Height increase, neuromuscular function, and back pain during 6 degrees head-down tilt with traction.
BACKGROUND
Spinal lengthening and back pain are commonly experienced by astronauts exposed to microgravity.


METHODS
To develop a ground-based simulation for spinal adaptation to microgravity, we investigated height increase, neuromuscular function and back pain in 6 subjects all of whom underwent two forms of bed rest for 3 d. One form consisted of 6 degrees of head-down tilt (HDT) with balanced traction, while the other was horizontal bed rest (HBR). Subjects had a 2-week recovery period in between the studies.


RESULTS
Total body and spinal length increased significantly more and the subjects had significantly more back pain during HDT with balanced traction compared to HBR. The distance between the lower endplate of L4 and upper endplate of S1, as measured by ultrasonography, increased significantly in both treatments to the same degree. Intramuscular pressures in the erector spinae muscles and ankle torque measurements during plantarflexion and dorsiflexion did not change significantly during either treatment.


CONCLUSIONS
Compared to HBR, HDT with balanced traction may be a better method to simulate changes of total body and spinal lengths, as well as back pain seen in microgravity.
Styf
J R
JR
Gravitational Research Branch, NASA Ames Research Center, Moffett Field, CA 94035-1000, USA.
Ballard
R E
RE
Fechner
K
K
Watenpaugh
D E
DE
Kahan
N J
NJ
Hargens
A R
AR
D000222:Adaptation, Physiological; D000328:Adult; D001416:Back Pain / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D001510:Bed Rest; D001696:Biomechanical Phenomena; D001827:Body Height; D018475:Head-Down Tilt; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011597:Psychomotor Performance; D015203:Reproducibility of Results; D013997:Time Factors; D014143:Traction; D014893:Weightlessness / Q000009:adverse effects; D018474:Weightlessness Simulation / Q000379:methods*