Back in the 1970s Dr. Ken Cooper's book on "Aerobics" suggested the key to preventing heart disease was regular aerobic exercise. Long distance running became increasingly popular in part because of its many purported health benefits. Perhaps the lead marathon running guru back then was Jim Fixx who wrote the best-selling book on running titled "The Complete Book of Running". The death of Fixx at age 52 from a heart attack while running in 1982 helped dispel one of the most popular myths about running marathons, which back then were claimed to confer almost complete protection against developing serious heart disease. Today Dr. Cooper recognizes that diet plays a major role in preventing heart disease. However, many avid runners continue to believe long distance running dramatically reduces their risk of developing heart disease although most now recognize it is far from a panacea.
At the American College of Cardiology (ACC) meeting a cardiologist who was an avid runner himself examined the arteries of 25 runners who had completed at least the last 25 Minneapolis-St. Paul Twin Cities Marathon with CT scans. They compared them to a control group who had all undergone cardiac CT scans for clinical reasons such as an abnormal stress test. Obviously this control group was more likely to have coronary heart disease than the general population. Risk factors such as total and LDL-cholesterol, blood pressure, and triglycerides were similar between the two groups but the runners had higher HDL-cholesterol levels and lower BMIs and heart rates than the control group. Based on conventional risk factors the runners would be expected to have less artery disease. Surprisingly the marathon runners had significantly more calcified plaque volume (274 cubic mm versus 169 cubic mm) than the far less active control group. Another study presented at the same ACC meeting on marathon runners by Dr. Kardara in Greece examined the BP of 42 long time marathon runners and 46 controls the same age. The runners had all been training 2 to 9 hours per week for 2.5 to 21 years. Even so Dr. Kardara reported that the runners had higher systolic blood pressure (126 vs. 115mmHg) and an increased pulse wave velocity indicating their aortas were likely stiffer than those of the control group.
Bottom Line: While these recent data should be cause for concern about a possible adverse affects from prolonged intense aerobic training they should not be viewed as an excuse to adopt a sedentary lifestyle. In moderation the evidence certainly shows that aerobic training's health benefits outweigh the risk. It may be that excessive training may directly damage the cardiovascular system and/or it may be those who train intensely eat more food and so more saturated fat, salt, and cholesterol. These dietary insults are now known to promote atherosclerosis and damage arteries even when their impact on CVD risk factors appears modest.
By James J. Kenney, PhD, RD, FACN
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.