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Body height change during upright and recumbent posture
M H Krag1, M C Cohen, L D Haugh
1Department of Orthopaedics and Rehabilitation, Loskeletal Research Center, University of Vermont, Burlington.
Spine
|March 1, 1990
Summary
Body height decreases when upright due to spinal loading, with most height loss occurring in the first hour. Recovery of height also happens rapidly when returning to a recumbent position.
Area of Science:
- Biomedical Engineering
- Human Physiology
- Biomechanics
Background:
- Body height fluctuates throughout the day due to spinal loading.
- Previous data on the timing of these changes, especially initial changes, is limited.
Purpose of the Study:
- To quantify body height changes over time in response to postural changes.
- To analyze the rate of height change during prolonged upright and recumbent postures.
- To model spinal loading effects on body height.
Main Methods:
- Ten healthy subjects underwent precise body height measurements.
- Measurements were taken frequently during 8 hours upright and 4 hours recumbent.
- Experimental errors were rigorously defined and quantified.
- A Kelvin-unit model was fitted to the collected data.
Main Results:
- Significant and rapid body height changes were observed.
- 26% of the total 8-hour height loss occurred within the first hour upright.
- 41% of the total 4-hour height recovery occurred within the first hour recumbent.
Conclusions:
- The spine exhibits rapid adaptation to changes in loading conditions.
- Initial postural changes induce the most substantial body height modifications.
- The findings provide valuable data for understanding spinal mechanics and daily height variations.