Stadiometers & Biomechanics

Graphic from co-inventor Jurgen Eklund
(co-invented with E Nigel Corlett).

Head shot of our version of the stadiometer

This page describes a widely recognized tool for assessing spinal shrinkage, the Stadiometer.

It was invented by Jurgen Eklund and Nigel Corlett, then of the University of Nottingham, to measure shrinkage in stature.

Spinal shrinkage is recognized as an index of the compressive forces acting on the spine. This shrinkage is caused by viscoelastic creep from compression of motion segments. When the discs are unweighted (such as during sleep) this process is reversed.

People’s spines may shrink a couple of centimeters over the course of the day, though researchers differ a bit in their estimates of the amount of shrinkage. The amount of shrinkage shrinkage also varies between individuals.

Stadiometric research should generally be performed in conjunction with subjective measures, such as body part discomfort scales

Research using the Stadiometer to evaluate the physical impact of products and processes on spinal shrinkage follows.

About the Stadiometer

Stadiometer Research (Abstracts)

Image  |  Both files, zipped

Sample study

Eklund, J. A.; Corlett, E. N. (1984) Shrinkage as a measure of the effect of load on the spine, Spine, 9,2,189-94.

Abstract: A new method for measuring spinal load is proposed, whereby changes in body height are used as a measure of disc compression. The rate and magnitude of disc compression are caused by the loading and its temporal pattern. A device is reported for measuring body height (SD < 1 mm).

Experiments showed the diurnal shrinkage during a working day and the rapid recovery when lying down. Other experiments demonstrated how the rate of shrinkage is a function of the load on the spine. Further, shrinkage when sitting in different chairs has been compared, and the results are in agreement with disc pressure measurements, reported in the literature. Finally, examples are given of how the method can be used in ergonomic evaluations.

Sample study

van Deursen, D. L., Goossens, R. H., Evers, J. J., van der Helm, F. C. and van Deursen, L. L. (2000) Length of the spine while sitting on a new concept for an office chair. Applied Ergonomics. 31-1, 95-98.

Abstract: Changes in spinal length were used to evaluate a new concept for an office chair. This so-called dynamic chair imparts passive forced motion to the seated subject. The passive forced motion is a rotary movement about an axis, perpendicular to the seat with amplitude of 0.6° and a frequency of 0.08 Hz. Change of stature is assumed to provide a measure for spinal load. Eight subjects were measured in two situations: static (without motion) and dynamic. In both situations the same office tasks were performed and the duration of the sitting period was 1 h. To allow for the normal shrinkage curve the starting time was the same on each of the measurement days.

The results indicated a significant difference: when sitting on the dynamic chair the average spinal length increased in comparison to the spinal length in the static chair, where average spinal length decreased. It was concluded that there is spinal distress relief due to the passive motion of the chair.

Sample study

Tyrrell, A. R.; Reilly, T.; Troup, J. D. (1985) Circadian variation in stature and the effects of spinal loading, Spine, 10,2,161-4.

Abstract: Using a method comparable with that of Eklund and Corlett (1984) stature was measured with an accuracy of I mm in eight young adults. The mean circadian variation was 19.3 mm (1.1% of stature).

Fifty-four percent of the diurnal loss in stature occurred in the first hour after rising. Approximately 70% was regained during the first half of the night. With static shoulder loads (2.5-40 kg), increases in the rate of shrinkage with increasing weight were nonlinear. Repetitive lifting led to greater shrinkage than with equivalent static loading. Rest in Fowler’s position gave more rapid regains in stature than post-exercise recovery in standing positions. The technique is therefore suitable for assessment of the effects of manual work with both occupational and therapeutic applications.

Sample study

Kanlayanaphotporn, R, Williams, M, Trott P. and Fulton I. (2001) Contribution of soft tissue deformation below the sacrum to the measurement of total height loss in sitting. Ergonomics, 44-7, p685-695.

Abstract: This study investigated the contribution of soft tissue deformation below the sacrum (S) and vertical spinal creep to total height loss (THL) measured in sitting. Eight asymptomatic subjects (four males, four females) aged between 21 and 51 years were measured. Simultaneous measurement of THL and S were commenced after the subjects had been sitting for 5 min. THL was recorded while subjects were positioned in a seated stadiometer, which controlled their spinal posture. S was measured by placing an ultrasound transducer at the level of the top of the subject’s sacrum. Over 25 min of sitting with loaded and unloaded interventions applied to their spine, different response characteristics between S and THL were noted.

This study demonstrated that soft tissues below the sacrum could contribute up to 30% on average of total height loss. This suggests that researchers should take into account the soft tissue deformation outside the spine when studying vertical spinal creep in sitting.

It was designed using the original blueprints sent by the University of Nottingham. Co-inventor Nigel Corlett shared his original blue-prints,and collaborated with us on building and testing our device over a two week period.

Our version of the stadiometer has some advanced features. These include:

• It has a prod at the front for aligning the nose to an exact position – with a marker to make sure the head position is exactly identical to when it was used previously. (This is critical, but no one else did it that I’ve ever seen)

• It has a sensor on the prods to make sure the pressure on the neck, lumbar and thoracic area is identical. The prods light up when the contact pressures are just reached. The other stadiometers just have probes, no contact sensors.

• We have a fourth probe to align position – the others just have 3.

• We have a probe on the head with a contact sensor to make sure the pressure on the head is identical when measurements are taken.

• The stature is measured electronically with an scientific readout using a scientific – the others that I’ve seen just work off of a ruler.

• Our device measures finer dimensions, easier to get it within a fraction of a millimeter.

• Ours has side bolsters at the hips as well as head to position the person laterally.

• We have a scientific scale to measure weight distribution standing.

• Ours is more sturdy – arc welded, solid like a Mac truck (but it can be relocated in a van).

The Stadiometer has the potential to provide more meaningful results than with EMGs.     Here’s why.