Endurance training is “one of the worst forms of exercise there is,” Dr. Joseph Mercola recently wrote in his online newsletter.
Mercola, who operates a popular alternative health Web site and runs a supplement business, cited a recent study published in the European Heart Journal which measured the effect of extreme exercise on the heart of 40 endurance athletes after four races of varying lengths.
The researchers found that “intense endurance exercise causes acute dysfunction of the right ventricle” or RV enlargement. Though the athletes appear to recover in the short term, the researchers found chronic structural changes and reduced function of the right ventricle in some of the athletes, and called for further study.
The response of the heart to prolonged and intense exercise has always caused some concern and used to be called ‘athlete’s heart,’” said David Nieman, a professor of health and exercise science at Appalachian State University. Moreover, there may be a few athletes who have some abnormal heart adaptations.
But an editorial that accompanied the study Mercola referred to emphasized that scientists know too little to get unduly alarmed until more research is conducted, said Nieman, the director of the Human Performance Labs at the North Carolina Research Campus in Kannapolis, NC.
Nieman also pointed out that the same research team, in another paper, also stated that “…relevant RV enlargement (is) expected in athletes and should not necessarily be interpreted as a sign of pathology.”
Instead of endurance training, Mercola recommends high-intensity-interval training (HIT) or super-slow weight training. “There’s compelling evidence showing that high-intensity interval training, which requires but a fraction of the time compared to conventional cardio, is FAR more efficient, and more effective,” Mercola wrote. “You can literally reap greater rewards in less time.”
Nieman, a marathoner runner and prolific exercise science researcher, disagrees. “Mercola mixes strong opinion with data,” Nieman said. “His opinion that HIT is the best exercise and that running, swimming and cycling (cardiorespiratory or aerobic) are undesirable, flies in the face of scientific consensus,” he said.
“HIT is fine, but should be mixed with aerobic and muscular fitness exercise,” Nieman said.