THE INNER UNIT provides the necessary joint stabilization for
the spine. If the inner unit does not activate properly, our spine,
pelvis, and joint structures are placed under undue stress. This
stress creates an atmosphere that leads to many orthopedic
injuries.
Muscles of the Inner Unit
I first learned about the inner unit while reading research by
Richardson, Jull, Hodges, and Hides. After reading The Pelvic
Girdle by Diana Lee and articles by Paul Chek, I came to
understand that the basic inner unit consists of the following
four muscles:
Transverse abdominis
Multifidus
Pelvic floor
Diaphragm
This research shows that the inner unit operates on a different
neurological loop from other core muscles. The actual anatomy
where these muscles attach is not the theme of this article;
however, you should have a good idea where these muscles are
and what they do.
Transverse Abdominis
The transverse abdominis (TV) is the deepest, innermost layer of
all abdominal muscles. Consider the TV as your body’s personal
weight belt. When the TV contracts it causes hoop tension
around your midsection like a girdle or corset. The transverse
abdominis will, if working properly, contract before the
extremities move, according to Diana Lee. If this muscle does
not tighten up, acting as a girdle around your waist, your spine
and pelvis are at higher risk of injury.
If the spine is unstable the nervous system will not recruit the
extremity muscles efficiently and assist with functional
movement correctly. For example, if you bend over to pick up
the laundry basket and your transverse abdominis does not
activate properly, this leads to all stabilization occurring at the
segmental (one-joint) level. This stress eventually leads to
overload of the segmental stabilizers and—POW! You have
massive lower back pain. This occurs because the segments of
your spine tighten down but the gross stabilizer (transverse
abdominis) does not leave the segments to work on their own.
They cannot provide enough muscular strength at the
segmental level to withstand such a movement. Now can you
imagine lifting weights, grabbing a suitcase off the conveyor
belt, or reaching overhead to get down a box of heavy tapes?
When the transverse abdominis does not work properly the
joints will begin early degeneration, leading to many
orthopedic problems.
To activate the transverse abdominis, draw your belly button up
and in toward your spine. This activation should be done before
bending over or reaching overhead, especially with heavy loads.
A little trick is to get a string and tie it around your waist at the
belly button level. Draw your abdomen up and in toward your
spine as far you can, then let it out about three-quarters of the
way and tie the string at that point. It should be tight, but not
noticeably. If your TV relaxes and extends your abdominal wall,
the string will tighten up and you will immediately get
feedback.
Multifidus
The next muscle we must look at is the multifidus. This muscle
lies deep in the spine, spanning three joint segments. The
multifidus works to provide joint stabilization at each segmental
level. Each vertebra needs stiffness and stability to work
effectively to reduce degeneration of joint structures.
Pelvic Floor
The pelvic floor is our next set of muscles that spans the area
underneath the pelvis. It is important for the pelvic floor and
the inner unit to work properly. In many cases because of
operations such as hernias, hysterectomies, and C-section
childbirth, the inner unit muscles have been cut, reducing
communication to the pelvic floor. By doing simple yet
important exercises we can re-establish communication, tighten
and tone the muscle group, prevent or diminish incontinence,
leakage, and pelvic dysfunction.
Diaphragm
Each of these three muscles, plus the diaphragm, are the target
of inner unit conditioning.
Exercises to Improve the Inner Unit
The basic exercises to improve the inner unit activation are:
4-point Transverse Abdominis Tuck
Horse Stance Series
Heel Slides
After doing inner unit exercises for a while you should notice
your lower abdominal region feeling tighter and firmer.
4-Point Transversus Abdominis Tuck
This exercise is great for isolating the transverse abdominis, for
correcting “pooch belly,” and reconnecting with the nervous
system. It is particularly valuable for pre-surgery preparation
and post-surgery rehabilitation. In surgical procedures such as
caesarean section and hernia, the muscles, nerves, and tissues
are cut, causing a loss of neurological impulse (your brain tries
to call your muscles to wake them up, but the muscles don’t
answer!). Lack of neural drive to the core muscles is one reason
for the belly hanging out. Certain exercises can help reconnect
the nervous and muscular systems so your “pooch belly” gets
the message from the brain loud and clear and pulls those
muscles in.
Note: Using a dowel rod can help you keep good neutral
exercise posture and provide biofeedback. (As the rod touches
different parts of your body, it makes you aware of your body
position.) If you use the dowel technique, place the rod along
your spine, making sure the back of your head, upper back, and
tailbone are in contact with the rod.
Position:
Get down on all fours as though you were going to
crawl. Place your hands directly underneath your shoulders and
your knees directly beneath your hips.
Movement:
1. Inhale and let the transverse abdominis hang out toward the
floor.
2. Exhale, drawing the belly button in toward the spine.
Avoid any spinal movement during this exercise such as
contracting the glutes, hamstrings, or external rotators.
Horse Stance Vertical
The first exercise in the Horse Stance series is the Horse Stance
Vertical, which integrates the stabilizer muscles of your spinal
column with the other muscles of the inner unit. It targets the
inner unit (multifidus, pelvic floor, transverse abdominis, and
diaphragm).
Position: Get down on all fours with your hands directly
underneath your shoulders and your elbows slightly bent. Your
knees should be directly beneath your hips at a 90-degree
angle.
Movement:
1. Raise your left hand and right knee approximately one
centimeter off the ground (that’s about the thickness of a
magazine—look closely at the center photograph and you
will see the hand slightly off the matt. The right knee is also
raised slightly off the matt, although it cannot be seen in the
photograph). Hold this position for 10 seconds.
2. Repeat with the right hand and left knee.
3. Alternate back and forth until you have done the exercise for
a total of 2 minutes.
To help you with proper exercise duration, use a kitchen timer.
Do not let your hamstrings flex the lower leg toward the ceiling.
Ensure that your pelvis does not shift into the hip that is in
contact with the ground.
Heel Slides
Note: This exercise requires a blood pressure cuff.
Heel slides are a great integration exercise for the inner unit,
lower abdominals, and lower extremities (your outer unit).
Position: Lie supine (back down, face up) on the floor with your
shoes off. Bend your hips and knees, placing your heels about 8
inches from the buttocks. Keep your spine in a neutral position.
Place a blood pressure cuff under your lumbar spine. Pump the
cuff up to 40 mm Hg and take a deep diaphragmatic breath.
Movement:
1. Slowly exhale and draw your belly button in toward your
spine.
2. Slowly slide the left leg out, away from the starting position.
There should be very little movement of the blood pressure
cuff needle. If the pressure on the cuff begins to increase or
decrease by more than 5 mm Hg, stop the movement and
slide your leg back to the beginning position. Make a note of
the distance. The distance is now your ending point.
The goal is to extend your leg farther out without the blood
pressure cuff changing its reading. The farther you can
extend your leg, the better the integration of your inner unit
and outer unit.
3. Repeat for the opposite leg.
4. Repeat for the prescribed number of reps.
Try to achieve 10 reps at a slow pace for each leg. Do not rush
this exercise.
Do this exercise daily until you can alternate sliding each leg in
and out, keeping the b
lood pressure cuff at 40 mm Hg.