DM: Physical Activity (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To study the potential beneficial effects of strength training versus endurance training on insulin resistance, muscular mass, and VO2 in patients with type 2 diabetes.
Inclusion Criteria:
  • diagnosis of type 2 diabetes that met WHO definition
  • no complications or comorbid conditions
  • ages between 50 and 70
Exclusion Criteria:
  • rapidly progressive or terminal illness
  • myocardial infarction, uncontrolled arrhythmias, third-degree heart blockage
  • blood pressure >200/100 mmHg on therapy
  • nephropathy (microalbuminuria >20 microgram/min albumin excretion
  • severe peripheral or autonomic neuropathy or diabetic proliferative retinopathy
  • severe musculoskeletal and neurologic abnormalities
Description of Study Protocol:

Recruitment Recruited 43 patients from the authors' diabetes outpatient department between September 2000 and May 2002.

Design : subjects randomized to a 4-month program of either endurance or strength training in a laboratory setting

Blinding used (if applicable):  not possible 

Intervention (if applicable)

Endurance Training (ET)

  • systematic training on a cycle ergometer on 3 non-consecutive days of the weeks
  • during first 4 weeks, ET group participants trained for 15 minutes per session, 3 times per week
  • exercise sessions were increased by 5 minutes per session every 4 weeks
  • training was controlled by a heart rate according to 60% of VO2 max

Strength Training (ST)

  • systematic strength training program on 3 non-consecutive days of the week
  • two-week run-in period to adapt patients to strength training
  • after the third week the training aimed at hypertrophy and began with 3 sets per muscle group
  • one set consisted on 10-15 repetitions until fatigue occurred and repetitions were impossible
  • weight was increased when more than 15 repetitions could be achieved and was set at a weight that would permit 10 repetitions
  • the number of sets igradually increased from 3 at the start of the program to 6 at the end

Statistical Analysis

  • 2-way analysis of variance to assess differences between groups at the same time
  • multivariate analysis of variance to assess signficant differences in changes of the same variable before and after training.
  • Pearson product moment correlation coefficients to compare changes in LBM and % BF with the changes in metabolic parameters before and after ST.


Data Collection Summary:

Timing of Measurements Baseline and end of study (4 months)

Dependent Variables

  • maximal muscle strength, based on 1-repetition maximum using the Concept 2 Dyno; this machine includes bench press, rowing, and leg press and creates resistance in direct proportion to the patient's effort
  • Respiratory gas exchange (VO2peak)  all subjects underwent a cycling test on an electrically braked cycle ergometer to the poisnt of exhaustion.  Heart rate was continuously monitored via EKG, and blood pressure was measured in the final minute of each work level.  Exercise started with a work load of 50W and was increased by 25W every 2 minutes until exhaustion
  • BMI
  • fat mass
  • lean body mass
  • blood glucose, HbA1c, insulin, and lipid assays
  • insulin resistance using homeostasis model assessment (HOMA)
  • blood pressure

Independent Variables

  • Endurance training or strength training

Control Variables


Description of Actual Data Sample:

Initial N:43; 22 men; consecutively randomized into the two groups

Attrition (final N):  39 subjects completed.  1 subject withdrew for health reasons, 3 for personal reasons.

Age: 56.4±1.1 years

Ethnicity: not specified

Other relevant demographics: both groups had similar profiles for demographics

Anthropometrics the ST group has significantly higher triglycerides (229±25 mg/dl versus 146±14 mg/dl; P=0.1) and significantly higher fasting blood glucose at baseline (204±16 vs 160±9; P=.04) than the ET group at baseline.

Location: Austria


Summary of Results:



Strength Training Group, Change from Baseline


ST Significance of change from baseline, P value

Endurance Training Group, change from baseline

ET Significance of change from baseline, P value

P, difference between groups at 4 months

Blood glucose, mg/dl

-57 <.001 -1 NS .002

Plasma insulin, pmol/l






HbA1c, %






HOMA-IR -2.0 .04 1.5 NS .009
Cholesterol, mg/dl -23 <.001 -3 NS .03
HDL, mg/dl 5 .004 1 NS NS
LDL, mg/dl -14 .001 -5 NS NS
Triglycerides, mg/dl -79 .001 -1 NS .002
SBP, mmHg -19 <.001 -20 .002 NS
DBP, mmHg -8 <.001 -13 <.001 NS


Cardiorespiratory endurance and muscle strength

  • Peak VO2 improved by 8% for ET and by 1% for ST, neither of which was significant.
  • maximum workload improved by 12% for both groups (ST, P<.01; ET P<.01)
  • the improvement in maximum strength of all muscle groups subjected to ST was highly significant (22-48% of intitial levels.  The percentage change in the ET group ranged from 0% improvement in bench press to 15% improvement in leg press.

Changes in medications

  • ST participants reduced use of sulfonylureas by 12.2%, no change in metformin, and for those using insulin the dose was reduced by 1.0 U per day. 
  • For ET participants sulfonylurea therapy was reduced by 1.7%, no change in metformin, and insulin use dropped by an average of 2.0 U per day

Changes in body composition

  • Percent body fat decreased by 9.1% in the ST group (P<.001) and by 3.4% in the ET group (P<.001)
  • LBM increased by 6.5% in the ET group (P<.001) but the difference was not significant in the ET group.
  • Fat mass decreased significantly in both groups.
Author Conclusion:

"We found significant improvements in long-term glycemic control, as shown by reduced HbA1c levles and an improved IR, estimated by HOMA in participants with diabetes on ST.  The effects of ET on the respective parameters were only moderate."

ST was better than ET in all metabolic parameters measured in regard to an improvement in metabolic parameters.  The positive changes observed in the muscular system coincided with highly significant improvement in metabolic control that resulted in a decreased atherogenic lipid profile.  With the advantages of an improved lipid profile. we recommend ST for the treatment of type 2 diabetes.

Funding Source:
Reviewer Comments:

There were two instances in this article where the wrong terms were used:  triglyceride values were given as 224 mmol/l and I assume they meant mg/dl.  "TC" was used as an abbreviation for triglycerides in a table.  At values for total cholesterol were already shown in the table, I made the assumption that the authors meant "TG" for triglycerides.

Significant differences at baseline between groups.  Authors note that values that are high and beyond the physiologic range can be reduced more easily than values lying closer to the normative range.

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? Yes
  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? Yes
3. Were study groups comparable? ???
  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? Yes
  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? No
  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? N/A
  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)? No
  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? 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