Monday, February 29, 2016

How to Eliminate Pathokinematics - Part IV

Last week we covered repetitions to substitution and lumbar-hip disassociation, two essential concepts to changing movement in our athletes.  This week let's continue the discussion by looking at proprioceptive training and concentric vs. eccentric training.

Proprioceptive Training

As defined by Wikipedia, proprioception is the sense that indicates whether the body is moving with required effort, as well as where the various parts of the body are located in relation to each other and in relation to space.  Proprioception is a sense provided by a combination of sensory receptors in the inner ear, the muscle spindle and the joint space that converge to give an overall sense of where the body is in space.  These inputs are sent to the higher centers of the brain (cerebellum) to compare the intended movement with the actual movement.  Once the intended and actual are compared (in the cerebellum) 
, minor adjustments can be made in the motor plan in the primary motor cortex of the brain in order to move the body into the desired position.

Proprioception provides us with a sense of where our body is in space which is an essential component in preventing injury and improving athletic performance.  Proprioception is something that can be learned, or re-learned, and is used extensively in rehabilitation settings to aid athletes in restoration of ability following injury.  However, current research suggests that training of this sense prior to injury also aids athletes in building the awareness of the lower kinetic chain during athletic activities, thereby improving performance.  Proprioceptive training is therefore an essential part of a program designed to aid in prevention of abnormal movement patterns or pathokinematics that can lead to injury and in improving overall athletic performance. 

In order to effectively use proprioceptive training, it is essential to ensure proper form and technique.  Due to the fact that you are attempting to train the “sense” of body position and how to maintain the correct body position, if done with improper form we are simply reinforcing bad movement patterns.  In the example here, if we let this athlete repeat this lateral shift during his squatting motion, then he will carry over this same poor movement patter when he does his squats with 225#.  Therefore, it is  important to keep in mind that multiple systems work together in the body to facilitate this sense of awareness.  Knowing this fact then, we can progress or regress this type of exercise by adding or removing some of the senses required to properly conduct them. 

Let’s look at an example to illustrate this point.  Vision is one way an athlete receives feedback about his or her current and desired body position.  An easier form of an exercise, requiring less proprioception, is to allow the athlete to watch themselves in a mirror while performing the desired movement.  As they progress in skill and endurance, you can have them do the exercise without the mirror (hence removing the visual input).  This is a technique that is often employed with the Squat Neuromuscular Retraining (SNMR) exercise, which will be discussed in a later blog. 

Another example is the sensation provided by receptors within the muscle spindle and joint space.  Performing exercises on an unstable surface (a Theraband Stability Trainer) can make it more difficult for this feedback system to provide input to the brain about body position and proper mechanics.  If combined with the removal of visual input, then a given exercise becomes increasingly difficult.  That said, as with any exercise, it is vital to first master the easiest levels of a given exercise prior to progressing to the next level, and in this case before removing or limiting other sensory input.

The purpose of proprioceptive exercise in our program is for the professional to teach the athlete to use his/her body to perform large movements while maintaining “healthy” alignment of the lower extremity, for example not allowing excessive internal rotation with valgus stresses at the knee and hip.  Considering the multiple senses involved, the athlete should start with one set of each exercise, performing the lowest number of repetitions recommended and slowly progress to 3 (or more as appropriate) sets of the highest repetitions recommended---using perfect form.  Progression is dictated by the athlete’s ability to perform the exercise with a moderate amount of effort without any decomposition of technique.

A final note is that proprioception should be considered throughout the entire program, during every exercise, and as part of every progression.  All too often we see professionals focus on proprioception during proprioceptive exercises and yet completely ignore it during dynamic stretches.  The dynamic valgus occurring during these stretches simply reinforces poor movement.  It is the proprioceptive sense that will enable the athlete to maintain the proper alignment of the lower limbs while performing many, if not all, of the exercises.  When and if movements revert to pathokinematic patterns, then we suggest revisiting proprioceptive retraining techniques such as the use of visual input, verbal cuing and regression of exercise to re-learn proper positioning.

Concentric Training vs. Eccentric Training

According to Merriam-Webster’s Medical Dictionary, ( a concentric contraction is a type of muscle contraction in which the muscles shorten while generating force.  During an eccentric contraction, the muscle elongates while under tension due to an opposing force being greater than the force generated by the muscle.  Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the repositioning of a load. 

This is the traditional understanding of concentric and eccentric contraction which has been applied to traditional training methodology.  However, the majority of training programs continue to focus solely on concentric strength training despite the abundance of evidence supporting the use of eccentric training protocols to improve performance and prevent injury.  Over the course of the last 10 years, LaStayo and others have done a tremendous amount of research on the benefits of eccentric strength training and the corresponding implications for improving strength and power.  In a 2009 study by LaStayo et al in Sport Health showed the strength gains that can be achieved with eccentric training versus concentric.  As such, these concepts have been widely used in rehabilitation settings and are beginning to be used in more frequently in performance training as well. 

In sports, our muscles act in both a concentric and eccentric fashions and therefore must be trained in both ways.  For example, when a basketball player is jumping for a jump shot, the quadriceps are functioning in a concentric fashion to generate enough force to produce a maximal vertical jump.  On the other hand, when a pitcher is pitching, the biceps acts in an eccentric fashion during deceleration phase to slow the arm.

We also know that in order to prevent injuries, we should train muscles in the fashion or similar contraction type that is similar to how they sustain injuries.  For example, sprinters often experience hamstring strains that occur during the eccentric phase (for the hamstring) of the running cycle.  Therefore training which focuses on concentric training of the hamstrings is less effective than training that focuses on training the hamstrings in an eccentric fashion.

In our program, we will describe exercises as having a concentric, eccentric or both concentric and eccentric focus.  The purpose is to train the muscles in the fashion that they perform during sport and to maximize the strength and power gains we achieve as a result.  However, it should be noted that caution must be used when incorporating more eccentric training protocols into established routines that have not traditionally used them, as these can lead to additional and/or new muscle work, resulting in more muscle soreness and/or injury if over used, or used before the body has a chance to adapt.  Close monitoring is required to ensure safety, proper form and to prevent overtraining.

Distal vs. Proximal Training

In exercise terminology, when we refer to distal placement of a weight or distal movement, we mean the weight or movement referred to is “far away” from the pivotal point or center of gravity.  When we use the word “proximal” we are referring to weight or movement that is closer to the joint, pivot point or center of gravity. 

Closed Chain vs. Open Chain Exercise
When we talk about ”open or closed chain” exercises, we are referring to the kinetic chain of the body, which is essentially the chain through which power is produced and off-loaded, resulting in movement and force attenuation.  Open chain exercises are those in which a given body part is free to move during the exercise as in a chest press, or leg extension.  These types of exercises usually isolate a single muscle, group or joint.  For example, during a leg extension exercise, the knee and quadriceps are isolated.  This type of exercise can be performed with or without added weight, but when weight is added, it is usually added distally (far away from the muscle group that is being isolated).  In this example, weight would be added at the ankle in order to maximally work the quadriceps in an open chain leg extension exercise.  Other types of open chain exercises in the gym might be biceps curls, hamstring curls, lat pull-downs and triceps kick-backs.

Closed chain exercises on the other hand are those that require your hands or feet to be in a fixed position during the exercise motion. The feet or hands are usually on the ground, but may also be fixed to a platform or other fixed machine or device.  Closed chain exercises work many joints and muscles at the same time.  An example of a closed chain exercise is the squat, which will be discussed in more detail later in this book.  The squat involves the knee, hip, and ankle joints and many muscle groups including the hamstrings, gluteal group (gluteus maximus, gluteus minimus, and gluteus medius), the quadriceps, the calf muscles, the lower back and abdominal muscles.  Different from open chain exercises, when additional weight is added to a closed chain exercise, it is placed in the proximal position, or closest to the center of gravity, where the core muscles can help control and move the weight safely.  In the squat example, additional weight, if added, would be placed on the shoulders or the front of the chest, versus a distal or “far away” placement of the weight. 

Of course, closed chain exercises can be performed very well without added weight, simply by using body weight.  They involve many more muscle groups, including smaller muscle fibers which are only recruited when balance and proprioception are required.   This makes closed chain exercises very efficient in that they work the most muscles in the body in the least amount of time.  They are also very effective in transferring strength and flexibility gains to activities of daily living and sports.  Consequently, they are often called “functional” exercises in that they help people gain fitness for all functions of life.  The picture to the right is a closed chain exercise (bottom leg) performed with poor technique.

Closed chain exercises more closely mimic real life movements as opposed to open chain exercises.  They are also usually safer for your joints, especially the knee, elbow and ankle.  If you remember our earlier discussion regarding forces to the joints and ligaments, you can see that closed chain exercises cause “compressive” force to the joints, which strengthen them over time.  Conversely, open chain exercises involve “shearing” forces, which stress the joint and can result in injury.  Other examples of closed chain exercises besides the squat are pull-ups, push-ups, and lunges.

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is Chairman of Medical Services for the International Obstacle Racing Federation and associate editor of the International Journal of Athletic Therapy and Training. 

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