Bone Density - Triathlete

Abstract

HISTROTY: A male triathlete aged 43 years underwent bone mineral density (BMD) screening after learning that some endurance athletes have low BMD. He was healthy with no fracture history or family history of bone disease. He was taking no prescription medications and denied using any performance-enhancing substances. He had been competing in triathlons for 16 years. BMD was assessed using dual-energy x-ray absorptiometry (DXA). He had low BMD at both the lumbar spine (L1 -4, L-spine) and total hip. After 6 months of his routine off-season weight training and continued endurance activity his BMD improved 9.5% at the L-spine and 2.5% at the hip. Following 6 months of continued endurance training and little weight training, his BMD decreased by 8.2% at the L-spine and 1% at the hip. For the first 6 months, his mean hours of training by modality were as follows: weight lifting 10.1+/− 3.3, cycling 19.0+/− 7.8, running 7.1+/− 3.8, swimming 5.0+/− 1.5. For the second 6 month period, his hours by modality were as follows: weight lifting 1.9+/− 2.4, cycling 16.7+/− 4.2, running 12.9+/− 2.7, swimming 5.0+/− 1.5. EXAMINATION: Examination revealed a well-nourished, well-developed fit male. Vital signs were normal. He had no boney deformities. Scleras were normal color with no bluish tint. He had no stigmata of thyroid dysfunction, malabsorption, hypogonadism or cortisol excess. DIFFERENTIAL DIAGNOSIS: Disturbed calcium homeostasis due to dermal calcium loss Disregulation of bone remodeling due to excess cortisol production Disregulation of bone remodeling due to hypogonadism TESTS AND RESULTS: L-spine BMD was 0.861, 0.943 and 0.871 g/cm2 at baseline, month 6 and month 12 respectively. Total hip BMD was 0.857, 0.879 and 0.870 g/cm2 at baseline, month 6 and month 12. Bone mass was 2.054, 2.140 and 2.051 kg at baseline, month 6 and month 12. Body weight varied from 57.76 to 58.95 and 57.82 kg at baseline, month 6 and month 12. WORKING DIAGNOSIS: Endurance exercise-induced loss of BMD. TREATMENT AND OUTCOMES: Recommend year-round weight training Consider limiting endurance activity, particularly weight supported activities such as swimming and cycling Consider increasing calcium and vitamin D intake through dietary modification or supplementation