In Part 1 of this series, I went over the basics of the anatomical position, planes of movement, how muscles work, and the muscles that are active in most upper-body movements.

In Part 2, we'll discuss muscles of the torso and lower extremity, along with my tips to help you write better, more balanced training programs.

Let's get it on like Marvin Gaye!

Muscles of the Lower Back

Muscle	Iliocostalis lumborum	Iliocostalis Thoracics	Iliocostalis cervicis
Origin	Common tendinous origin sacrum iliac crest spinous proceses of lower thoracic & most lumbar vertebrae	Upper border of ribs 6-12 (medial to I. lumborum's insertion)	Angles of ribs 1-6
Insertion	Lower border of angles of ribs 6-12	Lower border of angles of ribs 1-6 (sometimes transverse process of C7)	Transverse processes of C4-C6
Action(s)	Same for all erector spinae Bilateral Extension of vertebral column Maintenance of erect posture Stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity Unilateral Lateral bend to same side Rotation to same side Opposite muscles contract eccentrically for stabilization

 

Muscle	Longissimus thoracis	Longissimus cervicis	Longissimus capitis
Origin	Common tendinous origin sacrum iliac crest spinous proceses of lower thoracic & most lumbar vertebrae	Transverse processes of T1-T5(6)	Transverse and articular processes of middle and lower cervical vertebrae Transverse processes of upper thoracic vertebrae
Insertion	Transverse processes of all thoracic vertebrae All ribs between tubercles and angles Transverse processes of upper lumbar vertebrae	Transverse processes of C2-C6	Posterior aspect of mastoid process of temporal bone
Action(s)	Same for all erector spinae Bilateral Extension of vertebral column Maintenance of erect posture Stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity Unilateral Lateral bend to same side Rotation to same side Opposite muscles contract eccentrically for stabilization

 

Muscle	Spinalis thoracis	Spinalis cervicis	Spinalis capitis
Origin	Common tendinous origin sacrum iliac crest spinous proceses of lower thoracic & most lumbar vertebrae	Spinous processes of C6-T2	Spinous processes of lower cervical & upper thoracic vertebrae
Insertion	Spinous processes of T3(4)-T8(9)	Spinous processes of C2 (and possibly to C3 or C4)	Between superior and inferior nuchal lines of occipital bone
Action(s)	Same for all erector spinae Bilateral Extension of vertebral column Maintenance of erect posture Stabilization of vertebral column during flexion, acting in contrast to abdominal muscles and the action of gravity Unilateral Lateral bend to same side Rotation to same side Opposite muscles contract eccentrically for stabilization

Okay, so now that you're thoroughly bombarded with info, let's water it down a bit. Here's a snippet from my Erector Set article:

The erector spinae muscles run the length of the back, from the sacrum all the way up to the base of the skull. When working unilaterally, the erectors laterally flex the spine and/or head. When working in unison, their role is to extend the head and spine.

The common origin of these muscles is a large tendon that attaches to the posterior sacrum, iliac crest, sacro-iliac ligaments, and the lumbo-sacral spinous processes. The erector spinae can be broken down into three different groups:

• The iliocostalis muscles (the most lateral group). These muscles run from the common origin to their respective ribs.

• The spinalis muscles (the most medial group). These run from the common origin to their respective spinous processes.

• The longissimus muscles which lay in-between. These muscles run from the common origin to their respective transverse processes.

Each of these three groups can be sub-divided depending on which area of the spine they act upon:

• Iliocostalis lumborum, iliocostalis thoracis, iliocostalis cervicis

• Longissimus thoracics, iliocostalis cervicis, longissimus capitis

• Spinalis thoracics, spinalis cervicis, spinalis capitis

From Grant's Method of Anatomy	From Manual of Structural Kinesiology

So what's the moral of the story when we're training the spinal erectors? If you want to isolate one side, you're going to need to combine trunk extension with some rotation as well. In unison, they're going to extend the entire spinal column.

Isolation Exercises: Back extension, static back extension

Integration Exercises: Good mornings, RDL's, deadlifts

Training Implications:

Want bigger erectors? Increase your deadlift! Did you ever see a big deadlift with puny erectors? That's what I thought!

I didn't mention this before, but I sincerely hope you aren't still doing round-back variations of the lifts above. Round-back variations are the number one way to herniate a disc, so unless you like paying for your chiro or orthopod's new 300-C with the Hemi and the 20" chrome wheels, use a neutral spine on these lifts.

Abs and Obliques

Muscle	Rectus Abdominus	Internal Oblique	External Oblique	Quadratus Lumborum
Origin	Pubic crest	Iliac crest	Anterolateral borders of lower eight ribs	Inferior border of 12th rib
Insertion	5th, 6th and 7th Ribs Xiphoid Process	Cartilage of last 3-4 ribs	Anterior 1/2 of ilium, pubic crest, and anterior fascia	Apices of transverse processes of L1-L4 Iliolumbar ligament Posterior third of iliac crest
Action(s)	Flexion of trunk	Rotation of trunk Lateral flexion of trunk	Rotation of trunk Lateral flexion of trunk	Lateral flexion of trunk

Now we're getting to the fun stuff! Everyone wants to get that sexy "six-pack," but what other muscles are involved in abdominal movements? And what are their specific roles?

Rectus Abdominus

Let's start off with the easiest abdominal muscle, the rectus abdominus. The rectus is actually a fairly long muscle, spanning from the crest of the pubis to the xiphoid process of the sternum. The primary function of the rectus abdominus is flexion of the trunk.

Now, I'm sure some of you are wondering, "Mike, is there really an upper or lower abs?" Well, here's the answer: no, there's no such thing as an upper or lower ab. The rectus is one long, continuous muscle; however, I'd argue that the uppermost fibers tend to produce pure trunk flexion, while the lowermost fibers (along with the hip flexors) contribute to flexion at the hip joint as well.

Exercises: Crunches (all varieties), leg raises

Internal and External Obliques

The internal and external obliques sit laterally to the rectus abdominus, with the external layer sitting on top of the internal layer. While it could be prudent to break these into two separate groups, they're very reliant upon each other for producing movement, so let's examine them in this manner instead.

The obliques are very similar to the erectors in the fact that they're responsible for various movements dependent upon which sections are recruited. For example, when both sides contract equally, they produce a net movement of trunk flexion. However, I'm sure you're more interested in how it works in rotation based-movements, so let's give an example.

If you're lying on your back and want to perform a crunch with a twist taking your right arm to your left knee, you'll be using the right external oblique and the left internal oblique. In other words, you always use the internal oblique of the side you're twisting to, along with the opposite external oblique. As well, the obliques contribute to same-side lateral flexion; both the same-side external and internal obliques work together to perform the movement (e.g. right internal and external oblique produce right side-bending).

Exercises: Crunches with a twist, Russian twists, full-contact twists, med ball or cable woodchoppers

Russian twist with med ball

Quadratus Lumborum

Write it down: All chicks dig a sexy quadratus lumborum!

Seriously, the quadratus lumborum (QL) is one of those not-so-sexy muscles that can be a great friend or a deadly foe. With strong QL's you'll have better strength and stability in the trunk, allowing you to squat, pull, and overhead press more weight. However, if one side is significantly tighter or stronger than the other side, you greatly increase your risk for low back pain due to the ensuing pelvic obliquity. The primary role of the QL is lateral flexion (side-bending) of the trunk.

Exercises: Dumbbell side-bends, windmills, Saxon side bends, bent presses

Training Implications:

• Training your abs is important, but the rectus and its flexion-based exercises aren't all that's out there. Make sure to use different movements to strengthen all the various functions.

• If you haven't been doing them before, start using some hip-flexion based exercises in your programming. Focus on maintaining a posterior-pelvic tilt throughout to inhibit the hip flexor involvement, though.

• Rotation is probably the least-trained movement pattern of the abdominal muscles. If you've been skipping them, don't! Train them first if need be, but get it done.

• As well, many sports and everyday movements incorporate twisting with load, so don't be afraid to use some weighted rotational movements such as full-contact twists or cable woodchoppers.

The full-contact twist

• Lateral flexion is probably trained more frequently than rotation, but always with the same exercise (dumbbell side bends). Mix it up! There are tons of other options out there!

• As well, heavy rotation/lateral flexion movements don't give you a "spare tire" or love-handles; however, eating like a fat-ass does! Improve your diet and you'll most likely improve the midsection.

• Finally, heavy standing lifts like squats, deadlifts, and overhead presses can go a long way in developing strength in the abdominals, but some accessory work for these muscles never really hurts.

Muscles of the Posterior Hip

Muscle	Gluteus Maximus	Gluteus Medius	Gluteus Minimus
Origin	Outer rim of ilium (medial aspect) Dorsal surface of sacrum and coccyx Sacrotuberous ligament	Outer aspect of ilium (between iliac crest and anterior and posterior gluteal lines) Upper fascia (gluteal aponeurosis)	Outer aspect of ilium (between anterior and inferior gluteal lines)
Insertion	IT Band Gluteal tuberosity of femur	Superior aspect of greater trochanter	Greater trochanter (anterior to medius) Articular capsule of hip joint
Action(s)	Hip Extension External rotation of the hip Upper fibers aid in abduction of thigh Fibers of IT band stabilize a fully extended knee	Anterior and lateral fibers abduct and medially rotate the thigh Posterior fibers may laterally rotate thigh Stabilizes the pelvis and prevents free limb from sagging during gait	Abduct and internally rotate the thigh Stabilizes the pelvis and prevents free limb from sagging during gait

The gluteal muscles are often revered for their beauty on the correct female body, but here's a newsflash: they actually have very important biomechanical roles as well. Go figure!

Gluteus Maximus

The big dog on the block, the glute max is a very powerful hip extensor; however, it also aids in external rotation and abduction of the femur, and stabilization of the knee via the IT band.

The problem is, with our increasing reliance on computers (and therefore sitting down more frequently), the gluteals are quite often inhibited and not functioning at acceptable levels. Therefore, almost any program should focus on stretching of the hip flexors (the antagonists) as well as strengthening and motor control work for the gluteals. This small yet important concept could be all the difference between a healthy, optimally functioning body and one that's wrought with hip, back, and knee pain.

Isolation Exercises: Glute bridges, birddogs

Integration Exercises: Squats, lunges, Bulgarian squats, step-ups, deadlifts

Birddogs

Gluteus Medius and Minimus

These guys cover many of the same roles, so I'll cover them together. The roles of the glute medius and minimus are no less important than the major muscles, simply because they a) are again inhibited, and b) can play a significant role in injury prevention.

Now, I'm hoping you haven't been training on the seated abductor machine in hopes of getting those glutes working! Take my word on this one: not only do these machines suck in general, but they can get you injured, too. Leave them for the casual gym-goer. T-Nation faithful would be better off using either mini-band sidesteps or hip corrections for isolation, while virtually any single-leg movement is going to heavily recruit the gluteals.

Isolation Exercises: Mini-band walks, hip corrections.

Integration Exercises: Lunges, step-ups, Bulgarian squats

Training Implications:

• If you get nothing else out of this article series: train your glutes! When working properly, you'll have fewer orthopedic issues in the lower extremity and will move more weight in big lifts like squats and pulls.

• Motor control work for the glutes = good.

• Motor control + strength work for the glutes = better.

• If you aren't including single-leg work in your program, it'll catch up to you! God may save your soul, but he can't save your body from bonehead programming. Not only will most single-leg exercises develop glute max, but the small gluteal muscles as well.

The Hamstring Muscles

Muscle	Semitendinosus	Semimembranosus	Biceps Femoris
Origin	Ischial tuberosity	Ischial tuberosity	Long head – Ischial tuberosity Short head – Lateral lip of linea aspera and the lateral intermuscular septum
Insertion	Medial aspect of tibial shaft Contributes to the pez anserine	Posterior medial aspect of medial tibial condyle Fibers join to form most of oblique popliteal ligament (& medial meniscus)	Head of fibula Maybe to the lateral tibial condyle
Action(s)	Hip extension Knee flexion Internally rotates tibia	Knee flexion Hip extension Internally rotates tibia Pulls medial meniscus posteriorly during flexion	Knee flexion (mainly short head) Externally rotates thigh if the knee is flexed Hip extension (long head)

The hamstrings are an oft-maligned muscle group. In some programs, they're relegated to leg curl work and then forgotten. In others, they're simply not trained at all because said trainee can't see them in the mirror! Let's take a deeper look at the anatomy of the hamstrings, along with how to best train them.

Unlike the other muscle groups, I feel that the hamstrings are best trained via two-fashions: Hip extension work (semitendinosus, semimembranosus and long head of biceps femoris), and knee flexion work (same except primarily short head of biceps femoris vs. long head).

So what do we need to do to balance hamstring training? Balance our hip extension vs. our knee flexion work! Now, again, balance is a relative term. How many leg curls have you done in your life? Now compare that with how many deadlifts, RDLs, or good mornings you've done. Chances are there's a significant difference.

So, proper programming from this point forward will put a premium on training both movement patterns. As well, I'd recommend ditching the leg curl whenever possible for better qualified exercises such as glute-ham raises.

Knee flexion: Glute-ham raises, manual glute-hams, leg curls

Hip extension: RDLs, good mornings, deadlifts, rack pulls, reverse hypers

The good morning.

Training Implications:

• Train the hamstrings in both the knee flexion and hip extension movement patterns.

• If you've been training with primarily one function or the other (generally beginners gravitate to the leg curl and do nothing else), take some dedicated time to working on the opposite one.

• Unless working to correct a right-to-left knee flexion muscle imbalance, the leg curl should go the way of the dinosaur. Glute-hams give you a lot more bang for your buck and get you from point A to point B faster.

The Quadriceps

Muscle	Rectus Femoris	Vastus Lateralis	Vastus Medialis	Vastus Intermedius
Origin	Anterior head – Anterior inferior iliac spine (AIIS) Posterior head – Ilium just above the acetabulum	Greater trochanter Lateral lip of linea aspera Lateral intermuscular septum	Intertrochanteric line of femur Medial aspect of linea aspera	Anterior lateral aspect of the femoral shaft
Insertion	Common quadriceps tendon into patella Tibial tuberosity via patella ligament	Common quadriceps tendon via patella Tibial tuberosity via patellar ligament	Common quadriceps tendon into patella Tibial tuberosity via patella ligament	Common quadriceps tendon into patella Tibial tuberosity via patella ligament
Action(s)	Knee extension Hip flexion	Knee extension Can abnormally displace patella	Knee extension Thigh adduction Posterior fibers also extend and externally rotate thigh	Knee extension

When we discuss the quadriceps, we're talking about four separate muscles that fuse into one. We'll discuss briefly the vastus muscles, as well as the rectus femoris. As you can see in the table above, all four of these muscles insert on the common quadriceps tendon, making their functions (for the most part) largely similar.

Vastus lateralis, medialis and intermedius

These are three separate muscles that work together at the knee joint to produce knee extension (think the leg extension machine and you'll be fine). Both the vastus medialis and lateralis contribute in a small way to other movements, but I want to talk a little bit about our little friend, the Vastus Medialis Obliquus (VMO).

"Say hello to my little friend!"

The VMO is the most distal portion of the vastus medialis muscle. It gets the "oblique" reference due to the oblique fiber arrangement in this portion of the muscle. When the VMO doesn't fire correctly (or is dominated by other structures such as the vastus lateralis, ITB, lateral retinaculum, etc.), it can contribute to poor patellar tracking and knee pain in general. Couple that with the fact that just about any time you have surgery, swelling, or inflammation in your knee that your VMO shuts off, and you have one tricky little muscle.

Needless to say, you'd be wise to take good care of your VMO and include some prehab VMO work in your program.

Do your TKE's for healthy knees!

Rectus Femoris

The rectus is different from its vastus brethren simply because it starts on the anterior, inferior iliac spine, which means it crosses two joints (the hip and knee) versus just one. In fact, a tight rectus can often be mistaken for a tight iliopsoas complex.

Regardless, I personally don't feel it's necessary to train the hip flexion movement all that much, simply because the hip flexors are typically overactive and tight to begin with. Instead, focusing on knee extension via big exercises such as squats, lunges, and the like and you'll be fine.

Isolation Exercises: Leg extensions, terminal knee extensions

Integration Exercises: Squats (all varieties), lunges, step-ups, Bulgarian squats

Training Implications:

• For people with healthy knees, there's typically no reason for specific training of the VMO. However, in those with specific knee pathologies, TKE's and other similar exercises can provide some benefit.

• There's really no need to train the hip flexor portion of the rectus femoris; most people are overly tight in the anterior hip anyway.

• Basic quad exercises reign supreme here: squatting, lunging, and the like will give you all the strength and size you could ever want.

• With the exception of a few specific rehabilitation settings, leg extensions pretty much suck. Go with one of the above exercises to elicit maximum development.

Muscles of the Lower Leg

Muscle	Gastronemius	Soleus	Tibialis anterior
Origin	Medial head – Just above medial condyle of femur Lateral head – Just above lateral condyle of femur	Upper fibula Soleal line of tibia	Lateral tibial condyle Proximal 2/3 of anteriolateral surface of tibia Interosseous membrane Anterior intermuscular septum & crural fascia
Insertion	Calcaneus via lateral portion of Achilles tendon	Calcaneus via medial portion of Achilles tendon	Medial & plantar surface of base of 1st metatarsal Medial & plantar surface of the cuneiform
Action(s)	Plantarflexion of foot Knee flexion (when not weight bearing) Stabilizes ankle and knee when standing	Plantarflex the foot	Strongest dorsiflexor Inverts & adducts the foot

Last but not least, we have the muscles of the lower leg. This is one of those muscle groups that goes against the grain when it comes to movement. When you press the toes down (as in a calf raise), this is called plantarflexion. The opposite movement (pulling the toes up toward your shins) is called dorsiflexion.

While there are numerous other muscles located in the lower leg, let's stick to the basics and the ones you want to train!

Gastrocnemius

The gastroc is one-half of what we commonly refer to as our "calves." The fact of the matter is, there's no such thing as a "calf" muscle! The gastrocnemius crosses both the knee and ankle joints, contributing to knee flexion and plantar flexion. So, in order to properly train the gastroc, we need to perform exercises where the knees are extended.

Exercises: Standing calf raises, calf raises on leg press

Soleus

The other half of our "calf" is the soleus. The soleus, unlike the gastrocnemius, only crosses one joint (the ankle). However, since they both attach to the Achilles tendon, they work together to produce the same basic movement: plantar flexion.

In the previous example, we noted that to emphasize the gastroc, we need to extend the knee. In contrast, to emphasize the soleus, exercises that produce plantar flexion with the knees flexed will give us the best results.

Exercises: Seated calf raises

Tibialis Anterior

The tibialis anterior is the strongest dorsiflexor of the foot. Train it.

Exercises: DARD machine, DB dorsiflexion

Dumbbell dorsiflexion

Training Implications:

• Calves, like the triceps, need heavy reps to grow. Don't be afraid to load up the weights and get after it!

• Make sure to include both standing (gastroc-emphasis) and seated (soleus-emphasis) exercises for maximum development.

• The tibialis anterior should be trained to provide muscular balance around the lower leg.

Approved Links

While this article should give you a great start, I'm also going to link a bunch of other great articles that go into more detail on their respective topics. For those of you information hungry trainees out there, be sure to give them all a read at some point in time.

Cracking the Rotator Cuff Conundrum

Erector Set

Wanna Grow? Gotta Row!

Get Your Butt in Gear! Part 1 and Part 2

Neanderthal No More, Part 1

21^st Century Core Training

Old School Triceps

Debunking Exercise Myths Part 1 and Part 2

Construction by Adduction

Summary

This article series should give you a pretty good understanding of how the muscles of the body work, and how subtle changes in body position can significantly change the movement itself, along with the muscles emphasized.

It may be a lifelong process, but developing a greater understanding of functional anatomy will not only allow you to write better training programs, but reap all the rewards of better training programs: less injuries, improved function, and most importantly, better performance!