Head activator

Objectives: The main objective was to test the hypothesis of a neuromechanical link in humans between the head and forearm during running mediated by the biceps brachii and superior trapezius muscles. We hypothesized that this linkage helps stabilize the head and combats rapid forward pitching during running which may interfere with gaze stability. Materials and methods: Thirteen human participants walked and ran on a treadmill while motion capture recorded body segment kinematics and electromyographic sensors recorded muscle activation. To test perturbations to the linkage system we compared participants running normally as well as with added mass to the face and the hand. Results: The results confirm the presence of a neuromechanical linkage between the head and forearm mediated by the biceps and superior trapezius during running but not during walking. In running, the biceps and superior trapezius activations were temporally linked during the stride cycle, and adding mass to either the head or hand increased activation in both muscles, consistent with our hypothesis. During walking the forces acting on the body segments and muscle activation levels were much smaller than during running, indicating no need for a linkage to keep the head and gaze stable. Discussion: The results suggest that the evolution of long distance running in early Homo may have favored selection for reduced rotational inertia of both the head and forearm through synergistic muscle activation, contributing to the transition from australopith head and forelimb morphology to the more human-like form of Homo erectus. Selective pressures from the evolution of bipedal walking were likely much smaller, but may explain in part the intermediate form of the australopith scapula between that of extant apes and humans.

Background: Chin tuck against resistance (CTAR) exercise has been recently reported to be a new therapeutic exercise method that can help improve swallowing function in patients with dysphagia. However, due to the differences in exercise protocols, methods and the tools used across studies of CTAR exercise, an overall systematic review of these studies is necessary. Objective: The present study investigated the exercise protocols, methods and tools used in various studies of CTAR exercise and summarised their findings. Methods: We searched for studies related to CTAR exercise using electronic databases and selected nine articles for review. The articles were categorised on the basis of four criteria: study design and quality, training protocol, outcome measures and clinical effect. Results: Four articles reported that CTAR exercise not only helped activate the suprahyoid muscle in healthy adults, but also activated the sternocleidomastoid muscle less than Shaker exercise. In addition, five articles reported that CTAR exercise was effective in improving swallowing function and oral diet stage in the pharyngeal phase, including reduction of airway aspiration in patients with dysphagia after stroke. Conclusions: CTAR exercise more selectively activates the suprahyoid muscle and is an effective therapeutic exercise for improving swallowing function in patients with dysphagia. Because it is less strenuous than Shaker exercise, it requires less physical burden and effort, allowing greater compliance.