To examine the effects of aerobic exercise on resting blood-pressure in normotensive adults.

MEDLINE was searched for journal articles from 1963 to 1992. Cross referencing and handsearching was also undertaken.

Study designs of evaluations included in the review

Studies in which aerobic activity was the primary mode of training, and which included a control group. 67% of studies randomised participants to exercise and control groups, were included.

Specific interventions included in the review

Running, walking, cycling. On average, training programmes lasted 19 weeks (range: 10 to 24), 3 days per week, 36 minutes per session at moderate intensity (85% maximum heart rate).

Participants included in the review

Normotensive adults (resting blood-pressure less than 140/90 mmHg) were included (total n=438). Exercise groups (n=289) were sedentary before participation in an aerobic exercise programme; control groups (n=149) continued to be sedentary during the study. Most participants (greater than 90%) were male.

Outcomes assessed in the review

Diastolic and systolic blood-pressure were assessed.

How were decisions on the relevance of primary studies made?

The author does not state how the papers were selected for the review, or how many of the reviewers performed the selection.

The studies were coded on the basis of randomisation, study size and duration; also on variables which characterised the study population (age, weight, etc.) and details of measurement of blood-pressure. The author does not state how the papers were assessed for validity, or how many of the reviewers performed the validity assessment.

A table of mean blood-pressure data was produced from each of the 9 studies.

How were the studies combined?

The studies were combined in a meta-analysis of blood-pressure data.

How were differences between studies investigated?

Differences between the methods of blood-pressure measurement were discussed and tabulated, but not linked with results. Relationships between blood-pressure outcomes and 'potentially confounding variables' were investigated using Pearson's correlation coefficient.

There were 9 studies in total: 6 randomised controlled studies and 3 non-randomised controlled studies.

Statistically-significant reductions of 3 (95% confidence interval, CI: 1.30, 5.110) and 3 (95% CI: 0.05, 4.82) mmHg were found in exercise groups (absolute reductions of 2% and 4%) for resting systolic and diastolic blood-pressure, respectively.

None of the changes were significant for control groups.

Significant correlations were found between changes in resting blood pressure and duration of training (systolic, r=0.66; diastolic, r=0.80, both p<.05). No significant relationships were found for any other variables.

Aerobic exercise produces small reductions in resting systolic and diastolic blood-pressure among normotensive adults; however, such reductions may not be clinically important. More meticulous studies on this topic are needed.

This meta-analysis combined study results separately for the intervention group and the control group. Therefore, the combination of treatment effects from the primary studies was methodologically flawed.

More information on the differences between studies - specifically, on the nature of the interventions - would be helpful, since some appear to have had effects on blood-pressure while others did not. The only information about these differences is the correlation between changes in blood-pressure and duration of training.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.