Category: Anatomy

Pictured above are both heads of the Biceps Brachii and the Brachialis muscle underneath. 

Though summer is still a few months away, now is the time to start getting ready. Continuing to break down muscle groups, this newsletter is going to focus on the arms. For women, this can sometimes be a difficult area as we tend to store more subcutaneous fat in the arms (along with hips, thighs and calves…). This is what causes the wing/flap or hang at the back of the arm. Men on the other hand, tend to fight more visceral or belly fat. 

In the front of the arm is the biceps brachii muscle (commonly referred to as just the biceps). It is the most superficial muscle and the one often targeted in training for aesthetic purposes. As the “bi” in the name implies, there are two starting points or origins: a long head and a short head both beginning at the shoulder and then coming together for a common endpoint in the forearm. The biceps flexes or bends both the arm and the shoulder joint and also supinates (palm up position) the forearm.

Though the biceps gets lots of attention, it actually isn’t the strongest flexor of the arm. That title belongs to a muscle you probably have not heard of – the brachialis. It is deeper than the biceps and starts on the arm bone or humerus rather than at the shoulder like the biceps. The endpoint or insertion of the brachialis is also the forearm. Specifically, it attaches to the ulna bone in the forearm so the brachialis is not involved in either pronation or supination (palm down or up position) of the forearm.

At the back of the arm is the triceps brachii. Again, as the “tri” in the name implies, there are three heads or staring points – a long, a medial/inside and a lateral/outside. The long head of the triceps starts on the shoulder and extends or brings the arm back. The medial and lateral part of the triceps muscle start on the arm bone. These three come together to have a common insertion on the ulna. Only the long head of the triceps acts as an arm/shoulder joint extensor while all three heads act as an elbow joint extensor/straightener. 

The biceps and brachialis are antagonists to the triceps. A Pilates routine will help not only tone the arms but also the shoulders and most importantly the core which supports the extremities. Before it gets hot outside, begin training now so when summer comes you’ll be ready for a sleeveless summer.

The New Year’s newsletter kicked off with a look at Six Pack Abs. Continuing the theme of examining muscle groups we are going to give attention to the gluteal muscles in this edition. The abdominals are obviously considered part of the core, but what may not be as commonly thought of as part of the core are the gluteal muscles. 

There are three muscles that make up the gluteal group. They are the gluteus maximus, gluteus medius and gluteus minimus. The gluteus maximus is the outermost layer, followed by the medius and then the minimus.  

The gluteal muscles act to extend the hip or stretch out the leg in back, as in an arabesque. The gluteal muscles are antagonists to the hip flexor group. Where the hip flexors crease or fold the front of the hip joint, the gluteal muscles are meant to extend or open the front of the hip joint. With every step, the hip is meant to flex and then extend. Unfortunately, that hip extension may not happen optimally if the gluteal muscles are weak. 

The gluteus maximus is the largest muscle in the body. In addition to hip extension, the maximus also acts to externally rotate the leg so it works together with the external hip rotators, again as in an arabesque. It is a powerful muscle that is meant to be used, but with our sitting, sedenatary culture, the gluteal muscles, including maximus, are often underdeveloped. 

The gluteus medius is so important and far too often doesn’t get the attention it deserves. This muscle abducts the leg or lifts it to the side. The gluteus medius stabilizes the hip so every time you take a step your hip doesn’t drop as you lift your other leg up. Example: if you lift your right leg to take a step, your left gluteus medius will work to keep your hips level. It is also interesting to note that there is a correlation between gluteus medius weakness and low back issues.

The gluteus medius helps to move from a sitting to standing position and is important in balance. If you are standing on one leg and notice your ankle is wobbly, it might not be your ankle. There is a good chance that your gluteus medius is weak causing the instability.

The gluteus minimus is the inmost or deepest layer and the smallest of the gluteal muscles. Like the gluteus medius, the minimus abducts the leg and can internally or externally rotate the leg. For both the gluteus medius and minimus, there are fibers toward the front of the hip that can internally rotate the leg and there are fibers in back that externally rotate the leg.

While the abdominals are considered the core, the gluteal muscles play a pivotal role and some like to consider them part of the core as well. Without the gluteal muscles, you wouldn’t be able to stand up straight as they extend or open the hips to bring you upright. The gluteal muscles are also vital for gait.

Hopefully, this break down of the gluteal muscles inspires you to not only get your derrière in shape but also appreciate how important these muscles are to daily functional movements and to even having a strong core.

Our topic of study for this school year is well known muscles groups.  Last month, we looked at the hamstrings, examining the different muscles that compose the group and how these muscles act on the back of the leg and even the posture.  If you missed it, you can catch up here.

This month we are going to focus on another group of muscles that also gets attention, the hip flexors.  There are multiple muscles that make up the hip flexor group.  They are the Tensor Fascia Lata (TFL), Rectus Femoris, Satorius and the Iliopsoas.  Even the adductors (a whole other group of muscles on the inner thigh requiring a discussion for another time) have the potential to assist in hip flexion.

Of the hip flexor group, three of the muscles start on the front of the hip bone.  They are the TFL, the Rectus Femoris and Satorius.  As they attach to the front of the hip bone, these muscles can only flex or bring the leg to 90 degrees.  They obviously cannot pull the leg higher than hip bone level as that is where these muscles begin.

Which leads to the iliopsoas, the hip flexor muscle I particularly want to highlight.  The iliopsoas is composed of the psoas major, psoas minor and the iliacus.  Interesting to note that not everybody has a psoas minor.  The psoas major and minor have the same function so for those without a psoas minor they may never know it.

The psoas major starts deep in low back at the (lumbar) spine and runs across the front of the hip bone and attaches onto the leg (femur).  The iliacus starts inside the hip bone and then runs along with the psoas to attach at the same spot on the leg bone.  

As it has a higher starting point, the psoas major can bring the leg into hip flexion past 90 degrees.  Because the psoas attaches on the spine, it not only effects the hip and leg but also has an impact on the lower back.  If the psoas is tight, this can pull the lower back forward creating an arch.

Discussing the hip flexors so far we have focused on lifting or flexing the leg toward the torso.  It is important to mention that the psoas can flex or bring the trunk toward the legs as in a full sit up or roll up.  

The term hamstrings and hip flexors are something that you may hear a lot in Pilates and beyond.  I trust the break down of these muscle groups and how they act on the legs, hips and spine has been insightful.  Next time you hear one of these terms, hopefully you will have greater appreciation for the beauty and complexity of the human body and all it does for you on a daily basis without even thinking about it.

Last September the newsletter kicked off with Anatomy 101.  For back to school, we are going to revisit this topic with Anatomy 201.  Our theme for the year is going to be muscle groups.  Each month we will focus on a different “popular” muscle group.  This month we are going to cover the hamstrings.  

It is important to note about muscle groups, the hamstrings being a good example, that they are actually – a group of muscles.  That may sound obvious but because the group name is often referred to, it can sound like it is one muscle.  The general term (hamstrings) refers to multiple muscles that comprise a group.  

There are three muscles in the back of thigh that make up the hamstrings.  The three muscles that compose the hamstrings group are the biceps femoris, the semitendinosus and semimembranosus.  

The hamstrings, all three of them, begin or have what is called their origin on the sitz bone.  If you sit and put a hand underneath one hip, the bone you feel or sit on…is the sitz bone.  If you practice Yamuna® Body Rolling (YBR), the sitz bone is the point that is used to begin the hamstring routine.  It is also a good place to learn some of the principles of YBR as the sitz bone is one of the easier bony landmarks to find.

The biceps femoris is lateral or toward the outside of the back of the leg.  It begins on the sitz bone runs along the back, outside of the leg.  This muscle attaches below the knee at what is called the insertion.  If you sit and bend your knee and strum your fingers along the outside edge of the back of the knee, you can feel the biceps femoris tendon as it makes its’ way to attach below the knee.

Similarly, the semitendinosus and semimembranosus are medial or run more along the inside of the back of the leg.  They too attach below the knee.  If you sit with your knee bent and strum along the inside back of the knee, you can feel these two tendons as they run along the back of the knee.

As the hamstrings group start at the sitz bone and run behind and attach below the knee, you can see the obvious action of the hamstrings is to bend or flex the knee.  They also extend or bring the leg back at the hip joint.  What may not be as obvious is how these muscles impact posture.  Tight hamstrings pull on the sitz bone which pulls the pelvis down causing more of a tuck and a flat lower back posture.  

Of course, tight hamstrings can make it difficult for students to sit on the floor with straight legs while keeping the back straight or when standing to reach down and touch the toes.  People with tight hamstrings may try to make up for it by over rounding in their back.  

All three of the muscles that comprise the hamstrings group, run from the back of the hip to the back of the knee.  They impact not only knee movement but also pelvic movement and posture.  

Hamstrings is a word that is often referred to but not as often given much of a detailed description.  I hope defining the hamstrings has given you some clarity and insights.  Please stay tuned for the continued examination into muscle groups in the next newsletter as we explore the hip flexors.