Body symmetry and physical strength in human males

Handgrip Strength Asymmetry and Weakness Together Are Associated With Functional Disability in Aging Americans

Background

Evaluating handgrip strength (HGS) asymmetry may help to improve the prognostic value of HGS. This study sought to determine the associations of HGS asymmetry and weakness on future activities of daily living (ADL) disability in a national sample of aging Americans.

Methods

The analytic sample included 18,468 Americans aged ≥50 years from the 2006–2016 waves of the Health and Retirement Study. A handgrip dynamometer measured HGS. Those with HGS >10% stronger on either hand were considered as having any HGS asymmetry. Individuals with HGS >10% stronger on their dominant hand were considered as having dominant HGS asymmetry, while those with HGS >10% stronger on their nondominant hand were classified as having nondominant HGS asymmetry. Men with HGS <26 kg and women with HGS <16 kg were considered weak. ADLs were self-reported. Generalized estimating equations were used for analyses.

Results

Relative to those with symmetric HGS and no weakness, each HGS asymmetry and weakness group had increased odds for future ADL disability: 1.11 (95% confidence interval [CI]: 1.02–1.20) for any HGS asymmetry alone, 1.42 (CI: 1.16–1.74) for weakness alone, and 1.81 (CI: 1.52–2.16) for both any HGS asymmetry and weakness. Most weakness and HGS asymmetry dominance groups had increased odds for future ADL disability: 1.30 (CI: 1.13–1.50) for nondominant HGS asymmetry alone, 1.42 (CI: 1.16–1.74) for weakness alone, 1.72 (CI: 1.29–2.29) for both weakness and nondominant HGS asymmetry, and 1.86 (CI: 1.52–2.28) for both weakness and dominant HGS asymmetry.

Conclusions

HGS asymmetry and weakness together may increase the predictive utility of handgrip dynamometers.

Assessment of physical strength from gait: data from the Maasai of Tanzania

In industrialized societies, male gait provides information about physical strength. Male physical strength may be used by men and women to assess the fighting ability of rivals and the quality of potential mates, respectively. Women more than men discriminate between strong and weak walkers when assessing gait attractiveness. We presented videos of British men's gait-pre-categorized into strong and weak walkers-to male and female members ( n = 100) of the traditional Maasai in northern Tanzania in Africa. Maasai men and women judged the gaits of physically strong men less attractive than those of weak men and judged strong walkers to be weaker than weak walkers. These findings counter results from industrialized societies where participants accurately assessed strength from gait, thus arguing against a universal perception of physical strength from gait information.

Fluctuating body asymmetry in young Polish women in relation to childhood socioeconomic status

The aim of this study was to analyse the relationship between childhood socioeconomic conditions and body asymmetry in young Polish women. The study measured fluctuating asymmetry (FA), which refers to small random deviations from perfect symmetry in bilaterally paired body structures. Data were obtained from 620 female students aged from 19 to 25 years recruited from Jagiellonian University in Cracow, Poland. The research was carried out in the period from January 2016 to May 2017. A composite fluctuating asymmetry (cFA) of the women was calculated using five bilateral body traits. The lengths and widths of the women’s ears, lengths of their 2nd and 4th digits and wrist widths of the right and left sides of the body were measured twice using standard methodology. The following data were collected in a questionnaire: degree of urbanization of the woman’s place of residence during childhood, number of older siblings, parental education and woman’s dominant hand. The results showed a tendency for FA to fall with an increase in parental education, and to rise with an increase in number of older siblings. The level of FA was significantly lower in women from rural areas than in those from cities. The results of the study show that FA in early adulthood is significantly associated with socioeconomic status during childhood, and confirm that the level of FA in adulthood may be a good indicator of stress factors in the early stages of development.

Asymmetry patterns are associated with body size and somatic robustness among adult !Kung San and Kavango people

Asymmetry of bilateral anatomical structures is widely found in nature. Fluctuating asymmetry, i.e. mostly tiny random deviations from perfect symmetry in bilateral structures, is mainly interpreted within the framework of developmental instability. This interpretation is mainly due to the fact, that higher fluctuating asymmetry is often found in association with various pathological conditions but also from increased stress during somatic development. Directional asymmetry, in contrast, describes a distinct pattern of bilateral variation in a group of individuals, characterized by the tendency to find the larger side mainly at the same side for all individuals. This kind of asymmetry is mostly caused by behavioral lateralization. Somatic stress during development affect not only asymmetry patterns, it is has also an adverse effect on somatic growth. Therefore, the present study tested the hypothesis, that increased asymmetry is associated with decreased body height as well as postcranial length and robustness dimensions. The association patterns between fluctuating as well as directional asymmetry and parameters of somatic growth and robustness are analyzed among 236 !Kung San and 248 Kavango people of Namibia between the ages of 18 and 65 years. Fluctuating asymmetry was determined by ear length and ear breadth. Directional asymmetry was determined by hand length and hand breadth dimensions. Fluctuating as well as directional asymmetry correlated significantly negatively with body height and length dimensions, the correlations however, were weak. The results are interpreted as a corroboration of the theory that developmental stress may increase fluctuating asymmetry but on the other hand may decrease body size.

Differences in body positional bilateral symmetry between stance and supine positions, and the impact of attention and awareness on postural symmetry

BACKGROUND AND PURPOSE

Postural asymmetries may cause structural pathological conditions and impaired movement pattern. The influence of body position and awareness towards symmetry has not yet been elucidated. The aim of this study was twofold: First, to compare the body positional bilateral symmetry between standing and supine positions, and second, to examine whether the awareness to symmetry can modify posture perception and body positional bilateral symmetry.

METHODS

We analyzed the degree of anterior postural alignment symmetry of 34 healthy subjects by photogrammetric method (three photographs in a standing position and three in a supine position). Each photo captured different state of awareness: Subjective Comfortable Posture (SCP), Subjective Perceived Symmetrical Posture (SPSP), and Guided Posture Protocol (GPP).

RESULTS

The standing position increased the symmetrical alignment of the neck (p < 0.013) and the upper limbs (p < 0.011). However, the supine position demonstrated increased symmetrical alignment of the upper trunk (p < 0.019) and the feet (p < 0.002). In the standing position, GPP showed greater symmetry of the neck (p < 0.022), the shoulders (p < 0.014), the thorax midline (p < 0.009), the upper trunk (p < 0.000) and the upper limbs (p < 0.029). No significant changes were observed in the supine position between the three states of awareness.

CONCLUSIONS

Study results indicate that the supine position shows greater degree of upper trunk's symmetrical alignment than the standing position. It also indicates that while standing, focusing attention into symmetry improves body positional bilateral symmetry. These results might have clinical implications when working with patients who suffer from asymmetric posture.

REAC neuromodulation treatments in subjects with severe socioeconomic and cultural hardship in the Brazilian state of Pará: a family observational pilot study

PURPOSE

The purpose of this preliminary observational study was to evaluate the usefulness of a humanitarian initiative, aimed at improving the neuropsychological and behavioral attitude of children with severe socioeconomic and cultural hardship, in the Brazilian state of Pará. This humanitarian initiative was realized through the administration of two neuromodulation protocols, with radioelectric asymmetric conveyor (REAC) technology. During several years of clinical use, the REAC neuromodulation protocols have already proved to be effective in countering the effects of environmental stress on neuropsycho-physical functions.

PATIENTS AND METHODS

After the preliminary medical examination, all subjects were investigated with the Strengths and Difficulties Questionnaire (SDQ), including the impact supplement with teacher's report. After the SDQ, they received the neuromodulation treatment with REAC technology named neuro postural optimization (NPO), to evaluate their responsiveness. Subsequently, every 3 months all subjects underwent a treatment cycle of neuropsycho-physical optimization (NPPO) with REAC technology, for a total of three cycles. At the end of the last REAC-NPPO treatment cycle, all subjects were investigated once again with the SDQ. For the adequacy of the data, the Wilcoxon and the Signs tests were used. For the subdivision into clusters, the Kruskal-Wallis test was applied for the adequacy of the procedure. For all the applied tests, a statistical significance of p<0.5 was found.

RESULTS

The results showed that the REAC-NPO and REAC-NPPO neuromodulation protocols are able to improve the quality of life, the scholastic and socialization skills, and the overall state of physical and mental health in children of a family with severe socioeconomic and cultural hardship.

CONCLUSION

The REAC-NPO and REAC-NPPO neuromodulation protocols, due to their non-invasive characteristics, painlessness, and speed of administration, can be hypothesized as a treatment to improve the overall state of physical and mental health in a large number of people with socioeconomic and cultural discomfort.

Handgrip Strength as a Darwinian Fitness Indicator in Men

Handgrip strength (HGS) is a robust measure of overall muscular strength and function, and has long been predictive of a multitude of health factors and physical outcomes for both men and women. The fact that HGS represents such a ubiquitous measure of health and vitality may reflect the significance of this trait during human evolution. This trait is also highly sexually dimorphic due to influences of androgenic hormones and fat-free body mass, suggesting that it has been further elaborated through sexual selection. Consistent with this view, research within evolutionary psychology and related fields has documented distinct relationships between HGS and measures of social and sexual behavior, especially in men. Here, we review studies across different societies and cultural contexts showing that male HGS predicts measures of aggression and social dominance, perceived formidability, male-typical body morphology and movement, courtship display, physical attractiveness, and sexual behavior and reproductive fitness. These findings underscore the value of including HGS as an independent measure within studies examining human sexual selection, and corroborate existing research suggesting that specific features of physical strength have and continue to be under positive directional selection in men.

Testosterone level changes after perceiving the body odour of a possible rival in human males: the role of facial symmetry

An individual’s body odour is a characteristic that is used to obtain information about conspecifics. However, to our knowledge the role of body odour and the degree of facial symmetry on testosterone changes among men as indicators of possible rivals has not been investigated yet. A group of 113 men were photographed to obtain their degree of facial symmetry, i.e., the small random deviations in facial bilateral traits. They smelled and assessed the odour of men with different grades of facial symmetry, and donated two saliva samples (pre- and post-stimulus sample) to measure the change in their testosterone levels. We found that testosterone levels decreased in symmetrical men who perceived the odour of asymmetrical men. Our results suggest that men could perceive characteristics in other men that are highly valued by women through odour to identify possible rivals, and that the observed decrease in testosterone levels could be related to an inhibition of competitive behaviours.