A comparison of the mechanical properties of the first dorsal interosseous in the dominant and non-dominant hand

The electrically evoked and voluntary contractile properties of the first dorsal interosseous muscle were measured on both hands in 10 healthy adults. The force of abduction of the index finger interosseous muscle was measured using a transducer resting against the lateral side of the proximal interphalangeal joint. The mean values of time to peak tension measured on the dominant hands were significantly slower than the values on the non-dominant hands (P less than 0.01) in a paired t-test. Maximal tetanic tension, maximal voluntary contraction strength, and maximal twitch tension are not significantly different. Fatigue indices on the dominant hands in each subject were higher than those on the non-dominant hands. The correlation coefficient between fatigue indices on the dominant and the non-dominant hand was 0.92 (P less than 0.01).     

Muscle activation characteristics associated with differences in physiological tremor amplitude between the dominant and non-dominant hand

The aim of this study was to assess differences in physiological tremor amplitude of the hand between the dominant and non-dominant side of right-handed individuals. Mechanical loading of the hand and frequency analysis were used in an attempt to identify the physiological mechanisms involved in observed differences. Seventeen healthy right-handed adults participated in a single session where physiological tremor of the outstretched left and right hands was recorded under different loading conditions (0 g up to 5614 g). Physiological tremor amplitude was quantified through accelerometry and electromyographic (EMG) signals of wrist extensor and flexor muscles were also recorded. The main findings were: ～30% greater amplitude of fluctuations in acceleration for the non-dominant compared with the dominant hand, no difference in the frequency content of acceleration or demodulated EMG signals between dominant and non-dominant sides across all loads, and condition-dependent associations between the amplitude of fluctuations in acceleration and EMG amplitude and frequency content. These associations suggest a potential role of central modulation of neural activity to explain dominance-related differences in physiological tremor amplitude of the hand.     

Radiographic Structural Damage Is Worse in the Dominant than the Non-Dominant Hand in Individuals with Early Rheumatoid Arthritis

Objective

The relationship between mechanical stress and radiographic progression in rheumatoid arthritis (RA) is unclear. The assumption is that mechanical stress is greater in the dominant hand. Therefore, the aim of the present study was to compare the presence and progression of erosions and joint space narrowing (JSN) in the dominant and non-dominant hand.

Methods

Data from 194 patients recently diagnosed with seropositive RA, and with hand radiographs taken at the time of diagnosis and at 2-year follow-up, were analyzed retrospectively. Radiographs were scored using the van der Heijde-modified Sharp Score (HSS) method. Each joint group within each hand was rated separately by two independent examiners in a double-blinded manner.

Results

One hundred and ninety-four patients were enrolled (80% female, 88% positive rheumatoid factor, 92% positive anti-citrullinated protein antibody, and 95.4% right-handed). The baseline, follow-up erosion and JSN HSS were significantly higher in the dominant hand than in the non-dominant hand. The annual rate of radiographic progression was also higher in the dominant hand. The erosive progression in the wrist joints varied significantly according to handedness, but the erosion in the proximal interphalangeal joints and metacarpophalangeal joints was similar in both hands. The radiographic progression was associated with the dominant hand, an abnormal baseline C-reactive protein level, and joint damage at baseline. There was no significant difference in bone mineral density between the right and left hands.

Conclusion

Radiological damage was worse and progressed faster in the dominant hand, suggesting that mechanical stress is associated with radiographic joint damage in early and active RA.     

The practice effect and its difference of the pursuit rotor test with the dominant and non-dominant hands

The purpose of this study was to examine the practice effect and what difference it makes in the pursuit rotor test for the dominant and non-dominant hands in 30 right-handed Japanese male adults aged 18 to 23 years (Age 20.8+/-1.4 yrs). The subjects performed the pursuit rotor test for 1 min in 20 trials with a 1-min interval alternately using the dominant and non-dominant hands. After continuing for 10 trials, a 5-min rest was taken. The measurement order was randomly assigned. Contact time of a steel pen and a target was measured in units of 1/10 sec. The measurements showed a constant increasing tendency at every trial until the 6th trial in both hands. Significant linear regressions were identified, but the increase-rate of the dominant hand was significantly larger. Individual differences showed a decreasing tendency at every trial in the dominant hand, but in the non-dominant hand it increased until the 4th trial then decreased. The relationships between measurements of the 1st and 10th trials in both hands and both hands in the 1st or 10th trial were not high. The performance of the pursuit rotor test improves at every trial in both hands, but the improvement rate decreases after the 7th trial. The improvement rate of the dominant hand is high. The change in individual differences differs in both hands and the relationship between the measurements is not high. It can be judged that the practice effect of the pursuit rotor test differs in the dominant and non-dominant hands.     

Patterns of lateralized hand use in an arboreal primate, Simias concolor

Studies of hand use in nonhuman primates suggest that several species exhibit hand preferences for a variety of tasks. The majority of studies, however, focus on the lateralized hand use of captive nonhuman primate populations. Although captive settings offer a more controlled environment for assessing hand preferences, studies of wild populations provide important insights into how handedness is affected by natural environmental conditions and thus potential insights into the evolution of handedness. To investigate handedness in a population of wild nonhuman primates, we studied patterns of lateralized hand use during feeding in four simakobu monkeys (Simias concolor), an arboreal species inhabiting the Mentawai Islands, Indonesia. Our data show that individual variation in hand preferences for feeding existed among our study animals. In addition, each simakobu expressed a significant hand preference for supporting itself on a branch during feeding, an uncoordinated bimanual task. This bias was most prevalent when the branch used for support was a main branch rather than a terminal branch. When both hands were employed in a coordinated bimanual feeding activity (bimanual manipulation), only two subjects showed a significant bias for feeding. Our data suggest that these individuals are more likely to express significant hand preferences when feeding from stable, rather than precarious, positions within the canopy.     

Study on pottical type, palmar and plantar digital formulae, hand clasping, arm folding, handedness, leg folding and stride type in the Daur population, China

The pottical type, palmar and plantar digital formulae, hand clasping, arm folding, handedness, leg folding and stride type have been investigated on a sample of 143 male and 160 female students of the Daur population of Molidawa Banner, Inner Mongolia. The results of this study are the following: 1. the frequency of the hyperextensive pottical type is 49.17%, the relative length of index over annularis 12.21%, right hand clasping 45.87%, right arm folding 49.50%, right handedness 94.39%, right leg folding 72.28% and right stride type 44.88%, 2. pottical type, hand clasping, handedness, leg folding and stride type do not show significant sex differences, 3. there are some relations between hand clasping and arm folding as well as between arm folding and stride type, 4. compared with other population groups, the Daur population shows a low frequency of right hand clasping, a moderate frequency of right arm folding and a low frequency of left handedness.     

Laterality in hand use across four tool-use behaviors among the wild chimpanzees of Bossou, Guinea, West Africa

Population-level right handedness is a human universal, whose evolutionary origins are the source of considerable empirical and theoretical debate. Although our closest neighbor, the chimpanzee, shows some evidence for population-level handedness in captivity, there is little evidence from the wild. Tool-use measures of hand use in chimpanzees have yielded a great deal of variation in directionality and strength in hand preference, which still remains largely unexplored and unexplained. Data on five measures of hand use across four tool-use skills--ant-dipping, algae-scooping, pestle-pounding and nut-cracking--among the wild chimpanzees of Bossou, Guinea, West Africa, are presented here. This study aims to explore age- and sex-class effects, as well as the influence of task motor, cognitive and haptic demands, on the strength and directionality of hand preference within and across all five measures of hand use. Although there was no age- or sex-class effect on the directionality of hand preference, immature 相似文献   

A device for assessment of hand and wrist coronal plane strength

Diagnostic and rehabilitative assessments of hand function commonly omit measurement of twisting strength even though many activities of daily living require turning handles, lids, and objects of many sizes. A simple device to quantify twisting strength was designed and constructed to establish normative data and test hypotheses about hand function. The instrument is easy to use and includes an electronic torsional load cell and disks of several sizes. Tests were conducted on the dominant and nondominant hands of 64 normal subjects and 13 arthritic patients with arthritis of the thumb carpometacarpal joint. Hands were tested with disks ranging in diameter from 2.5 to 12.5 cm. A three-way repeated measures analysis showed that gender (p < 0.001), handedness (p < 0.001), and disk size (p < 0.001) had significant effects. There was no difference between radial and ulnar deviation strengths (p = 0.365). The arthritic group had significantly reduced strength (p < 0.02). Nine subjects were tested twice, with 1 day between tests: no differences occurred between the first and second testing (p = 0.930). The ability to distinguish the test groups with reproducible results proves that the device fulfills all basic requirements; continued testing and development are warranted.     

Gender differences in the echocardiographic characteristics of the athletic heart

Differences between males and females in the effects of regular physical training on the heart were investigated by echocardiography in 579 male (nonathletes: 122, athletes: 457) and in 336 (nonathletes: 84, athletes: 252) female subjects of variable age. The age groups were: children (<15 yr.), adolescent-young (15-18 yr.), young adult (19-30 yr.), adult (31-45 yr.) and people elder than 45 yr older (45<). Hypertrophy characterised by relative left ventricular muscle mass (rel.LVMM) of the athletic heart was manifest also in the females, but in comparison with the males female values were much lower both in the unconditioned and in the conditioned groups. In people belonging to the oldest groups no differences were seen either between the males and females or between athletes and nonathletes. In comparing nonathletic subjects, females showed smaller left ventricular contractility as reflected by a higher LVET/QT ratio and an increased ability of diastolic relaxation as indicated by a higher E/A ratio. Physical training induced a more marked development when the initial level was lower, namely, in the contractility of the females, and in the compliance of the males. No intersex difference was seen in the modified regulation of the athletic heart, characterised by a lower resting heart rate and slower circumferential shortening velocity (VCF).     

Characteristics and lateral dominance of hand grip and elbow flexion powers in young male adults

This study aimed to clarify the characteristics and the lateral dominance of hand grip power and elbow flexion power. The subjects were 15 healthy young males (mean age 22.1+/-0.7 yr, mean height 171.3+/-3.4 cm, mean mass 64.5+/-4.1 kg). All subjects were right-handed. Peak power was measured by both hands with 6 different loads of 20%-70% of maximum voluntary contraction. The maximum voluntary contraction of hand grip movement and elbow flexion movement was significantly larger in the dominant hand. Peak power of the dominant hand was larger in all loads in hand grip movement and in loads of 20% and 30% of maximum voluntary contraction in elbow flexion movement. In short, lateral dominance was confirmed. Peak power was significantly larger in hand grip movement than in elbow flexion movement in both hands. Peak velocity decreased with increasing loads in both movements, but peak power increased until about 50% of maximum voluntary contraction and then decreased. The peak power ratio of the dominant hand to the nondominant hand was significantly larger in hand grip movement than in elbow flexion movement in all loads and the peak power ratio in elbow flexion movement was more marked in light loads. In conclusion, both powers showed lateral dominance. Lateral dominance is more marked in hand grip power.     

Effects of handedness on visual sensitivity in perihand space

Recent studies have shown that changes in visual processing in perihand space are limited to the area around the right hand, at least in right-handers. One explanation for these findings is that perception is altered at locations where action is more likely to occur. To test this notion, we asked both right- and left-handers to perform an unspeeded visual discrimination task under four hand-position configurations: Left hand, right hand, both hands, or no hands near the display. Compared to the no-hands (control) condition, visual sensitivity (d') was higher in the dominant-hand condition for right-handers and higher in the dominant- as well as the non-dominant hand condition for left-handers. When both hands were near the display, sensitivity was similar to that in the dominant-hand condition for right-handers and to that in the non-dominant hand condition for left-handers. This shows that performance differed between the two handedness groups when their non-dominant hand was near the display (both alone and accompanied by their dominant hand). Thus, the pattern for left-handers did not correspond to a mirror image of the pattern for right-handers. In line with studies on bimanual action control, visual processing in perihand space seems to be determined by the different ways in which left- and right-handers use their hands.     

Hand clasping--an overview]

The literature concerning the asymmetry clasping hands is reviewed based on 192 studies. This paper describes the incidence, sex differences, age differences and genetical problems including twinning. The incidence of left hand clasping ranges from 30% to 75% (mean 43%). The review confirms the so-called east-west-gradient and there is a predominance of the left type in Europe. Age and sex differences are only small. There is only a small relationship between hand clasping and handedness. 18 authors examined hand clasping in families and 4 in twins. The family data suggest that hand clasping may be under genetic control, yet it is clear that no simple genetic model for the inheritance can be applied. Both monozygotic and dizygotic twins show a low concordance and the R-R, R-L and L-L pairs in monozygotic and dizygotic twins are in binomial distribution.     

Bilateral asymmetry in bone measurements of the hand and lateral hand dominance

Two hundred thirty–five (235) normal male participants of the Baltimore Longitudinal Study were classified as right handed, left handed, and ambidextrous on the basis of their grip–strength performance. Their left and right hands were also radiographed and the measurements of the second metacarpal bones were evaluated on the basis of hand dominance. The results indicated that, as a rule, the right hand measurements are higher than those of the left hand, regardless of hand dominance. The bilateral differences in total width, length, total area and cortical area are significant among the right hand dominant and nonsignificant among the left hand dominant. Regardless off hand dominance the bilateral differences in medullary width are nonsignificant. These results suggest an inherent tendency of the right second metacarpal to have more bone than the left regardless of hand dominance. Differential stress due to hand dominance will increase the bilateral difference in the right handed and reduce it in the left handed.     

The "beggar's" hand and the "unshakable" hand in children with total obstetric brachial plexus palsy

A total 12 consecutive children with secondary deformities following total obstetric brachial plexus palsy were included in this retrospective study. In all patients, the main complaints were two socially disabling hand postures: the "beggar's" hand and/or the "unshakable" hand. All children had a supinated forearm with no active pronation and were teased by their friends, who called them "beggars." When the impairment was severe and involved the right hand and wrist, children also complained that they were not able to shake hands. The management approach to these children was described, with the main aim of surgery being the correction of the abnormal posture. Other simultaneous tendon transfers were also performed to improve hand function if there were suitable musculotendinous units. Successful reconstruction was accomplished in all patients. Preoperatively, some children refused to go to school because of teasing, and most did not want to interact socially. After surgery, all children attended school regularly, and parents reported much better social interaction. However, the functional gain was never enough to dramatically improve the daily use of the limb. The contralateral normal limb remained the dominant one for all daily activities, including writing and eating.     

Assessment of gender-specific preventive cardiovascular knowledge among house staff: Potential impact on cardiovascular management

Background: Gender differences in cardiovascular prevention and treatment may be related to physicians' level of postgraduate training and gender.Objectives: This study was designed to assess resident physician knowledge concerning general and gender-specific preventive cardiology topics and to determine whether there were differences in that knowledge based on the physicians' level of postgraduate training or gender.Methods: A 29-item true/false questionnaire was administered to residents in a large, university-based internal medicine residency program. All questions were drawn from evidence-based practice guidelines, and a subset of questions pertained to gender-specific issues in cardiovascular disease prevention. Scores on the overall test and gender-specific subset were computed as a percentage of correct answers. Differences were compared by postgraduate year (PGY) of training and physician gender.Results: Of the 190 eligible residents, 159 (88 men, 67 women, 4 not specified) completed the questionnaire. Overall test scores differed significantly by PGY (PGY-1, 83.4% correct answers; PGY-2, 52.9%; PGY-3, 65.3%; P < 0.001 for each paired comparison), but did not differ significantly by physician gender (males, 73.5%; females, 70.0%). Performance on gender-specific items also differed by PGY (PGY-1, 72.2% vs PGY-2, 20.0%; P < 0.001; and PGY-1, 72.2% vs PGY-3, 45.1%; P < 0.001). Knowledge of gender-specific preventive cardiology did not differ significantly by physician gender (males, 56.4%; females, 49.0%).Conclusions: Residents in PGY-1 had better knowledge of preventive cardiology as assessed using this questionnaire than did residents in PGY-2 or PGY-3. Knowledge of general and gender-specific cardiology topics was not related to physician gender.     

Circadian rhythms and their association with body temperature and time awake when performing a simple task with the dominant and non-dominant hand

The two main aims of the study were to compare the dominant and non-dominant hand with regard to circadian rhythms of accuracy of performance at a task that required eye-hand coordination and sub-maximum muscle contraction, as well as to investigate if there were differences between the dominant and non-dominant hands in the associations between circadian rhythms of performance and core temperature and time awake. The task consisted of using a larger counter to flick a set of 20 smaller counters to land as near as possible to the center of a target. The nearer to the center of the target a counter landed, the higher the score awarded. Three measures of accuracy were calculated: the total score, the number of times the counter missed the target altogether, and the mean score for those counters that hit the target. Seventy-eight healthy participants performed the task at each of six test sessions distributed every 4 h throughout the day (at 08:00, 12:00... . 04:00 h), the participants then having been awake for about 1, 4... . 20 h, respectively. Before each test session, sub-lingual temperature (an estimate of core temperature) was measured, and estimates of the individual's alertness and fatigue were obtained. Temperature, alertness, and fatigue all showed circadian rhythms that were phased conventionally. Measures of accuracy of performance also showed significant circadian rhythms that were phased closer to the rhythms of alertness and fatigue than to that of oral temperature. In addition, and in support of our previous work, there were significant associations between performance and temperature (positive) and time awake (negative) for most measures of accuracy. Even though circadian rhythms of performance accuracy and effects of oral temperature and time awake were generally very similar between the dominant and non-dominant hand, there was a suggestion that time awake affected some aspects of performance of the non-dominant hand to a greater extent. There was little evidence to support the view that the 24-h rhythmicity was less marked in the non-dominant hand, which argues against internal desynchronization, at least for the task used in this study.     

Cortical activations in humans grasp-related areas depend on hand used and handedness

Background

In non-human primates grasp-related sensorimotor transformations are accomplished in a circuit involving the anterior intraparietal sulcus (area AIP) and both the ventral and the dorsal sectors of the premotor cortex (vPMC and dPMC, respectively). Although a human homologue of such a circuit has been identified whether activity within this circuit varies depending on handedness has yet to be investigated.

Methodology/Principal Findings

We used functional magnetic resonance imaging (fMRI) to explicitly test how handedness modulates activity within human grasping-related brain areas. Right- and left-handers subjects were requested to reach towards and grasp an object with either the right or the left hand using a precision grip while scanned. A kinematic study was conducted with similar procedures as a behavioral counterpart for the fMRI experiment. Results from a factorial design revealed significant activity within the right dPMC, the right cerebellum and AIP bilaterally. The pattern of activity within these areas mirrored the results found for the behavioral study.

Conclusion/Significance

Data are discussed in terms of an handedness-independent role for the right dPMC in monitoring hand shaping, the need for bilateral AIP activity for the performance of precision grip movements which varies depending on handedness and the involvement of the cerebellum in terms of its connections with AIP. These results provide the first compelling evidence of specific grasping related neural activity depending on handedness.     

Competitiveness,gender and handedness

We conduct an intercultural experiment in three locations on three different continents to elicit competitiveness and study whether individual differences in competitiveness are related to handedness. Being a “lefty” (i.e., having either a dominant left hand or a dominant left foot) is associated with neurological differences which are determined prenatally, and can therefore be seen as a proxy for innate differences. In large-scale data with incentivized choices from 3664 participants from India, Norway and Tanzania, we find a significant gender gap in competitiveness in all cultures. However, we find inconsistent results when comparing the competitiveness of lefties and righties. In north-east India we find that lefties of both genders are significantly more competitive than righties. In Norway we find that lefty men are more competitive than any other group, but women’s competitiveness is not related to handedness. In Tanzania, we find no relationship between handedness and the competitiveness of either gender. The merged data show weak evidence of a positive correlation between being a lefty and competitiveness for men, but no such evidence for women. Thus, our data provide suggestive but not robust evidence that individual and gender differences in competitiveness are partially determined by innate factors, where innate factors are proxied by the complex, prenatally shaped trait of handedness.     

On the handedness of Japanese monkeys

Forty-one monkeys living on the Koshima Island were tested for handedness by throwing a peanut 10 or 20 times toward each subject and recording which hand was used to pick it up. Handedness was judged at the 5% level of confidence. Animals showing no preference for the left or right hand after 20 trials were considered to be ambidextrous. The following distribution of handedness was found: left-handed, 17 (41%); right-handed, 8 (20%); ambidextrous, 16 (39%). These findings were compared with other studies on the handedness of Japanese monkeys. Handed monkeys outnumber the ambidextrous ones and the left-handed monkeys outnumber the right-handed ones. The characteristic distribution of handedness was shown to be irrespective of troop. By looking over the data from these different sources, the proportions of the left-handed, the ambidextrous, and the right-handed in Japanese monkeys were estimated at 39%, 33%, and 28% respectively. The method used in this study was compared withKawai's catching behavior and reasons for disagreement between judgments of handedness were discussed.     

Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers

Aims: To compare an ultra‐rapid hand dryer against warm air dryers, with regard to: (A) bacterial transfer after drying and (B) the impact on bacterial numbers of rubbing hands during dryer use. Methods and Results: The Airblade? dryer (Dyson Ltd) uses two air ‘knives’ to strip water from still hands, whereas conventional dryers use warm air to evaporate moisture whilst hands are rubbed together. These approaches were compared using 14 volunteers; the Airblade? and two types of warm air dryer. In study (A), hands were contaminated by handling meat and then washed in a standardized manner. After dryer use, fingers were pressed onto foil and transfer of residual bacteria enumerated. Transfers of 0–10⁷ CFU per five fingers were observed. For a drying time of 10 s, the Airblade? led to significantly less bacterial transfer than the other dryers (P < 0·05; range 0·0003–0·0015). When the latter were used for 30–35 s, the trend was for the Airblade to still perform better, but differences were not significant (P > 0·05, range 0·1317–0·4099). In study (B), drying was performed ± hand rubbing. Contact plates enumerated bacteria transferred from palms, fingers and fingertips before and after drying. When keeping hands still, there was no statistical difference between dryers, and reduction in the numbers released was almost as high as with paper towels. Rubbing when using the warm air dryers inhibited an overall reduction in bacterial numbers on the skin (P < 0·05). Conclusions: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing. Significance and Impact of the Study: The Airblade? was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands.