Test Device Research Articles

Fatigue-Induced Failure of Polysilicon MEMS: Nonlinear Reduced-Order Modeling and Geometry Optimization of On-Chip Testing Device.

In the case of repeated loadings, the reliability of inertial microelectromechanical systems (MEMS) can be linked to failure processes occurring within the movable structure or at the anchors. In this work, possible debonding mechanisms taking place at the interface between the polycrystalline silicon film constituting the movable part of the device and the silicon dioxide at the anchor points are considered. In dealing with cyclic loadings possibly inducing fatigue failure, a strategy is proposed to optimize the geometry of an on-chip testing device designed to characterize the strength of the aforementioned interface. Dynamic analyses are carried out to assess the deformation mode of the device and maximize the stress field leading to interface debonding. To cope with the computational costs of numerical simulations within the structural optimization framework, a reduced-order modeling procedure for nonlinear systems is discussed, based on the direct parametrization of invariant manifolds (DPIM). The results are reported in terms of maximum stress intensification for varying geometry of the testing device and actuation frequency to demonstrate the accuracy and computational efficiency of the proposed methodology.

A Study on the Volume Expansion of Vanadium-Based Alloy Powders and Compacts During Hydrogen Sorption

Storing hydrogen in solid metal hydrides provides a safe and efficient storage approach. However, the large volume expansion of metal hydrides during hydrogen absorption imposes substantial stresses on the wall of a hydrogen storage tank. In this study, volume expansion behavior of a V-based hydrogen storage alloy, V61Cr24Ti12Ce3, with body-centered-cubic, was investigated using a self-developed in situ expansion testing device. The lattice expansion of the V61Cr24Ti12Ce3 alloy after full hydrogenation was determined to be 37.85% using X-ray diffraction(XRD). The powder bed, composed of alloy powder with an average size of 3.35 mm in diameter, displays a large volume expansion ratio of 131% at the first hydrogen absorption cycle and 40–45% in the following four cycles. The stable compact bed, made of alloy powders, organic silicone gel, and graphite flakes, shows significantly smaller volume expansion ratio, which is 97% at the first cycle and 21% at the second cycle, and stabilizes at 13% in the following cycles. Also, the compact bed shows similar hydrogen absorption capacity, but faster absorption kinetics compared to the powder bed.

Smartphone-Enabled Point-of-Care Testing for Prehospital Stroke Diagnosis

Objectives The objective of this study was to evaluate the feasibility of point-of-care testing (POCT) devices for N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurement in prehospital settings, with the aim of improving the speed and accuracy of stroke diagnosis, thereby facilitating quicker and more effective patient care. Methods Prehospital blood samples were collected from suspected stroke patients, and NT-proBNP levels were measured using a POCT device in ambulances and hospitals. Results from the NT-proBNP POCT and smartphone images were analyzed. Plasma samples underwent Elecsys proBNP II immunoassay after storage at −80ºC. Results A total of 121 suspected stroke patients were included in the study. The correlation between POCT measured by the POCT and immunoassay for NT-proBNP was strong (R = 0.926). Smartphone images also strongly correlated with POCT values at 10 min (R²=0.9716) and 15 min (R²=0.9405). Stability analysis of samples showed consistent NT-proBNP results and a high correlation (R = 0.907) was observed between plasma and whole blood samples for NT-proBNP POCT. Conclusions This study highlights the potential of NT-proBNP POCT devices in ambulances to expedite stroke diagnosis and management within 10 min. Smartphone integration further enhances efficiency, adding advancement in prehospital stroke management.

A new telemedicine-based sleep service using WatchPAT® ONE for patients with suspected OSA: what does the patient experience?

Obstructive Sleep Apnea is a widespread disease but is very underdiagnosed and undertreated. The aim of this study is to assess the effectiveness and patient satisfaction of using the WatchPAT® ONE, a disposable home sleep apnea test device, within a telemedicine-based management pathway. All patients who used the telemedicine services for OSA diagnosis using the WatchPAT® ONE were prospectively enrolled in the study. Patients receive the device at home and download its associated application to learn how to perform the test autonomously at night. Clinicians then review automated results transmitted by the cloud and conduct the follow-up visit via telemedicine, providing diagnostic and therapeutic guidance. The study included 167 patients (78% male; mean age 55 ± 14 years; BMI: 27.5 ± 4.5kg/cm²), with a mean distance of 147.29 ± 172.35km from our hospital. The median time from test request to result delivery was 5 working days. The study cohort showed a median pAHI of 16.7 events/h, a median pODI was 7.9 events/h, and an pRDI of 20.7 events/h. 99% of respondents were satisfied with the remote management. Half of the subjects found both the application installation and the device operation extremely easy, and 60% of them were willing to recommend the use of WatchPAT® ONE. The telemedicine pathway represents an efficient and patient-friendly method for diagnosing OSA. This approach improves diagnostic ease and accessibility while reducing time to diagnosis and societal and healthcare costs. Further large-scale studies are necessary to confirm these results.

Experimental Study on Spectral Response Characteristics and Mechanical State of Coal Based on Artificial Acoustic Signals

With the increase in coal mining depth, the stress and strain state of coal and rock mass affects the formation of dangerous zones of dynamic phenomena. In order to study the relationship between the frequency spectrum characteristics of artificial acoustic signals and the stress state of coal and gas pressure, a test device and system that can generate acoustic signals by mechanical vibration excitation are developed by using the design idea of the unit module. Firstly, the basic mechanical parameters of coal under uniaxial compression are analyzed. On this basis, we use the test device to study the qualitative and quantitative relationships between the relative stress coefficient K value of the coal body and the axial loading stress, whether it contains gas, and the mechanical vibration force. The test results show that when the gas-containing coal and the gas-free coal are subjected to the same external mechanical vibration knocking force to stimulate the artificial acoustic signal test, the relative stress coefficient K value increases first and then decreases with the increase in axial loading stress. The relationship between the relative stress coefficient K and the axial loading stress σ can be expressed in the form of exponential function K=e−Cσ. When the axial loading stress and the external mechanical vibration force are both fixed values, the relative stress coefficient K value of the coal body with gas is smaller than that without gas. When the axial loading stress and gas-bearing pressure of the coal body are both fixed values, the relative stress coefficient K value decreases with the increase in the impact force of the external mechanical vibration. This experimental study can provide a reference for the identification and prediction of dynamic disasters based on artificial acoustic signals.

PROTOTYPE MANUFACTURING OF A NEW DYNAMIC-BASED PRESSURE MEASUREMENT TEST DEVICE FOR MEDICAL AND TEXTILE APPLICATIONS

Customers nowadays demand that their clothes be comfortable and suitable for their health in addition to the aesthetic features of the clothes they wear. Therefore, manufacturers following technological innovations to test their product capability are putting those devices on the market to measure the impact on health. The study describes the design, development, and prototype manufacturing stages of a new pressure measurement test device for measuring the pressure resulting from the interaction of human legs and stretch garments. The device can bend from the knee and move dynamically which has innovative aspects compared to the ones commercially available. After mass production of the device, it might be possible to measure the pressure levels of the garments to the human body, therefore, the effects of the fabrics on blood pressure in addition to body physiology can be evaluated with concrete values.

A Low-Cost Open-Source Uniaxial Tensile System for Soft Tissue Testing

The evaluation of soft tissue biomechanical properties is of paramount importance not only for a comprehensive understanding of human physiology and physiopathology, but also in the research and development of bio-compatible artificial tissues with viscoelastic properties. Contrarily to standard tensile testing devices, a system intended for biomaterials testing should consider low stress and high strain ranges, characteristic of human tissues; moreover, such a system should enable the ex vivo simulation of biological environmental conditions. Commercial solutions address these challenges, although they are expensive for most academic and research institutions. This study presents a low-cost open-source design solution for soft tissue tensile testing, offering an affordable solution, yet without compromising the high quality and precision of the results. The proposed uniaxial tensile system allows for sample testing at room temperature as well as in a temperature-controlled liquid environment. Moreover, custom clamps ensure the fixation of tissue samples without slipping or tearing. System validation is performed using the tensile testing of springs and 3D-printed soft polymeric samples, demonstrating accurate results compared to the available data. The system is suitable for educational, research, and development applications.

Recent advances in bioactive materials: Future perspectives and opportunities in oral cancer biosensing.

Bioactive materials and biosensing technologies are emerging as pivotal tools in the early detection and management of oral cancer, a disease characterized by high morbidity and mortality rates. Recent advancements in nanotechnology have facilitated the development of innovative biosensors that utilize bioactive materials for non-invasive diagnostics, particularly through salivary analysis. These biosensors, including electrochemical, optical, and molecular types, target specific biomarkers such as DNA, RNA, and proteins associated with oral cancer. For instance, metal oxide nanoparticles and gold nanoparticles have shown promise in enhancing the sensitivity and specificity of these diagnostic tools. The integration of these nanomaterials allows for real-time monitoring of biomarker levels in saliva, providing a rapid and accurate means of detecting oral cancer at its nascent stages. Furthermore, the utilization of biosensors can circumvent the limitations of traditional biopsy methods, which are often invasive and time-consuming. By focusing on salivary diagnostics, researchers aim to develop point-of-care testing devices that can be used in various settings, thus improving accessibility to early screening for at-risk populations. This innovative approach not only enhances diagnostic accuracy but also holds potential for personalized treatment strategies by enabling continuous monitoring of disease progression and response to therapy. As research continues to evolve, the combination of bioactive materials with advanced biosensing technologies promises to revolutionize oral cancer diagnostics, ultimately leading to improved patient outcomes through earlier intervention and tailored therapeutic approaches.

Improvement of the control performance of cable AC voltage withstand testers

Abstract The traditional cable AC withstand voltage test device has poor control accuracy and slow protection performance, and the inverter based on power switching devices can be applied to the test device to effectively solve the above problems. However, the LCL-type inverter contains resonance, which tends to cause system destabilization and reduces current quality, affecting the effectiveness of the device for testing. Differential feedback filter capacitor voltage can solve the problem and can save a high-accuracy sensor, but the differential limits its application. This paper proposes to use the negative-band pass filter (NBPF) connected to lag correction (LC) link to equivalent the differential, and it can not only effectively suppress the resonance, but also can significantly suppress high-frequency noise. An experimental platform is built for validation.

The detonation pressure measurement of lead azide based on PDV technology

Abstract In order to measure the detonation pressure of lead azide, a test method and device for the detonation pressure of lead azide was designed in this paper. Based on the PDV technology, the interface particle velocity tests of lead azide were carried out, and the heights of the charge were 1.5 mm, 2.0 mm and 4.0 mm respectively. Then, the interface particle velocity curves of lead azide with different heights were obtained by mediating the original data. Owing to the interface particle velocity variation process corresponding to the pressure distribution in its ZND detonation model, we can obtain the VM peak and CJ point of lead azide from interface particle velocity curve of 4.0 mm charge height. The VM peak and CJ point of lead azide is 1553±30 m/s and 1031 m/s, respectively. Finally, based on impedance matching formula, it can be obtained that the VN pressure is 25.097 GPa and the detonation pressure (CJ pressure) is 15.705 GPa, and the duration of the detonation reaction zone is about 49 ns.

A091: Proprioception and Strength No Longer Correlate with Mediolateral Stability Among Individuals with Functional Ankle Instability

Background/Purpose: Dynamic stability deficit is one of the strongest risk factors for ankle sprains. Proprioception and strength are crucial for maintaining dynamic stability and preventing sprains during sports and daily activities. The mechanisms by which humans maintain anteroposterior (AP) and medial-lateral (ML) stability are different. The correlations of AP and ML dynamic stability with its two factors, namely, proprioception and strength, may explain the recurrent sprains among individuals with functional ankle instability (FAI). The purpose of this project was to investigate the correlations of AP and ML dynamic stability with proprioception and strength within the two populations. Method: This was a cross-sectional study. A total of 80 participants were recruited into FAI (n = 40) or non-FAI (n = 40) groups. Dynamic stability was represented by time to stability (TTS) in the AP and ML directions and was measured by a force plate (AMTI, Inc., Watertown, MA, USA). Ankle muscle strength was tested by a strength testing system (D. & R. Ferstl GmbH, Hemau, Germany). Ankle proprioception was assessed by a proprioception test device (Proprioception device, Sunny, China). Pearson or Spearman correlations were used to determine the correlations of proprioception and strength to dynamic stability within the two groups. Results: Individuals with FAI (ankle plantarflexion, r = -0.409, p = 0.009) and those without FAI (ankle plantarflexion, r = -0.348, p = 0.028; ankle dorsiflexion, r = -0.473, p = 0.002) both demonstrated correlations of strength to TTSAP; Individuals without FAI demonstrated correlations of proprioception (ankle inversion, r = 0.327, p = 0.040; ankle eversion, r = 0.354, p = 0.025) and strength (ankle eversion, r = -0.479, p = 0.002) to TTSML, whereas those with FAI did not. Conclusion/Discussion: The ankle dorsiflexors and plantar flexors could control backward and forward movements of the body to prevent the center of mass from moving out of the posterior and anterior edges of the support base, helping to maintain and restore AP dynamic stability during movements. The disappearance of the relationship among individuals with FAI infers that proprioception and strength deteriorated to a point where they could not provide meaningful functional assistance to the ML dynamic stability. Since most ankle sprains occur in the ML plane (mostly during ankle inversion), this might reasonably explain the increased risk of ankle sprains among individuals with FAI. In conclusion, strength was correlated to AP dynamic stability among individuals with and without FAI; Proprioception and strength were correlated to ML dynamic stability among individuals without FAI, but not among those with FAI.

Examining the effect of verbal feedback vs. real-time software feedback on kinetic and kinematic metrics of the Nordic hamstring exercise

Abstract Purpose A wealth of research exists for the Nordic hamstring exercise and several devices provide real-time feedback on torque profiling. However, none currently offer feedback on technique execution. This study investigated the effect of verbal and software feedback on Nordic exercise kinetic and kinematic metrics. Methods 24 recreational participants completed two sets of three bilateral repetitions on a hamstring testing device. In a crossover design, one set was performed with verbal feedback, while the other set used software-based feedback. Hamstring strain injury risk metrics (peak torque, break-torque angle, and bilateral limb percentage difference) and exercise technique metrics (relative trunk-to-thigh angle and angular velocity of the knee) were recorded for analysis. Results The feedback type significantly affected eccentric knee flexor peak torque, by a mean decrease of 7.1 Nm when performed with software feedback (Cohen’s d = 0.238, p < 0.01). Altering feedback had no significant effect on bilateral limb difference percentage (Cohen’s d = 0.068, p = 0.578) or break-torque angle (Cohen’s d = 0.159, p = 0.115). Software feedback significantly decreased the mean of both the relative-trunk-to-thigh angle at peak torque by 5.7° (Cohen’s d = 0.514, p < 0.01) and the angular velocity of the knee at peak torque by 8.7 deg·s−1. Conclusions An integrated software feedback system significantly improves acute Nordic exercise technique, benefitting individuals initially exhibiting poorer technique the most.

Study on the gas pressure impact test of gun propellant and fluid-solid coupling dynamics simulation

Abstract In order to reveal the mechanical response characteristics of high-energy propellant under high pressure gas impact, the gas pressure impact test and fluid-solid coupling dynamics simulation of propellant are carried out. The propellant gas pressure impact test device is established. The propellant gas pressure impact tests are conducted under different quality of depressant and thickness of iron pressure relief fragments. The gas pressure-time curve, gas pressure rise and decreasing rate are obtained. It is found that longitudinal and transverse cracks occur locally in propellant under high pressure impact. In order to reveal that mechanical property change of propellant under gas impact, the simulation study on fluid-solid coupling dynamics of gas pressure impact test is carried out using ANSYS Workbench multi-field coupling platform. The flow field pressure in the device and the change process of fixed propellant stress and deformation are obtained. The error of monitoring point simulation and test pressure is 5.3%. The maximum peak value of internal flow field pressure reaches 71.6MPa. The average value of maximum stress and maximum deformation of fixed propellant reaches 220MPa and 1.77mm respectively. It reveals the mechanical response characteristics of propellant under high pressure gas impact.

A139: The Difference of Strength, Proprioception, Sensation Between with and without Sensory Deficit Elderly

PURPOSE: Sensory deficits can increase the risk of falls in older adults. At present, the difference of muscle strength, proprioception, tactile sensation between with and without sensory deficits elderly is still unclear. This study aimed to explore the difference of these three factors between the two groups. METHODS: Forty-five older adults (female=22, age=68.31±3.25 years, height=162.71±6.78 cm, body mass=64.32±10.00 kg) with (unable to detect a 5.07 Semmes–Weinstein monofilament on plantar positions) and forty nine older adults without (female=26, age=70.02±4.90 years, height=163.76±7.60 cm, body mass=65.83±10.31 kg) sensory deficits were recruited. No significant differences were observed between the two groups in age, height, and weight using independent-samples t-tests. Muscle strength, proprioception thresholds, and plantar tactile sensations were tests by a IsoMed 2000 strength testing system at an angular velocity of 60˚/s, proprioception test devices, and Semmes-Weinstein monofilaments, respectively. Shapiro–Wilk tests showed the data were normally distributed. Group differences were tested by independent-samples t-tests. RESULTS: Significant between-group differences were detected in proprioception, and tactile sensation, while not in strength: Proprioceptive of ankle plantarflexion (Sensory deficits: 5.06±4.25, Control: 2.99±2.62, η2=0.075, p=0.006) and dorsiflexion (Sensory deficits: 4.36±3.51, Control: 2.57±2.08, η2=0.106, p=0.001). Tactile sensation at the Great toe (Sensory deficits: 4.55±0.79, Control: 4.14±0.38, η2=0.133, p<0.001), 1st metatarsals (Sensory deficits: 4.58±0.78, Control: 4.10±0.38, η2=0.115, p<0.001), 5th metatarsals (Sensory deficits: 4.63±0.64, Control: 4.18±0.35, η2=0.226, p<0.001), Arch (Sensory deficits: 4.79±0.75, Control: 4.24±0.33, η2=0.242, p<0.001), Heel (Sensory deficits: 5.11±0.82, Control: 4.35±0.29, η2=0.310, p<0.001). Muscle strength of ankle plantarflexion (Sensory deficits: 0.35±0.19, Control: 0.38±0.14, d=0.180, p=0.356) and ankle dorsiflexion (Sensory deficits: 0.21±0.07, Control: 0.22±0.06, d=0.093, p=0.640). DISCUSSION: Proprioception and tactile sensitivity are important components of the somatosensory system, and both work in synergy and are interconnected through interneurons and alpha neurons. The connection of proprioception and tactile sensation may line in the sharing receptors (e.g., the rapidly adapting fiber receptors from Pacinian corpuscles), which are typical tactile receptors, make an essential contribution to proprioception. CONCLUSION: Older adults with sensory deficits have poorer proprioception and deficit postural stability than those without sensory deficits.

Whole process analysis on splitting tensile behavior and damage mechanism of 3D/4D/5D steel fiber reinforced concrete using DIC and AE techniques

In recent years, the application of a new type of end hook steel fiber (ESF) in concrete has gradually become a hot spot due to its excellent properties. In order to investigate the influences of ESF content, end hook number and aspect ratio on the splitting tensile properties and damage characteristics of end hook steel fiber reinforced concrete (ESFRC), a set of splitting tensile test device was improved in this study to measure the complete splitting tensile load-deformation curves of ESFRC. The influence of 3D/4D/5D steel fiber on the crack development and damage evolution of ESFRC specimens under splitting tensile load was analyzed by digital image correlation (DIC) and acoustic emission (AE) techniques. The results showed that the splitting tensile strength and crack resistance of ESFRC were gradually improved by increasing the content and end hook number of ESF. The splitting tensile load-deformation curves of the specimens with single-ended hook (3D) steel fibers could be divided into five stages, and the curves appeared two or even more fiber strengthening stages with the increase of end hook number, which mainly depends on the end hook form of steel fiber. Concrete cracking, ESF debonding and end hook straightening were the main reasons for the development of AE events and ringing counting. As the ESF content or the number of end hooks increased, the proportion of shear cracks gradually increased from 59.82% to 71.34%, and the AE energy of cracking damage also increased accordingly. The strain band at the failure interface first appeared in the middle of the specimen and gradually extended to the loading end, and the failure mode gradually changed from a single crack to a main crack, accompanied by multiple scattered cracks. Finally, a prediction model for the splitting tensile strength of ESFRC was proposed and verified based on the fiber pull-out bonding theory.

A072: Study on Respiratory Muscle Training Impact on Static Lung Function in Amateur Runners

Objective: Respiratory muscle training (RMT) is a specialized training method targeting the strength and endurance of respiratory muscles, aimed at enhancing lung function and the adaptability of the respiratory system. Common training techniques in RMT include deep breathing, inspiratory muscle training, expiratory muscle training, and diaphragm training. It is generally applicable to athletes, individuals with lung function impairments, the elderly, and those requiring high-intensity respiratory efforts. This study aimed to investigate the effects of an 8-week RMT on static lung function in amateur runners, comparing the performance between the training and control groups to determine the effectiveness of RMT. Methods: This study recruited 40 amateur runners, randomly assigning them to either the training or control group, with 20 individuals in each. Both groups continued their regular running exercises according, but the training group additionally underwent an 8-week RMT, with three 30-minute sessions per week. The control group maintained their routine without any pulmonary training. Pre- and post-training, static lung function parameters including VC, VE, BF, FVC, FEV1, and MVV were measured using a static lung testing device, followed by comparative analysis. Results: The findings showed that after the 8-week RMT, significant improvements (P < 0.05) were observed in the pulmonary function indicators of the training group, while the control group didn't exhibit as notable improvements. Specifically, the training group experienced a 7.1% increase in VC (Vital Capacity), a 6.2% increase in VE (Minute Ventilation), a 4.5% reduction in BF (Breathing Frequency), a 9.4% increase in FVC (Forced Vital Capacity), a 10.2% increase in FEV1 (Forced Expiratory Volume in 1 second), and an 8.6% increase in MVV (Maximum Voluntary Ventilation). Conclusion: In conclusion, on top of regular running exercises, RMT significantly improved static lung function in amateur runners. These results indicate that RMT is an effective method for pulmonary function training, enhancing lung function levels in amateur runners, which indirectly elevates their physiological levels, thereby improving running capability.

Research on Apples' Mechanical‐Structural Damage Behavior During Dropping Collision With High‐Speed Observation

ABSTRACTApples have been constantly damaged in collecting, transporting, and processing, leading research focus on apples' mechanical‐structural damage behavior. To research apples' mechanical‐structural damage behavior during collision, a dropping collision damage testing device was self‐established, with PLC control, data acquisition‐processing, in situ high‐speed observation. The effect of impact material, drop height, impact orientation on apple deformation and bruise area was investigated with self‐established device, considering three typical kinds of apples. The results indicated that apple dropping collision can be divided into two stages: dropping down contact deformation stage and recovering contact deformation stage. Three kinds of apples demonstrate the largest deformation and bruise area when the impact material is steel and acrylic plate. The deformation is similar when apples collide with soil and foam, apples have no bruise area when the impact material is foam. The correlation between apple deformation, bruising area, and drop height was established, reflecting the relationship between drop height and apples' mechanical‐structural damage behavior. Yellow Marshal apple deformation is the largest compared to other two kinds of apples under the same collision condition. Red Fuji apple bruise area is the largest compared to other two kinds of apples. The largest bruise area of Yellow Marshal apple and Guoguang apple are in apple transverse, and Red Fuji apple is in apple top. The study can provide basic theoretical and practical guidance for apples postharvest work.

Automation of a Tribotechnical Test Device for Friction Pairs

Automation of a Tribotechnical Test Device for Friction Pairs

Validation of the Affordable, Portable International Visionkeys System for Visual Acuity and Stereopsis.

A new, portable computerized distance vision testing (screen plus remote) system called VisionKeys has been developed by the missions equipment developer EyeMobil so we validated it compared to conventional research testing devices. Using a standardized protocol of surround HOTV optotype presentation, the VisionKeys was compared to M&S for patched monocular distance visual acuity. A different VisionKeys function with anaglyph spectacle distance stereopsis was compared to near stereo on Titmus circles with Polaroid goggles and PDI Check on an autostereoscopic screen. Raw scores were converted to logarithm and compared with non-parametric and Bland Altman tests. We recruited 145 ethnically diverse patients with range of acuity -0.4 to 2.6 (NLP) logMAR from a pediatric eye and adult strabismus practice showing median logMAR acuity of 0.0 with VisionKeys significantly finer resolution than 0.1 for M&S (Mann-Whitney z=2.6, p=0.01, n=290). VisionKeys acuity correlated very well with M&S and children under age 7 scored coarser than teens and young adults. Median distance log arc seconds stereo on VisionKeys (2.00) differed from near Titmus circles (1.78) and PDI Check (1.89, Kruskal-Wallis X2(2)=9.8, p=0.007) however they all correlated well by Bland Altman. The new, portable VisionKeys system gives valid distance visual acuity with slightly finer estimate compared to M&S and the distance stereo compared well with near Titmus and PDI Check. As such, it should be valuable for testing children and adults in remote locations.

Countermovement Jump and Isometric Strength Test-Retest Reliability in English Premier League Academy Football Players.

To examine the test-retest reliability of countermovement jump (CMJ) and isometric strength testing measures in elite-level under-18 and under-23 academy football players. A total of 36 players performed 3 maximal CMJs and isometric abductor (IABS), adductor (IADS), and posterior chain (IPCS) strength tests on 2 separate test days using dual force plates (CMJ and IPCS) and a portable strength testing device (IABS and IADS). Relative (intraclass correlation coefficient) and absolute (coefficient of variation, standard error of the measurement, and minimal detectable change [MDC%]) reliabilities for 34 CMJ, 10 IABS, 10 IADS, and 11 IPCS measures were analyzed using between-sessionsbest, mean, and within-session methods. For all methods, relative reliability was good to excellent for all CMJ and all IADS measures and poor to good for all IABS and IPCS measures. Absolute reliability was good (ie,coefficient of variation < 10%) for 27 (best) and 28 (mean) CMJ variables and for 6 (IABS and IADS) and 2 (IPCS) isometric measures. Commonly used CMJ measures (jump height, eccentric duration, and flight-time:contraction-time ratio) had good to excellent relative reliability and an MDC% range of 14.6% to 23.7%. Likewise, commonly used isometric peak force measures for IABS, IADS, and IPCS had good to excellent relative reliability and an MDC% range of 22.2% to 26.4%. Commonly used CMJ and isometric strength measures had good test-retest reliability but might be limited by their MDC%. Rate-of-force-development measures (for all isometric tests) and impulse measures (IPCS) are limited by poor relative and absolute reliability and high MDC%. MDC% statistics should be considered in the context of typical responsiveness.