Pozzi F, Snyder-Mackler L, Zeni J. Relationship Between Biomechanical Asymmetries During A Step Up and Over Task and Stairclimbing After Total Knee Arthroplasty. Clin Biomech 2015, 30: 78-85
Nott CR, Zajac FE, Neptune R, Kautz SA. All joint moments significantly contribute to trunk angular acceleration. Journal of Biomechanics 2010, 43: 2648-2652.
The purpose of this study was to build on previous research, sometimes conflicting, to determine if “one joint more strongly accelerates the trunk.” They also looked at coupling between the sagittal plane joint moments and the frontal plane trunk accelerations. Using an instrumented treadmill and 3-D motion analysis, their model calculated joint moments at the ankle, knee, and hip, to determine the relative affect of each joint on the trunk. Caution must be taken when interpreting the results because the model was employed on only one subject, but they “checked” their findings with previous research for validation.
There are three conclusions, summarized in the abstract, that are important for all movement practitioners. The first demonstrates the Chain Reaction® approach to training and rehabilitation taught at Gray Institute®. They conclude that “each joint moment can produce linear and angular acceleration of all body segments.” There does not need to be a direct connection between joints. These “non-adjacent joint” effects are hard to appreciate from an anatomically / structural perspective. But the functional approach to movement requires that we go beyond the anatomical model to understand muscle activity (coined “Functional Muscle Function” by Gray Institute®). This also validates the six degrees-of-freedom approach, where rotations produce translations, and translation produce rotations.
The second conclusion that “the ankle, knee, and hip joint moments all affect the angular acceleration of the trunk” is important as well. Instead of finding that one joint is more important than another, which has been postulated in the research literature, their results suggest that the importance of each joint moment increases and decreases throughout the gait cycle. The complexity of the movement system requires that practitioners utilize exercises that are as close to the actual activity as possible. If our training movements are authentic to the function, then the system can learn to recognize and utilize the joint moments in the most efficient combination.
The authors also concluded that “inter-planar coupling exists.” The Chain Reaction® Biomechanics taught in Gray Institute® courses has been based on this kinematic and kinetic truth of human movement. The Principle of 3-D states that movement in one plane can’t be separated from the other two planes. The Principle of 3-D necessitates that all joints and all muscles function in three planes simultaneously. This 3-D coupling is founded in joint structure, muscle architecture, alignment of fascia, and neuro-perceptual coordination. It is the truth of human movement.
How should this influence movement practitioners? At Gray Institute®, the Principles (truths) guide the Strategies (plans) that determine which Techniques (exercises / movements) make up our training, rehabilitation, and injury prevention programs. We call this the “PST Process” that serves as the foundation of Applied Functional Science®!