Comparison of sustain and dynamic back hyperextension exercises on spinal height in asymptomatic subjects: a pilot study

Abstract

Prolonged sitting during working or crass room sitting is a potential cause of compressive stress on spinal column, especially intervertebral disc due to upper trunk body weight and muscle pull from back and abdomen. This activity can lead to fluid leakage from disc and result in spinal height loss. Previous studies showed short duration back hyperextension while sitting in different pattern may reduce compressive stress and help spinal height recovery. This type of exercise is practical for sedentary tasks in classroom or workplace. The objective of this study was to compare the effect of two types of back hyperextension exercises (i.e., sustained and dynamic hyperextensions) on spinal height (SH) changes and lumbar range of motion (L-ROM) in asymptomatic subjects. A randomized cross-over study was conducted in 12 subjects (6 males and 6 females with a mean age of 23.89 ± 2.37 years) on 3 consecutive days. Each subject was randomly assigned to different sequences of conditions, including: 1) no exercise (control condition); 2) sustained hyperextension and; 3) dynamic hyperextension. The experimenter measured SH using a stadiometer at the beginning of the trial (use as a baseline) and immediately after the first, second and third periods of sitting tasks. Each period included working on a laptop computer for 25 minutes and performing an exercise intervention for 1 minute. L-ROM was also measured at the beginning of the trial and immediately after the third period. Results from repeated measures ANOVA revealed that SH was significantly decrease over time (P < 0.001) and significant different among the conditions (P = 0.023). However, no interaction effect was found between time and conditions (P = 0.396). As compared with the control group, sustained and dynamic back hyperextension were found to be significant (P = 0.043) and marginal significant (P = 0.057) less SH reduction, respectively. However, there was no significant difference in SH reduction between both hyperextension conditions. A decrease on L-ROM in flexion was found after all conditions. However, L-ROM in lumbar extension was increased for the hyperextension conditions and decreased in control condition. In conclusion, both sustained and dynamic back hyperextension exercises every 25 minutes of prolonged sitting may help to reduce potential effect of spinal shrinkage.