Asymmetry of arm-swing not related to handedness:
Authors: Kuhtz-Buschbeck, Brockmann, Gilster, Koch, Stolze,
Gait and Posture 27 (2008) 447-454
During my recent certification process to become a PRC, I found an article whose findings are supported by PRI science. I felt like I had stumbled upon a pot of gold! I want to share the wealth with PRI nation!
This 2008 article identified a predominant trend of patterned posterior arm swing occurring more on the left than the right in subjects walking at various walking speeds. They found this event to not be related to handedness. The author’s provide insight into why this pattern of movement was observed including underlying mechanisms of side differences in muscle tone and/or strength and also neural motor programming. PRI’s apriori understanding of normal human asymmetry, the development of adaptive muscular recruitment patterns around a left AIC, right BC and a left type1 scapular pattern can explain why the authors observed this pattern.
Around the time of finding this evidence, I had two clients who demonstrated L AIC/RBC patterns. Because of these patterns of movements they had developed asymmetries of a left and right triceps and posterior deltoid muscle groups. Their pictures are below:
The left arm swing findings are understood when you consider that left arm swing occurs during left trunk rotation of the right stance phase of gait and that the human body is always oriented to be in this right stance phase pattern. PRI courses and previous blogs provide excellent and thorough explanations for why our body has a right stance dominant pattern, so I will not describe them in depth. Anatomical asymmetries that orient our spine to the right create imbalance in the AICs with the left AIC becoming more influential and orienting the pelvis and lumbar spine to the right. As a compensation to a right oriented spine the thorax rotates back to the left creating an imbalance in the BCs with the right BC becoming more dominant. This pattern of counter-rotation, between the pelvis and ribcage, will be the dominant pattern occurring during walking, so even though a person will move into a left stance of gait they may not achieve full and opposite counter-rotation. Thus the left arm will always have a tendency to move more frequently and activate more into extension or posterior flexion as the authors described it vs. into flexion or anterior flexion. The degree to which a person is limited in moving out of their LAIC/RBC and into a RAIC/LBC will vary and the results of this study show this. Clinically, I have observed this and have found that the individual needs for a PRI program will vary from one person to the next person.
In closing, I think one of the take home messages from this article is that the underlying pattern of a LAIC and RBC can be observed in a real world situation, walking. The power of PRI is that it understands why the person maybe walking in an unbalanced manor, it provides an evaluation to determine the extent to which a person’s systems are influencing the patterned movement and it provides a management program that helps people become sensory-motor aware and find the floor to maintain balanced walking.