The effects of gravity inversion on exercise-induced spinal loading

Abstract

Changes in stature reflect the creep behaviour of the intervertebral discs when loaded and unloaded. Running, weight-training and bounding are exercises which load the spine and cause a loss in stature. Gravity-facilitated traction (inversion) has been shown to unload the spine and increase stature. This study examined the use of a gravity-inverted posture for attenuating the shrinkage induced by a bounding exercise regimen.

Eight male subjects, aged 20–26, performed the experimental protocol twice, at the same time of day (14·00 hours) with an alteration only to their 10min pre-exercise behaviour. The first occasion involved standing and the second involved gravity inversion at an angle of 50 degrees to the vertical. Prior to testing, each subject stood for a period of 20 min. Measurements of stature were taken at the beginning of the experiment, before and after the pre-exercise treatments, after the exercise period and at 5 min intervals during a 20 min standing recovery. A stadiometer, accurate to within 0·5 mm, was used to record alterations in stature. The exercise regimen consisted often sets of five standing broad jumps with 15 s recovery between each set.

Standing pre-exercise caused little change in stature, whereas, gravity inversion caused a mean increase in stature of 2·7mm (p<0·001). Exercise caused a mean shrinkage of 1·7 mm and 3·5 mm when it followed standing and gravity inversion, respectively (p<0·05). These results suggest that the benefits gained by unloading the spine are short-lived.

Keywords:

• Bounding
• Gravity inversion
• Shrinkage