Handgrip Force Research Articles

The Role of Cystic Fibrosis Transmembrane Conductance Regulator in Skeletal Muscle Contractile Function

Purpose: Genetic mutations in cystic fibrosis (CF) result in CF transmembrane conductance regulator (CFTR) dysfunction. CFTR is expressed in human skeletal muscle; its effect on skeletal muscle abnormalities is unknown. The study objective is to investigate the role of CFTR in skeletal muscle contractile function. Methods: We conducted a prospective, cross-sectional study comparing 34 adults with minimal and 18 with residual function CFTR mutations, recruited from Toronto Adult CF Centre, St. Michael's Hospital, Unity Health Toronto. Quadriceps, biceps brachii, and handgrip strength was measured with dynamometers; leg muscle power with the stair climb power test. Quadriceps muscle contractility was determined by quadriceps muscle strength normalized to quadriceps muscle size, measured with ultrasound images. Multivariable regression was used for analysis. Results: People with residual function CFTR mutations had higher quadriceps muscle torque normalized to quadriceps layer thickness and to rectus femoris cross-sectional area by 27.5 Nm/cm [95% CI (2.2, 52.8) Nm/cm, P = .034] and 5.6 Nm/cm2 [95% CI (0.3, 10.9) Nm/cm2, P = .041], respectively, compared with those with minimal function CFTR mutations. There were no differences in quadriceps muscle torque (P = .58), leg muscle power (P = .47), biceps brachii muscle force (P = .14), or handgrip force (P = .12) between the 2 mutation groups. Conclusions: CFTR protein may play a role in muscle contractility, implying a limited capacity to exert muscle force per unit of muscle size in people with CF. This suggests that building a greater muscle mass through resistance exercises focusing on muscle hypertrophy in exercise prescription may improve muscle strength in people with CF.

Population-specific equations of age-related maximum handgrip force: a comprehensive review.

The measurement of handgrip force responses is important in many aspects, for example: to complement neurological assessments, to investigate the contribution of muscle mass in predicting functional outcomes, in setting realistic treatment goals, evaluating rehabilitation strategies. Normative data about handgrip force can assist the therapist in interpreting a patient's results compared with healthy individuals of the same age and gender and can serve as key decision criteria. In this context, establishing normative values of handgrip strength is crucial. Hence, the aim of the this study is to develop a tool that could be used both in rehabilitation and in the prevention of work-related musculoskeletal disorders. This tool takes the form of population-specific predictive equations, which express maximum handgrip force as a function of age. In order to collect data from studies measuring maximum handgrip force, three databases were searched. The search yielded 5,058 articles. Upon the removal of duplicates, the screening of abstracts and the full-text review of potentially relevant articles, 143 publications which focussed on experimental studies on various age groups were considered as fulfilling the eligibility criteria. A comprehensive literature review produced 1,276 mean values of maximum handgrip force. A meta-analysis resulted in gender- and world region-specific (general population, USA, Europe and Asia) equations expressing maximum force as a function of age. The equations showed quantitative differences and trends in maximum handgrip force among age, gender and national groups. They also showed that values of maximum handgrip force are about 40% higher for males than for females and that age-induced decrease in force differs between males and females, with a proved 35% difference between the ages of 35 and 75. The difference was lowest for the 60-64 year olds and highest for the 18-25 year-olds. The equations also showed that differences due to region are smaller than those due to age or gender. The equations that were developed for this study can be beneficial in setting population-specific thresholds for rehabilitation programmes and workstation exposure. They can also contribute to the modification of commonly used methods for assessing musculoskeletal load and work-related risk of developing musculoskeletal disorders by scaling their limit values.

Reference data for the hand grip and palmar pinch force sense errors and the relationship between school-entry-age in young adults.

Hands execute intricate tasks vital for everyday life and professions such as cooking, tailoring, and craftsmanship. This study aimed to establish reference data for hand grip and palmar pinch force sense in young adults, accounting for gender differences, and to determine the correlation between these data and school-entry ages. The cross-sectional observational study comprised 284 participants (156 females and 128 males). Demographic details, including age, gender, weight, and height, were recorded. Participant ages ranged from 18 to 29, representing the youth workforce population as defined by the International Labour Organization. Factors like hand dominance and school-entry age were ascertained based on participants' self-reports. Hand grip and palmar pinch force senses were separately assessed in the dominant and non-dominant hands of 130 randomly chosen participants to evaluate test-retest reliability. Hand grip (dominant: p < 0.001, non-dominant: p = 0.002) and palmar pinch force sense errors were significantly lower in male participants compared to females. Palmar pinch force sense error for the dominant hand was reduced in males (p = 0.002), but no significant disparity existed between genders for the non-dominant hand (p = 0.222). Healthy adults who began school at age five or earlier exhibited a decreased force sense error rate (p < 0.05). Force sense error reference values vary based on gender and school-entry age. This reference data will aid rehabilitation specialists working with young adults in physiotherapy and occupational therapy fields in identifying potential impairments.

Effects of home-based EEG neurofeedback training as a non-pharmacological intervention for Parkinson's disease

ObjectivesAberrant movement-related cortical activity has been linked to impaired motor function in Parkinson's disease (PD). Dopaminergic drug treatment can restore these, but dosages and long-term treatment are limited by adverse side-effects. Effective non-pharmacological treatments could help reduce reliance on drugs. This experiment reports the first study of home-based electroencephalographic (EEG) neurofeedback training as a non-pharmacological candidate treatment for PD. Our primary aim was to test the feasibility of our EEG neurofeedback intervention in a home setting. MethodsSixteen people with PD received six home visits comprising symptomology self-reports, a standardised motor assessment, and a precision handgrip force production task while EEG was recorded (visits 1, 2 and 6); and 3 × 1-hr EEG neurofeedback training sessions to supress the EEG mu rhythm before initiating handgrip movements (visits 3 to 5). ResultsParticipants successfully learned to self-regulate mu activity, and this appeared to expedite the initiation of precision movements (i.e., time to reach target handgrip force off-medication pre-intervention = 628 ms, off-medication post-intervention = 564 ms). There was no evidence of wider symptomology reduction (e.g., Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III Motor Examination, off-medication pre-intervention = 29.00, off-medication post intervention = 30.07). Interviews indicated that the intervention was well-received. ConclusionBased on the significant effect of neurofeedback on movement-related cortical activity, positive qualitative reports from participants, and a suggestive benefit to movement initiation, we conclude that home-based neurofeedback for people with PD is a feasible and promising non-pharmacological treatment that warrants further research.

Characterization of muscle oxygenation response in well-trained handcyclists.

Peripheral responses might be important in handcycling, given the involvement of smallmusclescompared to other exercise modalities. Therefore, the goal of this study was to compare changes in muscle oxygen saturation (∆SmO2) and deoxyhemoglobin level (∆[HHb]) between different efforts and muscles. Handcyclists participated in a Wingate, a maximal incremental test and a 20-min time-trial (TT). Oxygen uptake (VO2)as well as ∆SmO2, ∆[HHb], deoxygenation and reoxygenation rates in the triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD) and extensor carpi radialis brevis (ER) were measured. ER ∆[HHb]max was 37% greater in the incremental test than in the Wingate (ES = 0.392, P = 0.031). TT mean power (W/kg) was associated with BB ∆SmO2min measured in the incremental test (r = -0.998 [-1.190, -0.806], P = 0.002) and in the Wingate (r = -0.994 [-1.327, -0.661], P = 0.006). MAP (W/kg) was associated with Wingate BB ∆SmO2min (r = -0.983 [-0.999, -0.839], P = 0.003), and Wingate peak (r = 0.649 [0.379, 0.895], P = 0.008) and mean power(W/kg) (r = 0.925 [0.752, 0.972], P = 0.003) was associated with right handgrip force. The strongest physiological predictor for TT performance was BB ∆SmO2min in the incremental test (P = 0.002, r2= 0.993, SEE 0.016W/kg), Wingate BB ∆SmO2min for MAP (P = 0.003, r2= 0.956, SEE 0.058W/kg) and right handgrip force for Wingate peak power (P = 0.005, r2= 0.856, SEE 0.551W/kg). Peripheral aerobic responses (muscle oxygenation) were predictiveof handcycling performance.

Aging Impairs Unimanual and Bimanual Hand-Grip Force Control Capabilities

This study examined age-related changes in unimanual and bimanual hand-grip force control capabilities by focusing on absolute and relative outcome measures. Thirty-two older adults and thirty-two younger adults performed isometric hand-grip force control tasks across three hand conditions (unimanual dominant, unimanual non-dominant, and bimanual) and two submaximal targeted levels (10% and 40% of maximal voluntary contraction). Force control performances were evaluated by calculating absolute and relative variables on force accuracy and variability. Furthermore, to determine which force control variables and experimental conditions effectively indicate age-related sensorimotor control deficits, we conducted receiver operating characteristic curve analyses. Older adults demonstrated impaired force control capabilities at 10% of maximal voluntary contraction collapse across the three hand conditions compared with younger adults, and these deficits were identified by both relative force accuracy and relative force variability. Moreover, relative force accuracy showed a good diagnostic quality at 10% of maximal voluntary contraction. These findings suggested that aging may induce unimanual and bimanual hand-grip force control deficits at a lower targeted level, and these motor impairments were sensitively estimated by quantifying relative force control outcome measures that may reflect age-related muscle weakness as compared with absolute measurements.

Motor unit loss and neuromuscular junction degeneration precede clinically diagnosed sarcopenia

Background: Degeneration of motoneuron and neuromuscular junctions (NMJ) and loss of motor units (MUs) contribute to age-related muscle wasting and weakness, leading to sarcopenia. However, these features have not been adequately investigated in humans. This study aimed to compare neuromuscular system integrity and function across different stages of sarcopenia, with a particular focus on NMJ stability and MU properties. We hypothesized that progressive impairment of the neuromuscular system would be a hallmark of the progression of sarcopenia. Methods: We recruited 42 healthy young individuals (Y) (aged 25.98±4.6 yr; 57% females) and 88 older individuals (aged 75.9±4.7 yr; 55% females). The older group underwent a sarcopenia screening according to the revised guidelines of the European Working Group on Sarcopenia in Older People (EWGSOP2). In all groups, knee extensor muscle force was evaluated by isometric dynamometry, muscle size by ultrasound and MUP properties by intramuscular electromyography (iEMG). MU number estimate (iMUNE) was also obtained. Blood samples and muscle biopsies were collected to assess biomarkers of neuromuscular degeneration. Results: 39 older individuals were non-sarcopenic (NS), 31 pre-sarcopenic (PS) and 18 sarcopenic (S). A progressive decline in quadriceps force, cross-sectional area and appendicular lean mass was detected with the different stages of sarcopenia. Handgrip force and short physical performance battery (SPPB) scores were also progressively reduced. iEMG recordings showed increased near fiber segment jitter in NS, PS and S compared to the Y group, highlighting a decreased NMJ transmission stability. Elevated concentration of serum C-terminal agrin fragment and altered Cav3 protein expression further supported the finding of age-related NMJ instability in all the older groups. The iMUNE was lower in all older groups, confirming age-related loss of MUs. Motoneuron firing rate was decreased in S vs Y. Age-related increases in MU potential complexity were also observed. These observations were accompanied by increased muscle denervation and axonal damage, respectively, indicated by the increase in NCAM-positive fibres and the increase in serum concentration of neurofilament light chain. Notably, most of these MU and NMJ parameters did not differ in older individuals with or without sarcopenia. Conclusion: Alterations in MU properties, axonal damage, altered innervation profile and NMJ instability are signatures of neuromuscular system ageing. These neuromuscular impairments are accompanied by muscle atrophy and weakness, however, they appear to precede clinically diagnosed sarcopenia, as they are already detectable in older NS individuals. These are important parameters to monitor in order to counteract these impairments and slow down the onset and progression of sarcopenia. The present work was funded by the PRIN project ‘NeuAge’ (2017CBF8NJ_001) to MVN and MAP and the Milky Way Foundation, the Baxter Foundation and the Li Ka Shing Foundation to HMB. EM was supported by the Stanford Wu Tsai Human Performance Institute fellowship and Marie Skłodowska-Curie Actions postdoctoral fellowship. We also acknowledge co-funding from Next Generation EU to MVN, in the context of the National Recovery and Resilience Plan, Investment PE8 — Project Age-It: “Ageing Well in an Ageing Society”. This resource was co-financed by the Next Generation EU [DM 1557 11.10.2022]. The views and opinions expressed are only those of the authors and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Predicting hand grip force based on muscle electromyographic activity using artificial intelligence and neural networks

The research aims to find predictive values for hand grip strength based on electromyographic activity, in addition to identifying differences between measured grip strength and the predicted grip strength. The research sample included 12 advanced handball players, with their medical records verified. Researchers measured grip strength using a device designed to read Newton force, recording data in real-time with a sampling window of 0.1 seconds. This measurement was synchronized with the recording of muscle electromyographic activity (sEMG) using the Noraxon myoMOTION technique, with a frequency and number of channels set at 400Hz and 8 channels, respectively. The recommended methodology and conditions were strictly adhered to, with the process repeated for each player with complete rest intervals. The following research variables were adopted: peak electromyographic activity, root mean square, time to peak, time ratio between peak and minimum values, average peaks, area under the curve, peak sustain time, peak changes, and voluntary maximum contraction. Grip strength measurements using the designed device were conducted at three stages (50%, 75%, 100%), maintaining the specified intensity for 3 seconds. After data collection, preliminary processing involved isolation and purification to identify the most influential factors. IBM Statistical was the chosen technique for implementing neural networks and using artificial intelligence techniques to process data with a database synchronized using Python. The results generally supported some of the proposed ideas, with interesting findings revealing statistically insignificant and slight differences between recorded and expected grip strength

Ability of Adjusting Grip Strength From Childhood to Adulthood

Purpose: This cross-sectional study aimed to investigate the ability to adjust grip strength by comparing the characteristics of force generation and relaxation from childhood to adulthood. Method: This study included 225 participants aged 6, 11, 17, and 19–23 years (adults) who performed isometric hand-grip force as follows: maximum, half generation, and half relaxation. The force was recorded, and relative values and errors were calculated for half tasks. Results: The maximum task values increased with age, but there was no significant age difference between 17-year-olds and adults. The difference between sexes was significant; males were stronger than females in both 17-year-olds and adults. Both sexes in all age groups had greater errors in half relaxation than in half generation tasks. Females had negatively greater constant error than males in half tasks. The errors of 6-year-olds were greater than the other age groups in half tasks. Conclusion: There is a developmental trend for producing maximal strength that is similar across sexes until adolescence when males are stronger and females plateau. The ability of force relaxation was more difficult to accurately control than force generation for all age groups and was adult-like by middle childhood.

Force Production and Electromyographic Activity during Different Flywheel Deadlift Exercises.

This study aimed to characterize and compare force production and muscle activity during four flywheel deadlift exercises (bilateral [Bi] vs. unilateral [Uni]) with different loading conditions (vertical [Ver] vs. horizontal [Hor]). Twenty-three team-sport athletes underwent assessments for exercise kinetics (hand-grip force), along with surface electromyography (sEMG) of the proximal (BFProx) and medial biceps femoris (BFMed), semitendinosus (ST), and gluteus medius (GM). Mean and peak force were highest (p < 0.001) in Bi + Ver compared with Bi + Hor, Uni + Ver, and Uni + Hor. Although no significant differences were observed between Bi + Hor and Uni + Ver, both variants showed higher (p < 0.001) average force and peak eccentric force when compared with Uni + Hor. The presence of eccentric overload was only observed in the vertically loaded variants. Bi + Ver and Uni + Ver showed higher (p < 0.05) sEMG levels in BFProx and BFMed compared with the Uni + Hor variant. In addition, Uni + Ver registered the largest GM and ST sEMG values. In conclusion, the vertical variants of the flywheel deadlift exercise led to higher muscle force production and sEMG compared with their horizontal counterparts. Both Bi + Ver and Uni + Ver may be effective in promoting an increase in hamstring muscles activity and muscle force at long muscle length, while the Uni + Ver variant may be more effective in promoting GM and ST involvement.

Activity in the pontine reticular nuclei scales with handgrip force in humans.

The neural pathways that contribute to force production in humans are currently poorly understood, as the relative roles of the corticospinal tract and brainstem pathways, such as the reticulospinal tract (RST), vary substantially across species. Using functional magnetic resonance imaging (fMRI), we aimed to measure activation in the pontine reticular nuclei (PRN) during different submaximal handgrip contractions to determine the potential role of the PRN in force modulation. Thirteen neurologically intact participants (age: 28 ± 6 yr) performed unilateral handgrip contractions at 25%, 50%, 75% of maximum voluntary contraction during brain scans. We quantified the magnitude of PRN activation from the contralateral and ipsilateral sides during each of the three contraction intensities. A repeated-measures ANOVA demonstrated a significant main effect of force (P = 0.012, [Formula: see text] = 0.307) for PRN activation, independent of side (i.e., activation increased with force for both contralateral and ipsilateral nuclei). Further analyses of these data involved calculating the linear slope between the magnitude of activation and handgrip force for each region of interest (ROI) at the individual-level. One-sample t tests on the slopes revealed significant group-level scaling for the PRN bilaterally, but only the ipsilateral PRN remained significant after correcting for multiple comparisons. We show evidence of task-dependent activation in the PRN that was positively related to handgrip force. These data build on a growing body of literature that highlights the RST as a functionally relevant motor pathway for force modulation in humans.NEW & NOTEWORTHY In this study, we used a task-based functional magnetic resonance imaging (fMRI) paradigm to show that activity in the pontine reticular nuclei scales linearly with increasing force during a handgrip task. These findings directly support recently proposed hypotheses that the reticulospinal tract may play an important role in modulating force production in humans.

Impaired performance of rapid grip in people with Parkinson's disease and motor segmentation

Bradykinesia, or slow movement, is a defining symptom of Parkinson's disease (PD), but the underlying neuromechanical deficits that lead to this slowness remain unclear. People with PD often have impaired rates of motor output accompanied by disruptions in neuromuscular excitation, causing abnormal, segmented, force-time curves. Previous investigations using single-joint models indicate that agonist electromyogram (EMG) silent periods cause motor segmentation. It is unknown whether motor segmentation is evident in more anatomically complex and ecologically important tasks, such as handgrip tasks. Aim 1 was to determine how handgrip rates of force change compare between people with PD and healthy young and older adults. Aim 2 was to determine whether motor segmentation is present in handgrip force and EMG measures in people with PD. Subjects performed rapid isometric handgrip pulses to 20–60% of their maximal voluntary contraction force while EMG was collected from the grip flexors and extensors. Dependent variables included the time to 90% peak force, the peak rate of force development, the duration above 90% of peak force, the number of segments in the force-time curve, the number of EMG bursts, time to relaxation from 90% of peak force, and the peak rate of force relaxation. People with PD had longer durations and lower rates of force change than young and older adults. Six of 22 people with PD had motor segmentation. People with PD had more EMG bursts compared to healthy adults and the number of EMG bursts covaried with the number of segments. Thus, control of rapid movement in Parkinson's disease can be studied using isometric handgrip. People with PD have impaired rate control compared to healthy adults and motor segmentation can be studied in handgrip.

Towards hand grip force assessment by using EMG estimators

The purpose of this study was to propose a method to assess individual regression (calibration) curves to establish a relationship between an isometric grip force and surface electromyography (EMG) estimator. In this study 18 healthy volunteers (12 male (23.0 ± 2.0 years) and 6 female (23.2 ± 0.7 years)) had been examined. Ten EMG estimators (mean absolute value, root mean square, entropy, energy, turns per second, mean of zero crossings, median power frequency, mean power frequency, and Hilbert transforms), two EMG locations (brachioradialis and flexor digitorum superficialis) and five types of regression curves (linear, exponential, power, logarithm, and quadratic polynomial) have been tested. Using a quadratic polynomial regression curve and energy EMG estimator of the flexor digitorum superficialis muscle, it was obtained the lowest dispersity of EMG estimator and the most accurate prediction of grip isometric force among all tested EMG estimators.

Prevalence and associations of keratokonus among children, adults and elderly in the population‐based ural eye studies

Aims/Purpose: To estimate prevalence and associations of keratoconus in populations in Russia with an age from childhood to seniority.Methods: The study population consisted of the cohorts of three population‐based studies performed in urban and rural areas within the same geographical region in Bashkortostan/Russia: The Ural Children Eye Study (UCES; age: 6–18 years; n = 4890), Ural Eye and Medical Study (UEMS; age: 40+ years; n = 5314) and Ural Very Old Study (UVOS; age: 85+ years; n = 651). Based upon Scheimflug imaging, keratoconus was defined by a keratometric reading of ≥48 D in any eye.Results: The mean maximal and minimal corneal refractive power increased from the UCES (43.58 ± 1.50 dioptres (D) and 42.70 ± 1.42D, respectively) to the UEMS (44.26 ± 1.70 D and 43.61 ± 1.76D, resp.) and to the UVOS (45.1 ± 1.72D and 43.98 ± 1.68D, resp.). Correspondingly, keratoconus prevalence increased from the UCES (42/4890; 0.086%; 95% CI: 0.060, 0.112) to the UEMS (112/5314; 2.11%; 95% CI: 1.72, 2.49) and to the UVOS (42/651; 6.45%; 95% CI: 4.56, 8.34). In the UCES, higher keratoconus prevalence was associated (multivariable analysis) with higher birth order (OR: 2.34; 95% CI: 1.32, 4.15; p = 0.004), lower birthweight (OR: 0.99; 95% CI: 0.99, 0.99; p &lt; 0.001), and shorter axial length (OR: 0.15;9 5% CI: 0.08, 0.30; p &lt; 0.001). In the UEMS, keratoconus prevalence correlated with shorter axial length (OR: 0.15; 95% CI: 0.10, 0.23; p &lt; 0.001), larger corneal volume (OR: 1.17; 95% CI: 1.09, 1.25; p = 0.001), thicker lens (OR: 2.27; 95% CI:1.06, 5.28; p = 0.04), cortical cataract degree (OR: 1.02; 95% CI:1.01, 1.04; p = 0.01), and higher stage of age‐related macular degeneration (OR: 1.65; 95% CI: 1.09, 2.51; p = 0.02). In the UVOS, keratoconus prevalence correlated with lower educational level (OR: 0.84; 95% CI:0.71, 0.99; p = 0 0.04) and lower dynamometric hand grip force (OR: 0.92; 95% CI: 0.88, 0.97; p = 0.003).Conclusions: In this study on multiethnic groups from Russia, keratokonus prevalence increased from the paediatric group (0.09%) to the adult group (2.11%) and seniority group (6.45%), correlated mostly with biometric ocular parameters, and was in all age groups statistically independent of most systemic parameters.

Resistance band training with functional electrical stimulation improves force control capabilities in older adults: a preliminary study.

Resistance band training (RBT) with functional electrical stimulation (FES) may be an effective exercise regimen for improving age-related motor impairments. This preliminary study investigated the potential effects of bimanual RBT with FES on upper limb motor functions in older adults. This study randomly assigned 22 elderly people to the bimanual RBT with FES (Bi-RBT+FES) group and the RBT without FES (Bi-RBT) group. All participants performed isometric hand-grip force control tasks in unimanual (dominant and non-dominant) and bimanual conditions before and after four weeks of exercise for each group. We quantified the mean force, force accuracy, force variability, and force regularity at two targeted force levels (i.e., 10 % and 40 % of maximum voluntary contraction; MVC) to estimate changes in force control capabilities. The results revealed that the Bi-RBT+FES group demonstrated a greater force accuracy in the dominant hand at 10 % of MVC after training. Non-dominant hands in the Bi-RBT+FES group increased force accuracy at 40 % of MVC and reduced force variability collapsed across two targeted force levels. Both groups showed a decrease in force regularity after training. These preliminary results indicate that Bi-RBT+FES may be a viable option to facilitate functional recovery of the upper limbs in older adults.

Exercise pressor responses are exaggerated relative to force production during, but not following, thirty-minutes of rhythmic handgrip exercise.

This study tested the hypothesis that blood pressure responses would increase relative to force production in response to prolonged bouts of muscular work. Fifteen individuals performed two minutes of static handgrip (SHG; 35% MVC), followed by three minutes of post-exercise-cuff-occlusion (PECO), before and after thirty minutes of rest (control), or rhythmic handgrip exercise (RHG) of the contralateral and ipsilateral forearms. Beat-by-beat recordings of mean arterial pressure (MAP), heart rate (HR), and handgrip force (kg) were averaged across one-minute periods at baseline, and minutes 5, 10, 15, 20, 25, and 30 of RHG. MAP was also normalized to handgrip force, providing a relative measure of exercise pressor responses (mmHg/kg). Hemodynamic responses to SHG and PECO were also compared before and after contralateral RHG, ipsilateral RHG, and control, respectively. Similar to the RHG trial, areas under the curve were calculated for MAP (blood pressure index; BPI) and normalized to the time tension index (BPInorm). HR and MAP significantly increased during RHG (15.3 ± 1.4% and 20.4 ± 3.2%, respectively, both p < 0.01), while force output decreased by up to 36.6 ± 8.0% (p < 0.01). This resulted in a 51.6 ± 9.4% increase in BPInorm during 30min of RHG (p < 0.01). In contrast, blood pressure responses to SHG and PECO were unchanged following RHG (all p ≥ 0.07), and only the mean HR (4.2 ± 1.5%, p = 0.01) and ΔHR (67.2 ± 18.1%, p < 0.01) response to SHG were exaggerated following ipsilateral RHG. The magnitude of exercise pressor responses relative to force production progressively increases during, but not following, prolonged bouts of muscular work.

The Effect Of Automated Component Impaction On The Surgeon’s Ergonomics, Fatigue And Stress Levels In Total Hip Arthroplasty

Background Total Hip Arthroplasty (THA) surgery is physically and cognitively challenging. Sub-optimal posture during component impaction may influence surgeon’s ergonomics and fatigue. Methods Thirty THA procedures were executed for 3 days. Only during the first day, manual impaction (MI) was performed. Postural risk was evaluated with Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA) score. Three cognitive tasks (Simon, pattern comparison and pursuit rotor test) and five physical tests (isometric wall-sit, plank-to-fatigue, handgrip, supra-postural task, and shoulder endurance) assessed surgeon’s psycho-physiological load in the morning, midday, and afternoon. Surgeon’s cortisol concentration and sound level of the broaching process was also recorded. Results RULA and REBA scores were 1.7 to 3 times lower with automated impaction (AI). Physical exhaustion was lower with AI: isometric wall-sit test (10.6% vs. 22.9%), plank-to-fatigue (2.2% vs. 43.8%), supra-postural task (-0.7% vs. -7.7%), handgrip force production (dominant hand -6.7% vs. -12.7%; contralateral +4.7% vs. +7.7%), and in shoulder endurance (-15s vs. -56s). After AI, the cognitive performance showed faster response times and lower error rates for all cognitive tests compared to MI. The salivary cortisol level decreased during the AI-days by 51% in comparison to a 38% increase following the MI-day. Mean broaching time with AI was 7’3’’ compared to 6’20’’ with MI. The mean sound level with the AI-device was 64.3 dBA compared to 68.2 dBA with manual impaction. Conclusions Automated THA component impaction improved the surgeon’s ergonomics which resulted in reduced hormonal stress levels and lower physical and cognitive exhaustion.

The ulnar collateral ligament response to valgus stress, repetitive pitching, and elbow muscle contraction in asymptomatic baseball pitchers

In baseball, repetitive pitching leads to medial elbow injuries, particularly to the ulnar collateral ligament (UCL). To prevent pitchers from UCL injuries, it is important to quantify the response to elbow stress. Repetitive elbow external valgus torque and muscular fatigue induced by repetitive pitching could affect markers of the response, that is, humeroulnar joint gap and UCL morphology. The aims of the study were three-folded: to investigate the effect of (1) exerted handgrip force on the humeroulnar joint gap, (2) repetitive pitching on the humeroulnar joint gap and the UCL morphology, and (3) exerted handgrip force on the humeroulnar joint gap for different levels of elbow valgus stress is different after compared to before repetitive pitching in asymptomatic baseball pitchers. Medial elbow ultrasound images were collected in 15 asymptomatic male baseball pitchers. Three levels of static elbow valgus stress (0N, 50N, 100N) were applied with a TELOS device before and after repetitive pitching and with or without handgrip force. These images were used to assess the humeroulnar joint gap size and UCL length and thickness. After 110 fastball pitches or when 80% self-perceived fatigue on a VAS scale was reached, participants were instructed to stop throwing. Repeated measures ANOVAs were used to statistically test significant differences. Handgrip force did not significantly affect the humeroulnar joint gap. The UCL thickness and length and the humeroulnar joint gap were also not different after compared to before repetitive pitching. While higher levels of applied valgus stress significantly increased the humeroulnar joint gap (P < .001), this effect was not significantly different in the interaction with handgrip force and repetitive pitching. The humeroulnar joint gap changes for different levels of elbow valgus stress. However, adult baseball pitchers did not respond to elbow stress after a single pitching session with or without submaximal handgrip force in the humeroulnar joint gap and UCL morphology.

Prevalence and Associations of Keratoconus Among Children, Adults, and Elderly in the Population-Based Ural Eye Studies.

To estimate prevalence and associations of keratoconus in populations in Russia with an age from childhood to seniority. The study population consisted of the cohorts of 3 population-based studies performed in urban and rural areas within the same geographical region in Bashkortostan/Russia: the Ural Children Eye Study (UCES; age = 6-18 y; n = 4890), the Ural Eye and Medical Study (UEMS; age = >40 y; n = 5314), and the Ural Very Old Study (UVOS; age = >85 y; n = 651). Based on Scheimflug imaging, keratoconus was defined by a keratometric reading of ≥48 diopters (D) in any eye. The mean maximal and minimal corneal refractive power increased from the UCES (43.58 ± 1.50 D and 42.70 ± 1.42 D, respectively) to the UEMS (44.26 ± 1.70 D and 43.61 ± 1.76 D, respectively) and to the UVOS (45.1 ± 1.72 D and 43.98 ± 1.68 D, respectively). Correspondingly, keratoconus prevalence increased from the UCES (42/4890; 0.086%; 95% CI = 0.060, 0.112) to the UEMS (112/5314; 2.11%; 95% CI = 1.72, 2.49) and to the UVOS (42/651; 6.45%; 95% CI = 4.56, 8.34). In the UCES, higher keratoconus prevalence was associated (multivariable analysis) with higher birth order [odds ratio (OR) = 2.34; 95% CI = 1.32, 4.15; P = 0.004], lower birth weight (OR = 0.99; 95% CI = 0.99, 0.99; P < 0.001), and shorter axial length (OR = 0.15; 95% CI = 0.08, 0.30; P < 0.001). In the UEMS, keratoconus prevalence correlated with shorter axial length (OR = 0.15; 95% CI = 0.10, 0.23; P < 0.001), larger corneal volume (OR = 1.17; 95% CI = 1.09, 1.25; P = 0.001), thicker lens (OR = 2.27; 95% CI = 1.06, 5.28; P = 0.04), cortical cataract degree (OR = 1.02; 95% CI = 1.01, 1.04; P = 0.01), and higher stage of age-related macular degeneration (OR = 1.65; 95% CI = 1.09, 2.51; P = 0.02). In the UVOS, keratoconus prevalence correlated with lower educational level (OR = 0.84; 95% CI = 0.71, 0.99; P = 0.04) and lower dynamometric handgrip force (OR = 0.92; 95% CI = 0.88, 0.97; P = 0.003). In this study on multiethnic groups from Russia, keratoconus prevalence increased from the pediatric group (0.09%) to the adult group (2.11%) and seniority group (6.45%), correlated mostly with biometric ocular parameters and was in all age groups statistically independent of most systemic parameters.

Electromyography Indices of Handgrip Force with Swinging Motion

Electromyography (EMG) is a powerful tool for studying muscle activity, but there is limited research on EMG signals in the muscles of the human forearm, which poses challenges for prosthetic hand development. This study utilized the maximum voluntary contraction (MVC) normalization method to analyze the flexor carpi radialis muscle during handgrip and swinging motions. The MVC indices revealed a significant proportion of high-amplitude MVC results. We conducted three statistical analyses to validate the indices. One-way ANOVA showed significant differences in mean values among the seven subjects during the percent MVC test. RMS study demonstrated a linear correlation between muscle contraction and movement. Boxplot analysis revealed variations within the interquartile range and median values across the entire MVC range. To achieve these results, we employed an eighth-order Gaussian function for curve fitting and exponential weighted moving average. The median interquartile range showed high discrepancies, while the differences between MVC increments were minimal, providing reliable indices for swinging motion. This suggests that the fat layer thickness may influence the muscle signal's frequency characteristics. In summary, our study highlights the untapped potential of EMG signals in the forearm muscles for prosthetic hand development. By employing MVC normalization and conducting rigorous statistical analyses, we uncovered significant findings that contribute to advancements in this field. Our insights provide hope and inspiration for researchers and practitioners seeking to enhance prosthetic technology.