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Biomedical subjects

A M Hanna

Publications and source records attributed to A M Hanna.

6 recordsLinked to original sources
PubMed1989

The phenomenology of spatial integration: data and models.

A briefly presented visual stimulus followed by darkness seems to persist beyond its physical offset. We are concerned here with the relation between two characteristics of this visible persistence: first, its phenomenological resemblance to the stimulus that spawned it and second, its usefulness as a basis for integrating visual stimuli that are separated in time. We describe two experiments using a task in which two halves of a visual stimulus were presented successively and observers reported how complete the stimulus appeared to be. Stimuli appeared less complete with increases in both the duration of the interval intervening between presentation of the two halves and the duration of the initially presented stimulus half. This data pattern is similar to that obtained in tasks in which spatial integration of two temporally disparate stimuli is necessary for correct responding. On the basis of this similarity, we argue that phenomenological appearance and ability to integrate stimuli over time are two facets of the same perceptual events. We describe a formal model to account for these and other data.

Adult↗
PubMed1989

Running-related injury prevention through innate impact-moderating behavior.

The purpose of these experiments was to test the Robbins and Hanna hypothesis, which relates differences in discomfort from localized deformation at certain positions on the plantar surface to protective behavior (intrinsic foot shock absorption). A penetrometer was used to quantify the relations between localized load and pain and between load and depth of deformation. The magnitude of load required to elicit pain varied significantly (P less than 0.005) in relation to position on the plantar surface. With a load of 9 kg and a 10 mm spherical end on the penetrometer, 6% of the sample reported pain at the heelpad, 32% at the distal first digit, and 66% at the first metatarsal-phalangeal joint. This pattern was predicted by the Robbins and Hanna thesis. Two deformation patterns were observed which were best explained by deformation constraint by tight trabecular tethering of the epithelial membrane at the heelpad and distal first digit and unrestricted deformation due to loose trabecular tethering of the epithelial membrane at the first metatarsal-phalangeal joint. These data provide insight into how, when barefoot, the plantar surface resists perforation yet provides protection to local bony structures. These data further support the notion that plantar sensory feedback plays a central role in safe and effective locomotion.

Adipose Tissue↗
PubMed1988

Overload protection: avoidance response to heavy plantar surface loading.

Current footwear which are designed for use in running are examples of intentional biomechanical model integration into device design. The inadequacy of this footwear in protecting against injury is postulated to be due to fixation on inadequate models of locomotory biomechanics that do not provide for feedback control; in particular, an hypothesized plantar surface sensory-mediated feedback control system, which imparts overload protection during locomotion. A heuristic approach was used to identify the hypothesized system. A random series of loads (0 to 164 kg) was applied to the knee flexed at 90 degrees. In this testing system, plantar surface avoidance behavior was the difference between the sum of the leg weight and the load applied to the knee, and the load measured at the plantar surface; this was produced by activation of hip flexors. Significant avoidance behavior was found in all of the subjects (P less than 0.001). On all surfaces tested, including modern athletic footwear (P less than 0.001), its magnitude increased directly in relation to the load applied to the knee (P less than 0.001). There were significant differences in avoidance behavior in relation to the weight-bearing surfaces tested (P less than 0.05). With the identification of a feedback control system which would serve to moderate loading during locomotion, an explanation is provided as to why current athletic footwear do not protect and may be injurious; thus allowing the design of footwear which may be truly protective.

Athletic Injuries↗
PubMed1987

Running-related injury prevention through barefoot adaptations.

A number of reports indicate an extremely low running-related injury frequency in barefoot populations in contrast to reports about shod populations. It is hypothesized that the adaptations which produce shock absorption, an inherent consequence of barefoot activity and a mechanism responsible for the low injury frequency in unshod populations, are related to deflection of the medial longitudinal arch of the foot on loading. It is also hypothesized that the known inability of this arch of the shod foot to deflect without failure (foot rigidity) is responsible for the high injury frequency in shod populations. To evaluate these hypotheses, 17 recreational runners were analyzed to study the adaptive pattern of the medial longitudinal arch of the foot due to increased barefoot weight-bearing activity. Changes occurred in the medial longitudinal arch which allowed deflection of this arch on loading which substantiated the hypotheses. Other evidence suggests that sensory feedback largely from the glabrous epithelium of the foot is the element of barefoot activity which induced these adaptations. The sensory insulation inherent in the modern running shoe appears responsible for the high injury frequency associated with running. The injuries are considered "pseudo-neuropathic" in nature.

Athletic Injuries↗