0 0.03
Fat, %  12 34.4(7.5) 11 31.6(8.8) -8.1 11 30.4(5.7) 7 31.2(6.0) +2.6 0.10
FBG, mg/dL  18 106.8(6.7) 16 100.4(7.0)* -6.0 18 107.9(7.5) 16 99.1(9.9)* -8.2 0.19
TC, mg/dL  18 229.8(35.1) 16 226.4(34.0) -1.5 18 222.6(44.2) 16 231.3(28.9) +3.9 0.31
HDL-C, mg/dL  18 50.6(15.8) 16 48.9(9.5) -3.4 18 59.2(13.6) 14 59.6(17.0) +0.7 0.38
Pmax, watts  18 133.5(39.1) 18 137.5(40.3) +3.0 18 133.3(38.6) 18 123.8(40.8)* -7.1 0.04
METsmax  18 6.8(1.2) 18 7.1(1.5) +4.4 18 7.2(1.1) 18 6.7 (1.3)* -6.9 0.01
HRmax, b/min  18 146(20) 18 148(18) +1.4 17 142(20) 18 136(21) -4.2 0.12
BPmax, mmHg                      
Systolic  18 192(20) 18 207(27) +7.8 17  190(31) 18 194(29) +2.1 0.12
Diastolic  18 94(10) 18 92(11) -2.1 17  89(12) 17 88(13) -1.1 0.59
Lactatemax, mmol/L  17 4.4(2.4) 17 4.3(1.9) -2.3 15  3.4(1.1) 15 3.6(1.1) +5.9 0.83

 *Significant differences between pre- and retests within groups.

**Significant differences between groups at baseline.

SD, standard deviation; FBG, fasting blood glucose; TC, total cholesterol; HDL-C, high-density lipoprotein cholesterol; Pmax, maximal power output; METsmax, maximum oxygen consumption calculated in metabolic equivalent tests; HRmax, maximum heart rate; BPmax, systolic and diastolic maximum blood pressure; Lactatemax, maximum blood lactate.

P value (analysis of variance) for different changes between groups (group x time).

N varies because of missing measurements.  

Other Findings

  • The supervised exercise group (218±105 minutes per week) was two-fold as active as the counseling alone group (111±166 minutes per week) 
  • Counseling alone was not sufficient to maintain or increase exercise capacity; however, counseling and exercise was sufficient to maintain exercise capacity
  • Change in exercise capacity was related to the frequencies of exercise sessions per week (R2=0.7; P<0.05); and total duration of exercise per week (R2=0.6; P<0.05). 
Author Conclusion:

Adequate counseling of patients with IFG with and without supervised exercise does improve fasting glucose levels after a 12-month intervention period.

Two sessions of supervised training per week in addition to counseling, helps to maintain exercise capacity and to lose body mass. 

More than two sessions of exercise per week may be needed to improve exercise capacity.

Funding Source:
Government: Government of Vorarlberg
University/Hospital: University of Innsbruck, Innsbruck, Austria
Other: Austrian National Bank (OENB)
Reviewer Comments:

BMI was significantly different between the groups at baseline.

The authors made a point to discuss study limitations which were largely due to the early termination of the study and the incomplete log books. As a result, the statistical power of the comparison may have been decreased. However, the authors also state that despite the small groups studied here, the fact that there still were statistically significant results indicate that there is a definite potential benefit of exercise in diabetes prevention. 

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? No
  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? No
  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? ???
  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? No
  6.6. Were extra or unplanned treatments described? No
  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? ???
  8.1. Were statistical analyses adequately described and the results reported appropriately? ???
  8.2. Were correct statistical tests used and assumptions of test not violated? ???
  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)? No
  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