Handgrip Force Research Articles

Physical Activity in Long COVID: A Comparative Study of Exercise Rehabilitation Benefits in Patients with Long COVID, Coronary Artery Disease and Fibromyalgia.

Exercise in long COVID is poorly studied. Nevertheless, exerciserehabilitation could improve cardiorespiratory, muscular and autonomic functions. We aimed to investigate improvement in physical and autonomic performances of long COVID patients (n = 38) after a 4-week exercise rehabilitation program (3 sessions/week) compared to two control groups composed of coronary artery disease (n = 38) and fibromyalgia patients (n = 38), two populations for whom exercise benefits are well known. Efficacy of exercise training was assessed by a cardiopulmonary exercise test, a handgrip force test, and a supine heart rate variability recording at rest before and after the rehabilitation program. Cardiorespiratory and muscular parameters were enhanced after exercise rehabilitation in the three groups (p < 0.001). No significant difference was observed for the autonomic variables. Through this comparative study with control groups, we confirm and reinforce the interest of caring for long COVID patients without post-exertional symptom exacerbation by exercise rehabilitation of both strength and endurance training, by personalizing the program to the patient and symptoms.

A Smart Iot-Based Prototype System For Rehabilitation Monitoring

Smart healthcare is growing significantly in the healthcare sector due to the Internet of Things. A remote monitoring system is one of the smart healthcare implementations for rehabilitating stroke patients. Nowadays, as the COVID-19 pandemic continues tospread, patients undergoing home rehabilitation have difficulty meeting with their physicians due to movement constraints. In addition, the healthcare facilities are devoted to treating patients with COVID-19. As a result, physicians and patients could not frequently meet to gather their rehabilitation progress. This study involves developing a prototype to monitor a post-stroke patient's rehabilitation process using the Arduino Nano 33 Bluetooth Low Energy (BLE) and force-sensing resistor (FSR). The prototype analyzes critical aspects of the rehabilitation process based on handgrip, heart rate, sleep, and step tracking measurements. The results of the handgrip, heart rate, sleep, and step tracking measurements are evaluated for various types of subjects and six testing approaches showed an accurate and consistent results. However, experiments partially success with a small error is detected while tracking the steps of each subject. Several recommendations are highlighted to improve the prototype using othersensors such as force sensing resistor and flex sensor for handgrip force transducer, electromyogram (EMG) sensor for stroke-patients rehabilitation, and others.

Fibromyalgia: one year in review 2023.

Fibromyalgia (FM) is a chronic syndrome characterised by widespread pain that affects millions of people worldwide. This article discusses various aspects of FM described in scientific papers published in 2022 and indexed in the PubMed database, including the most recent diagnostic acquisitions (especially in relation to the juvenile form of FM), risk factors, co-morbidities and objective measures. Emphasis is placed on the importance of identifying FM early and improving diagnostic methods (e.g. physical measurements, including walking test performance, hand grip force, and autonomic tests). The article also considers hypotheses concerning the pathophysiology of FM, including the role of inflammation, gut dysbiosis, and neuroinflammation, and possible treatment options, including medications such as antioxidants and kinin antagonists, neurostimulation, and mind-body interventions. Although ketamine, vitamin D, and hormone therapy have shown promise in reducing FM symptoms, further research is needed to optimise their use. Neurostimulation techniques, such as transcutaneous electrical nerve stimulation, transcranial direct-current stimulation and transcranial magnetic stimulation, have been investigated in terms of their efficacy in reducing pain and improving the quality of life. Finally, the role of nutrition is discussed as study findings suggest that weight control, modified high-antioxidant diets, and nutritional supplementation can help to alleviate the symptoms of FM.

Effect of teeth clenching on handgrip force in adult men: role of periodontal mechanoreceptors.

Voluntary teeth clenching is shown to increase the strength of muscle reflexes contributing to the improvement of postural stability. However, the interaction between the handgrip strength and teeth clenching is not yet understood. In this study, we aimed to evaluate the change in handgrip force in response to voluntary teeth clenching, and its relation to the peripheral receptors that play a central role in the control of mastication. Thirty-six healthy men were divided into two groups: aged 50-59years, no dental prosthesis, and 53-62years with total dental prosthesis. Each individual was given handgrip and teeth clenching instructions for five experiments: only handgrip, teeth clenching followed by handgrip without teeth clenching, teeth clenching followed by handgrip with teeth clenching, and the repetition of the last two instructions while wearing mouth guards. Our findings showed that maximum handgrip force decreased and the resistance to fatigue increased in complete edentulous individuals using appropriate prostheses. Also, the significantly lower maximum handgrip force and higher resistance to fatigue values of the participants with dental prosthesis using a mouth guard while teeth clenching, revealed the central roles of periodontal mechanoreceptors. Decreases in masticatory sensory information processes influence handgrip force values which is the most important indicator of motor function. The lack of periodontal mechanoreceptors associated with dental prosthesis usage may lead to a loss in muscle strength.

Factors associated with quality of life in patients receiving lung transplantation: a cross-sectional study

BackgroundWith improved prognosis after lung transplantation (LTx), improving health-related quality of life (HRQL) in patients who have undergone LTx is a key goal. Although HRQL is improved significantly after transplantation, it is poorer than that in ordinary healthy people. However, the factors associated with poor HRQL remain unclear. This cross-sectional study aimed to identify the factors associated with poor HRQL in patients who have undergone LTx.MethodsBetween December 2018 and May 2022, 80 patients who had undergone LTx completed St. George’s Respiratory Questionnaire (SGRQ) as a disease-specific quality of life measure, the Short Form-12 (SF-12) as a generic quality of life measure, and modified Medical Research Council (mMRC) scale of dyspnea. The groups were assigned according to the median SGRQ-total score and the Japanese population standard for SF-12, and those with good HRQL were compared with those with poor HRQL. Independent factors were evaluated using multivariate analysis.ResultsWith regard to the SGRQ, there were significant differences in the forced expiratory volume in 1 s (FEV1) (P = 0.041), use of bronchodilators (P = 0.026), 6-min walk distance (6MWD) (P < 0.001), and Mmrc (P < 0.001) between better and poorer HRQL. For the SF-12 physical component summary score (PCS), age (P = 0.017), sex (P = 0.011), FEV1 (P < 0.001), forced vital capacity (FVC) (P < 0.001), diagnosis (P = 0.011), handgrip force (P = 0.003), 6MWD (P < 0.001), and Mmrc (P < 0.001) varied. Multivariate analyses revealed that Mmrc was the only independent factor in the SGRQ (P < 0.001, odds ratio [OR] = 6.65, 95% confidence interval [CI]: 2.49–17.74) and SF-12 PCS (P = 0.001, OR = 0.185, 95% CI: 0.07–0.52). There were significant correlations between the SGRQ-Total score and SF-12 PCS (correlation coefficient = -0.612, P < 0.001).ConclusionsDyspnea may be an independent factor of poor disease-specific and generic HRQL in LTx patients. The management of dyspnea may improve the HRQL in patients who have undergone LTx.

Factors associated with postural balance in patients with end-stage renal disease on hemodialysis

BackgroundPatients with end-stage renal disease on hemodialysis have postural balance impairments due to uremic syndrome and hemodialysis complications. This study evaluated the factors associated with postural balance in patients on hemodialysis. MethodsThis cross-sectional study included patients on hemodialysis [n = 93, 62.0 (16.0) years]. Postural balance was evaluated using a force plate in a static position with eyes opened and eyes closed on a firm surface and with eyes opened on a foam surface to register the center of pressure path length. Physical function was assessed by isometric handgrip force, the 5-repetition sit-to-stand test, and gait speed. The level of physical activity and quality of life were evaluated by accelerometry and the 36-Item Short Form Health Survey, respectively. FindingsAfter adjustment for potential confounders, the multiple linear regression analysis showed that the presence of diabetes mellitus and neurological disease and gait speed were significantly associated with the center of pressure path length in the eyes opened test (R2 = 0.263; p < 0.001). The center of pressure path length in the eyes closed test was significantly associated with the presence of neurological disease (R2 = 0.177; p = 0.002). The center of pressure path length in the eyes opened on a foam surface test was significantly associated with the presence of diabetes mellitus (R2 = 0.223; p < 0.001). InterpretationPoor postural balance was associated with the presence of diabetes mellitus and neurological disease and a slower gait speed in patients on hemodialysis.

AUTOMATED VERSUS MANUAL COMPONENT IMPACTION IN TOTAL HIP ARTHROPLASTY: EFFECTS ON COGNITIVE FUNCTION, PHYSICAL FATIGUE, AND STRESS LEVEL

Total Hip Arthroplasty (THA) surgery is a physical and cognitive challenge for surgeons. Data on stress levels, cognitive and physical load of orthopaedic surgeons, as well as ergonomic impact, are limited. With and without the use of an automated impaction device, operational efficiency and the surgeon's ergonomic, mental, and physical load was investigated.In a total of thirty THA procedures, a standard manual technique was compared with an automated impaction device. Three computerized cognitive tasks (Simon, pattern comparison, and pursuit rotor) and five physical tests (isometric wall-sit, plank-to-fatigue, handgrip, supra-postural task, and shoulder endurance) were used to assess psychophysiological load of the surgeon. Surgeon's cortisol concentration was evaluated from saliva samples. Postural risk was assessed by Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA). Efficiency was assessed by timing surgical steps and instrumentation flow.Cognitive performances after automated impaction showed faster response times and lower error rates with a greater time-on-target (+1.5 s) and a lower mouse deviation from target (−1.7 pixels). Manual impaction showed higher physical exhaustion in the isometric wall-sit test (10.6% vs. 22.9%), plank-to-fatigue (2.2% vs. 43.8%), the number of taps in the supra-postural task (−0.7% vs. −7.7%), handgrip force production in the dominant (−6.7% vs. −12.7%) and contralateral hand (+4.7% vs. +7.7%), and in shoulder endurance (−15s vs. −56s). An increase of 38.2% in salivary cortisol concentration between the midday (1.31 nmol/l) and afternoon session (1.81 nmol/l) was observed with manual impaction. After using automated impaction, salivary cortisol concentration decreased (−51.2%). Manual broaching time was on average 6′20’’ versus 7’3’’ with automated impaction. RULA of manual impaction scored 6 for cup impaction and 5 for femoral broaching, versus 3 and 3 for automated impaction, respectively. REBA of manual impaction scored 9 for cup impaction and 5 for femoral broaching, versus 4 and 3 for automated impaction, respectively.Automated impaction lowers surgeons’ cognitive and physical fatigue and leads to reduced stress and improved ergonomics without loss of surgical efficiency.

Long-Term Modeling and Monitoring of Neuromusculoskeletal System Performance Using Tattoo-Like EMG Sensors

This paper introduces stretchable, long-term wearable, tattoo-like dry surface electrodes for highly repeatable electromyography (EMG). The tattoo-like sensors are hair thin, skin compliant and can be laminated on human skin just like a temporary transfer tattoo, which enables multiday noninvasive but intimate contact with the skin even under severe skin deformation. The new electrodes were used to facilitate a system-based approach to tracking of long-term fatiguing and recovery processes in a human neuromusculoskeletal (NMS) system, which was based on establishing an autoregressive moving average model with exogenous inputs (ARMAX model) relating signatures extracted from the surface electromyogram (sEMG) signals collected using the tattoo-like sensors, and the corresponding hand grip force (HGF) serving as the model output. Performance degradation of the relevant NMS system was evaluated by tracking the evolution of the errors of the ARMAX model established using the data corresponding to the rested (fresh) state of any given subject. Results from several exercise sessions clearly showed repeated patterns of fatiguing and resting, with a notable point that these patterns could now be quantified via dynamic models relating the relevant muscle signatures and NMS outputs.

Handgrip Strength and its Association with Anthropometric Measurements at Different Anatomical Positions of Arm among Young Individuals

Many studies have studied the relationships between handgrip strength and different Anthropometric variables. However, the hand anatomical position when measuring the handgrip strength was not clear in many studies. This study aims to investigate the relationship between the anthropometric measurements and the handgrip strength at different anatomical positions of the arm among young individuals. 59 young males and 41 females were asked to squeeze the hand dynamometer to their maximum capacity. The maximum handgrip force was recorded for 7 different arm anatomical positions. Using SPSS, an Independent student's t-test was used to compare male and female groups. Pearson’s correlation coefficients were used to determine the correlations between handgrip strength and the anthropometric measurements, weight, and BMI at different arm anatomical positions. Furthermore, the dominance weight was computed to determine the most important predictors of grip strength. Significant correlation between handgrip strength and height and weight at all positions and with hand length for all positions except when the arm was abducted and extended 180 ͦ at the shoulder joint and 180 ͦ at the elbow joint. Arm length, forearm length and handbreadth were also correlated to handgrip strength at three positions, when the arm was adducted with 90 ͦ forward at the elbow joint, when the Arm was abducted with 90 ͦ at the shoulder joint and 180 ͦ at the elbow, and when the arm was abducted with 90 ͦ at the shoulder joint and 90 ͦ at the elbow joint with the forearm perpendicular to the frontal plane. However, these correlations were different when males and females were considered separately. Furthermore, the results showed that the height followed by hand length had the highest prediction power of handgrip strength among young adults. The current results showed the importance of considering the different anatomical positions of the arm when studying the relationship between anthropometric measurements and hand grip strength.

Agility performance in healthy older adults is associated with handgrip strength and force development: results from a 1-year randomized controlled trial

Key summary pointsAimDoes a multicomponent agility training improves handgrip strength (maximum force and rate of force development) in healthy older adults and what is the link between handgrip strength dimensions and agility in healthy older adults?FindingsNeither maximum handgrip strength nor rate of force development of handgrip strength in healthy older adults is influenced by a 1-year multicomponent agility training. However, maximum handgrip strength and rate of force development are associated with agility performance measured via the agility challenge for the elderly.MessageHandgrip strength is not influenced by multicomponent agility training but could serve as an indicator for agility performance in older adults.

Handgrip force and bite force in dentulous and edentulous individuals.

The literature is unclear about bite force (BF) and handgrip force (HF) in a specific group of different ages and dentate conditions, or even a predictive model for each specific group, using BF and HF as factors. To establish the correlation between HF and BF in female participants with distinct ages and dentate conditions; also create a predictive model of BF as a function of HF. Participants were divided into three groups (GI: young natural dentate women, n = 65; GII: adult natural dentate women, n = 67; and GIII: edentulous women users of bimaxillary complete dentures, n = 67) and subjected to an HF measurement test using a digital dynamometer. Subsequently, BF was measured using a digital gnathodynamometer in the molar region. Pearson correlation coefficient (r) and multivariate analysis of variance (α = 0.05) were performed, and simple linear regression was used to obtain a model to predict BF from HF for each group separately (α = 0.05). All groups presented moderate and strong correlations among the variables (GI: r = 0.838; GII: r = 0.714; GIII: r = 0.646). A significant difference in BF was observed (GI > GII > GIII; p < .05). GIII presented a significantly lower HF than the other groups (p < .05). Besides, three equations predicting BF, using HF, were obtained for use in young/adult dentate and edentulous women. All groups found a positive and significant correlation between BF, HF and groups. HF can be a simple and efficient method for predicting BF using the predictive models developed for women with good health.

Repeated unilateral handgrip contractions alter functional connectivity and improve contralateral limb response times

In humans, motor learning is underpinned by changes in sensorimotor network functional connectivity (FC). Unilateral contractions increase FC in the ipsilateral primary motor cortex (M1) and supplementary motor area (SMA); areas involved in motor planning and execution of the contralateral hand. Therefore, unilateral contractions are a promising approach to augment motor performance in the contralateral hand. In a within-participant, randomized, cross-over design, 15 right-handed adults had two magnetic resonance imaging (MRI) sessions, where functional-MRI and MR-Spectroscopic Imaging were acquired before and after repeated right-hand contractions at either 5% or 50% maximum voluntary contraction (MVC). Before and after scanning, response times (RTs) were determined in both hands. Nine minutes of 50% MVC contractions resulted in decreased handgrip force in the contracting hand, and decreased RTs and increased handgrip force in the contralateral hand. This improved motor performance in the contralateral hand was supported by significant neural changes: increased FC between SMA-SMA and increased FC between right M1 and right Orbitofrontal Cortex. At a neurochemical level, the degree of GABA decline in left M1, left and right SMA correlated with subsequent behavioural improvements in the left-hand. These results support the use of repeated handgrip contractions as a potential modality for improving motor performance in the contralateral hand.

Association between masseter muscle volume, nutritional status, and cognitive status in older people

ObjectivesClinical evidence has suggested that oral function is associated with cognitive, physical, and nutritional status of older people. A smaller volume of masseter, a crucial muscle for mastication, was associated with frailty. It has remained unknown if smaller masseter is associated with cognitive impairment. The current study investigated the association between masseter muscle volume, nutritional status, and cognitive status in older people. Materials and methodsWe recruited 19 patients with mild cognitive impairment (MCI), 15 patients with Alzheimer's disease (AD), and 28 sex and age-matched non-cognitive impairment (non-CI) older subjects. The number of missing teeth (NMT), masticatory performance (MP), maximal hand-grip force (MGF), and calf circumference (CC) were assessed. The masseter volume index (MVI) was calculated based on the masseter volume measured using magnetic resonance imaging. ResultsThe MVI was significantly lower in the AD group, compared to the MCI as well as the non-CI group. Multiple regression analyses revealed that the MVI was significantly associated with nutritional status (as indexed by CC) in the analysis of combination of NMT, MP, and the MVI. Moreover, the MVI was a significant predictor of CC only in patients with cognitive impairment (i.e., MCI+AD) but not in the non-CI group. ConclusionsOur findings suggested that in addition to the NMT and MP, masseter volume is a critical oral factor associated with cognitive impairment. Clinical relevance. Reduction of MVI should be carefully monitored for patients with dementia and frailty, to whom a lower MVI may indicate worse nutrient intake.

Force/moment tracking performance during constant-pose, force-varying, bilaterally symmetric, hand-wrist tasks.

Bilateral movement is widely used for calibration of myoelectric prosthesis controllers, and is also relevant as rehabilitation therapy for patients with motor impairment and for athletic training. Target tracking and/or force matching tasks can be used to elicit such bilateral movement. Limited descriptive accuracy data exist in able-bodied subjects for bilateral target tracking or dominant vs non-dominant dynamic force matching tasks requiring more than one degree of freedom (DoF). We examined dynamic trajectory (0.75Hz band-limited, white, uniform random) constant-posture, hand open-close, wrist pronation-supination target tracking and matching tasks. Tasks were normalized to maximum voluntary contraction (MVC), spanning a±30% MVC force range, in four 1-DoF and 2-DoF tasks: (1, 2) unilateral dominant limb tracking with/without visual feedback, and (3, 4) bilateral dominant/non-dominant limb tracking with mirror visual feedback. In 12 able-bodied subjects, unilateral tracking error with visual feedback averaged 10-15%MVC, but up to 30%MVC without visual feedback. Bilateral matching error averaged∼10%MVC and was affected little by visual feedback type, so long as feedback was provided. In 1-DoF bilateral tracking, the dominant side had statistically lower error than the non-dominant side. In 2-DoF bilateral tracking, the side providing mirror visual feedback exhibited lower error than the opposite side. In 2-DoF tasks (assumed to be more challenging than their constituent 1-DoF tracking tasks), hand grip force errors grew disproportionately larger than those of each wrist DoF. In unilateral 1-DoF tasks, both hand vs target and wrist vs target latency averaged 250-350ms. In unilateral 2-DoF tasks, wrist vs target latency also averaged 250-350ms, while hand vs target latency averaged>500ms. These results provide guidance on bilateral 2-DoF hand-wrist performance in target tracking, and dominant vs non-dominant force matching tasks.

Digital health metrics reveal upper limb impairment profiles in ARSACS

ObjectiveAdults with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) often present with reduced upper limb coordination affecting their independence in daily life. Previous studies in ARSACS identified reduced performance in clinical assessments requiring fine and gross dexterity as well as prehension. However, the kinematic and kinetic aspects underlying reduced upper limb coordination in ARSACS have not been systematically investigated yet. In this work, we aimed to provide a detailed characterization of alterations in upper limb movement patterns and hand grip forces in 57 participants with ARSACS. MethodsWe relied on a goal-directed technology-aided assessment task, which provides eight previously validated digital health metrics describing movement efficiency, smoothness, speed, and grip force control. ResultsFirst, we observed that 98.3% of the participants were impaired in at least one of the metrics, that all metrics are significantly impaired on a population level, and that grip force control during precise manipulations is most commonly and strongly impaired. Second, we identified high inter-participant variability in the kinematic and kinetic impairment profiles, thereby capturing different clinical profiles subjectively observed in this population. Lastly, abnormal goal-directed task performance in ARSACS could be best explained by reduced movement speed, efficiency, and especially force control during precise manipulations, while abnormal movement smoothness did not have a significant effect. InterpretationThis work helped to refine the clinical profile of ARSACS and highlights the need for characterizing individual kinematic and kinetic impairment profiles in clinical trials in ARSACS.

A Study of Handgrip Force Prediction Scheme Based on Electrical Impedance Myography

Handgrip force prediction is widely used in the rehabilitation of the arm and prosthetic control. To investigate the effects of different measurement positions and feature parameters on the results of handgrip force prediction, a model based on electrical impedance myography (EIM) and long short-term memory (LSTM) networks was proposed to compare and determine a better scheme for handgrip force prediction. We conducted the signal acquisition experiments of impedance and handgrip force on the anterior forearm muscles and brachioradialis muscle. Afterwards, three evaluation metrics were introduced to compare the prediction results of various models, and the variability between models was analyzed using paired sample t-tests. The results showed that the model of handgrip force prediction based on anterior forearm muscles exhibited better performance in predicting. The evaluation metrics of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {R^{2}}$</tex-math></inline-formula> , explained variance score (EVS) and normalized mean square error (NMSE) for the model fusing the feature parameters resistance (R) and reactance (X) were 0.9023, 0.9173 and 0.0114, respectively. Therefore, the feature parameters fusing R and X are the optimal input for the handgrip force prediction model. The anterior forearm muscles are the preferred position for impedance measurement over the brachioradialis muscle. This paper validated the feasibility of EIM for handgrip force prediction and provided a new reference and implementation scheme for muscle rehabilitation training and prosthetic control.

Home-based respiratory muscle training on quality of life and exercise tolerance in long-term post-COVID-19: Randomized controlled trial.

To evaluate the effects of a home-based respiratory muscle training programme (inspiratory [IMT] or inspiratory/expiratory muscles [RMT]) supervised by telerehabilitation on quality of life and exercise tolerance in individuals with long-term post-COVID-19 symptoms. The secondary objective was to evaluate the effects of these programmes on respiratory muscle function, physical and lung function, and psychological state. 88 individuals with long-term symptoms of fatigue and dyspnoea after COVID-19 diagnosis were randomly (1:1 ratio) assigned to IMT, IMTsham, RMT or RMTsham groups for an 8-week intervention (40min/day, 6 times/week). Primary outcomes were quality of life (EuroQol-5D questionnaire) and exercise tolerance (Ruffier test). Secondary outcomes were respiratory muscle function (inspiratory/expiratory muscle strength; inspiratory muscle endurance), physical function (lower and upper limb strength [1-min Sit-to-Stand and handgrip force]), lung function (forced spirometry), and psychological status (anxiety/depression levels and post-traumatic stress disorder). All outcomes were measured pre-, intermediate- (4th week), and post-intervention. At post-intervention, there was a statistically significant and large (d>0.90) improvement in quality of life, but not in exercise tolerance, in the RMT group compared with the RMTsham group. Both of the real training groups produced a statistically significant and large increase in inspiratory muscle strength and endurance (d≥0.80) and in lower limb muscle strength (d≥0.77) compared with the 2 sham groups. Expiratory muscle strength and peak expiratory flow showed a statistically significant and large (d≥0.87) increase in the RMT group compared with the other 3 groups. Only an 8-week supervised home-based RMT programme was effective in improving quality of life, but not exercise tolerance, in individuals with long-term post-COVID-19 symptoms. In addition, IMT and RMT programmes were effective in improving respiratory muscle function and lower limb muscle strength, but had no impact on lung function and psychological status.

Altered Bimanual Kinetic and Kinematic Motor Control Capabilities in Older Women.

Older women may experience critical neuromuscular impairments interfering with controlling successful bimanual motor actions. Our study aimed to investigate altered bimanual motor performances in older women compared with younger women by focusing on kinetic and kinematic motor properties. Twenty-two older women and 22 younger women performed bimanual kinetic and kinematic motor tasks. To estimate bimanual kinetic functions, we calculated bimanual maximal voluntary contractions (i.e., MVC) and force control capabilities (i.e., mean force, accuracy, variability, and regularity of the total force produced by two hands) during bimanual hand-grip submaximal force control tasks. For bimanual kinematic performances, we assessed the scores of the Purdue Pegboard Test (i.e., PPT) in both hands and assembly tasks, respectively. For the bimanual MVC and PPT, we conducted an independent t-test between two groups. The bimanual force control capabilities were analyzed using two-way mixed ANOVAs (Group × Force Level; 2 × 2). Our findings revealed that the older women showed less bimanual MVC (p = 0.046) and submaximal force outputs (p = 0.036) and greater changes in bimanual force control capabilities as indicated by a greater force variability (p = 0.017) and regularity (p = 0.014). Further, the older women revealed lower scores of PPT in both the hands condition (p < 0.001) and assembly task condition (p < 0.001). The additional correlation analyses for the older women showed that lower levels of skeletal muscle mass were related to less bimanual MVC (r = 0.591; p = 0.004). Furthermore, a higher age was related to lower scores in the bimanual PPT assembly task (r = -0.427; p = 0.048). These findings suggested that older women experience greater changes in bimanual motor functions compared with younger women.

F-waves induced by motor point stimulation are facilitated during handgrip and motor imagery tasks.

The F-wave is a motor response elicited via the antidromic firings of motor nerves by the electrical stimulation of peripheral nerves, which reflects the motoneuron pool excitability. However, the F-wave generally has low robustness i.e., low persistence and small amplitude. We recently found that motor point stimulation (MPS), which provides the muscle belly with electrical stimulation, shows different neural responses compared to nerve stimulation, e.g., MPS elicits F-waves more robustly than nerve stimulation. Here, we investigated whether F-waves induced by MPS can identify changes in motoneuron pool excitability during handgrip and motor imagery. Twelve participants participated in the present study. We applied MPS on their soleus muscle and recorded F-waves during eyes-open (EO), eyes-closed (EC), handgrip (HG), and motor imagery (MI) conditions. In the EO and EC conditions, participants relaxed with their eyes open and closed, respectively. In the HG, participants matched the handgrip force level to 30% of the maximum voluntary force with visual feedback. In the MI, they performed kinesthetic MI of plantarflexion at the maximal strength with closed eyes. In the HG and MI, the amplitudes of the F-waves induced by MPS were increased compared with those in the EO and EC, respectively. These results indicate that the motoneuron pool excitability was facilitated during the HG and MI conditions, consistent with findings in previous studies. Our findings suggest that F-waves elicited by MPS can be a good tool in human neurophysiology to assess the motoneuron pool excitability during cognitive and motor tasks.

Development and Validation of a System for the Assessment and Recovery of Grip Force Control.

The ability to finely control hand grip forces can be compromised by neuromuscular or musculoskeletal disorders. Therefore, it is recommended to include the training and assessment of grip force control in rehabilitation therapy. The benefits of robot-mediated therapy have been widely reported in the literature, and its combination with virtual reality and biofeedback can improve rehabilitation outcomes. However, the existing systems for hand rehabilitation do not allow both monitoring/training forces exerted by single fingers and providing biofeedback. This paper describes the development of a system for the assessment and recovery of grip force control. An exoskeleton for hand rehabilitation was instrumented to sense grip forces at the fingertips, and two operation modalities are proposed: (i) an active-assisted training to assist the user in reaching target force values and (ii) virtual reality games, in the form of tracking tasks, to train and assess the user's grip force control. For the active-assisted modality, the control of the exoskeleton motors allowed generating additional grip force at the fingertips, confirming the feasibility of this modality. The developed virtual reality games were positively accepted by the volunteers and allowed evaluating the performance of healthy and pathological users.