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PDM: Prediabetes (2013)

Citation:

Black LE, Swan PD, Alvar BA. Effects of intensity and volume on insulin sensitivity during acute bouts of resistance training. J Strength Cond Res. 2010; 24(4): 1,109-1,116.

PubMed ID: 20093961
 
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 measure the acute effects of two different resistance exercise intensities (moderate vs. high) under two different volumes (single set or multiple set) on 24-hour insulin sensitivity in individuals with impaired fasting glucose.

Inclusion Criteria:
  • Impaired fasting glucose (100 to 125mg per dL)
  • Little to no strength training experience.

 

Exclusion Criteria:
  • Fasting blood glucose less than 100g per dL or greater than 125mg per dL
  • History of smoking, cardiovascular disease, renal or liver disease
  • Taking hypoglycemic or hypertensive medication
  • Any conditions that would be contraindicated for exercise.
Description of Study Protocol:

Recruitment

Participants were recruited from the Phoenix metropolitan area.

Design

Participants were used as their own controls in a randomized, 2 x 2 factorial analysis of variance (ANOVA) crossover design. 

Blinding Used

Implied with measurements.

Intervention

  • The participants had two orientation days and four exercise testing days over a total of four to five weeks
  • Two different resistance exercise intensities (moderate, 65% one repetition maximum [1RM] vs. high, 85% 1RM) under two different volumes (single set or multiple set)
  • On each exercise testing day, after blood samples were drawn, participants consumed a pre-exercise meal of a bagel and 6oz of orange juice 20 minutes before the resistance exercise portion of the session
  • Participants performed one of four randomly selected resistance exercise protocols each testing day lasting between 30 and 55 minutes
  • 24 hours after the exercise session, participants returned for a second fasting blood draw.

Statistical Analysis

Normality of variables was assessed by the Shapiro-Wilkes test. Differences of pre-exercise insulin sensitivity were compared with 24-hour post-exercise within subjects and between treatments using a 2 x 2 factorial ANOVA. Statistical analyses were performed using SPSS 15.0 for Windows (Chicago, IL).

Data Collection Summary:

Timing of Measurements

Participants participated in a maximum of two exercise sessions per week for consecutive weeks until all four protocols had been completed. A minimum washout of 72 hours was used between test days to prevent a carryover effect from previous testing. All resistance exercise sessions were conducted in a climate-controlled setting in a weightlifting laboratory.

Dependent Variables

  • Anthropometrics: Height (cm) and weight (kg) were determined at baseline to calculate body mass index (BMI), weight was taken on a calibrated digital scale and height was measured using a wall-mounted stadiometer
  • Body composition assessment: Fat mass, lean mass and body density were measured using whole body air displacement
  • Blood glucose and insulin sensitivity: Venous blood samples were taken from antecubital vein in the morning between 6 a.m. and 9 a.m., insulin sensitivity was calculated from the homeostasis model of assessment HOMA-IR.

Independent Variables

Two different resistance exercise intensities (moderate, 65% one repetition maximum [1RM] vs. high, 85% 1RM) under two different volumes (single set or multiple set).

Description of Actual Data Sample:
  • Initial N: 17 (12 males and five females)
  • Attrition (final N): 15
  • Age: 18 to 45 years old
  • Anthropometrics: No differences in age or body mass index were found between sexes at baseline
  • Location: Phoenix, AZ.
Summary of Results:

Key Findings

  • There were no significant differences in baseline fasting glucose levels between males and females across each of the four exercise protocols (P=0.804)
  • All of the exercise protocols improved subsequent insulin sensitivity (P=0.002) and glucose (P=0.001)
  • There was significantly greater decrease in glucose (P=0.021) 24 hours after multiple set bouts
  • High intensity showed significant decreases in insulin sensitivity as compared with moderate intensity protocols (P=0.046)
  • High intensity protocols resulted in greater effect sizes for insulin sensitivity (0.83 multiple set, 0.53 single set) as compared with moderate intensity protocols
  • The high intensity, multiple set bout yielded the greatest treatment effect in both fasting glucose (0.61) and insulin sensitivity (0.83)
  • Overall, single set protocols were less effective than multiple set protocols in lowering fasting blood glucose.
Author Conclusion:

The authors concluded the data suggest a dose-response relationship between volume and intensity on insulin sensitivity and fasting blood glucose.

Funding Source:
University/Hospital: Arizona State University, Chandler-Gilbert Community College
Reviewer Comments:
  • Small sample size
  • Sample was not well described.
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? ???
  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? 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? 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? 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? Yes
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)? Yes
  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? 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes