While we know that exercise generally helps the cardiovascular system, we don't exactly know how the benefits arise or what you can expect in different people when they exercise to improve their health.
In an effort to gain a more precise understanding how exercise improves health and who it helps the most, 160 randomized clinical trials involving about 7,500 people were analyzed. The review was published in the Journal of the American Heart Association.
The researchers noticed nuances that could be important to doctors and their patients when they consider whether to suggest exercising.
For some of the measures the studies tracked, men often benefited more than women, people under 50 benefited more than people over that age, and people with either Type 2 diabetes, hypertension or hyperlipidemia benefited more than people with none of those conditions. This finding included the review's main clinical indicators of cardiorespiratory fitness (CRF), which measures how well the heart and lungs deliver oxygen to the muscles during physical activity. CRF is a strong predictor of cardiovascular disease (CVD)
A key implication from the findings may be that while exercise appears to affect total cholesterol, lowering "bad" LDL cholesterol for at least some people and raising "good" HDL for most, the proportion of CVD risk that could have been reduced by exercise via effects on total cholesterol and LDL cholesterol is much lower than what has been observed previously. Instead, the researchers note some of the significant benefits of exercise appear to lie in reducing insulin resistance and inflammation based on how those biomarkers performed in the studies.
While the review confirms wide-ranging benefits of exercise, it's still just one of the levers doctors and patients should consider manipulating.
Our meta-analysis is one of the first studies to systematically and comprehensively evaluate the effectiveness of exercise interventions in affecting various health outcomes," said lead author Xiaochen Lin, a doctoral student in the Brown University School of Public Health. "Because the exact mechanisms linking exercise to intermediate health outcomes are not clear, we also wanted to examine the effects of exercise on intermediate biomarkers that may potentially mediate the cardioprotective effects of exercise."
"Based on our findings, exercise interventions are not universally effective across different intermediate outcomes and subgroups of participants," added corresponding author Dr. Simin Liu, a Brown professor of epidemiology and of medicine. "Even though exercise may benefit most people under most circumstances, it does not mean that the same exercise program or therapy should be prescribed to everyone. Besides exercise there are many modifiable lifestyle factors that could be the potential target of interventions for cardiometabolic health. If a subgroup of people cannot benefit from exercise, other alternatives should be considered. That's one of the most important implications of evaluating the heterogeneity of exercise interventions."
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