Bone mineral density and serum testosterone in chronically trained, high mileage 40-55 year old male runners

Objectives-To identify physical activity that is beneficial for the mainten ance of bone strength with increasing age by examining the relation between bone mineral density (BRID) and chronic endurance training in men. BMD at the proximal femur, its subregions, and the lumbar spine, and serum testost erone were compared between two groups of long distance runners with more t han 20 years of training experience and non-athletic controls. Methods-Runners (n = 12) were divided into (a) high volume runners (n = 7), running 64-80 km a week, and (b) very high volume runners (n = 5), running more than 95 km a week, and compared with non-athletic male controls, exer cising in non-endurance oriented activities two to four times a week. BMD ( g/cm(2)) at the total proximal femur, femoral neck, trochanteric region, an d lumbar spine was measured by dual energy x ray absorptiometry. Total test osterone (nmol/l) and free testosterone (pmol/l) in serum were measured by radioimmunoassay from single fasting blood samples. Results-Height, weight, and age (range 40-55 years) were not significantly different between groups. The high volume runners had significantly higher BMD at the total proximal femur (1.09 (0.17) v 0.93 (0.056)), femoral neck (0.91 (0.16) v 0.78 (0.071)), and trochanteric region (0.85 (0.14) v 0.73 ( 0.053)) than controls (p<0.05). The differences in BMD for the proximal fem ur between the very high volume runners and the other two groups were not s ignificant. There was no difference in lumbar spine BMD, total testosterone , or free testosterone between groups. However, there was a significant neg ative correlation between total testosterone (r = -0.73, p < 0.01) and free testosterone (r = -0.79, p < 0.005) and running volume in the distance run ners. Conclusions-Long term distance running with training volumes less than 80 k m a week had a positive effect on BMD of the proximal femur. With running v olumes greater than 64 km a week, training was inversely related to testost erone levels, but levels remained within the normal range.