Table 5.
Adaptation of the skeletal system to microgravity in humans - Study characteristics
| Author, Year | Mission | Subjects | Exercise Regimen | Test & Methods | Anatomic site | Main Outcomes |
|---|---|---|---|---|---|---|
| (Mack et al. 1967) | Gemini 4: 4 days, Gemini 5: 8 days, Gemini 7: 14 days | N=6 G4: n=2 G5: n=2 G7: n=2 |
A planned exercise program was used for the first time in Gemini VII | BMD, x-rays | CAL, talus, phalanges, & capitate | Length of SF and other variables determined amount of bone loss |
| (Whedon 1971) | Gemini 7: 14 days | N=2 | Unstated | Urinary analysis | Total body | Urinary calcium levels increased |
| (Mack and Vogt 1971) | Apollo 7: 11 days, Apollo 8: 6 days | N=6 Apollo 7: n=3 Apollo 8: n=3 |
Isotonic & isometric exercise in a recumbent position. | x-rays | Distal ulna, phalanges, wrist, CAL, & talus | Loss of calcium and bone density were influenced by dietary intake of calcium & exercise |
| (Vogel 1975) | Apollo 14, 15, & 16: various days | N=27 SF: n=9 BR CON: n=15 SMEAT CON: n=3 |
Unstated | Bone mineral changes using x-rays | CAL, RAD & ulna | Trabecular & weight-bearing bones are more susceptible to the negative effects of SF |
| (Smith 1977) | Skylab 2, 3, 4: 28–84 days | N=22 Flight: n=9 Control: n=13 |
Unstated | BMC using photon absorptiometry | CAL & RAD & ulna | Os calcis mineral losses varied among individuals |
| (Rambaut and Johnston 1979) | Skylab 2, 3, 4; 28–84 days | N=unclear | Unstated | Body calcium, BMD, measured by urinary, & fecal analysis | CAL, whole body | Urinary calcium began to increase almost immediately |
| (Oganov et al. 1991) | Saljut-7, 150, 211, 237 days | N=7 | The exercise regimen is not described in detail | BMD was determined using QCT analysis | Lumbar vertebral, & back muscles | Volume and density of back muscles slightly decreased due to exercise countermeasures |
| (Collet et al. 1997) | EuroMir 94, 30–180 days | N=2 | Unstated | BMD and bone metabolism using QCT, ultrasound & bone markers | Tibia, & RAD | Longer duration SF lead to greater negative changes in BMD & bone metabolism |
| (Smith 1999) | MIR 18, 115 days | N=3 | Unstated | Calcium analysis using urinary samples & biomarkers | Whole body | Urinary calcium excretion and bone resorption increased and recovered slowly |
| (Vico et al. 2000) | MIR 30–180 days |
N=15 | Unstated | BMD was measured by pQCT system | Distal RAD & tibia | Greater bone loss occurred in the trabecular bone than in the cortex |
| (Lang et al. 2004) | ISS 2–6, 120–180 days | N=14 | Unstated | DXA, vQCT & QUS | Hip, lumbar spine, heel | Greater bone losses occurred in the hip compared to bone losses in the spine |
| (Smith et al. 2005) | Shuttle-Mir Science, 120–180 days | N=13 | Unstated | Blood & urine analysis to determine bone & calcium metabolism | Total bone & calcium markers | Bone loss is caused by high bone resorption and low intestinal calcium absorption |
| (Keyak et al. 2009) | ISS, 135–195 days | N=13 | Customized exercise regimen. 2 h/day, 4 days/week. Using a treadmill, cycle, & iRED | Bone strength was measured using QCT scan | Proximal FEM | Reductions of proximal femoral strength could lead to an enhanced risk for hip fractures |
| (Vico et al. 2017) | ISS (2007–2013), 120–180 days | N=13 | Unstated | QCT and blood sample analysis | Lumbar spine, femoral neck, total hip, distal RAD & tibia | Certain changes could be partly irreversible |
Note: All the studies in this section have a pre-posttest design, with or without control arms.