Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner
Although exercise is recommended to sustain good health, some people on exercise regimens experience adverse changes in cardiovascular and diabetes biomarkers, researchers found.
An analysis of six exercise studies showed that between 8% and 14% of participants had adverse changes in fasting insulin, systolic blood pressure, triglycerides, and HDL-C, according to Claude Bouchard, MD, from the University of Missouri in Columbia, and colleagues.
About 7% of participants had adverse responses in two or more risk factors, the researchers reported in a study published online in PLoS ONE.
Bouchard and colleagues noted that these risk factors are for chronic diseases and differ from cardiac events related to exertion, which are typically associated with cardiomyopathy, coronary artery disease, or a congenital abnormality.
Whether different exercise regimens or durations could negate the adverse response remains to be seen, they said.
Also, it is "highly unlikely" that the adverse effects were the result of exercise-drug interaction because many adverse responders were not on medications for diabetes, high blood pressure, or high cholesterol, they noted.
The definition of an adverse response allowed for at least two standard deviations within participants. Therefore, adverse responses occurred when biomarker levels were recorded as:
An increase of 10 mm Hg or more in systolic blood pressure An increase of 37.2 mg/dL or more in triglycerides An increase of 3.4 mU/L or more in fasting insulin A decrease of 4.6 mg/dL or more in HDL-C
The six studies encompassed 1,687 men and women, both blacks and whites. The mean age in five of the studies was 54, and was 35 in the sixth one, known as the HERITAGE study.
The overall average body mass index was in the overweight range, between 25 and 31 kg/m2. The duration of the exercise programs was between 20 and 24 weeks.
The presence of adverse effects from exercise was first noticed in the HERITAGE study, which comprised 473 whites and 250 blacks. In that study, between 6% and 9% of participants had an adverse response in each of the four categories, with no difference between the two ethnic groups nor between men and women. Researchers then compared the other five studies to HERITAGE and concluded that the results were not "unique to the HERITAGE subjects and exercise protocol."
In the overall analysis, Bouchard and colleagues found that 8.3% of participants experienced an adverse response to their fasting insulin, while 13.3%, 10.3%, and 12.2% were similarly adversely affected regarding HDL-C, triglycerides, and systolic blood pressure, respectively.
In the studies, participants were subjected to various exercise regimens. Researchers analyzed whether low or high intensity exercise made a difference in the rate of adverse response. Among a range of energy expenditure of 4 to 12 kcal/kg of body weight per week, researchers found no differences in the rate of adverse effects.
They noted that it was "remarkable" that each study contained participants that were adversely affected by exercise, "even though the age and health status of the subjects were widely divergent and the exercise programs were quite heterogeneous."
The investigators also examined whether the adverse response in biomarkers translated into a negative effect on cardiorespiratory fitness. They found no such correlation.
"The challenge," they said, "is now to investigate whether baseline predictors of adverse responders can be identified to screen individuals at risk so that they can be offered alternative approaches to modifying cardiometabolic risk factors."
They suggested that further research be conducted examining other cardiometabolic markers such as LDL-C; small, dense LDL particles; markers of low-grade inflammation; adiposity traits; and ectopic fat depots.