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Background and aims The nociceptive system appears to have evolved a range of protective characteristics that are of great interest in understanding both acute and chronic pain. Spatial summation is one important characteristic, whereby increasing area of a stimulus, or distance between multiple stimuli, results in more intense pain—not only greater area of pain. One of the mysteries of chronic pain is why spinal pain is so prevalent relative to pain at other sites. Since pathological tissue models have failed to fully explain spinal pain, we theorized that body region specific differences in sensory processing—such as a greater propensity for spatial summation—may help to explain its vulnerability. We aimed to examine this by comparing the properties of summation at different body parts: the dorsal forearm, neck, and back. Methods Spatial summation of pain was investigated using noxious intra-dermal electrical stimuli in healthy pain-free adults (14 males, 6 females), and the perceived pain intensity was rated on a 0-100 pain scale. Area-based stimulation was investigated by doubling the stimulation area with the addition of a second electrode placed adjacent to the first. Distance-based summation was investigated by randomly varying the separation distance between paired noxious electrical stimuli at separations of 0,10,15, and 20 cm. Results This study demonstrated that the properties of area- and distance-based summation are uniform across the neck, back, and forearm in healthy adults. Spatial summation of pain was also found to be greatest at 15- and 20-cm paired separations for all body regions tested, confirming that noxious information can be integrated over an extensive anatomical area. Conclusion Data from this investigation refutes the thesis that spatial summation of pain may be a contributing factor for the reported difference in chronicity rates between spinal and peripheral sites. It remains, however, a potentially important mechanism by which noxious inputs from multi-level pathology might integrate and contribute to pain. Implications While data from this project suggest that there are no regional differences in the properties of spatial summation of noxious stimuli, regional differences in other characteristics of the nociceptive system may yet provide insight into why some spinal pain is so highly prevalent; nociceptive distance-based summation may be highly relevant where two or more conditions co-exist in close proximity.

Thesis (PhD)--University of South Australia, 2012. Includes bibliographical references (pages 234-245) The drop punt is one of the most important skills of Australian Football. A comprehensive systematic review of the available literature was undertaken which revealed that the analysis of this unique technique of ball progression had limited peer reviewed publications. Of the work that was reported very few studies presented research on non-sagittal plane motion, kinematic variability, limb coordination and muscle activity. The initial phase of this research investigation quantified kinematic variables (hip rotation, hip ab/adduction, pelvic tilt) which may potentially influence drop punt performance. A considerable range of motion but no significant association with drop punt performance was observed for these variables. The second study quantified the variability of three-dimensional kinematics across a competitive season. Repeatability and variability values for kinematic data were calculated from one testing session (within session) and from three sessions (between session). The third study explored the coordination between the joints (hip-knee) and segments (thigh-shank) of the kicking leg. Greater delays between motion of the thigh and motion of the shank were significantly associated with maximum foot velocity. The final study was a cross-sectional observational study of the muscle activity of the thigh muscles during the drop punt. There was high between-subjects variability for both hamstrings muscle activity and coactivity of the quadriceps and hamstrings. This thesis provides information regarding the variability and repeatability of commonly reported kinematic variables for the drop punt. Exploratory data has been presented for the association of: non-sagittal plane hip motion, pelvic motion, coordination of the kicking limb joints and segments, coactivity of the quadriceps and hamstrings and the amplitude of eccentric quadriceps activity with drop punt performance. The findings of this thesis provide a context with which to interpret kinematic data for the drop punt, including variables that may be related to kick performance, and the expected variability of the three-dimensional kinematics.