Back Muscles & Nerves

Blaine MitchelAll, Spinal AnatomyLeave a Comment

There are two fundamental types of muscles in the body: skeletal (those which we control) and smooth (those which move by themselves, including the digestive and heart muscles). Both kinds can become stronger and more resilient through exercise. We’re going to focus on the skeletal muscles which move and maintain the spine. Absence of muscle strength and flexibility is often a cause of back pain.

Muscles are layered in the back. Certain types are found deeper and others are more superficial or found at the surface. The deeper muscles are designed for stabilizing— assisting to secure bones.

A health professional may have already informed you that to have a good back you require strong abdominal muscles; these will stabilize your entire torso. There are four types of abdominal muscles. The deepest, transversus abdominis, wraps around your body, similar to a corset. You should be able to feel these muscles if you put your hands on your waist and cough. Located on the sides of your body, are the “oblique” muscles, the internal obliques are deeper; the external obliques are found closer to surface. Obliques allow you to twist and side bend.

Lastly, there’s rectus abdominis, more commonly known as the “six pack.” While you can shape these into those attractive washboard abs (with a whole lot of work), they’re not especially helpful in stabilizing your back. Their main role is to pull your torso forward (think sit-ups and crunches). They will help you squeeze the deeper ab muscles, but when it comes to steadying the spine, you want to reinforce the deepest ab muscles, transverses and internal obliques, along with the back muscles. One of the most efficient ab and back workouts are Pilates exercises, which target all abdominal and spine muscles very well.

Deep inside the body are two muscles, one on each side of the body, referred to as the iliopsoas muscles, or the psoas. These are hip and thigh flexors, they elevate the thighs, think going upstairs, walking. When your legs are motionless, the psoas allow you to bend forward or flex in the hips. Whilst sitting, the psoas keep you in an upright position. The psoas is one of the largest and thickest muscles in the body; they spread from your lumbar vertebrae, cross in front of each hip bone, and join to the inside-top of the thigh bone. Sitting down for long periods of time can result in shortening of the psoas, which can cause pain whilst standing.

Similar your abs, spinal muscles are layered. The deepest are small and link vertebra to each another. At the deepest level, interspinalis muscles link to your spinous processes; these allow you to stretch backward. The transversospinalis group displays a chevron-like pattern along the back of your spine and assists you when you side bend and twist, and it also plays a role in back bending. The next layer up is the erector spinae. Their job is also related to back bending, although they also help with side bending. When people have muscle spasms in the back, it’s very often the erector spinae muscles.

The next level comprises of the rhomboids, found between your shoulder blades, which, by exercise or physical therapy can help realign your vertebrae. The large, winglike muscles on each side of your back are known as latissmius dorsi. As well as stabilizing the back, these muscles help you do all sorts of things, such as pull-ups. Lastly, the trapezius muscles expand from your neck and midback to your shoulders. These muscles are involved in moving your neck and lifting your shoulder blades. If we get tense, we tend to lift our shoulders, which can make these muscles quite tight and sore.

Communications Central

All nerves eventually link to the brain. There are essentially two major types of nerves: sensory and motor. Sensory nerves relay information including touch, temperature, and pain to the brain and spinal cord. Motor nerves transmit signals from the brain back into the muscles, causing a response, either voluntarily or reflexively.

The nerves in the peripheral nervous system (PNS) reach down the spinal canal and branch out in 31 pairs at openings in the vertebrae known as foraminae. They are basically just messengers to and from your brain (or central nervous system), which send pain signals and cause movement—like, ‘Oi, take your hand off the pan handle, it’s hot!’ These nerves automatically cause your spine to twist and turn when you walk to keep you in balance. And they keep you fastened to your car seat as you go around a corner at high speeds!

The peripheral nervous system (PNS) is a collection of millions of nerves throughout your torso and limbs. The PNS nerves send messages to your central nervous system (CNS), which is the essentially the brain and spinal cord. If you’re wondering, cranial nerves (the ones in your head) supply the sense organs and muscles in your head.

The Spinal Cord

The spinal cord is a hollow, cylindrical structure occupied by a bundle of nerves and cerebrospinal fluid, which shields and nourishes the cord. Other protectors of the spinal cord are linings known as meninges and vertebral bones. The spinal cord is around an inch in width (at its widest point) and around 18 inches long.

The three kinds of membranes which surround the spinal cord are known as meninges. From the external to the internal, they are dura mater, arachnoid mater, and pia mater. These membranes can be damaged through disease or trauma. Arachnoiditis is a result of inflammation of the arachnoid lining resulting in severe stinging and burning pain. It can strike after surgery or due to scarring of nerves.

Nerves leave the spinal column in pairs and branch in a delicate web-like structure throughout the rest of the body. Each area of the body is operated by specific spinal nerves. The placement is as you would expect. For instance, nerves in the cervical spine (neck area) branch out into your arms, this is why occasionally a neck issue can result in pain radiating down through your arms. Nerves in the thoracic area are responsible for the middle of the body, those in the lumbar spine region spread into the outer legs, and the sacral nerves control the middle of the legs and organ functions of the pelvis.

high_9781101478608_oeb_031_r1Spinal Cord & Nerve Structures


When the issue is in one part of your body yet pain is sensed elsewhere, it is known as referred pain.


As mentioned earlier, the nerves which leave the spinal cord do so in pairs: one is a sensory nerve whilst the other is a motor nerve. It’s probably not a shock to learn that motor nerves stimulate movement and bodily functions. Should a motor nerve be damaged, weakness in a muscle or loss of function could result. If you can’t feel the pain of a pin in your foot, you’ve lost some feeling, which is indicative of a problem with sensory nerves; they govern pressure, pain, temperature, and other such feelings. This is why a doctor might gently poke you with a pin and question your bowel movements. If you are unable to feel the pin or have had an issue with bowel movements, it’s a sign of nerve damage.

An issue with a sensory nerves can sometimes manifest as sudden, sharp, electrical pain, this is why good athletic instructors will tell anyone to stop ever feel this sort of pain. Any activity which causes this sensation could result in nerve damage.

Cauda Equina

The spinal cord finishes at the lumbar spine, where the nerves extend in a bundle of strands known as cauda equina, named so due to the mass looking similar to a horse tail. The nerves in this area provide motor and sensory function to the legs, intestines, genitals, and bladder. Compression of these nerves is considered to be a medical emergency and requires immediate attention.

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