Table 3 Studies of bone-loss in humans subjected to simulated microgravity.
From: The effects of microgravity on bone structure and function
Technique | Duration (days) | Sample size | µG-related observations | Reference |
|---|---|---|---|---|
HDT | 30 | 12 | • Increased markers of bone resorption by 20% and urinary calcium • Markers of bone formation, such as ALP remain unchanged | Morgan et al.72 |
HBR | 6, 14 | 8, 9 | • Serum calcium levels and ALP unchanged • Urinary calcium excretion greater in 14 days compared to 6 days bed rest • Increased bone resorption despite increased dietary calcium | Baecker et al.74 |
HDT | 60 | 24 | • Cortical bone density and thickness increased at non-weight-bearing distal radius, but trabecular density decreased • Trabecular density increased at weight-bearing distal tibia, but decreased in cortical compartment • Differential effects in different bones and bone compartments | Belavy et al.75 |
HBR | 90, 56, 35, 24 | 8, 10, 10, 8 | • Bone-loss more pronounced in trabecular compared to cortical compartment • Continued bone-loss after initial days of re-ambulation, and more cortical bone lost during this time | Cervinka et al.77 |
HBR / HDT | 6 | 8 | • Increased urinary calcium excretion and bone resorption markers • Osteoclast activity increased following 24 h of bed rest | Baecker et al.65 Heer et al.66 |
HBR | 119 | 18 | • Decreased BMD in spine, hip, calcaneus, pelvis and total body • Unchanged bone-specific ALP, decreased parathyroid hormone, but increased osteocalcin | Shackelford et al.69 |
HBR | 30 | 8 | • Increased markers of bone resorption and urinary calcium • Markers of bone formation unchanged | Smith et al.70 |
HDT | 90 | 9 | • Decrease in proximal femoral BMD • Increased bone resorption markers and urinary calcium • Resistive exercise increased bone formation but did not reduce bone resorption | Watanabe et al.71 |
HDT | 21 | 15 | • Decreased bone ALP and total ALP • Artificial gravity treatment by centrifugation failed to prevent BMD changes | Smith et al.73 |
HDT | 60 | 8 | • Reduced bone density in distal tibia and trabecular distal radius • Cortical thickness decreased at distal tibia but not distal radius • Exercise and nutrition countermeasures failed to prevent BMD changes | Armbrecht et al.78 |
HBR | 56 | 10 | • BMC loss in distal tibia epiphysis, but less severe in those subjected to resistive exercises • Most BMC loss recovered by 12-month follow-up | Rittweger et al.79 |
HDT | 90 | 9 | • BMC loss in tibia, but prevented in groups subjected to flywheel resistive exercise or pamidronate treatment | Rittweger et al.150 |
HBR | 30 | 7 | • Increased bone resorption markers and urinary calcium • Lower body negative pressure reduced BMD loss | Zwart et al.151 |
HDT | 60 | 8 | • Increased bone resorption markers • Resistive and aerobic exercise improved bone formation markers compared to controls • Exercise mitigated BMD loss in hip and leg | Smith et al.73 |
