Sex differences in laterality of motor unit firing behavior of the first dorsal interosseous muscle in strength-matched healthy young males and females

PURPOSE

The purpose of this study was to compare laterality in motor unit firing behavior between females and males.

METHODS

Twenty-seven subjects (14 females) were recruited for this study. The participants performed ramp up and hold isometric index finger abduction at 10, 30, and 60% of their maximum voluntary contraction (MVC). High-density surface electromyography (HD-sEMG) signals were recorded in the first dorsal interosseous (FDI) muscle and decomposed into individual motor unit (MU) firing behavior using a convolution blind source separation method.

RESULTS

In total, 769 MUs were detected (females, n = 318 and males, n = 451). Females had a significantly higher discharge rate than males at each relative torque level (10%: male dominant hand, 13.4 ± 2.7 pps vs. female dominant hand, 16.3 ± 3.4 pps; 30%: male dominant hand, 16.1 ± 3.9 pps vs. female dominant hand, 20.0 ± 5.0 pps; and 60%: male dominant hand, 19.3 ± 3.8 vs. female dominant hand, 25.3 ± 4.8 pps; p < 0.0001). The recruitment threshold was also significantly higher in females than in males at 30 and 60% MVC. Furthermore, males exhibited asymmetrical discharge rates at 30 and 60% MVC and recruitment thresholds at 30 and 60% MVC, whereas no asymmetry was observed in females.

CONCLUSION

In the FDI muscle, compared to males, females exhibited different neuromuscular strategies with higher discharge rates and recruitment thresholds and no asymmetrical MU firing behavior. Notably, the findings that sex differences in neuromuscular activity also occur in healthy individuals provide important information for understanding the pathogenesis of various diseases.

Whole-hand and regional bone mineral density involvement in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by symmetric polyarthritis that can lead to joint deformity, disability, and osteoporosis. We aimed to evaluate whole hand and regional BMD in RA patients compared to controls. In addition, we evaluated the BMD of dominant versus non-dominant hands in healthy subjects. We included adult female and male RA patients and control subjects matched by age, sex, and BMI. BMD (g/cm2) was measured by DXA in lumbar spine (LS), whole hand, and three regions of interest: carpus, metacarpal bones, and phalanges. Results: 44 control subjects (49.5±11.8 y) and 60 with RA (52.7±12.7 y) were included. Significant lower BMD in RA patients was found in LS (-8.7%), dominant whole hand (-9.5%), carpus, metacarpal bones, and phalanges, and non-dominant whole hand (-8.7%), metacarpal bones, and phalanges compared to controls. A significant positive correlation was found between LS and whole-hand BMD (dominant r=.63, non-dominant r=.67). Finally, the whole hand, metacarpal bones, and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalangeal ROI. In conclusion, hand BMD was significantly lower in RA patients compared to control subjects and there was a significant correlation with LS BMD. We demonstrated that BMD measurements of the whole-hand, and different ROI (carpus, metacarpal bones, and phalanges) by DXA would be an easily reproducible technique to evaluate bone loss. In addition, the whole hand, metacarpal bones and carpus BMD measurements were significantly higher in the dominant hand compared to the non-dominant hand without differences in the phalanges.

Retrospective multicenter (TRON group) study of humeral shaft fragility fractures: Analysis of mortality rates and risk factors

AIMS

This study aimed to show the mortality rate following humeral shaft fragility fractures (HSFF) in the elderly. The secondary aim was to examine the predictors associated with mortality in elderly patients who have sustained HSFF.

METHODS

From 2011 to 2020, all elderly patients aged 65 years and older with HSFF managed at our nine hospitals were retrospectively identified from our TRON database. Patient demographics and surgical characteristics were extracted from medical records and radiographs, and multivariable Cox regression analysis was used to identify factors affecting mortality.

RESULTS

In total, 153 patients who sustained HSFF were included. The mortality rate for HSFF in the elderly was 15.7% at 1 year and 24.6% at 2 years. Multivariable Cox regression analysis showed significant differences in survival for the following variables: older age (p < 0.001), underweight (p = 0.022), severely ill (p = 0.025), mobility limited to indoors (p = 0.003), dominant-side injury (p = 0.027), and nonoperative treatment (p = 0.013).

CONCLUSION

The outcome following HSFF in the elderly population appears to be relatively grim. The prognosis of elderly patients with HSFF is closely related to their medical history. In the elderly patients with HSFF, operative treatment should be positively considered while taking into account their medical status.

A smart tablet application to quantitatively assess the dominant hand dexterity

BACKGROUND AND OBJECTIVE

The Nine-Hole Peg Test (NHPT) is the most used test to assess hand dexterity in clinical practice and is considered the gold standard but only evaluates the time needed to complete the task. The aim of this work is to describe a graphic test on a smart tablet to assess in a quantitative as well qualitative way the dominant hand dexterity and to validate it in a cohort of neurological subjects and healthy controls.

METHODS

The task consists in asking the subject to connect with a graphic line the start and the end point of a pre-defined path, with two different widths, in the most precise and fastest way possible. The path is constituted by a 'meander' and a 'spiral' part. The subjects perform the task on a smart tablet with a capacitive pen four times. The three parameters of interest considered at each trial are the execution time, length path, and number of interactions with the border. The app automatically computes these three parameters and stores the completed test files. The results of the digital graphic test are compared to the NHPT results. Healthy and pathological subjects are compared to each other, and performances obtained in different repetitions are compared to assess the learning effect in each population.

RESULTS

53 subjects with a definitive diagnosis of neurodegenerative/genetic neurological disorders (34 men, mean age 59.1 ± 16.1) and 78 healthy controls (33 men, mean age 42.5 ± 16.3) were recruited. Among the pathological subjects, 31 also performed the NHPT. The graphic test clearly distinguish between the two populations for all parameters of interest. Moreover, compared to the gold standard NHPT, time has a moderate positive correlation (r = 0.57, p ≤ 0.001), whereas interactions and length have a strong positive correlation (r = 0.81, p ≤ 0.001) and (r = 0.69, p ≤ 0.001), respectively.

CONCLUSIONS

The proposed digital test can measure in an accurate, quantitative and qualitative way dominant hand disability and can result more informative with respect to the gold standard NHPT. In homogeneous cohort of subjects (for example affected by multiple sclerosis or Parkinson disease), the digital test can be used as an outcome measure in clinical trials as well as a tool for monitoring disease progression at the dominant hand level.

Using immersive virtual reality to remotely examine performance differences between dominant and non-dominant hands

Circle drawing may be a useful task to study upper-limb function in patient populations. However, previous studies rely on expensive and bulky robotics to measure performance. For clinics or hospitals with limited budgets and space, this may be unfeasible. Virtual reality (VR) provides a portable and low-cost tool with integrated motion capture. It offers potentially a more feasible medium by which to assess upper-limb motor function. Prior to use with patient populations, it is important to validate and test the capabilities of VR with healthy users. This study examined whether a VR-based circle drawing task, completed remotely using participant's own devices, could capture differences between movement kinematics of the dominant and non-dominant hands in healthy individuals. Participants (n = 47) traced the outline of a circle presented on their VR head-mounted displays with each hand, while the positions of the hand-held controllers were continuously recorded. Although there were no differences observed in the size or roundness of circles drawn with each hand, consistent with prior literature our results did show that the circles drawn with the dominant hand were completed faster than those with the non-dominant hand. This provides preliminary evidence that a VR-based circle drawing task may be a feasible method for detecting subtle differences in function in clinical populations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10055-023-00794-z.

Dominant versus non-dominant hand during simulated infant CPR using the two-finger technique: a randomised study

Aims

The aim of this randomised study was to compare the two-finger technique (TFT) performance using dominant hand (DH) and non-dominant hand (NH) during simulated infant CPR (iCPR).

Methods

24 participants performed 3-min iCPR using TFT with DH or NH followed by 3-min iCPR with their other hand. Perceived fatigue was rated using visual analogue scale. Primary outcomes - (i) difference between DH and NH for compression depth (CCD), compression rate (CCR), residual leaning (RL) and duty cycle (DC); (ii) difference between first and last 30 s of iCPR performance with DH and NH. Secondary outcomes - (i) perception of fatigue between DH and NH; (ii) relationship between perception of fatigue and iCPR performance.

Results

No significant difference between DH and NH for any iCPR metric. CCR (DH: P = 0.02; NH: P = 0.004) and DC (DH: P = 0.04; NH: P < 0.001) were significantly different for the last 30 s for DH and NH. Perception of fatigue for NH (76.8 ± 13.4 mm) was significantly higher (t = -3.7, P < 0.001) compared to DH (62.8 ± 12.5 mm). No significant correlation between iCPR metrics and perception of fatigue for DH. However, a significant correlation was found for CCR (r = 0.43; P = 0.04) and RL (r = -0.48; P = 0.02) for NH.

Conclusion

No difference in performance of iCPR with DH versus NH was determined. However, perception of fatigue is higher in NH and was related to CCR and RL, with no effect on quality of performance. Based on our results, individuals performing iCPR can offer similar quality of infant chest compressions regardless of the hand used or the perception of fatigue, under the conditions explored in this study.

A cross-educational approach on skill-related movement technique performance: Central neuronal motor behaviour preceding the short badminton backhand serve

Training in a particular sport not only leads to a higher accuracy in movement, it also creates neuronal modulations in different areas of the brain. Electroencephalography (EEG) has been on the rise to detect these neuronal modulations to address applied research approaches in sports-specific setups with focus on movement-related cortical potentials (MRCP) especially the readiness potential (RP). While many studies considered the RP in laboratory settings using button pressing, there is little research on sport-specific movements performed in realistic setups. Therefore the aim of this study was to examine the short backhand serve of expert and novice badminton players. 16 healthy, right-handed men participated in this study, eight experts and eight novices. A surface EMG was recorded from limb muscles and simultaneous EEG was recorded. RP peak increased significantly (p < 0.05) in expert compared to novices when serving with the dominant hand. RP onsets revealed no significant changes (p = 0.70). In line with previous reports, this study pointed out that complex movements such as the short badminton backhand serve produces higher RP peaks when performed precisely, indicating for long lasting practice and level of experience.

Sensibility of the Hand in Children With Conservatively or Surgically Treated Upper Neonatal Brachial Plexus Lesion

BACKGROUND

The aim of this study was to assess the sensibility of the hand in children with a neonatal brachial plexus palsy (NBPP) involving the C5 and C6, and to correlate results with dexterity.

METHODS

Fifty children with NBPP (30 after nerve surgery, mean age 9.8 years) and 25 healthy controls (mean age 9.6 years) were investigated. Sensibility was assessed with two-point discrimination and Semmes-Weinstein monofilaments. Dexterity was evaluated with a single item from the Movement Assessment Battery for Children-2. We compared the affected side with the nondominant hand of the control group.

RESULTS

The sensibility in the first and second fingers was significantly diminished in the NBPP for both two-point discrimination (P = 0.005 and P = 0.014, respectively) and monofilament test (P < 0.001). Dexterity was significantly lower in the NBPP group than in control group, corrected for age (P = 0.023). There was a significant difference toward decreasing hand function with decreasing sensibility according to the Semmes-Weinstein test for the thumb (Jonckheere-Terpstra nonparametric trend test, P = 0.036).

CONCLUSIONS

The sensibility of the thumb and index finger in children with an upper plexus lesion (either surgically or conservatively treated) is diminished. The decreased sensibility has a negative impact on hand function. Appreciation of diminished hand function in patients with NBPP involving C5 and C6 is important to optimize treatment.

Effects of dominant and non-dominant passive arm manoeuvres on the neurovascular coupling response

PURPOSE

Models designed to study neurovascular coupling (NVC) describe a possible cerebral hemisphere dominance dependent on task completed and preference in handedness. We investigated whether passive arm manoeuvre performed with dominant (Dom-Arm) or non-dominant arm (ND-Arm) stimulated haemodynamic differences in either contralateral (Cont-H) or ipsilateral (Ipsil-H) cerebral hemisphere.

METHODS

Healthy individuals lying in supine position, had measurements of beat-to-beat blood pressure (BP, mmHg), electrocardiogram (HR, bpm), end-tidal CO₂ (etCO₂, mmHg), and bilateral insonation of the middle cerebral arteries (MCA, cm s^-1). Arm movement was performed for 60 s with passive flexion and extension of the elbow (1 Hz), before manoeuvre was repeated on other arm. Data were normalised and effect of treatment was analysed for differences between manoeuvres and within each time period.

RESULTS

Seventeen (eight males) healthy volunteers, aged 56 ± 7 years, were studied. Dom-Arm and ND-Arm manoeuvres stimulated a comparable temporal response in peripheral and cerebral haemodynamic parameters between Cont-H and Ipsil-H.

CONCLUSIONS

Both manoeuvres can be used to evoke similar bilateral MCA responses in assessing NVC. This finding should lead to more efficient protocols when using passive arm movement for NVC studies in healthy subjects.

Effects of two-handed task training on upper limb function of chronic hemiplegic patients after stroke

[Purpose] The purpose of this study was to determine whether two-handed task training is effective on motor learning of injured cerebral cortex activation and upper extremity function recovery after stroke. [Subjects and Methods] Two hemiplegic subjects participated in this study: one patient was affected on the dominant side of the body and the other was affected on the non-dominant side of the body, and both scored in the range of 58–66 in the Fugl-Meyer assessment. The excitability of the corticospinal tract and Manual Function Test were examined. [Results] The excitability of the corticospinal tract and the Manual Function Test showed significant differences in the activation of both sides of the cerebral cortex and in the variation in learning effect of upper extremity motor function recovery in patients with hemiplegic non-dominant hand (left). [Conclusion] The results suggested that two-handed task training had a different influence on dominant hand (right) and non-dominant hand (left) motor recovery.

Objects rapidly prime the motor system when located near the dominant hand

Objects are said to automatically "afford" various actions depending upon the motor repertoire of the actor. Such affordances play a part in how we prepare to handle or manipulate tools and other objects. Evidence obtained through fMRI, EEG and TMS has proven that this is the case but, as yet, the temporal evolution of affordances has not been fully investigated. The aim here was to further explore the timing of evoked motor activity using visual stimuli tailored to drive the motor system. Therefore, we presented three kinds of stimuli in stereoscopic depth; whole hand grasp objects which afforded a power-grip, pinch-grip objects which afforded a thumb and forefinger precision-grip and an empty desk, affording no action. In order to vary functional motor priming while keeping visual stimulation identical, participants adopted one of two postures, with either the dominant or non-dominant hand forward. EEG data from 29 neurologically healthy subjects were analysed for the N1 evoked potential, observed in visual discrimination tasks, and for the N2 ERP component, previously shown to correlate with affordances (Proverbio, Adorni, & D'Aniello, 2011). We observed a link between ERPs, previously considered to reflect motor priming, and the positioning of the dominant hand. A significant interaction was detected in the left-hemisphere N2 between the participants' posture and the object category they viewed. These results indicate strong affordance-related activity around 300ms after stimulus presentation, particularly when the dominant hand can easily reach an object.

Generalized joint hypermobility in healthy female koreans: prevalence and age-related differences

OBJECTIVE

Objective To evaluate the prevalence of generalized joint hypermobility (GJH) in healthy female Koreans and to determine whether the degree of GJH differs between children and adults.

METHODS

Two groups of females were enrolled, a group of girls from an elementary school (n=404) and women from a call center (n=266). GJH was diagnosed using the Beighton score, which is composed of an evaluation of bilateral knees, elbows, thumbs, and fifth fingers as well as thoracolumbar joint. The GJH and localized hypermobility of each joint was compared between the two groups, and the pattern of hypermobility according to age and dominant hand was investigated.

RESULTS

Total prevalence of GJH was 50.0% (335/750), and it was more frequently observed in the group of girls (58.9%, 238/404) than women (36.5%, 97/266). The degree of GJH expressed in terms of Beighton score was inversely correlated with age (p<0.05). Significant differences in localized hypermobility of the thumb and fifth finger were found between the two groups and were postulated as the cause for the decline in GJH with age. The pattern of decreased mobility proportional to aging differed between the two joints. Decreased mobility occurred equally on both sides of the thumb but was biased toward the fifth finger of the dominant side (mostly the right).

CONCLUSION

The female Koreans appeared to have a high prevalence of GJH. The incidence of GJH decreased as age increased as a result of decreased mobility of the fifth finger on the dominant side.