DLM and Physical Activity

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To assess the influence of the characteristics of the exercise program, particularly exercise intensity, on the blood pressure response to dynamic physical training in otherwise healthy normotensive and hypertensive subjects.
Inclusion Criteria:

Randomized controlled trials

At least 4 week duration

Normotensive, hypertensive, or both types of subjects

No history or presence of cardiovascular disease

Random allocation to intervention groups and control groups or control phases in case of crossover design

Full publication in a peer-reviewed journal

Absence of confounding by some other intervention during the intervention of interest

Actual blood pressures for the intervention and the control groups or phases, or the pressure changes during the intervention and control periods had to be provided

Exclusion Criteria:

Did not explicitly state exclusion criteria, however, this is what I assumed:

1)Nonrandom-control trials

2)<4 week duration

3)Presence or history of cardiovascular disease

4)Never published in a peer-reviewed journal

5)Confounding variables

6)Unavailable access to blood pressure values

Description of Study Protocol:

Recruitment - Articles were identified by a computer-assisted literature search  and by checking the reference lists of published articles on the topic.  The database used for the meta-analysis contained articles published before August of 1998 (however, one of the tables did include an article published in 1999).

 

Design - 1)Meta-analysis  2)Description of studies

 

Blinding used (if applicable)- N/A

 

Intervention (if applicable) - N/A

 

Statistical Analysis - Performed whe SAS software:  1) Meta-analysis used analysis of pooled data with study groups as the units of analysis, w/ weighting for the number of participants in each group  2)  Net effects of physical training were assessed by weighted pooled analyses of the changes in the intervention groups, adjusted for control data  3) Results reported as weighted means & 95% Confidence limits  4) Weighted metaregression analysis was appled to assess whether variations in the results were related to variations in study group or training characteristics

 

Data Collection Summary:

Timing of Measurements - Before exercise training program began and after duration of the study

 

Dependent Variables

  • Change in blood pressure (both systolic and diastolic) in response to training 

Independent Variables - baseline age, sex, blood pressure (systolic and diastolic), BMI, heart rate, peak VO2

 

Control Variables - Duration of training (4-52 weeks), training frequency (1-7x/week), length of each training session [30-60 minutes, except two programs (15 minutes), after exclusion of warm-up and cool-down], type of exercise [(walking, jogging, running)- 69% of the studies, cycling- 50% of the studies, swimming- 3% of the studies, & other exercises- 23% of the studies], intensity of training (30-87% of net maximal exercise performance)

 

Description of Actual Data Sample:

Initial N: Overall results- 44 RCT (comprising 68 training groups/programs for analysis)

                Across-Study Analysis- 35 RCT (comprising 45 study groups or interventions)

                Within-Study Analysis- 14 studies

*They were able to look at more training groups than available studies because some of the studies involved several groups of subjects or appled different training regimens in the same participants. 

Attrition (final N): Overall results:  2674 participants

Age: Overall results:  Average age of the group ranged from 21-79 yrs (mean, 44 yr)

Ethnicity: N/A

Other relevant demographics: 65% of the 2674 participants were men.  Nineteen studies comprised only of men, 4 included only women, sex was unknown in one study, and the other studies included both sexes.

Anthropometrics:  Mean baseline systolic BP- 126.2 mmHg, Mean baseline diastolic BP- 79.9 mmHg, Mean baseline peak VO2- 31.4 mL/min/kg, Mean baseline heart rate- 71.1 beats/min, Mean baseline BMI- 25.6 kg/m2 

Location: Researchers from University of Leuven KULeuven (Leuven, Belgium)

 

Summary of Results:

Overall Results

Table 1.  Baseline data and net changes in response to training

                             Baseline                                                Net Change   

                        N           Mean (95% CL)            Mean(95% CL)          P Value

Systolic BP       68          126.2 (123.3, 129)       -3.4 (-4.5, -2.3)        <0.001

Diastolic BP      68            79.9 (77.9, 82)           -2.4 (-3.2, -1.6)        <0.001

Peak VO2         59            31.4 (29.6, 33.2)        +3.7 (+3.2, +4.3)     <0.001

Heart rate        48            71.1 (69.3, 72.9)         -4.9 (-5.9, -3.9)       <0.001

BMI                   64            25.6 (25, 26.1)            -0.34 (-0.46, -0.22) <0.001

*N=number of groups; VO2 represented as mL/min/kg; Heart rate represented as beats/min

*Changes in blood pressure response to training, after adjustment for the conrol observations, ranged from +9 to -20 mmHg for systolic and from +11 to -11 mmHg for diastolic.  The overall net changes as shown in Table 1, that is, after adjustment for control observations and after weighting for the number of trained participants who could be analyzed in each study group, their total number was 1529.

*Baseline BP was an important determinant of the BP response.  The training induced weighted net change of BP averaged -2.6(95% CL, -3.7, -1.5)/-1.8 (95%CL, -2.6, -1.1) mmHg in the 52 normotensive gourps and -7.4 (95% CL, 5.5%, 8.2%) and 1.2% (95% CL, -8.0, -3.5) mmHg in the 16 hypertensive groups.

Across-study Analysis (Influence of Training Characteristics)

Weighted single metaregression analysis showed that the net changes in systolic and diastolic BP and net training intensity were significant for neither systolic (y=-9.24+0.087*x; r=0.19; P=0.21) nor diastolic (y=-2.56-0.004*x; r=-0.01; P=0.93) blood pressure. 

Changes in blood pressure were not significantly related to the weekly training frequency (P>0.44) or to the time per session (P>0.61)

Total duration of the training program was a significant determinant of the response of systolic (r=0.32; P<0.05), but not of diastolic pressure (P=0.37), the blood pressure reductions becoming less pronounced with longer program duration.

Within-study Analysis (Influence of training characteristics)

There is no convincing evidence that the BP response to dynamic aerobic training differs accoring to training intensity when between 40% and 70% of net maximal exercise performance.  Insufficient data on the effects of light and very hard exercise.

BP response to dynamic aerobic training appears to be similar for frequencies between 3 & 5 sessions per week and for session times between 30 and 60 minutes.  Few data on other exercise regimens except that 7 sessions per week may elicit a slightly greater BP response than 3 sessions/week.

Influence of Volume on Physical Activity

Data:  57 of the 68 study groups (30 from single program randomized controlled studies and 27 from studies in which subjects were randomized to different training regimens and that included a control group or period).

Net extra energy expenditure:  363-1866 kcal/wk (median, 850 kcal/wk)

Overall, no significant relationships between net changes of systolic BP (y=-5.66  + 0.0021*x; r=0.14; P=0.20) and of diastolic BP (y=-2.34 - 0.0002*x; r=-0.02; P=0.86) with the net weekly energy expenditure.

            

 

 

 

 

Author Conclusion:

The BP lowering effect is small, but significant in normotensive subjects, averaging approx 3/2 mmHg after adjustment for control data, and the net effect is more pronounced in hypertensives who benefit from an average BP reduction of 7/6 mmHg.

Training from 3-5x/week during 30-60 minutes per session reduces BP, particularly in hypertensives.  There is some evidence that exercising 7x/week would be slightly more effective than 3x/week.  Training at about 40-50% of net maximal exercise performance (moderate exercise) does not appear to be less effective than training at about 70% (hard exercise) with regard to BP reduction.  Insufficient data are available on exercise intensities of less than 40% (light and very light exercise) and of more than 84% (very hard exercise).

Funding Source:
University/Hospital: University of Leuven KULeuven
Reviewer Comments:

The reviewer did state some flaws in the studies that were analyzed, such as regular follow-up of control subjects, attention ot other lifestyle factors, adequacy of the statistical analyses, and blinded or automated BP measurements.

In studies where groups were assigned a home-based exercise program, how do you know they achieved the proper intensity?  What if they exercised above or below the assigned intensity?

The studies never indicated what race the subjects, therefore, we can't generalize the findings to a particular ethnicity.

Exclusion criteria was never explicitly given.  It was abstracted from the readings.

Articles used supposedly came from a database that contained articles published before August of 1998, however, the tables display a study that was done in 1999 (Moreira et al, 1999) and i don't know how they got that study. 

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
 
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? Yes