Mechanical properties of animal ligaments: a review and comparative study for the identification of the most suitable human ligament surrogates.

The interest in the properties of animal soft tissues is often related to the desire to find an animal model to replace human counterparts due to the unsteady availability of human tissues for experimental purposes. Once the most appropriate animal model is identified, it is possible to carry out ex-vivo and in-vivo studies for the repair of ligamentous tissues and performance testing of replacement and support healing devices. This work aims to present a systematic review of the mechanical properties of ligaments reported in the scientific literature by considering different anatomical regions in humans and several animal species. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. Moreover, considering the lack of a standard protocol for preconditioning of tissues, this aspect is also addressed. Ninety-six studies were selected for the systematic review and analysed. The mechanical properties of different animal species are reported and summarised in tables. Only results from studies reporting the strain rate parameter were considered for comparison with human ligaments, as they were deemed more reliable. Elastic modulus, ultimate tensile stress, and ultimate strain properties are graphically reported identifying the range of values for each animal species and to facilitate comparison between values reported in the scientific literature in animal and human ligaments. Useful similarities between the mechanical properties of swine, cow, and rat and human ligaments have been found.

Reaction to cutaneous (tickle) and sexual pleasure by normal and dermapathic subjects.

We examined separately tickle perception and pleasure and anxiety during sexual sequence of 40 dermapathic (20 men and 22 women) and 39 normal subjects (20 men and 19 women) aged between 35 and 40 yr. The dermapathic patients have an inhibitory attitude towards tactile perception of tickling and high anxiety during the sexual sequence. Furthermore, they show positive association of anxiety and pleasure unlike the control group for whom the correlation between the two emotions is negative.

Barrier and penetration scores in relation to some objective and subjective somesthetic measures.

Barrier and Penetration scores in relation to some variables, such as muscular tone at rest, sensitivity to tickle, and body perception were studied in a group of 35 female subjects. While no correlations appear within the whole group of subjects between Barrier scores and the other variables, on the left side of the body. Dividing subjects on the basis of Barrier scores, three groups with different characteristics appear: 12 subjects with high Barrier scores show an inverse relation of Barrier scores with sensitivity to tickle on the right side of the body; 12 subjects with middle Barrier scores show a direct relation of Barrier scores with muscular tone and an inverse one with both latency of tickle on the right half of the body and body perception; 11 subjects with low Barrier scores show an inverse relation of Barrier scores with durations of tickle on both sides of the body.

Muscular tone at rest: relationship with cutaneous pleasurable experience, an interpretation according to the dimensional approach to cerebral dominance.

This study examined some aspects of the relationship between muscular tone at rest and a particular kind of pleasurable tactile stimulation (tickle) in the light of the dimensional approach to cerebral dominance. Electromyographic scores, latencies, and tickle durations for six muscles and corresponding skin areas were taken both on the right and left sides of the body from 40 female students in psychology. There was an inverse relationship between muscular tone at rest and sensitivity to tickle stimulation, which is lower (long latency and brief duration of perception) when the levels of muscular tone increase. So we hypothesize that the muscular system (especially because the correlations of tone and latency are positive) plays a role through the afferents of inhibition of tactile pleasurable experience. This role is more evident for the left side of the body. The dimensional approach to cerebral dominance on the basis of myographic score identified three groups of subjects (right, left, and non-dominant). The subjects classified as right-dominant on the basis of myographic score show a longer duration of tickle on the right half of the body than on the left and longer latency on the left. The left-dominant subjects do not show any difference between the two halves of the body in duration of tickle but show longer latency on the left side. The non-dominant subjects show also no difference between the two sides of the body for both tickle duration and latency.

Body perception in relation to muscular tone at rest and tactile sensitivity to tickle.

Two aspects of body image (body perception and body acceptance), muscle tone at rest, and disposition to perceive positively connoted stimuli (tickle) were studied with 35 female subjects. Our hypothesized relation of muscle tension and body perception was confirmed by an inverse correlation between these variables. Also evident was the link of the good acceptance of the body with the disposition to perceive pleasurable stimuli (tickle perception) longer and the link of level of body awareness and resistance to change (latency to tickle). Also a direct relationship between body perception and body acceptance emerged.

Tickle perception as micro-experience of pleasure: its phenomenology on different areas of the body and relation to cerebral dominance.

We examined the tickle sensitivity of 46 female psychology students with reference to different areas of the body and cerebral dominance. Analysis indicated a significant difference between two halves of the body for latency and not for duration. The dimensional approach, as we have suggested for other research on cerebral dominance, singled out for both latency and duration of tickle three groups of dominance: right, left, and nondominant subjects.

Rhythmic reproduction, arousal, and chosen time.

The relationship between rhythmic reproduction of four stimulus frequencies (44, 80, 126, 200 beats a minute), chosen time, and arousal was studied with 32 subjects of both sexes. The following findings emerged: at the frequency of 44, the group is divided into equal numbers of subjects who either accelerate or slow down; a frequency of 80 induces a general slowing down and a frequency of 200 a general acceleration. Also, the maximum absolute error occurred at a frequency of 200 and the minimum, at the frequency of 80. With regard to chosen time, subjects who tended to accelerate showed a tendency to choose faster rhythms. With regard to level of arousal, the highest frequency was associated with a faster reproduction during relaxed wakefulness and a slower reproduction at the higher and lower activation levels; a state of reduced alertness also produced slowing down at a frequency of 126 and a state of relaxed wakefulness, an acceleration at a frequency of 44.

Effects of body image on tactile sensitivity to a tickle:: a study of pregnancy.

A group of 20 middle-class women between 20 and 40 yr. of age and in the third trimester of pregnancy was compared with a control group of 20 non-pregnant women for cutaneous sensitivity (to a tickle) and for modifications of body schema which were hypothesized to occur during pregnancy. Latency and actual duration were considered in the perception of the tickle. Body schema were studied using two of Fisher's tests, Body Prominence and Body Cathexis. Pregnancy leads to modifications in sensitivity to tickle, specifically with regard to the right half of the body and to some extent in body schema.