. Exercise within lower body negative pressure partially counteracts lumbar spine deconditioning associated with 28-day bed rest. J Appl Physiol 99: 39 -44, 2005. First published March 10, 2005; doi:10.1152/japplphysiol.01400.2004.-Astronauts experience spine deconditioning during exposure to microgravity due to the lack of axial loads on the spine. Treadmill exercise in a lower body negative pressure (LBNP) chamber provides axial loads on the lumbar spine. We hypothesize that daily supine LBNP exercise helps counteract lumbar spine deconditioning during 28 days of microgravity simulated by bed rest. Twelve sets of healthy, identical twins underwent 6°head-down-tilt bed rest for 28 days. One subject from each set of twins was randomly assigned to the exercise (Ex) group, whereas their sibling served as a nonexercise control (Con). The Ex group exercised in supine posture within a LBNP chamber for 45 min/day, 6 days/wk. All subjects underwent magnetic resonance imaging of their lumbar spine before and at the end of bed rest. Lumbar spinal length increased 3.7 Ϯ 0.5 mm in the Con group over 28-day bed rest, whereas, in the Ex group, lumbar spinal length increased significantly less (2.3 Ϯ 0.4 mm, P ϭ 0.01). All lumbar intervertebral disk heights (L5-S1, L4-5, L3-4, L2-3, and L1-2) in the Con group increased significantly over the 28-day bed rest (P Ͻ 0.05). In the Ex group, there were no significant increases in L 5-S1 and L4-5 disk heights. Lumbar lordosis decreased significantly by 3.3 Ϯ 1.2°d uring bed rest in the Con group (P ϭ 0.02), but it did not decrease significantly in the Ex group. Our results suggest that supine LBNP treadmill exercise partially counteracts lumbar spine lengthening and deconditioning associated with simulated microgravity. simulated microgravity; lumbar spine length; intervertebral disk height; spinal curvature; countermeasures MANY ANATOMICAL AND PHYSIOLOGICAL changes occur when the human body is exposed to microgravity. These changes include cardiovascular deconditioning, loss of exercise capacity, muscle atrophy, and bone loss. Moreover, there are several reports concerning spine deconditioning during adaptation to microgravity, such as spine lengthening (4, 28, 32), intervertebral disk alterations (15), spine curvature increase (29), and back muscle atrophy (17).Because the lumbar spine normally bears ϳ50% body weight (BW) during upright posture on Earth (14, 22, 23), this portion of the spine may be uniquely adapted to gravity. On Earth after overnight bed rest, lumbar length increases ϳ2.7 mm (15). During spaceflight, 4-to 6-cm increase of body height occurs in astronauts (4, 28, 32). Additionally, intervertebral disk volume and cross-sectional area (CSA) increase during simulated and actual microgravity (11,15). Animal experiments document disk biochemistry and degeneration during microgravity (12,25). Thornton and collaborators (29) found a decrease in spinal curvature with exposing to microgravity. Moreover, LeBlanc and coworkers (17) report that even short-duration spacefligh...

The purpose of this study was to determine whether lower body negative pressure (LBNP) treadmill exercise maintains lumbar spinal compressive properties, curvature, and back muscle strength after 28 days of 6 degrees head-down tilt (HDT) bed rest (BR). We hypothesize that LBNP treadmill exercise will maintain lumbar spine compressibility, lumbar lordosis and back muscle strength after 28 days of 6 degrees HDT bed rest. Fifteen healthy identical twin pairs (14 women and 16 men) participated in this study. One identical twin was randomly assigned to the nonexercise control (Con) group, and their sibling was assigned to the exercise (Ex) group. The lumbar spine was significantly more compressible Post-BR compared with Pre-BR in the Con (P=0.01). Lumbar spine compressibility Post-BR was not significantly different compared with Pre-BR in the Ex group (P=0.89). In both the Con and Ex groups, there were no significant changes Post-BR in lumbar lordosis compared with Pre-BR. Back muscle strength significantly decreased in the Con group Post-BR (P=0.002), whereas in the Ex group back muscle strength was not significantly different from Pre-BR values. A significant increase in lumbar spine compressibility in the Con group suggests that spinal deconditioning to gravity occurs during 28-day bed rest. Changes in the mechanical properties of the lumbar spine may be an early indicator of lumbar intervertebral disk degeneration. Supine LBNP treadmill exercise provides axial loads to the lumbar spine and may prevent lumbar spine deconditioning associated with HDT bed rest.

OBJECTIVETo investigate the risk of acute myocardial infarction (AMI) following stress hyperglycemia after hip fracture.RESEARCH DESIGN AND METHODSFrom February 2007 to February 2012, we carried out a prospective observational analysis of 1,257 consecutive patients with no history of diabetes who suffered hip fractures. Fasting blood glucose (FBG) and glycosylated hemoglobin tests as well as electrocardiography, ultrasonic cardiography, and chest X-ray examinations were performed after admission. All selected hip fracture patients were divided into stress hyperglycemia and non-hyperglycemia groups according to their FBG, and the incidence of AMI was monitored.RESULTSAmong the patients enrolled, the frequency of stress hyperglycemia was 47.89% (602/1,257) and that of AMI was 9.31% (117/1,257), and the occurrence of AMI in the stress hyperglycemia group was higher than in the non-hyperglycemia group (12.46 vs. 6.41%, P < 0.05). In the stress hyperglycemia patients, FBG reached maximum levels at 2–3 days after hip fractures and then decreased gradually. The AMI incidence (62.67% [47/75]) of the stress hyperglycemia group was highest in the initial 3 days after hip fracture, significantly coinciding with the FBG peak time (P < 0.05). In all patients with AMI, non–ST-segment elevation myocardial infarction occurred more often than ST-segment elevation myocardial infarction (62.39% [73/117] vs. 37.61% [44/117]).CONCLUSIONSStress-induced hyperglycemia after hip fracture increased the risk of AMI.

An interferometric technique capable of accurately measuring wave speed in liquids is reported. The hardware is adapted from a design to measure nonlinear responses of biological tissues to pressure changes (pressure derivatives) and temperature changes (temperature derivatives). It is used with the highly sensitive variable frequency pulsed phase-locked loop (VFPPLL) instrument. The system uses well-understood and well-characterized components and systems. The apparatus covers a temperature range from below 5 degrees C to above 45 degrees C. The system with the high-sensitivity VFPPLL is capable of measurement of wave speed to an uncertainty of less than 0.1%, and changes in wave speed to better than 0.001%. The transducer is an undamped temperature-characterized PZT-5A 500-kHz plate, whose output is corrected for off-resonance operation and for diffraction effects. To test the accuracy of the technique, measurement of ultrasonic compressional wave speed in water at temperatures from 10 degrees C to 45 degrees C are reported, with an estimated uncertainty of 0.07% and a temperature uncertainty of 0.15 degrees C. The agreement between mean values and literature values is better than 0.05%.