Wednesday, January 2, 2013

Are you shorter after you go to the gym?

If we can maintain our temporary spinal height, we can maintain our morning height into the night.

The effects of upper limb loading on spinal shrinkage during treadmill walking.

"Walking tasks were performed on seven healthy males and motion analysis was used to track four reflective markers at 100 Hz, dividing the spine into three segments. Static data was collected in 5-min intervals over a 30-min period{the height loss probably tapers off after a certain point but the study was too short, however height loss started to taper dramatically between 25 and 30 minutes}.
Total spinal length and lumbar segment decreased with respect to time. Load affected the percentage length change at each spinal segment{so the more time you spend doing the treadmill and the heavier the load on each spinal segment the more (temporary) height you lose}, with the lumbar segment showing greatest height loss at the highest load. The upper and lower thoracic segments showed greater anterior lean with the heavier loads and the lumbar segment showed the opposite trend.
The body adopts less anterior lean with an immediate load-bearing demand, to decrease the necessary extension moment generated by the spinal extensors for spinal stability. Further postural alteration in the same direction is observed with prolonged loading. In combination with lumbar spinal shrinkage, such postural changes are likely to increase the loading on the facet joints and subsequently unload the discs which may be beneficial for those with low back pain."

"The shrinkage that occurs during walking and load carriage is part of the normal diurnal height change where approximately 1 % of total stature loss occurs throughout the day"

"Before each trial participants were required to lie in a supine position for 2 h to standardise the baseline condition of the spine. After 1 h 45 min, the participants changed into black Lycra™ shorts and height and weight were recorded using a standard stadiometer "

"On day 1 they walked unloaded, acting as the control and on days 2 and 3 carrying randomly assigned loads, in a similar fashion to shopping bags, equivalent to 7.5 and 15 % body weight, respectively, equally distributed across both arms. Participants refrained from physical activity for the 48 h preceding each laboratory visit. "

It should be noted that 15% loading actually reduced height loss in the upper and lower thoracic spinal segment and possibly even resulted in height gain in the lower thoracic segment.  Although 15% loading dramatically increased height loss.

"The reduction in both anterior lean during instantaneous loading and with time and the straightening of thoracolumbar curvature with load are both suggestive of a spinal shape compensation mechanism to reduce the flexion moment of the load about the lumbar spine."

Stature loss from sustained gentle body loading.

"The effects of low levels of loading on spinal creep have been investigated in nine young men aged between 19 and 24 years. Subjects were measured on a precision stadiometer before and after 25 minutes of free standing and quiet walking, and the resultant stature losses compared with the more substantial losses observed following steady running. All measurements were made following the same presession routine, at exactly the same time on three separate mornings. It was observed that while no appreciable stature loss followed standing (mean = 0.01 mm; SE = 0.65 mm) even quiet walking had a measurable and statistically significant effect (mean = 1.82 mm; SE = 0.49 mm). Compared with these, steady running produced almost 2 1/2 times as great a loss (mean = 4.32 mm; SE = 0.83 mm)."

Standing causes almost no impact so maybe impact is the primary cause of the temporary height loss and not gravity as the height loss following standing was minimal. 

Body mass as a factor in stature change

"Twenty volunteers were divided into two equal groups; obese: BMI > 30 kg/m2, non-obese: BMI < 25 kg/m2. Stature was measured at 3 min intervals during a 30 min walking task and a 30 min standing recovery period. Tests were performed on two occasions, once with participants loaded during the walking task (10% body mass) and once unloaded. 
In both groups the stature loss was greater in the loaded than unloaded condition (mean (SD)) (6.52 (1.45) mm and 3.55 (0.93) mm non-obese; 8.49 (1.75) mm and 7.02 (1.32) mm obese). The obese presented a greater reduction in stature in both task conditions. The obese group were unable to recover stature regardless of the task condition during the recovery period (loaded: 0.06 (0.3) mm; unloaded: 0.32 (0.6) mm)."
"The non-obese individuals were able to regain approximately 76% of their initial stature during the standing recovery in contrast to the obese group who did not recover from loading. Some of the obese individuals continued to loose stature during the standing recovery period (−0.7% loaded; −4.55% unloaded)."<-So maybe pure loading does have an effect and not just impact.  Although it could be due to inflammatory microenvironment caused by obesity that inhibits statural recovery.  One way to test this would be to take very heavy and muscular individuals to see if the effect is due to weight or changes in the microenvironment caused by fat.

Relationship between everyday activities and spinal shrinkage

"spinal load was ascertained by stadiometric measurement of the decrease in standing height, “spinal shrinkage”, quantified by the exposure of a 1-h adopted posture or activity. Ten subjects performed five daily life activities: standing, sitting, walking, cycling and lying down.
By doing different activities during 1 h, immediate after getting up in the morning, following average values for shrinkage were measured: standing −7.4 mm (SD 0.5); sitting −5.0 mm (SD 0.6); walking −7.9 mm (SD 0.5); cycling −3.7 mm (SD 0.4) and lying down +0.4 mm (SD 0.5).{interesting that this study got similar measures for standing and walking in contrast to the study which found only a 0.01mm loss after 25 minutes}"

"remaining in bed after a normal night’s rest mostly does not further increase spinal height"

"Spinal shrinkage was correlated with mean IDP[intradiscal pressure] values during these activities, i.e., for lying down 0.11 MPa (ranging from 0.10 MPa for lying prone to 0.12 MPa for lying laterally); relaxed standing 0.50 MPa; sitting 0.38 MPa (ranging from 0.30 MPa for nonchalant sitting to 0.46 MPa for sitting unsupported); walking 0.59 MPa (ranging from 0.53 MPa to 0.65 MPa)."

"spinal shrinkage during sitting on a chair with seat pan moving in the horizontal plane was also lower than in the static sitting situation"

Length of the spine while sitting on a new concept for an office chair.

"Changes in spinal length were used to evaluate a new concept for an office chair. This 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 degrees 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."

All but one of the eight subjects increased height in the dynamic versus one individual who lost the same amount of height in both the static and dynamic chair.

"The intervertebral disc is capable of increasing its thickness because of the swelling pressure."

Changes in spine length during and after seated whole-body vibration.

"The authors examined the relation between exposure to seated whole-body vibration (WBV) and an increase in the loss of height of the spine over and above normal diurnal changes. The mean change in body height (diurnal reduction) during two normal days in five men aged 23 to 25 years was 10.6 mm, (SD, 3.2 mm). On the third day, the change in sitting height was measured before and after vertical vibration (5 Hz with a peak-to-peak amplitude of 3 mm, and peak acceleration less than 2 m/s2) and again at the end of the day. The mean reduction in sitting height over the half hour of vibration exposure was 9.0 mm versus less than 1 mm for the control condition. The mean height loss over the third day (the day of 30 minutes of vibration exposure) was only 3.6 mm (compared with 10.6 mm lost over a control day with no vibration exposure). Hence, exposure to vibration increased the creep response in all subjects during exposure but, at the end of the day, there was a recovery in height, such that subjects were taller at the end of the day of vibration exposure. It is hypothesized that this "rebound" effect is due to an inflammatory response in the spine."

So you lose 7 mm less of height with vibration.  It'd be interesting if this rebound effect occurred in response to other forms of exercise.

1 comment:

  1. Great post! Is good to see that you're doing researches on spine growth. Keep it that way man.