PDM: Metabolic Syndrome (2013)


Kim MK, Tanaka K, Kim MJ, Matsuo T, Ajisaka R. Exercise training-induced changes in heart rate recovery in obese men with metabolic syndrome. Metab Syndr Relat Disord. 2009 Oct; 7 (5): 469-476.

PubMed ID: 19450157
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine whether moderate-intensity physical training for three months changed post-exercise heart rate recovery (HRR) in obese men with and without metabolic syndrome.

Inclusion Criteria:

Middle-aged obese men (metabolic syndrome, N=20; non-metabolic syndrome, N=22) classified on the basis of Adult Treatment Panel III criteria were investigated in this study.

Exclusion Criteria:
  • Individuals taking any medication
  • Individuals reportedly free of diagnosed cardiovascular disease
  • Any contraindication to exercise
  • Any known metabolic disorder
  • For analysis, the researchers also removed individuals who were unable to perform exercise for impaired exercise tolerance at pre-test (N=4), personal reasons and orthopedic problems (N=9) over the course of the exercise training.
Description of Study Protocol:
  • Recruitment: Subjects were recruited through advertisements in local newspapers
  • Design: Non-randomized clinical trial
  • Blinding used: Implied with measurements.


12-week exercise training program and diet record:

  • Target 60% to 70% of maximal heart rate, 60 minutes per day, three days per week
  • Supervised aerobic exercise was conducted at a fitness studio
  • Aerobic exercise intensity was based on the percentage of each subject's maximal heart rate at the initial fitness test, and then the exercise intensity was increased gradually over time
  • Subjects were encouraged not to alter their dietary intake during the course of the study and the subjects were asked to monitor their diets by completed dietary records on a weekly basis.

Statistical Analysis

  • Descriptive statistics were used to describe the data
  • Alpha was set at 0.05 and statistical power was 80% to detect a clinically important difference equal in size to the population standard deviation (SD) for HRR and HRR decay constant
  • A paired T-test was used to analyze change in parameters
  • A two-way analysis of variance (ANOVA) with repeated measures was used to analyze the data
  • A post hoc Tukey test and a Bonferroni-corrected 95% confidence interval were used for further evaluation after adjusting for change of body weight
  • P<0.05 was considered statistically significant.
Data Collection Summary:

Timing of Measurements

Baseline and at 12 weeks post-intervention.

Dependent Variables

  • Maximal aerobic capacity and HRR:
    • Subjects underwent maximal graded exercise test on a cycling ergometer to evaluate cardiovascular function and to determine simultaneously the individual's peak oxygen uptake (VO2) and anaerobic threshold (AT)
    • HRR data was calculated and exercise capacity was measured and converted to maximum oxygen consumption calculated as metabolic equivalents (MET).
  • Biochemistry analysis: All fasting blood sample measurements were performed after an abstinence of caffeine and an overnight fast
  • Anthropometric measures:
    • Anthropometric measures including height, weight, body mass index (BMI) and waist circumference (WC) were taken
    • Total energy expenditure and activity energy expenditure were measured by both uniaxial accelerometry sensor
    • Abdominal visceral fat and subcutaneous fat were measured by computer tomography.

Independent Variables

12-week exercise training program and diet record:

  • Target 60% to 70% of maximal heart rate, 60 minutes per day, three days per week
  • Supervised aerobic exercise was conducted at a fitness studio
  • Aerobic exercise intensity was based on the percentage of each subject's maximal heart rate at the initial fitness test and then the exercise intensity was increased gradually over time
  • Subjects were encouraged not to alter their dietary intake during the course of the study and the subjects were asked to monitor their diets by completed dietary records on a weekly basis.

Control Variables

Change of body weight.

Description of Actual Data Sample:

Initial N

  • N=20 metabolic syndrome males
  • N=22 non-metabolic syndrome males.

Attrition (Final N)



Approximately 50 years old.


Not identified.

Other Relevant Demographics



Both groups of men were similar in anthropometric measures at the beginning of the study.


University of Tsukuba, Tsukuba, Ibaraki, Japan.

Summary of Results:

Key Findings

  • Peak heart rate (HR) remained unchanged
  • HR at anaerobic threshold significantly decreased for both groups after exercise training (metabolic syndrome group, 115.5 to 109.1, P<0.05; non-metabolic group, 118.4 to 114.2, P<0.05)
  • HR at rest was significantly decreased in the metabolic syndrome group after training (71.2 to 67.7, P<0.05)
  • HRR significantly improved in the metabolic syndrome group (-26.1±3.6 beats per minute vs. -33.5±3.8 beats per minute, at one minute; -39.9±4.9 beats per minute vs. -49.5±4.9 beats per minute, at two minutes, P<0.05) with no change for the non-metabolic syndrome group (P>0.05)
  • HRR decay constant values showed significant improvement in the metabolic syndrome group (0.31±0.02% per second vs. 0.35±0.02% per second, P=0.038) after exercise training, but not the non-metabolic syndrome group (P>0.05)
  • In the subjects with metabolic syndrome, there were significant reductions in body weight (from 88.1±2.7 to 85.1±2.5kg, P<0.01) and waist circumference (from 104.1±2.0 to 99.6±1.8cm, P<0.01) after the exercise training program
  • While there were no significant changes in HDL cholesterol, triglyceride levels were significantly reduced from 193.2±25.5 to 143.6±11.7mg/dL (P<0.01) 
  • While there were no significant changes in fasting glucose, glycosylated hemoglobin was significantly reduced from 6.2±0.2% to 5.9±0.2% (P<0.01) 
  • There were no significant changes in systolic or diastolic blood pressure.
Author Conclusion:

This study demonstrated that moderate-intensity physical training without caloric restrictions improves HRR in obese men with metabolic syndrome, possibly due to a reduction in the resting HR. Therefore, weight loss-induced exercise training would help in improving the resting HR, and the responsiveness of the autonomic nervous system in obese men with metabolic syndrome. 

Funding Source:
Other: Grant-in-Aid for Scientific Research from the Japan Ministry of Education, Culture, Sports, Science & Technology
Reviewer Comments:
  • Small numbers of subjects in groups and only males studied; unclear if the subjects were representative of the local population. Sample size not well described in terms of demographic information.
  • Authors note the following limitation: Autonomic nervous system function was not measured directly; HRR was thought to be a measure of autonomic nervous system function.
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? No
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? No
  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? N/A
  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? N/A
  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? 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)? N/A
  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? N/A
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