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Obtaining large biomechanical datasets for machine learning is an ongoing challenge. Physics-based simulations offer one approach for generating large datasets, but many simulation methods, such as computed muscle control (CMC), are computationally costly. In contrast, interpolation methods, such as inverse distance weighting (IDW), are computationally fast. We examined whether IDW is a low-cost and accurate approach for interpolating muscle activations from CMC.IDW was evaluated using lateral pinch simulations in OpenSim. Simulated pinch data were organized into grids of varying sparsity (high, medium, and low density), where each grid point represented the muscle activations associated with a unique combination of mass and height of a young adult. For each grid, muscle activations were calculated via CMC and IDW for 108 random mass-height pairs that were not coincident with simulation grid vertices. We evaluated the interpolation errors from IDW for each grid, as well as the sensitivity of lateral pinch force to these errors. The root mean square error (RMSE) associated with interpolated muscle activations decreased with increasing grid density and never exceeded 4%. While CMC received a target thumb-tip force of 40 N, errors from the interpolated muscle activations never impacted the simulated force magnitude by more than 0.1 N. Furthermore, the computation time for CMC simulations averaged 4.22 core-minutes, while IDW averaged 0.95 core-seconds per mass-height pair.These results indicate IDW is a practical approach for rapidly estimating muscle activations from sparse CMC datasets. Future works could adapt our IDW approach to evaluate other tasks, biomechanical features, and/or populations.

Background No previous studies have investigated the test–retest reliability of tip, key, and palmar pinch force sense in healthy adults. The present study explores the test-retest reliability of tip, key, and palmar pinch force sense for different force levels in healthy adults during an ipsilateral force reproduction task. Methods Fifty-six healthy subjects were instructed to produce varying levels of reference forces (10, 30, and 50% maximal voluntary isometric contraction (MVIC)) using three types of pinches (tip pinch, palmar pinch, and key pinch) and to reproduce these forces using the same hand. The subjects were tested twice by the same experienced testers, 1 week apart. Results Based on the high values of the intraclass correlation coefficient (ICC), the tip pinch (0.783–0.895) and palmar pinch (0.752–0.903) force sense tests demonstrated good reliability for all the variables. The ICCs for the key pinch (0.712–0.881) indicated fair to good relative test-retest reliability. Conclusion 1) This study demonstrates that high test-retest reliability of tip, key, and palmar pinch force sense in healthy adults can be achieved using standardized positioning and the proposed approach. 2) According to the reliability measurements, 30 and 50% maximal voluntary isometric contraction (MVIC) are the most reliable pinch force sense levels.

Musculoskeletal models and computer simulations enable non-invasive study of muscle function and contact forces. Hand models are useful for understanding the complexities of hand strength, precision movement, and the dexterity required during daily activities. Yet, generic models fail to accurately represent the entire scope of the population, while subject-specific models are labor-intensive to create. The objective of this study was to assess the efficacy of scaled generic models to represent the broad spectrum of strength profiles across the lifespan. We examined one hundred lateral pinch simulations using a generic model of the wrist and thumb anthropometrically scaled to represent the full range of heights reported for four ages across childhood, puberty, older adolescence, and adulthood. We evaluated maximum lateral pinch force produced, muscle control strategies, and the effect of linearly scaling the maximum isometric force. Our simulations demonstrated three main concepts. First, anthropometric scaling could capture age-dependent differences in pinch strength. Second, a generic muscle control strategy is not representative of all populations. Lastly, simulations do not employ optimal fiber length to complete a lateral pinch task. These results demonstrate the potential of anthropometrically-scaled models to study hand strength across the lifespan, while also highlighting that muscle control strategies may adapt as we age. The results also provide insight to the force–length relationship of thumb muscles during lateral pinch. We conclude that anthropometric scaling can accurately represent age characteristics of the population, but subject-specific models are still necessary to represent individuals.

The effects of Kinesio taping (KT) in carpal tunnel syndrome are controversial. This study aimed to examine whether KT has any effect on the skin, subcutaneous tissue, and median nerve measurements and to compare the effects of two different KT applications. This is a prospective, double-blinded, randomized trial. This study was prospectively registered on the clinicaltrials.gov (NCT05475197). A total of 34 wrists (21 patients) who were clinically and electrophysiologically diagnosed with mild/moderate carpal tunnel syndrome were randomly divided into two KT intervention groups (group 1: neural technique and area correction technique and group 2: area correction technique). At baseline and immediately after the removal of KT (48 hours), pain was assessed with visual analog scale, hand grip strength with a hand-held dynamometer, and pinch strength using a pinch meter. Likewise, using ultrasound, skin and subcutaneous tissue thicknesses, median nerve cross-sectional area and flattening ratio, as well as median nerve depth were measured at the carpal tunnel inlet and outlet levels. While there was significant improvement in the pain scores (compared to the baseline) immediately after the KT in both groups (group 1: p = 0.03, ηp2 = 0.44; group 2: p < 0.001, ηp2 = 0.71), there was no difference in between (p = 0.07, ηp2 = 0.10). Grip strength significantly increased only in group 2 (p = 0.01, ηp2 = 0.35). None of the sonographic measurements displayed significant difference either within or between groups at baseline and after KT (all p > 0.05). While pain scores improved after KT, they were not coupled with any morphologic changes assessed by ultrasound. •Kinesio taping (KT) has physiological effects on musculoskeletal system.•The effects of KT in carpal tunnel syndrome are controversial.•Ultrasound is an easily accessible method for imaging carpal tunnel.•While pain scores improved after KT, median nerve morphology did not change.

FAETON-I is the highest direct-charged voltage plasma focus (PF), at 100 kV, 1 MA peak current. F-I produces consistent D-D neutrons/shot, over 3 MeV X-rays and keV deuterons, demonstrating unique combined neutron-gamma environment. Its peak neutron yield was recorded at neutrons/shot at 12 Torr deuterium. The best peak dynamics-induced pinch voltage was measured at 194 kV. A major difficulty anticipated for PF operation at high-voltage and high-current is the likelihood of re-strikes which divert current away from the compressing plasma. F-I shows excellent current sheath dynamics and above-scaling D-D neutron yield, despite severe re-strikes. This study, correlating current and voltage time profiles with radial trajectories, reveals that the dynamics-induced voltage peak of kV, produces deuteron beam first, then the re-strikes, which do not affect the target pinch plasma in geometry and areal density. Thus, this first neutron pulse is hardly affected by re-strikes, and the very high-voltage results in above-scaling out-performance, despite degradation of the second neutron pulse from pinch instabilities. Moreover, upgrading to D-T operation, it is expected that the first pulse at keV (peak D-T cross section) ion energy, will completely dominate the second pulse with micro-beams at MeV (low D-T cross section).

Thumb tendon transfer surgical procedures in patients with cervical spinal injury engage the paralyzed flexor pollicis longus (FPL) muscle to enable lateral pinch grasp. However, functional outcomes are mixed, in part because the FPL cannot consistently produce force at the thumb-tip to promote a stable grasp. We used simulation to investigate whether a multiple recipient muscle tendon transfer, targeting sets of paralyzed muscles driven by a single donor muscle, could outperform a single recipient muscle tendon transfer with the FPL alone and restore lateral pinch. We formed 36 groups of 2 muscles, 84 groups of 3 muscles, and 126 groups of 4 muscles. We used nonlinear optimization and in-situ measurements of muscle endpoint forces in 3 lateral pinch postures. In each posture, we primarily compared the orientation of the endpoint force of each muscle group to that produced by the FPL alone. We found that 116 of the 246 muscle groups produced endpoint forces that were more closely aligned with the direction perpendicular to the thumb (palmar direction) than the FPL was for wide and narrow lateral pinch postures and a posture in between. When averaged across the three postures, muscle force ranged from 0.1 to 90.4 N, muscle group endpoint force magnitudes ranged from 2.5 to 14.9 N, and muscle group endpoint force directions ranged from 17° to 49° relative to the palmar direction. The muscle group endpoint force directional range represented a mean improvement of 8° to 40° over the FPL’s mean endpoint force direction across all three postures. Our findings highlight the possibility of using multiple recipient muscle tendon transfers to restore grasp following cervical spinal cord injury.

This study addresses the need for highly sensitive tools to evaluate hand strength, particularly grasp and pinch strength, which are vital for diagnosing and rehabilitating conditions affecting hand function. Current devices like the Jamar dynamometer and Martin Vigorimeter, although reliable, fail to measure extremely low force or pressure values required for individuals with severe hand impairments. This research introduces a novel device, a modified Martin Vigorimeter, utilizing an ultra-soft latex chamber and differential pressure measurement to detect minute pressure changes, thus significantly enhancing sensitivity. The device offers a cost-effective solution, making advanced hand strength evaluation more accessible for clinical and research applications. Future research should validate its accuracy across diverse populations and settings, exploring its broader implications for hand rehabilitation and occupational health.

Acceleration of high energy ions was observed in z-pinches and dense plasma foci as early as the 1950s. Even though many theories have been suggested, the ion acceleration mechanism remains a source of controversy. Recently, the experiments on the GIT-12 generator demonstrated acceleration of ions up to 30 MeV from a deuterium gas-puff z-pinch. High deuteron energies enable us to obtain unique information about spatial, spectral and temporal properties of accelerated ions. In particular, the off-axis ion emission from concentric circles of a ∼1 cm diameter and the radial lines in an ion beam profile are germane for the discussion of acceleration mechanisms. The acceleration of 30 MeV deuterons can be explained by the fast increase of an impedance with a sub-nanosecond e-folding time. The high (>10 ) impedance is attributed to a space-charge limited flow after the effective ejection of plasmas from m = 0 constrictions. Detailed knowledge of the ion acceleration mechanism is used with a neutron-producing catcher to increase neutron yields above 1013 at a current of 2.7 MA.

Sarcopenic obesity (SO) represents a complex nutritional state associated with adverse health outcomes, especially in older adults. While grip strength has been extensively studied in relation to functional status, the role of pinch strength remains underexplored. This study aimed to investigate the associations between pinch strength parameters and different body composition phenotypes and to explore its potential role in the relationship between SO and functional status, including physical performance, cognitive function, and frailty. This cross-sectional study included 954 community-dwelling older adults, categorized into four groups: healthy controls (HC), obesity only, sarcopenia only, and SO. We assessed body composition via bioelectrical impedance analysis, muscle strength (grip and pinch dynamometry), physical performance, cognitive function, and frailty. Sex-stratified correlation networks and mediation analyses were performed to elucidate relationships between body composition, muscle strength parameters, and functional status. The SO and sarcopenia groups demonstrated significantly reduced pinch strength compared to the HC and obesity groups (e.g., women: 2.2 ± 0.8 kg in SO vs. 3.5 ± 1.1 kg in HC, P < 0.001), with higher pinch/grip ratios (0.20–0.25 vs. 0.15–0.20, P < 0.05). Notably, the SO groups exhibited significantly greater pinch strength variability (Coefficient of Variation) in both men and women (CV for women: 18.5% in SO vs. 12.1% in HC, P < 0.001), suggesting impaired neuromuscular control of fine motor function. The SO group exhibited the poorest functional performance. Mediation analyses suggested that pinch strength was a significant intermediary in the association between SO and cognitive impairment, and partially in the association with frailty in women ((indirect effect log-OR = −0.07, 95% CI [−0.12, −0.03] in women). Pinch strength and its variability are strongly associated with SO and represent important markers of functional status. This finding identifies pinch strength as a potential clinically accessible biomarker for the early detection of functional decline in older adults with this double burden of malnutrition. The differential preservation of pinch versus grip strength and sex-specific potential pathways highlights the need for comprehensive hand function assessment in the nutritional and clinical evaluation of SO. •Sarcopenic obesity is associated with lower pinch strength and higher pinch/grip ratio.•Pinch strength variability is significantly increased in sarcopenic obesity.•Increased pinch strength variability suggests impaired neuromuscular control.•Pinch strength is a statistical mediator of the SO-cognitive impairment association.•Pinch strength is a potential clinical biomarker for functional decline in SO. [Display omitted]

This study aimed to examine the roles that the index finger and thumb play in tip pinch force sense at different force levels in both males and females. Forty-two healthy participants (21 females and 21 males) underwent an ipsilateral force reproduction assessment employing three different fingers (thumb, index finger, and tip pinch) at 3 distinct forces of 5, 10, and 20% of maximal voluntary isometric contraction (MVIC). The findings revealed no significant between incorrect (absolute error) or consistent (variable error) force sense errors among the pinch, thumb, and index finger. The results further revealed significant correlations between the pinch and index finger of a constant error at 5%, 10%, and 20% MVIC (r = 0.460, P  = 0.036; r = 0.735, P  < 0.001; r = 0.839, P  < 0.001, respectively) in males. Significant correlations were also observed in females between the pinch and thumb of a constant error at 5%, 10%, and 20% MVIC (r = 0.436, P  = 0.048; r = 0.464, P  = 0.034; r = 0.565, P  = 0.008, respectively). These findings demonstrated that when the thumb and index finger are employed simultaneously (tip pinch), females rely more on the thumb, while males rely more on the index finger for accurate pinching forces. A higher force level led to a higher contribution of the individual finger (thumb for females and index finger for males) to the pinch force sense.