Exercise within lower body negative pressure partially counteracts lumbar spine deconditioning associated with 28-day bed rest

Abstract

. 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...

Lower body negative pressure treadmill exercise as a countermeasure for bed rest-induced bone loss in female identical twins

“…Supine treadmill exercise within LBNP effectively mitigated bone loss and changes in bone metabolism associated with simulated microgravity in men [9,36], and while the results from women in the present study were not as consistent as those for men, similar trends existed. Femoral shaft and total hip BMD in the CON group was lower after bed rest than at baseline, but in the EX group there were no differences after bed rest.…”

“…We have previously published reports [9,19,28,36,49] of a study with male subjects in which we used procedures identical to those used for the study reported here. Although in this report we compare the data from female subjects with data from male subjects published earlier [36,49], none of the data from female subjects, nor the heritability data for men or women, have been published previously.…”

“…The EX subjects exercised in an LBNP chamber with a sealed flexible waist seal [9,28,36,43]. On 6 d per week, during LBNP, the EX subjects exercised for 40 min (40-80% pre-bed rest peak oxygen consumption) and then rested for 5 min during LBNP.…”

“…In a recent study of male identical twins [28], we found that supine treadmill exercise within lower body negative pressure (LBNP) mitigated some of the muscle [9] and bone [36] deconditioning associated with microgravity simulated by head-down-tilt bed rest. Moreover, dietary patterns in these subjects had a noticeable effect on the degree of bone loss during bed rest [49].…”

Disc herniations in astronauts: What causes them, and what does it tell us about herniation on earth?

“…However, IVD swelling in spaceflight can be inferred from increases in spine length [5] and body height [6] during spaceflight and from IVD swelling observed in vivo following bed rest (Fig. 2) for a few hours [7,8], overnight [9][10][11][12], and for a number of weeks [13][14][15][16][17][18][19]. At the end of overnight bed-rest, lumbar intradiscal pressure is increased [20].…”