GDM: Physical Activity (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To study the effects of circuit-type resistance training on the need for insulin in women with GDM.
Inclusion Criteria:
  • Maternal age between 20 and 40 years
  • Gestational age between 26 and 32 weeks
  • BMI below 40
  • Nonsmokers not involved in regular exercise
Exclusion Criteria:
Not described.
Description of Study Protocol:

Recruitment  Subjects were recruited from the Diabetic Outpatient Clinics at local hospitals. 38 women with GDM were recruited

Design  Randomized trial.  Subjects were randomly assigned to groups with the use of a random numbers table.

Blinding used (if applicable)  Allocation into groups was concealed in sequentially numbered opaque envelopes.

Intervention (if applicable)  Subjects assigned to the diet alone group were treated with a standard diabetic diet that consisted of 40% carbohydrate, 20% protein and 40% fat, which was calculated at 24 to 30 cal/kg per day on the basis of the subjects' ideal prepregnant body weight and divided into 3 meals, 3 snacks.  IBW was defined as a BMI between 20-25.  Weight gain was monitored weekly.  The women in this group were asked not to begin a structured exercise program for the remainder of the pregnancy.

Women who were assigned randomly to the diet-plus-resistance exercise group followed the same standard diet while participating in a progressive physical conditioning.  An experienced instructor supervised three introductory sessions and made weekly contact to ensure the safety of participants and encourage adherence to the program.  These participants were instructed to perform circuit-type resistance training 3x/week.  Eight exercises were performed with a 1 minute rest in between.  Subjects were instructed to exercise at a level that felt "somewhat hard".  The exercises were progressed each week as follows: 

  • week 1, 2 sets of 15 repetitions
  • week 2, 2 sets of 15 repetitions
  • week 3, 3 sets of 15 repetitions
  • week 4 to delivery 3 sets of 20 repetitions

Subjects were taught to monitor their own heart rate during exercise to ensure that it did not rise above 140 beats/min.  All exercise sessions were recorded.

Statistical Analysis The Chi-Square test was used to analyze the primary end point of requirement for insulin.  The independent samples t test was used to analyze the secondary end points.  Variables that were not distributed normally were analyzed with the Mann-Whitney U test.

 

Data Collection Summary:

Timing of Measurements  Between 26 and 32 weeks gestation.

Dependent Variables 

  • Need for insulin

Independent Variables

  • Diet alone or diet plus circuit-type resistance training
  • Adherence to diet not measured

Control Variables  Not described

 

Description of Actual Data Sample:

Initial N: 38

Attrition (final N):  32 (84%); 3 dropped due to pregnancy induced hypertension; 2 randomly assigned to exercise program did not participate; 1 dropped due to time constraints

Age: 31.3 + 5.0 y diet alone; 30.5 + 4.4 y diet plus exercise

Ethnicity: Not described

Other relevant demographics: Not described

Anthropometrics

Characteristic Diet Alone Diet Plus Exercise P value
Maternal age (y)

31.3 + 5.0

30.5 + 4.4

.63

Height (cm)

165.1 + 8.5

159.6 + 7.1

.06

Prepregnant body mass (kg)

77.1 + 19.2

65.9 + 8.4

<.05

Prepregnant BMI

28.0 + 5.7

25.9 + 3.4

.21

Gestational age at first visit

29.6 + 2.1

29.0 + 2.0

.44

Wt gain up to dx (kg)

9.5 + 4.8

10.4 + 3.5

.56

Total pregnancy wt gain (kg)

11.2 + 5.7

11.3 + 4.4

.96

Hx of GDM (n)

3

3

1

Location: Edmonton, Alberta, Canada

 

Summary of Results:

The groups were similar in physical characteristics (see anthropometrics above).

Diagnostic Results

Diagnostic Test Diet Alone Diet plus exercise P value
GDM Screen

11.6 + 1.1 (n = 7)

11.1 + .08 (n = 9)

.37

GTT      

Fasting

5.5 + .6 (n = 9)

4.8 + .6 (n = 7)

.03

1 hour

12.2 + .8 (n = 9)

11.3 + .6 (n = 7)

.03

2 hour

9.6 + 1.4 (n = 9)

9.9 + 1.0 (n = 7)

.61

The diet-plus-exercise group participated in an average of 2.0 + .9 sessions of resistance exercise per week.  The diet alone group reported little activity other than walking.  Overall, the number of women whose condition required insulin treatment was not significantly different between the two groups.  Within the diet-plus-exercise group, 30% of the women who exercised 2 to 3 times per week were prescribed insulin therapy.  67% of those women who exercised 0-1.9x/week were prescribed insulin therapy.

The amount of insulin prescribed was signficantly lower in the diet-plus-exercise group compared with the diet-alone group.  Also the latency period between the first clinic visit and the initiation of insulin therapy was significantly longer in the diet-plus-exercise group compared with the diet-alone group (see table below).

Outcome

Diet Alone

(n=16)

Diet Plus Exercise

(n=16)

P value
Required Insulin 9 (56.3%) 7 (43.8%) .48
Amount of insulin required (units/kg) .48 + .3 .22 + .2 <.05
Latency to insulin requirement (wk) 1.11 + .8 3.71 + 3.1 <.05

Other Findings

A subgroup analysis that examined only the women who had a prepregnant BMI of > 25 showed a significantly lower incidence of insulin use in the diet-plus-exercise group.  In this analysis, 8 of 10 women in the diet-alone group were prescribed insulin therapy; only 3 of 10 women in the diet-plus-exercise group were prescribed insulin (p<.5).

There were no differences between the treatment groups regarding home-monitored blood glucose measurements.  When all postmeal values were pooled, the diet-plus-exercise group demonstrated lower blood glucose values compared with the diet-alone group. 

 

 

 

Author Conclusion:

The results demonstrate that in our sample population, resistance training did not reduce significantly the number of women who were prescribed insulin to treat persistent hyperglycemia.  The power to detect a 25% difference in insulin requirement was approximately 55%.  56 subjects would have been required to demonstrate that the effect that was shown (12.5%) was significant.  Although this study did not have the power to show a significant difference in the primary outcomes, the analyses of secondary variables support a beneficial effect of resistance exercise in accordance with our hypotheseis.

The women in the diet-plus-exercise group were prescribed significantly less insulin and had a signficantly longer latency period to insulin use than those women in the diet-alone group, suggesting that resistance training has a positive influence on glycemic control.

As with other studies, this study suggests that there is a difference in the mechanism of GDM in normal weight women versus overweight women.

Adherence to the exercise program was satisfactory because women in this group exercised an average of two sessions per week of the three sessions that had been recommended.

A limitation of this study is the significantly higher initial levels of hyperglycemia in the diet-alone group compared with the diet-plus-exercise group.

Future research with a larger sample size is needed to confirm that resistance training is an effective alternative in lowering the need for insulin therapy.

Funding Source:
Reviewer Comments:

The authors provide adequate justification for looking at resistance training as a means of decreasing and/or preventing insulin use in women dx with GDM, especially given that use of insulin with GDM is so high (50%) in the Edmonton area.

When the power calculations were run is unclear, but it would have been more beneficial to run the power analysis prior to the study so that required sample size could have been achieved.

The authors conclude that adherence to the exercise program was satisfactory, but then go on to reference other studies on aerobic activity with compliance rates of 90-100% and 75-100%.  This study had a compliance rate of 67% with only 2 workout sessions/wk on average.  Perhaps results would have been stronger had subjects increased their frequency levels.

Because the authors did not measure adherence to the diet, they were unable to control for this variable.  Thus, it is difficult to know with certainty whether or not the results seen were due to exercise and/or diet.

No information was provided on ethnicity.

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? 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? No
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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.) ???
  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? ???
  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? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  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? ???
  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? No
  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? ???
  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? Yes
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? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes