Thune et al1 are to be commended for a thorough study documenting an inverse dose-response relationship between certain metabolic risk factors and physical activity. In their study, the cardiovascular risk factor profile consistently improved when exercise levels increased from "hard to very hard." We recently made a similar observation in marathon runners who were divided according to their marathon running time (MRT) into 3 fitness groups: the fit (MRT, 265 ± 8 minutes), the fitter (MRT, 222 ± 5 minutes), and the fittest (MRT, 178 ± 12 minutes).2 All measured laboratory values such as high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, triglycerides, blood glucose, and uric acid were superior in the fastest when compared with the slowest runners. Resting blood pressure was similar in the 3 groups but consistently lower at all levels of exercise in the fittest when compared with the less fit runners.
Messerli FH, Ketelhut RG, Ketelhut K. Cardiovascular Risk Factors and Physical Activity: How Much Is Enough?. Arch Intern Med. 1999;159(8):882. doi: