Explore the vast range of titles available.

An in-depth, sometimes whimsical look into the physics behind effective fighting techniques and examining the core principles that make them work: momentum, energy, center of mass, levers and wedges. It also exposes the illusion of safety provided by gloves and helmets, aiding the reader in reducing traumatic brain injury in marital arts, boxing, and other contact sports.--Publisher.

Understanding hand and wrist forces during activities of daily living (ADLs) are pertinent when modeling prosthetics/orthotics, preventing workplace-related injuries, and understanding movement patterns that make athletes, dancers, and musicians elite. The small size of the wrist, fingers, and numerous joints creates obstacles in accurately measuring these forces. In this study, 14 FlexiForce sensors were sewn into a glove in an attempt to capture forces applied by the fingers. Participants in this study wore the glove and performed grasp and key turn activities. The maximal forces produced in the study were 9 N at the distal middle finger phalanx and 24 N at the distal thumb phalanx, respectively, for the grasp and key turn activities. Results from this study will help in determining the minimal forces of the hand during ADLs so that appropriate actuators may be placed at the appropriate joints in exoskeletons, orthotics, and prosthetics.

The purpose of this study was to compare the in-water force of young competitive swimmers using tethered swimming and differential pressure sensors. Thirty-one swimmers (16 girls and 15 boys) were randomly assigned to perform two in-water tests. Swimmers completed two maximum bouts of 25 m front crawl with a differential pressure system and a 30 s maximum bout with an attached load cell (tethered-swimming). The peak force (FPEAK, in N) of dominant and non-dominant upper limbs was retrieved for further analysis. Comparison between methods revealed significant differences in all force variables (p ≤ 0.05) and the biases (mean differences) were large in girls (FPEAK dominant, 45.89 N; FPEAK non-dominant, 43.79 N) and boys (FPEAK dominant, 67.26 N; FPEAK non-dominant, 61.78 N). Despite that, simple linear regression models between the two methods showed significant relationships with a moderate effect in all variables for girls, whereas in boys a high and moderate effect was verified for FPEAK of dominant and non-dominant limbs (respectively). It seems that using pressure sensors and tethered swimming leads to different FPEAK values in young competitive, where correction factors are needed to compare data between both methods.

Force myography (FMG) signals can read volumetric changes of muscle movements, while a human participant interacts with the environment. For collaborative activities, FMG signals could potentially provide a viable solution to controlling manipulators. In this paper, a novel method to interact with a two-degree-of-freedom (DoF) system consisting of two perpendicular linear stages using FMG is investigated. The method consists in estimating exerted hand forces in dynamic arm motions of a participant using FMG signals to provide velocity commands to the biaxial stage during interactions. Five different arm motion patterns with increasing complexities, i.e., “x-direction”, “y-direction”, “diagonal”, “square”, and “diamond”, were considered as human intentions to manipulate the stage within its planar workspace. FMG-based force estimation was implemented and evaluated with a support vector regressor (SVR) and a kernel ridge regressor (KRR). Real-time assessments, where 10 healthy participants were asked to interact with the biaxial stage by exerted hand forces in the five intended arm motions mentioned above, were conducted. Both the SVR and the KRR obtained higher estimation accuracies of 90–94% during interactions with simple arm motions (x-direction and y-direction), while for complex arm motions (diagonal, square, and diamond) the notable accuracies of 82–89% supported the viability of the FMG-based interactive control.

Hand strength data are needed to understand and predict hand postures and finger loads while placing the hand on an object or surface. This study aims to analyze the effect of hand posture and surface orientation on hand force while pressing a flat surface. Twelve participants, 6 females and 6 males ages 19–25, performed three exertions (100%, 30% and 10% MVC- Maximum Voluntary Contraction) perpendicular to a plate in 4 angles (−45°, 0°, 45° and 90° with respect to the horizontal plane) at elbow height. Exertions involved pushing in two postures: (1) whole hand and (2) constrained to only using the fingertips. Inter-digit joint angles were recorded to map hand and finger motions and estimate joint moments for each condition. Participants exerted twice the force when pushing with whole hand vs. fingertips. 72–75% of the total force was exerted over the base of the palm, while only 11–13% with the thumb for exertions at 90°, 45° or 0° plate angles. Males maximum force for pushing at 0°, 45° and 90° plates averaged 49% higher than females for the whole hand and 62% for the fingertips (p < 0.01). There was no significant sex difference (p > 0.05) for the −45° plate. Thumb joint loads were generally higher than the other individual fingers (p < 0.05) in all % MVC and accounted for 12% of total force during whole hand exertions. On average, joint moments were 30% higher during fingertip conditions vs. whole hand. Thumb and finger joint moment magnitudes when pushing the plate at 100% MVC indicated that Metacarpophalangeal (MCP) joint moments were higher (p < 0.05) than Distal Interphalangeal joints (DIP) and Proximal Interphalangeal joints (PIP) under whole hand and fingertips conditions.

Measuring finger forces during activities of daily living and how these forces change for individuals with pathologies such as arthritis is valuable to our understanding of hand function. The purpose of this study was to determine the forces of individual fingers during the performance of daily activities in healthy participants and determine the envelope of these applied forces. This is a cross-sectional study investigating twenty-five healthy participants (12 female: 22-65 years old and 13 male: 20-53 years old) and participants with osteoarthritis (12 female: 52-79 years old and 9 male: 64-79 years old) examined at one time point. The force sensors were calibrated for each individual using a load cell to provide force output in Newtons. Each participant performed 19 activities of daily living two times. Force was plotted over time for each task, and the maximum force in each finger during that task was evaluated. The range of applied forces was 1.4 ± 0.6 N to 34.8 ± 1.6 N for healthy participants and 2.3 ± 1.0 N to 30.7 ± 3.7 N for those with osteoarthritis. Sensors allowed for real-time monitoring of finger forces during tasks of daily life. This provides the opportunity to isolate hand grips based on finger recruitment and provide information about the magnitude of forces during the activity. Measurement of individual finger forces can provide more accurate biomechanical models of the hand and determine the effect of disease on hand functions. •Joint protection programs are not evidence based and poorly adhered to.the envelope of applied forces applied by the fingers during 19 activities of daily living was measured.•Study examines reduction in hand forces that these programs using finger sensors In healthy individuals, this envelope of applied forces was 1.4 ± 0.6 N to 34.8 ± 1.6 N.•This envelope was similar in participants with hand arthritis: 2.3 ± 1.0 N to 30.7 ± 3.7 N.

Objective This paper aimed to quantify exposure-response relationships between the American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV) for hand-activity level (HAL) and incidence of carpal tunnel syndrome (CTS). Methods Manufacturing and service workers previously studied by six research institutions had their data combined and re-analyzed. CTS cases were defined by symptoms and abnormal nerve conduction. Hazard ratios (HR) were calculated using proportional hazards regression after adjusting for age, gender, body mass index, and CTS predisposing conditions. Results The longitudinal study comprised 2751 incident-eligible workers, followed prospectively for up to 6.4 years and contributing 6243 person-years of data. Associations were found between CTS and TLV for HAL both as a continuous variable [HR 1.32 per unit, 95% confidence interval (95% CI) 1.11-1.57] and when categorized using the ACGIH action limit (AL) and TLV. Those between the AL and TLV and above the TLV had HR of 1.7 (95% CI 1.2-2.5) and 1.5 (95% CI 1.0-2.1), respectively. As independent variables (in the same adjusted model) the HR for peak force (PF) and HAL were 1.14 per unit (95% CI 1.05-1.25), and 1.04 per unit (95% CI 0.93-1.15), respectively. Conclusion Those with exposures above the AL were at increased risk of CTS, but there was no further increase in risk for workers above the TLV. This suggests that the current AL may not be sufficiently protective of workers. Combinations of PF and HAL are useful for predicting risk of CTS.

•The intrarater reliability and ecological validity of a novel and true-to-form jar instrument was tested in women with hand osteoarthritis•Intrarater reliability of the jar instrument was good to excellent and participants reported the experience of using it to be highly representative of jar-opening at home.•The jar tool may be used in future study of the required hand kinetics for successful opening of a sealed jar and for testing of joint protection strategies in this population. Clinical Measurement Jar opening is a task that relies heavily on the ability to generate adequate hand forces and is often reported in the literature as being difficult for women with hand arthritis. Many have studied relationships between diminished grip/pinch strength and occupational performance but few have investigated how much hand force is necessary to successfully engage in manual tasks. Those who studied this have relied on approaches and tools which lack ecology. Additionally, few have instrumented daily objects to understand if joint protection techniques do, in fact, reduce the hand force generation when performing manual tasks. The objectives of this study were to one) determine the within session repeatability of a device used to quantify these forces and two) probe into the ecological validity of a novel device to be used in the future study of women with hand osteoarthritis to measure hand force requirements and study the impact of joint protection interventions on hand force profiles. A plastic jar was instrumented with a torque limiter, 6-axis load cell, and six force sensing resistors so as to capture the grip and compressive hand forces which act on a jar lid when opening a sealed jar. To assess intra-rater reliability of the tool and its testing procedures, 31 adult women with hand osteoarthritis were asked untwist the jar's lid so as to break its seal with each hand twice while stabilizing the base with the opposing hand. The agreement between trials of peak forces and torques from each hand was assessed through statistical approaches including Intraclass Correlation Coefficient, Standard Error of the Measurement, and Minimal Detectable Change. The jar's ecological validity was then assessed via survey. This instrument and methods yielded good to excellent repeatability across all force outputs. The majority of our subjects (87%) reported the jar to be similar to those used at home, 87% reported to use a similar jar 2-3 times/month or greater, and rated the importance of opening such a jar as being, on average, 8.7/10. The jar instrument appears to have high reliability and ecologic validity. It has the potential to reveal hand force requirements for a population known to have difficulties opening jars and understanding these force thresholds could help to inform therapy goal-setting. Beyond this, it has the potential to support the study of the hand forces used across various joint protection approaches so as to inform best “jar-opening” practices. This tool was designed to represent the qualities of a standard, large sealed jar while still housing sophisticated kinetic measurement capacities. Our findings support that we have presented a tool which can be used in future study within this population to better understand the hand kinetics associated with the highly problematic task of jar-opening and joint protection strategies intended to reduce hand loads.

The different characteristics of the four swimming strokes affect the interplay between the four limbs, acting as a constraint to the force produced by each hand and foot. The purpose of this study was to analyze the symmetry of force production with a varying number of limbs in action and see its effect on velocity. Fifteen male swimmers performed four all-out bouts of 25-m swims in the four strokes in full-body stroke and segmental actions. A differential pressure system was used to measure the hands/feet propulsive force and a mechanical velocity meter was used to measure swimming velocity. Symmetry index was calculated based on the force values. All strokes and conditions presented contralateral limb asymmetries (ranging from 6.73% to 28% for the peak force and from 9.3% to 35.7% for the mean force). Backstroke was the most asymmetric stroke, followed-up by butterfly, front crawl, and breaststroke. Kicking conditions elicited the higher asymmetries compared with arm-pull conditions. No significant associations were found between asymmetries and velocity. The absence of such association suggests that, to a certain and unknown extent, swimming may benefit from contralateral limb asymmetry.