Chronic head‐down‐tilt sleeping as physiological regulator of bone remodelling during diminished muscular activity in humans

Summary Objectives Head‐down‐tilt (HDT) sleeping with periodic fluid redistribution (PFR) assumes a significant importance by the possibility of regulating bone remodelling. We hypothesized that HDT sleeping with chronic PFR which expands fluid volume would contribute to and/or increase bone formation. Therefore, we studied the potential benefits of osteogenesis with HDT sleeping of chronic PFR during diminished muscular activity (hypokinesia; HK). Methods Studies were conducted on 40 male healthy volunteers. They were divided into four groups: head‐down‐tilt sleeping control subjects (HDTSCS), head‐down‐tilt sleeping hypokinetic subjects (HDTSHS), active control subjects (ACS) and hypokinetic subjects (HKS). The iliac crest cancellous bone and trabecular bone volume and cortical thickness were measured during pre‐experimental period of 390 days and experimental period of 360 days. Results Iliac crest cancellous bone and trabecular bone volume and cortical thickness were increased (P