Disc Height loss response

A study 1 in the journal of Ergonomics investigated the likelihood of variability of height loss in the sitting position being impacted by the time of day. The day-to-day variability in asymptomatic participants was also analyzed. The results shared data about height loss changes in the morning and the afternoon.

LBP and Height Loss

Millions of people (ranging from the young to the elderly) suffer from low back pain, or LBP, around the world. Such a condition has physical, psychological, and social implications. Sedentary work (which involves sitting for long periods) has become quite common for students, office workers, and more. Prolonged sitting increases the risk of lumbar disc pathology (which is, in part, associated with loading on the lumbar discs).

Spinal loading is considered as a cause for LBP as it causes spinal tissue shrinkage. Such shrinkage is known as height loss. Studies do show that prolonged sitting can lead to height shrinkage and thus, LBP.

Effects of Time of Day in Height Loss

Certain studies display a significant difference between height loss following loading activity applied during the morning and in the afternoon. Changes in height seem to occur in a ‘fast’ and ‘slow’ phase. The rate of change is higher when individuals wake up in the morning, and then it slows down throughout the day. That’s why, for ergonomic researchers, the influence of time of day is essential to consider when it comes to height loss. Day-to-day variability of height loss response is another factor to observe the influence of activities done during the day.

The Study

The research utilized a test-retest design to assess the effects of time of day on the variability of height loss. A total of fifty asymptomatic participants (25 males and 25 females) were involved. The study only included participants without current neck or back pain.

Take note, the participants were requested to sleep for eight hours (before every test) as well as to avoid vigorous activity for 24 hours before every test.

A seated stadiometer device was used for measuring height loss response.

What was found?

The current study is deemed to be the first of its kind to investigate the effects of time of day on the height loss response variability because of sitting for two consecutive days.

No significant difference in the magnitude of height loss during the morning and the afternoon was observed. Take note, changes higher than 0.886 mm (morning) and 1.128 mm (afternoon) can be attributed to intervention effects.

The study suggested the collection of future data during the morning or in the afternoon. Also, more significant responses are needed to confidently state that height loss responses have been influenced by an intervention.


ligamentum flavum, posterior stability, facets

An MRI study of 162 patients with lower back pain (LBP) and/or leg pain (LP) measured and analyzed the thickness of the ligamentum flavum (LF) at different levels of the lumbar spine and concluded that, though the LF thickness increased with the age of the patient, there was no apparent correlation between a decrease in disc-height and LF thickness. In fact, researchers found that LF thickness had already begun to increase in patients under 40, refuting the theory that LF thickness was caused by buckling of the LF into the spinal canal due to age-related degeneration.


The Study

The researchers involved in this study wanted to examine the theory that hypertrophy of the LF—which covers the postural-lateral spinal canal—is caused by age-related degeneration. Subjects included 87 female and 75 male LBP patients whose mean age was roughly 52-years-old. Patients with scoliosis, spinal fracture, or other deformities of the spine were excluded from the study. Radiographs were conducted, and the thickness of 648 LF was measured at various levels of the lumbar spine, and an analysis was performed by the researchers using Pearson’s coefficient test.


Three important findings were achieved during analysis of the MRI results in this study: LF thickness increases with age; this thickness is not as pronounced at the L2-3 and L5-S levels as in other levels; the LF thickness was extremely pronounced at the L4-5 levels, particularly in younger subjects. Researchers concluded that LF thickening was already in progress in the back-pain study patients between the ages of 30-39.


The results of this study indicate that practitioners should pay close attention to posterior, as well as anterior, elements of disc herniation patients prior to planning for surgical procedures. Thickening of the LF in LBP patients is more likely to occur prior to the age of 40 and is not caused by disc degeneration and LF buckling into the spinal canal, as has been previously suggested. Patients with obvious thickness of the LF at L2-3 should be examined for lumbar spinal canal stenosis, as the results of the study indicate a correlation between the two conditions.

Blurb: A study of lower back pain patients measured and analyzed ligamentum flavum (LF) at different levels of the lumbar spine and concluded that LF thickening occurs in younger (30-40) LBP patients and is not caused by buckling of the LF into the spinal canal due to age-related degeneration.