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31-05-2012 | Article

Exercises worsens metabolic measures in a minority of people

MedWire News: A small percentage of people appear to derive harm rather than benefit from regular exercise, report investigators.

A review of data on 1687 participants in six exercise studies showed that 7% had at least two adverse changes in metabolic risk factors, including blood pressure, plasma lipids, or fasting insulin after engaging in regular exercise, write Claude Bouchard (Pennington Biomedical Research Center, Baton Rouge, Louisiana) and colleagues in the open-access journal PLoS ONE.

"We conclude that it is critical to search for potential physiological and molecular predictors so that individuals at risk for adverse response patterns can be identified and offered proper guidance in an exercise medicine preventive or therapeutic context," they write.

The investigators questioned whether individual variations in response to exercise could result in adverse as well as positive changes in four metabolic risk factors: resting systolic blood pressure (SBP), fasting plasma triglycerides, fasting plasma high-density lipoprotein cholesterol (HDL cholesterol), and fasting insulin.

They measured change in technical errors, defined as "the within-subject standard deviation as derived from repeated measures (or assays) over a given period of time." An adverse response to exercise was considered to be two or more technical errors in the direction toward worsening of one of the risk factors.

Adverse responses were considered to be a rise in resting SBP of 10 mmHg or greater, 0.42 mmol/L or more for triglycerides, 24 pmol/L or more for fasting insulin, or a decline of 0.12 mmol/L in HDL cholesterol.

They found that 8.4% of the participants had adverse fasting insulin responses, 12.2% had adverse SBP changes, 10.4% had adverse triglyceride elevations, and 13.3% had an adverse decrease in HDL cholesterol.

There were no significant differences in adverse response between Black and White patients, or between males and females, the authors say.

"The challenge is now to investigate whether baseline predictors of [adverse responses] can be identified to screen individuals at risk so that they can be offered alternative approaches to modifying cardiometabolic risk factors," Bouchard et al write.

By Neil Osterweil