Dynamic Concentric and Eccentric Muscle Movements

In my last blog post I discussed and demonstrated static concentric and eccentric muscle movements and I would now like to compare them to dynamic movements where the body is in a state of motion. 

Reducing risk of injury

In my recent posts I have discussed the risk of mainly lower back injury with improper performance of the push up secondary to increased acceleration of the movement. This risk actually holds true for any select exercise technique if proper stability isn't maintained around the joint. One of Newton's laws states F=ma (force=mass x acceleration) and this means that any change in either the resistance or the acceleration can cause an increase in the force. Since the joint is the movable segment in any exercise technique, there must be sufficient strength in the tissues surrounding the joint to offer the required stability. Although explosive motions offer good training results, the resistance offered by the bodies weight is usually more that adequate and there is less risk of over-stressing the joint.

Cobra Exercise vs Push-Up

The photo below is a picture of me doing a yoga exercise called the "Cobra". Notice that my back is arched during my performance of this exercise, and this may look like it goes against what I stated yesterday about keeping your back straight. The reason this exercise is good for you is due to the duration of time it is held to provide a slow relaxed stretch to the abdominal region and hip flexor muscles of the body. It also provides a gentle pressure on the joint and discs of the vertebrae which increases proper fluid transfer. The danger of doing a push up with the back in this position is the increased acceleration required to lift the body back off the floor. This explosive movement causes an enormous increase in the forces upon the lumbar spine and increased risk of injury.

Proper Push-Up Form

When performing a push up make sure that your abdominal muscles are strong enough to support your lower back and keep it from arching. This arching not only puts pressure on the facet joints of the posterior lumbar vertebrae, but also increased pressure in an anterior direction on the lumbar discs. Start out doing the push up on your knees or leaning in against the wall and progress as you get stronger.

Static Concentric and Eccentric Muscle Motions Explained

Below is a short video further illustrating concentric and eccentric muscle motions as I discussed in recent blog posts.

Concentric and Eccentric Exercises

In my last blog post, I described the differences in concentric and eccentric muscle contractions. I would now like to relate these actions to strength training exercises. When performing any strengthening exercise, I feel both the concentric and the eccentric contraction should be included to provide the most efficiency and practical application to daily physical activity.

The concentric motion occurs when the muscle shortens under load, such as the deltoid muscles of the shoulder shortening as you lift a  weight overhead. The same muscles are then called upon to perform the work in the eccentric phase when the weight is lowered from overhead back to its starting (or resting) position. Other surrounding muscle groups are again being brought into play throughout the full range of motion to stabilize and protect the joint, and allow the deltoids to perform the prime movement. I feel it is more efficient to increase the duration of the eccentric phase of a movement to avoid acceleration and thus decrease the risk of injury. Also, science has show that the longer time a muscle is under tension, the greater strength gain is achieved.

All the activities of our daily lives, such as, taking the dishes out of the cupboards, lifting boxes up onto shelves, getting the groceries into and out of the car, all require both concentric and eccentric muscle contractions. Working a muscle throughout both these phases strengthens it and makes these tasks easier and more efficient to perform.

Concentric vs. Eccentric Muscle Contractions

A muscle has two actions referred to as concentric and eccentric contractions. A concentric contraction occurs when the actin and myosin filaments slide over each other through a motion of their cross-linking connections to provide an increase in the overlap resulting in a shortening of the contractile unit. This shortening of every unit of the total length and width of the muscle results in a movement of the human joint through its full range of motion. A great example is the shortening of the biceps muscle when performing a biceps curl and another the shortening of the hamstring muscles in the back of the thigh to bend the knee.















An eccentric contraction is a lengthening of the muscle under load. Lengthening then occurs through the application of forces sufficient enough to pull the cross-links apart and return the contractile unit to its normal resting overlap. Applied forces come in the following three forms:

By the weight of the individual body part moving with the assistance of gravity.

The action of the muscle opposing the prime mover as the triceps straightening of the elbow.

Resistance as that provided by a free weight, strengthening equipment, or a resistance band.

It is during this motion that the actin and myosin filaments are strained leading to a condition referred to as delayed onset muscle soreness or DMOS. DMOS will usually subside within a day or two as the body adapts to the greater load and is a natural occurrence with any fitness program.

There is, however, an increased risk of injury to the joint and surrounding tissues during the eccentric phase if the motions performed at too great a speed with increased resistance. The muscles should have enough strength and flexibility to combat this increase in force if attempting this form of exercise. I always suggest my clients perform all plyometric exercises without additional resistance for this reason. I also feel that no one should walk or run while carrying weights in the hands or wearing them on their legs secondary to altering their normal gait pattern and increasing the risk of injury to the lower back.

Muscle Physiology Continued

I would like to continue my discussion on the physiology of human muscle by talking about the chemical reactions that produce the energy required for human movement. Food is broken down within segments of our cells called mitochondria in a process known by the name metabolism.

The eventual result is the production of a chemical called adenosine triphosphate or ATP. It is the removal of the phosphate molecule from this chemical that causes the release of energy required for muscle contraction. Some of the food is broken down into a sugar referred to as glucose, with the remainder stored in a form called glycogen that can broken down into glucose as the body requires it.

These stores of glycogen are what fuels our bodies during long endurance exercises, and depletion of these stores during physical activity is called "bonking" or "hitting the wall." To avoid this occurrence, you should drink an energy drink containing small amounts of sugar to replenish these stores if the activity is longer than one hour. I always make it a point to take along a bottle of energy drink with both small amounts of sugar and electrolytes when going out for long bike rides.

Muscle Physiology

Yesterday I discussed muscles unique ability to change its required action in a joint movement depending on its angle to the main orientation of force. Another unique ability of muscle is its ability to lengthen or shorten depending on the amount of constant force on the protein filaments of the contractile units. Each unit has a normal overlap length, and with all units connected in series over the entire length of the muscle fiber, the fiber will add or remove units in that chain depending on the force distributed over the connection points of these overlapping filaments.

In simple terms this means that if a muscle is physically stretched that it will in time lengthen by adding additional contractile units in that series chain to keep that normal overlap length over all units in the fiber. This also means that if a muscle is kept in a shortened state (sitting for a prolonged period with the knees bent is a great example) resulting in greater filament overlap, then contractile units will be removed (broken down into proteins) to return the remaining units to their normal overlap length.


I feel have just given you one of the greatest reasons to add a stretching program to your daily fitness routine.

Changing muscle function throughout joint ROM

To continue my discussion on human tissue let's now look at a unique type, and that is muscle. A muscle has the unique ability to perform many select tasks during one motion of a human joint. It can be the prime mover, provide the opposing force, work in synergy with other muscle groups, stabilize the articulating joint surfaces, or neutralize unwanted motions. These functions all come into play as the joint moves through its range of motion and the orientation of force changes. 

All joint motion is in the form of angular rotation and the articulating bones aren't fixed, but free to move in all directions. If there is to much excess play or pressure on these surfaces; injury can result. This is why it is important to maintain good strength and flexibility in all these muscles. I have included 2 photos below to better illustrate these functions. 

I ask you to first look at the image of the posterior shoulder and notice all the muscles attaching to, or crossing the scapula (shoulder blade). Now view the gymnast and visualize the different actions of these muscles as he performs his technique. You should realize that different muscles are constantly changing their main action as the joint travels through it's full range of motion.

Self tissue massage

Lately I've been discussing the benefits of tissue massage by use of the foam roller, but let's not rule out the benefits derived from hands on massaging of the tissues. The fingers of the hands contain thousands of nerve endings which can become very skilled at noticing regions of fibrous adhesions and trigger points within the tissues while probing the skins surface. The strength of the hands can then be brought into play with the use of many learned techniques such as shiatsu, Swedish massage, trigger point therapy, and/or myofascial release, to break up these regions of tightness and pain and restore blood flow to the region. This can be administered either by a qualified massage therapist or self applied for the required results. 

Anything is better then nothing and if you keep the self treatment gentle, and don't apply exorbitant amounts of pressure in a small region; good results should be achieved.

Trigger Point Description

My last post was a description of tissue adhesions and I would now like to now compare those to trigger points within the body.

Trigger points develop within the regions of a muscle fiber that contain the contractile units that slide over each other and result in a contraction of the entire muscle. These units get the message to engage and release through a series of chemical messengers. The main element released into this region to activate and cause contraction; is calcium. The unit will remain in a shortened state until the calcium is pumped from the region by a process called active transport. 

The chemical reaction to activate these pumps requires oxygen, and with the unit in a contracted state the blood vessels are pinched and unable to deliver it. Also pinched within this unit are the nerves leading to pain when pressure is administered to this region. The "Foam Rolling Techniques" I described in a recent video and also below, provide the pressure required to work the blood containing the oxygen and other required chemicals back into this contractile unit to allow it to release and return to it's relaxed state. Another great reason to include these exercises into your daily routine.
https://youtu.be/H5tzz0_G9aM