Earlier this week I was at my neighbourhood Globo Gym (reference
from the movie Dodgeball), when I saw a personal trainer put what looked like a
65 year old man with a stenotic antalgic posture onto an inversion table. Now I have to admit I have limited use/knowledge
of these tables so my curiosity took over and I was hooked. The grey haired, over weight man was strapped
onto the table and then without hesitation he was flipped 180 degrees to
weightless tranquility… right? Well, probably
not. As I continued to ride nowhere on
my stationary bike I watched the man go all the way up and then back to the
inverted position every few minutes for multiple reps until he was literally
red in the face. That, my friends, is
the reason I asked myself, what happens your body when you are flipped upside
down?
I searched the databases for academic research on the
effects of inversion therapy on the lumbar spine (low back) and the
cardiovascular system. The first thing I
realized was that inversion tables were all the rage in the 1980's as not
much research has been done since.
I found one study that took x-rays of the low back while the
subjects were standing and a second x-ray while the subjects were
inverted. The study did not use an
inversion table, instead the authors made an inversion harness that was suspended
from what looked like a chin up bar. Let
me tell you, the inversion table that I saw at the gym looked much more comfortable
than this contraption. Anyways, the
authors noted an increase in both anterior and posterior disc spaces, with a
31mm total increase in distance from the L1-S1 vertebrae in patients with disc
injury, and a 23mm total increase in the same distance in healthy subjects. This means that there is an increase in disc
space while inverted. However, when you
are lying on your back there is 75% less compression in the low back compared
to standing. So, does being inverted
decrease the compressive force in your spine more significantly than simply lying on
your back? A newer study compared MRI
images of the supine position (lying on your back) to that of standing. What they found was when supine the posterior
disc spaces open while the anterior disc space lessens. However, the first study noted increases in
both the anterior and posterior disc space, therefore there maybe
further benefit using inversion tables compared to simply lying on your back.
The second reason for digging into this topic was to find
out the increased stress placed on the body while inverted,
and to see if increases are time dependant or not. The first thing I found was that heart rate
does not increase. However, there are
significant increases in systolic blood pressure (ie. The “120” in the 120/80
measure) and the pressure in the eyes. It is
important to know that both of these measures do not increase significantly
from 2.5 minutes of inversion to 5 minutes of inversion. In essence, the increased strain has reached
maximum significance by 2.5 minutes. I did
not find a study that looks at the effects beyond 5 minutes.
The other variable that plays no effect on the increase of blood
pressure and or eye pressure is the type of inversion used. Whether you are suspended from your thighs,
knees or ankles, they all lead to the increased pressures.
Now going back to the Globo Gym story, maybe the inversion
table was helping the man, as many report personal success stories with this
therapy. My biggest concern was the
trainer’s apparent lack of knowledge of the stress placed on the body when flipped
immediately upside down. Although, this
is an in-home therapy that any Joe Schmoe can perform, I’m sure somewhere in
the instruction manual it says something about progressive inversion to limit
the immediate strain on your body, even if you are an inversion veteran.
So, if you have the chance to try out an inversion table,
remember there is no rush to go completely inverted, as slight inversion may
yield positive benefit without putting rapid strain on your body!
Until next time, stay healthy my friends.
Dr. Adam
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