April 24, 2011

What Everyone Needs To Know About Load Sharing To Avoid Pain, And Maximize Results

Pattern overload is an unofficial term that defines an injury to soft tissues (muscles, tendons & ligaments) resulting from repetitive motion in an isolated pattern of movement, or a restricted movement in one or more planes of motion.

Pattern overload and/or repetitive stress injuries result primarily from:

1. An inability to properly load share (using the right muscles, but at the wrong time)

The human body is remarkably efficient in a sense that it will recruit as many muscles as it can across as many joints as possible to naturally provide optimal load sharing. The body will always attempt to take the path of least resistance for any task you ask of it.

A common example of improper load can be seen by one who attempts to perform a rowing type of movement with the shoulders pre-retracted (pulled back, prior to initiating the pull). This ineffective technique disrupts the natural load sharing recruitment sequence and leaves the muscles in the shoulders and arms to take on more work than would otherwise be necessary. Performing rows in this manner will lead to strain and trigger point development in both teres muscles, as well as parts of the rotator cuff, and will ultimately result in shortened/tightened retractor muscles of the back, and non-functional shoulder girdle movement patterns will develop. When this happens, the shoulders blades are inhibited from moving freely due to the lack of mobility, which will negatively affect performance of any movement while increasing the chance of injuries.

A loss of mobility in the scapula (shoulder blades) due to short/tight retractors can lead to anterior subluxation (partial dislocation in the front part of the shoulder) in the shoulder joint, and a popping sound will start to manifest (commonly while doing the same movements that lead to pattern overload of the shoulder in the first place).

Depending on the severity of the damage, restoring natural and optimal function may never regenerate 100%. If permanent damage is done, creating a structurally balanced shoulder girdle by developing the lower traps and external rotators is your best bet at making the joint as functional and pain/injury free as possible. Pattern overload can happen in any joint throughout the body, the shoulder was simply used as an example in this case because of how common it is due to the versatility of the joint.

2. Being restricted to a specific motion with loss of natural movement in one or more planes (as is the case when using a machine, and to a lesser extent a barbell because it is a fixed piece of equipment)

Repetitive stress injuries are due to repetitive exposure to a particular movement, and can happen to anyone who regularly performs the same movements, in the same manner, with the same amount of effort/difficulty, on a daily basis. Common examples of this are athletes, musicians, office workers, assembly line workers, and even, people that primarily workout on machines or just do the same workouts for years on end.

To prevent faulty recruitment patterns from developing, a smart trainee will focus on creating a structurally balanced physique, with the use of free weights that enable the body to move and recruit naturally, and devote time to training muscles that are not worked in the lifters everyday life or sport. For example, if you take an athlete who’s sport calls for lots of lunging and running type movements, and then focus on more lunging type movements (which is the same thing they do all day, every day, as is) in the gym, the chance of them developing an injury to any of the muscles used in the lunge, or their sport, are more likely to get injured because of the repetitive stress (machines, and some barbell movements are included as they can promote repetitive stress injuries by restricting you from moving freely).

3. Over-use of any given pattern of movement, regardless of freedom of joint motion (doing the same movements again and again irrespective of whether or not you are using machines or free weights)

The body has a finite amount of neurological energy with which to drive its population of roughly 250 million muscle fibers. The nervous system is not only capable of recruiting a specific muscle to perform a task, but to also selectively recruit specific motor units within a given muscle. As stated above, the body will naturally attempt to conserve as much energy as possible by choosing the path of least resistance, while attempting to keep the desired movement you intend to do as smooth as possible (which further conserves energy).

Neuromuscular isolation (muscle control, or the ability to activate and isolate, as demonstrated when a bodybuilder makes a muscle pop for example) is what is needed to produce optimal intramuscular tension. If you want to build the most muscle and/or strength possible it’s necessary to recruit and fatigue as many motor units as possible. The greater intramuscular tension that can be produced, the faster progress will be regardless of the goal.

Neurological efficiency (the ability to recruit as many motor units as possible) is a developed trait which takes place over a sustained period of time. A beginner, or someone with little training experience may only be capable of recruiting up to 60% of their available motor units, where as a lifter with significantly more proper training experience may be able to recruit up to, and over, 85% of available motor units.

Exercises that are performed seated or lying down are generally the least neurologically demanding, although they offer an increased level of recruitment to the muscle being targeted. Obviously greater levels of recruitment allow for more weight to be used, meaning more strength and/or muscle can be developed. Exercises that are performed standing, or are of a high coordination nature like Olympic lifts, or plyometrics, are the most neurologically demanding and will fatigue the nervous system faster. Machines, and some barbell movements, don’t allow the nervous system the freedom it needs to protect the working joints and muscles from injury by trapping the body into an unnatural fixed position.

If you were to carefully analyze the execution of any free weight lift, you would fail to see the exact same rep performed twice in a row, regardless of how well the person performing the exercise has mastered it. The path in which the weight travels will change with each rep as the nervous system attempts to take the path of least resistance by distributing the load differently as the muscles fatigue, and it does so by varying the path of resistance (bar/dumbell path) which is just another mechanism for conserving energy and preventing unwanted overload in specific areas.

When using a machine, or in some cases a barbell, the path is restricted and unchanging unless you contort yourself while under tension, and this is what can lead to the development of faulty recruitment patterns, and possibly do irreversible damage to the capsular structures surrounding the relative joints (as well as set you up for long term injuries). When using machines or barbells, the population of muscle fibers experiencing maximum load is isolated (which may be the goal, as it generally is for those solely looking to build muscle). The motor units and muscle fibers most suited to move the working weight in the given pattern and movement plane dictated by the machine will experience fatigue much sooner than when performing the same exercise without such restriction. As the muscle fibers specific to the movement pattern, dictated by a machine/barbell fatigue, one is left with progressively less dynamic control over the load and working joints, and this can result in insult, and possible damage, to the working connective tissue, tendons, and muscle fibers.

As support for the relative joints fail, it's common to see one of two things happen. One will either squirm around on the machine attempting to find new fiber populations to move the load (which is a dangerous means of changing fiber populations), or they attempt to rely on the stretch reflex of working connective tissues to complete the final reps of the set by bouncing out of the bottom position of a lift (examples being bouncing the bar off the chest during barbell presses, bouncing the thighs off the torso during a leg press, springing the shoulders at end range of motion on the pec deck, or bouncing out of the bottom position of a full range of motion squat). This leads to damage to the ligaments and capsular structures of joints, not to mention the potential derangement of the joint itself.

This is pretty serious when you consider the fact that connective tissue heals considerably slower than muscle tissue, and that motor control may be compromised secondary to damaged mechanoreceptors in relevant capsular and ligamentous tissues. Muscle injuries heal quickly whereas tendons and ligaments will have little regeneration at best. A muscle injury, like a sprain, can almost fully recover in just 7 days, whereas a soft tissue injury will take up to, and sometimes even longer than, 12 months, and that's just referring to it healing to the best of its ability, not getting back to where it was prior to the injury.

Surrounding each joint is a capsule that aids in joint stability at end ranges of motion, serves to lubricate the joint surfaces, and is loaded with proprioceptive neurons called mechanoreceptors that are constantly communicating with your brain and monitoring your every move.

When an individual trains on machines and/or overuses any form of guided resistance, the fatigue and loss of motor control in the relevant movement pattern and plane of movement often leads to overload of the joint structures. These structures, predominantly consisting of collagen, do not stretch well, or bounce back well from repeated stretch. The best analogy is that of a 6-pack of pop – after removing a can from the connective plastic, it is impossible to jam the can back in where it came from. This is pretty much how joint capsules react from ineffective load sharing, repeatedly performing the same movement patterns, or just using poor form when lifting weights regardless of the implement employed (free weights or machines).

A joint with stretched capsular structures begins to lose its optimal working relationships and eventually tries to fall out in positions specific to the dysfunction. This is especially common in the shoulder joint due to its versatility. With decreased support from capsular structures, there must be a directly proportionate increase of dynamic support by the surrounding muscles.

Should a joint complex be even mildly traumatized, the stabilizing muscles, such as the rotator cuff in the case of the shoulder for example, will be taxed with the burden of trying to maintain an optimal axis of rotation in the now dysfunctional joint. Should the muscles become fatigued from repetitive work and overuse, combined with the now added burden of trying to maintain optimal working relationships in the joint, an eccentric rotation (partial dislocation) of the most mobile segment in the joint is likely.

As an eccentric motion (partial dislocation) is produced secondary to failure of the respective stabilizing muscles, the joint's ligamentous and capsular structures are progressively challenged. Without restoration of dynamic stability, joint derangement is likely to occur.

A partial dislocation of the joint results in what is called a subluxation. The joint complex demonstrating some level of instability, as a result of pattern overload, will begin to make popping sounds. If the condition progresses, pain is associated with the unusual joint sounds and the person suffering from it can usually tell a therapist precisely what movement causes it, often the movement that causes popping sounds or pain, mimics the exercise which induced the injury.

As the capsule and ligaments related to a specific joint become more and more imbalanced (ex. tighter in some areas in relation to others), there's progressive dysfunction in the proprioceptive messages being sent to the central nervous system with regard to where the joint is in space. This produces what is called a proprioceptive deficit, which basically means that the brain thinks, because it is being told so by the mechanoreceptors in the joint, that the joint is somewhere that it actually isn't. It is deceived, for the lack of a better term.

A person with a proprioceptive deficit may develop a pattern for the work of varying muscle recruitment order in an attempt to effect changes in joint position, leading to pathological motions. When this happens you’ll notice a loss of performance during activities that require fine motor control, like a golf swing. For example, if you’re a golfer, and happen to develop pattern overload in the shoulder, which happens from performing behind the neck pulldowns when your available range of motion doesn’t allow for that movement to be performed, or using the pec deck with extreme ranges of motion, you may increasingly experience swing errors.

Due to poor form, regardless of the chosen implement (machine, barbell, etc), many people repetitively insult their working joints and muscles while working out. As you may know, pulling the bar behind the head places the arm in full horizontal abduction and full external rotation which places maximum stress and strain on the anterior joint capsule of the shoulder, especially if there is a lack of available range of motion or flexibility in the shoulder due to tight/short pecs and/or lats. As the capsular and ligamentous structures become progressively more lax, the brain begins to receive faulty information from the articular (structural component of a joint) proprioceptors. This leads to a loss of motor control and an increase in pain and inflammation, both of which may lead to permanent loss of performance.

This results in an imbalance in the capsular and ligamentous structures of the shoulder that will not only send faulty information to the brain, but the body will attempt to make things easier by activating key muscles around the shoulder and possibly beyond. When a joint is functioning normally, the motor command leaving the brain expresses itself quite accurately in the body.

When there is a proprioceptive deficit in one or more joints, the motor command leaving the brain contains the necessary information to produce the desired movement, yet the movement itself actually looks completely different. This is often a source of frustration for athletes that have noticed a loss of performance in their sport after experiencing one or more injuries to joints. They basically ask their body to do something but physically can’t do it, and what they’re trying to do looks completely different than what they are doing.

When performing movements such as various types of rows and shoulder abductions, the movement will be initiated from the upper trapezius with a shoulder-hiking action. In the case of shoulder abduction (lateral raise), there is often increased effort from the upper traps in the beginning of the movement to carry the arm through mid and upper ranges of abduction and there may be an associated pain with this movement.

Pattern overload isn’t always a local issue specific to the joint where pain is felt. It is common for people with pattern overload to complain of abnormal nagging pains in an unknown origin. This is likely to result from faulty motor recruitment of muscles at distant locations taking on unnecessary stress during normal activities. As it relates to the shoulder, it’s generally the lower traps and retractors that fail to activate to provide the shoulder with the stability needed to avoid anterior subluxation. In some studies researchers placed traction and electrically stimulated mechanoreceptors at the C3-4 level and were able to record significant EMG (electrical activity) responses in muscles such as the traps, triceps, abs and hamstrings.

These findings suggest that the messages sent to the brain, as produced by varying intensities and lines of pull on the joint capsule, may make the brain respond as if a preprogrammed pattern of motion were taking place. For someone suffering from pattern overload, this may present itself as an unknown strain or spasm in an unrelated region.

The easiest ways to avoid developing pattern overload is to avoid machines that don’t fit your body, and if you’re going to use machines, avoiding relying on them, and alternat machine exercises in and out of your routine. Doing so will at least decrease your chance of injury because you're allowing a healing response in the fatigued or traumatized tissues related to a specific pattern of motion.

Common sense would suggest never training an area experiencing joint or muscle pain as well. Pain always equals inhibition, and if you train in pain, you can rest assured that the muscles crossing any joint in pain are being shut off, resulting in progressive instability of the joint(s) related to that muscle.

If you have any questions about the use of machines in your own, or a clients weight training program, feel free to contact me at ben@paramounttraining.ca. I'm available for online consulting and personalized program design, as well as one on one training if you are located in the Greater Toronto Area (GTA).

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