understanding muscles and the way we move

Teaching clients how their muscles work in daily life will enable you to design truly effective exercise programs that can decrease pain and improve performance.

As fitness professionals, we are experts in muscles. Theoretically, this knowledge should help us design more effective exercises and keep our clients pain-free and functioning well. The truth, however, is that much of what we learn about the function of muscles isn’t going to help our clients move better.

Most textbooks on anatomy have resulted from the study of cadavers and dissection of bodies post mortem to see where the muscles attach to certain parts of the body (Gray, 1995). The resultant discoveries from this approach to anatomy have created the framework for the most widely held views regarding muscle function and the way we learn anatomy; namely, ‘Muscle A’ goes from ‘Bone 1’ to ‘Bone 2’, and when it contracts it pulls these two bones together. For example, a typical anatomy text might explain that the quadriceps muscles of the leg are responsible for extending or straightening the knee (Golding & Golding, 2003). That is why we teach our clients the leg extension exercise to strengthen their quadriceps, and this would seem like a valid rationale for doing this exercise. However, in real life, muscles function very differently.

While the quadriceps muscles do extend the leg when contracted, the other, real-life function of the quadriceps muscles is to slow down knee flexion (i.e. bending of the knee) when we walk, squat or lunge (Price & Bratcher, 2010). Real-life muscle function explains how the quadriceps perform when people are on two feet, not sitting on a machine (or lying on an examination table), and gravity and ground reaction forces come into play. Thinking about anatomy in this alternate way and teaching clients about how their muscles work in everyday life will enable you to design truly effective exercise programs that can simultaneously decrease pain and improve performance.

Gravity, ground reaction forces and …bungee cords?

The real-life function of most muscles is to limit unnecessary stress from the ever-present forces of gravity and the transfer of energy (i.e. ground reaction forces) throughout the body. Muscles do this by lengthening in order to slow the rate at which parts of our body move toward and away from each other as we go about our daily activities or exercise. This lengthening action of the muscles also helps us maintain balance and decreases stress to the joints. In essence, our muscles tend to work in a fashion similar to bungee cords in that tension increases as the fibres elongate, simultaneously slowing down force and storing energy for use when the fibres subsequently contract (Chasan, 2002).

In order to better appreciate how our muscular system is akin to a bungee cord system, visualise a person who is attached by their feet to the end of a bungee cord as they jump off a bridge. If the bungee cord gets the right amount of tension on it as the person nears the ground, then he or she will be saved from smashing into the earth. However, if the bungee cord doesn’t pull tight at the right time, the person will impact the ground with dire consequences. The muscles of our body act in a similar way. If these ‘bungee cords’ work together they can protect our musculoskeletal structures (especially the joints) from excessive stress by pulling tight at the right moment to help slow down force through our body as it moves and interacts with the ground or an object.

In addition to controlling forces through the body, our body’s muscular bungee cord system also stores energy that can be used to create strong, powerful movements as this energy is released (i.e. when the muscle fibres contract). Just like when the bungee cord reaches its maximum stretch and pulls the person powerfully back up to where the bungee cord is anchored, our muscles contract powerfully to create and continue movement.

A fresh approach to anatomy and exercise

Understanding anatomy in real-life terms and thinking about how muscles in the body work to slow down the forces of nature by lengthening like bungee cords will enable you to create effective exercises that build strength, improve function and eliminate pain.

Here are two examples of how you might apply this new way of thinking about muscle function to design better exercises.

1. The lower leg

The Achilles tendon is a very important structure in the lower leg that connects the calf muscles (gastrocnemius and soleus) to the calcaneus, or heel bone. The Achilles tendon and calf muscles help produce a lot of energy to assist with powerful movements like squatting, lunging, walking, jogging and running.

When a person is performing actions such as squatting, lunging, or going up stairs, the lower leg (i.e. tibia and fibula) moves forward over the foot as the heel remains planted on the ground. This forward movement of the lower leg causes the Achilles tendon and soleus to elongate which helps load the ‘bungee cord’ feature of these tissues (see Figure 1).

Traditionally, we have been taught that the primary action of the soleus muscle is to plantarflex the ankle when the knee is bent (Kendall. et. al., 2005). This is why seated calf raises are commonly recommended as an exercise to work the soleus muscle. However, in real-life movements (e.g. squatting and lunging) the stored energy in these structures created by lengthening subsequently assists the soleus muscle to shorten and contract to help plantarflex the ankle (i.e. push the foot down) and straighten the knee.

Hence, the real-life function of the soleus muscle (via the Achilles tendon) is to slow down dorsiflexion (i.e. bending) of the ankle and flexion (i.e. bending) of the knee. As such, a more appropriate functional exercise for strengthening the soleus muscle would be deep squats where the ankle and knee are flexing together. This exercise would help train and strengthen the tissues of the lower leg to better absorb shock to the ankle and knee, and maximise the stored energy potential of the muscle to improve performance.

Bear in mind that most people will not be used to performing exercises that work muscles in primarily an eccentric (i.e. lengthening) fashion, and doing so can be surprisingly taxing to the muscles and joints. Therefore, before beginning or recommending any program of functional strengthening that includes exercises that place the muscles under a lengthening load, perform self-myofascial and isolated stretching exercises to help prepare the tissues for these additional stressors. For example, before attempting the deep squat above, have clients massage and stretch their calf muscles and quadriceps (as the knee will also be flexing) (Price and Bratcher, 2010).

2. The erectors and abdominals

Traditional anatomy teaches that the erector spinae group of muscles helps straighten the spine into extension and keep it erect over the pelvis (Gray, 1995). That’s why we typically try to strengthen peoples’ back muscles by giving them exercises such as the Superman that extend their spine, or repetitions on the back extension machine. Similarly, we are typically taught that the rectus abdominis helps flex the spine (Golding and Golding, 2003), and therefore recommend that clients do sit ups. However, the real-life function of the erector spinae muscles is to slow down forward flexion of the spine as a person bends forward, like when reaching over to pick something up or over the sink when brushing teeth (Price and Bratcher, 2010). Conversely, the real-life function of the rectus abdominis is to slow down extension of the trunk, like when reaching up over your head to throw a ball (see Figure 2).

Erector spinae muscles that are able to lengthen under load are effectively helping to slow the spine as it bends forward. The tension generated as they lengthen can then be used to pull the spine back up again into an upright position. The abdominals function as a counterpart to the erector spinae group by lengthening to ensure the spine doesn’t extend too far backward as the torso is pulled back upright. When these groups of muscles are healthy and functional, they work together like alternate sets of bungee cords to prevent the spine from arching or rounding too far or too quickly, thereby minimising unnecessary stress to the spine (Myers, 2001).

This means the performance of spine extension exercises and abdominal crunches are not the most functional ways to strengthen the back and abdominal muscles. An exercise that would more effectively train these two sets of muscles would see you instructing your client to bend down and pick up a medicine ball and then reach back over their head and throw it to you. This exercise would require the erectors to lengthen to slow down the spine as it bends forward to pick up the ball and the abdominals to lengthen to slow down the spine as it arches backward in preparation for throwing the ball (see Figure 2).

As mentioned previously, it is important to warm up and stretch the target muscles before loading a client’s program with the increased demand of functional, real-life exercises. Furthermore, if you suspect your client has a back injury, it is recommended that you obtain clearance from a medical professional before facilitating the exercises outlined above.

An understanding of the real-life function of muscles will help you design both corrective and performance enhancement exercise strategies that train muscles to react appropriately to the forces of nature (i.e. gravity and ground reaction forces). By progressively integrating these types of exercises into your clients’ programs, they will reach their goals more easily and you will set yourself apart as an industry expert who understands the true nature of muscle function.


Chasan, N. 2002. Total Conditioning for Golfers.  The Swing Reaction System Biomechanical Golf Fitness Program. Bellevue: Sports Reaction Productions.
Golding, L.A. & Golding, S.M. 2003. Fitness Professional’s Guide to Musculoskeletal Anatomy and Human Movement. Monterey, CA: Healthy Learning.

Gray, H. 1995. Gray’s Anatomy. New York: Barnes & Noble Books.

Kendall, F.P. et al. 2005. Muscles Testing and Function with Posture and Pain (5th ed.). Baltimore, MD.: Lippincott Williams & Wilkins.

Myers, T. 2001. Anatomy Trains. Myofascial Meridians for Manual and Movement Therapists.  Edinburgh: Churchill Livingstone.

Price, J. & Bratcher, M. 2010. Understanding Muscles and Movement: Module 2. The BioMechanics Method.  www.thebiomechanicsmethod.com.


Justin Price, MA is the creator of the Network Corrective Exercise Trainer Specialist Certification course, The BioMechanics Method®. His techniques are used in over 25 countries by specialists trained in his unique pain-relief methods. fitnessnetwork.com.au/biomechanics