Mixed longitudinal study (6 years) of bone mineral density, muscle mass and muscle strength in the leg of aged females--relations to gravitational load and aging.

NASA: Researchers examined the relationship between changes in physiological function in space and aging in older females. The hypotheses were that some of the changes may be due to a decrease in gravitational stimulation, but that some could be caused by aging itself. Data are based on a mixed longitudinal research study performed in aged females since 1995.^ieng

Ultrasound measurement of transcranial distance during head-down tilt.

Exposure to microgravity elevates blood pressure and flow in the head, which may increase intracranial volume (ICV) and intracranial pressure (ICP). Rhesus monkeys exposed to simulated microgravity in the form of 6 degrees head-down tilt (HDT) experience elevated ICP. With humans, twenty-four hours of 6 degrees HDT bed rest increases cerebral blood flow velocity relative to pre-HDT upright posture. Humans exposed to acute 6 degrees HDT experience increased ICP, measured with the tympanic membrane displacement (TMD) technique. Other studies suggest that increased ICP in humans and cats causes measurable cranial bone movement across the sagittal suture. Due to the slightly compliant nature of the cranium, elevation of ICP will increase ICV and transcranial distance. Currently, several non-invasive approaches to monitor ICP are being investigated. Such techniques include TMD and modal analysis of the skull. TMD may not be reliable over a large range of ICP and neither method is capable of measuring the small changes in intracranial volume that accompany changes in pressure. Ultrasound, however, may reliably measure small distance changes that accompany ICP fluctuations. The purpose of our study was to develop and evaluate an ultrasound technique to measure transcranial distance changes during HDT.

Gender differences in muscle strength after 20 days bed rest.

In the previous studies, when Bed rest (BR) was prolonged over 2 weeks, muscle mass and strength began progressively to become reduced. There are many publications investigating the changes in skeletal muscles during inactivity. However it is still unclear whether the changing degrees of muscle mass and strength not only in antigravity muscles but also in non-antigravity muscles differ between males and females. So, the purpose of this study is to investigate gender difference in the effect of 20 days of BR (BR 20) on regional muscle mass and strength of the arm and leg.

Water intake and urinary volume during 20 days bed-rest in young woman.

During the bed-rest in the young subjects, the water intake should be depressed, because the diuretic is probably accelerated, and then the total body water and body weight is decreased by the water loss. In our previous study in 1991, we have reported that urinary volume was gradually increased, while water intake was decreased. Therefore, it was concluded that the decrease in the water intake and the increase in the urinary volume should bring to the negative water balance. In the present study, it is studied whether urinary volume is independent on water intake during 20 days horizontal bed-rest in young woman.

Effects of 20 days bed-rest on cardio respiratory functions during sub-maximal exercise in young woman.

The purpose of present study is to know the effects of 20 days bed-rest on cardio-respiratory functions during sub-maximal exercise in different body positions which were in sitting, supine and 30 degrees head-down position respectively.

Effects of 10-days bed rest and moderate training on LBNP tolerance in young woman.

The tolerable capacity against LBNP was decreased by bed rest and recovered by physical training. The tolerable capacity was related to VO2max and LVEDd. However, the LBNP tolerance capacity should be primarily limited by factors involving venous return in LVEDd, because VO2max must be controlled by the factors.