Design: Blocked, counter-balanced repeated measures. Background: Altered scapular kinematics have been documented in many shoulder injuries and pathologies. Assessing faulty movement of the scapulae on the thorax and retraining activation of periscapular and spinal intrinsic musculature should enhance a neuromuscular pattern’s quality to establish a punctum fixum at the thoracic spine and physiological scapula-thoracic articulation (PSTA). Establishing proper fixation of the scapulae on the thorax requires a stiffening of the thoracic spine. Optimal muscle activation pattern from the scapula’s stabilization on the thorax establishes a point of fixation from which the scapula glide, tilt, and rotate about the shoulder girdle axes. This is accomplished by a “stiffening” of the thoracic spine. A specific muscle activation pattern creates an ideal intra-abdominal pressure, stiffening not only the lumbar spine, but also the thoracic spine. This activity establishes a point of fixation and determines the direction of muscle pull of muscles that centrate the PSTA position on the thorax, allowing for an optimal mechanical advantage for upper extremity motion and support functions. Aims: This study aims to 1) determine if a balanced abdominal wall activation augments mechanical support of the thoracic spine and 2) determine if a balanced abdominal wall activation affects scapula-thoracic kinematics, specifically scapular upward rotation on the thorax. Method: Healthy males and females who met the criteria for the study were recruited from the local community. Thoracic spine stiffness to posteroanterior (PA) glides, electromyography (EMG) activity of the abdominal wall regions and simultaneous kinematic motion analysis of the scapulae were recorded pre- and post-balanced adbominal wall activation training. Results: All participants, regardless of age or gender, were able to increase thoracic spine stabilization, as measured by EMG activity and spinal stiffness measure, through a neuromuscular activity or proportional, synchronized abdominal wall activation pattern during bilateral upper extremity (UE) reach task in sagital, scapular, and frontal planes. This reach in multiple planes. Conclusion: A balanced abdominal wall muscle activation pattern stiffens the thoracic spine, creating a punctum fixum, altering neuromuscular control of the scapula, resulting in decreased upward rotation on the thorax during bilateral reaching activities. Ideal stabilization of the shoulder girdle requires preparatory muscle activity in the abdominal wall, and it is part of a neuromuscular pattern necessary to achieve a punctum fixum at the thorax and the PTSA. This central mechanism of neuromuscular adbominal wall activity on the quality of scapular fixation on the thorax should be considered when describing ideal kinematics at the PSTA.
