Bone metabolic responses to bed rest in young and older men

Abstract

It is well known that immobilization, through reduction of musculoskeletal forces, leads to bone loss. This is well established for clinical conditions, such as stroke, spinal cord injury as well as for spaceflight and disuse models, such as experimental bed rest. Age is another condition that predisposes to bone loss, which is intimately linked to fractures in the elderly population. Bone turn-over is known to be reduced in the elderly, and animal studies suggest ablunted response of bont to mechanical stimuli at old age, and that old age might 'shield' against immobilization-reduced bone loss. Whether this applies also to humans is currently unknown. The aim of the present study therefore was to compare bone metabolic responses to bed rest in a group of young (23.4 (SD2.9) Years, n=7) and older men (59.1 (SD 2.5) Years, n=8). It was hypothesized that bone metabolic responeses would be generally blunted in older men.