Fitness in the fit: does physical conditioning affect cardiovascular risk factors in middle-aged marathon runners?

The study was designed to assess cardiovascular risk factors in marathon runners with different degrees of fitness.

A total of 30 male middle-aged marathon runners were divided according to their marathon running time into fit (265 +/- 8 min), fitter (222 +/- 5 min) and fittest (178 +/-12 min). The three groups of 10 runners each were comparable in age, weight, and body surface area. Cardiovascular risk factors were assessed by measuring arterial pressure before and during exercise (150 watts) and determination of plasma lipoproteins, uric acid, glucose and white blood cell count before and after a marathon run.

All measured laboratory values such as high-density lipoprotein cholesterol (P < 0.05), low-density lipoprotein cholesterol (P < 0.05), total cholesterol (non-significant), triglycerides (non-significant), blood sugar (non-significant), uric acid (P < 0.01) and white blood cell count (P < 0.05) indicated a lower cardiovascular risk in the fastest when compared with the slowest runners. Resting blood pressure was similar in the three groups but consistently lower at all levels of exercise in the fittest when compared with the less fit runners. The fittest runners also showed greater increases in high-density lipoprotein cholesterol after the marathon run (14% vs 8% in the slowest runners, P < 0.005).

We conclude that even at the extreme end of a continuum such as represented by well-conditioned, middle-aged marathon runners, cardiovascular risk factors are related to the degree of fitness, as measured by the marathon running time.