Dr. Gabe Mirkin was approached by a relative youngster, age 66, with a question: "Am I harming myself by riding 40 miles (64 km) hard three times a week?"

This prompted the 75-year-old cycling physician to do some research, which he posted in his free e-zine available at http://www.drmirkin.com

According to Dr. Mirkin, "Norwegian researchers reported their findings that high-intensity interval training maximally improves every conceivable measure of heart function and heart strength. It also helps to prevent both the pre-diabetic metabolic syndrome and the heart damage it causes (Exercise and Sports Sciences Reviews, July 2009).

"This is more evidence that older people who compete in vigorous sports, such as biking and running, live longer and suffer less disease than people who exercise at a more casual pace."

We'd add that before exercising this way, get clearance from your physician (no matter what your age).

Here's more of Dr. Mirkin's report:

---"The most intense exercise includes interval training -- running or cycling very fast to become severely short of breath, then resting and repeating these almost maximum efforts several times in the same workout.

---"High-intensity interval training raises the good HDL cholesterol far more than less-intense exercise (Journal of Strength and Conditioning Research, March 2009). Intense exercise for older people is still a controversial subject, but these new results concur with many earlier studies.

---"Intense exercise is far more effective than casual exercise in preventing and treating diabetes (Circulation, July 2008) and reducing belly fat (Medicine & Science in Sports & Exercise [MSSE], November 2008).

---"Vigorous exercise protects obese people from heart attacks and prolongs their lives, even if they don't lose weight (MSSE, October 2006).

---"Death rate from cardiovascular disease is lowered by high-intensity activities such as running, swimming, hiking, tennis and climbing stairs, but not by lower-intensity activities such as walking, bowling, sailing, golf and dancing (Heart, May 2003).

---"Intense exercise is more effective in preventing heart attacks than less-intense exercise done more frequently (MSSE, July 1997)."