Postural sway and heart rate were recorded in young men viewing emotionally engaging pictures. It was hypothesized that they would show a human analog of "freezing" behavior (i.e., immobility and heart rate deceleration) when confronted with a sustained block of unpleasant (mutilation) images, relative to their response to pleasant/arousing (sport action) or neutral (objects) pictures. Volunteers stood on a stabilometric platform during picture viewing. Significantly reduced body sway was recorded during the unpleasant pictures, along with increased mean power frequency (indexing muscle stiffness). Heart rate during unpleasant pictures also showed the expected greater deceleration. This pattern resembles the "freezing" and "fear bradycardia" seen in many species when confronted with threatening stimuli, mediated by neural circuits that promote defensive survival.

In stabilometry, the sway of the human body in an upright posture is studied by monitoring the displacement of its centre of pressure in the lateral (x) and anterio-posterior (y) directions. The area covered by this trace has been defined as that of an ellipse fitted to the data. Conventionally, its angle of inclination is found through linear regression (LR) on the data in the x-y plane. In the present paper, principal component analysis (PCA) is proposed as providing a more suitable basis for the estimation of angle and area. Results of simulations and stabilometric tests confirm large differences between area and angle estimates obtained by regression of x over y, and y over x, with PCA generally agreeing with either one or the other of the LRs. The PCA technique is therefore recommended as an improved basis for measuring area and inclination of stabilograms, or similar data sets.

To describe changes in the VL and BF muscle tendon unit using US after a long-term stretching program to identify which structures are responsible for ROM increase.

No abstract