Measurement Of Maximum Force Research Articles

Design and Fabrication of Test Rig for Static Pushing and Pulling Experiments

Muscular strength data associated with pushing and pulling forces are crucial for ergonomists to design tasks and equipment in manual materials handling. Usually, ergonomists measure pushing and pulling forces using a force gauge. Subjects participating in the pushing and pulling experiments need to grip and hold the force gauge. Additional weight from the force gauge can affect the muscular strength of the subjects, which impacts the validity and reliability of the pushing and pulling data. However, research on the design and fabrication of test rigs for facilitating pushing and pulling experiments seems to be scarce. This study aimed to design and fabricate a test rig to facilitate ergonomists and subjects in performing symmetric two-handed static pushing and pulling experiments. To develop the test rig, the researchers performed a maximum force measurement, a computer-aided design model, materials selection, a finite element analysis, a functionality test, and a reliability test. Seven subjects with a body mass of more than 120 kg participated in the validation of the developed test rig. Key findings of this study showed that the test rig could sustain the pushing and pulling forces up to 900 N, representing almost double the muscular strength of the subjects. This study concluded that the developed test rig was sturdy and helpful for facilitating ergonomists in quantifying the magnitude of pushing and pulling forces.

Cable pull – an alternative method for the isometric maximum force measurement

Cable pull – an alternative method for the isometric maximum force measurement

DROP IMPACT ONTO A CANTILEVER BEAM: BEHAVIOR OF THE LAMELLA AND FORCE MEASUREMENT

In this work, the process of drop impact onto an elastic surface (a cantilever beam) was studied. Different from previous studies which typically focused on the behavior of the elastic surface (e.g., deformation and oscillation), the focus of this work is to examine the behavior of the resulting lamella during the impact. It was found that the maximum contact diameter of the lamella in an elastic impact compared to impact onto a ridged surface is significantly smaller (e.g., 17% for impact at 2 m/s). The results were explained through an analysis of impact energy and the stored elastic energy in the beam. In this work, we also demonstrated how to use a cantilever beam to measure maximum drop impact force. It was found that a large natural frequency of the cantilever beam is needed for the maximum force measurement to produce acceptable values.

Correlation of Descriptive Analysis and Instrumental Puncture Testing of Watermelon Cultivars.

The textural properties of 5 seedless watermelon cultivars were assessed by descriptive analysis and the standard puncture test using a hollow probe with increased shearing properties. The use of descriptive analysis methodology was an effective means of quantifying watermelon sensory texture profiles for characterizing specific cultivars' characteristics. Of the 10 cultivars screened, 71% of the variation in the sensory attributes was measured using the 1st 2 principal components. Pairwise correlation of the hollow puncture probe and sensory parameters determined that initial slope, maximum force, and work after maximum force measurements all correlated well to the sensory attributes crisp and firm. These findings confirm that maximum force correlates well with not only firmness in watermelon, but crispness as well. The initial slope parameter also captures the sensory crispness of watermelon, but is not as practical to measure in the field as maximum force. The work after maximum force parameter is thought to reflect cellular arrangement and membrane integrity that in turn impact sensory firmness and crispness. Watermelon cultivar types were correctly predicted by puncture test measurements in heart tissue 87% of the time, although descriptive analysis was correct 54% of the time.

The effect of scaling physiological cross-sectional area on musculoskeletal model predictions

Personalisation of model parameters is likely to improve biomechanical model predictions and could allow models to be used for subject- or patient-specific applications. This study evaluates the effect of personalising physiological cross-sectional areas (PCSA) in a large-scale musculoskeletal model of the upper extremity. Muscle volumes obtained from MRI were used to scale PCSAs of five subjects, for whom the maximum forces they could exert in six different directions on a handle held by the hand were also recorded. The effect of PCSA scaling was evaluated by calculating the lowest maximum muscle stress (σmax, a constant for human skeletal muscle) required by the model to reproduce these forces. When the original cadaver-based PCSA-values were used, strongly different between-subject σmax-values were found (σmax=106.1±39.9Ncm−2). A relatively simple, uniform scaling routine reduced this variation substantially (σmax=69.4±9.4Ncm−2) and led to similar results to when a more detailed, muscle-specific scaling routine was used (σmax=71.2±10.8Ncm−2). Using subject-specific PCSA values to simulate an shoulder abduction task changed muscle force predictions for the subscapularis and the pectoralis major on average by 33% and 21%, respectively, but was <10% for all other muscles. The glenohumeral (GH) joint contact force changed less than 1.5% as a result of scaling. We conclude that individualisation of the model's strength can most easily be done by scaling PCSA with a single factor that can be derived from muscle volume data or, alternatively, from maximum force measurements. However, since PCSA scaling only marginally changed muscle and joint contact force predictions for submaximal tasks, the need for PCSA scaling remains debatable.

Investigation of the parameters important in the measurement of small particle impact forces

Impact forces in pneumatic conveying bends are becoming more significant in industry, and in research centres, as the size of pneumatic conveying pipeline bores increase to achieve high product throughput with the greater efficiency possible from a dense phase conveying system. This paper continues the authors' work in investigating this issue by undertaking a detailed comparison of the equations given for contact time and maximum contact force, from a range of literature with applications to various impact events both practical and theoretical. These predictions are also compared: to experimental results presented previously by the authors, to further results from an electrical resistance measurement system, and to a limited extent to experimental results from existing literature. The equations that are most reliable consider the elasticity of the particle and the elasticity of the impact surface, as well as the particle size, and also reflect a weak dependence on impact velocity. Whilst the electrical resistance measurement method has provided a useful verification of a number of theoretical predictions, its application is limited and is not suitable for the majority of particles that are conveyed pneumatically. Future work will expand on the particles tested using this method, and will also work on understanding better the influence of the force sensor on contact time and maximum force measurement.

Effects of the Alignment Between a Haptic Device and Visual Display on the Perception of Object Softness

Virtual reality (VR) has been gaining popularity in surgical planning and simulation. Most VR surgical simulation systems provide haptic (pertinent to the sense of touch) and visual information simultaneously using certain alignments between a haptic device and visual display. A critical aspect of such VR surgical systems is to represent both haptic and visual information accurately to avoid perceptual illusions (e.g., to distinguish the softness of organs/tissues). This study compared three different alignments (same-location alignment, vertical alignment, and horizontal alignment) between a haptic device and visual display that are widely used in VR systems. We conducted three experiments to study the influence of each alignment on the perception of object softness. In each experiment, we tested 15 different human subjects with varying availability of haptic and visual information. During each trial, the task of the subject was to discriminate object softness between two deformable balls in different viewing angles. We analyzed the following dependent measurements: subject perception of object softness and objective measurements of maximum force and maximum pressing depth. The analysis results reveal that all three alignments (independent variables) have similar effect on subjective perception of object softness within the interval of viewing angles from -7.5° to +7.5°. The viewing angle does not affect objective measurements. The same-location alignment requires less physical effort compared with the other two alignments. These observations have implications in creating accurate simulation and interaction for VR surgical systems.

Muscle fatigue does not lead to increased instability of upper extremity repetitive movements

Muscle fatigue alters neuromuscular responses. This may lead to increased sensitivity to perturbations and possibly to subsequent injury risk. We studied the effects of muscle fatigue on movement stability during a repetitive upper extremity task. Twenty healthy young subjects performed a repetitive work task, similar to sawing, synchronized with a metronome before and after performing each of two fatiguing tasks. The first fatigue task (LIFT) primarily fatigued the shoulder flexor muscles, while the second fatigue task (SAW) fatigued all of the muscles of the arm. Subjects performed each task in random order on two different days at least seven days apart. Instantaneous mean EMG frequencies (IMNF) decreased over both fatiguing tasks indicating that subjects did experience significant muscle fatigue. The slopes of the IMNF over time and the decreases in maximum force measurements demonstrated that the LIFT fatigue task successfully fatigued the shoulder flexors to a greater extent than any other muscle. On average, subjects exhibited more locally stable shoulder movements after the LIFT fatigue task ( p=0.035). They also exhibited more orbitally stable shoulder ( p=0.021) and elbow ( p=0.013) movements after the SAW fatigue task. Subjects also had decreased cocontraction at the wrist post-fatigue for both tasks ( p=0.001) and at the shoulder ( p<0.001) for the LIFT fatigue task. Therefore, increased dynamic stability of these repeated movements cannot be explained by increased muscle cocontraction. Possible alternative mechanisms are discussed.

The effect of random modulation of functional electrical stimulation parameters on muscle fatigue

Muscle contractions induced by functional electrical stimulation (FES) tend to result in rapid muscle fatigue, which greatly limits activities such as FES-assisted standing and walking. It was hypothesized that muscle fatigue caused by FES could be reduced by randomly modulating parameters of the electrical stimulus. Seven paraplegic subjects participated in this study. While subjects were seated, FES was applied to quadriceps and tibialis anterior muscles bilaterally using surface electrodes. The isometric force was measured, and the time for the force to drop by 3 dB (fatigue time) and the normalized force-time integral (FTI) were determined. Four different modes of FES were applied in random order: constant stimulation, randomized frequency (mean 40 Hz), randomized current amplitude, and randomized pulsewidth (mean 250 micros). In randomized trials, stimulation parameters were stochastically modulated every 100 ms in a range of +/-15% using a uniform probability distribution. There was no significant difference between the fatigue time measurements for the four modes of stimulation. There was also no significant difference in the FTI measurements. Therefore, our particular method of stochastic modulation of the stimulation parameters, which involved moderate (15%) variations updated every 100 ms and centered around 40 Hz, appeared to have no effect on muscle fatigue. There was a strong correlation between maximum force measurements and stimulation order, which was not apparent in the fatigue time or FTI measurements. It was concluded that a 10-min rest period between stimulation trials was insufficient to allow full recovery of muscle strength.

Reducing Muscle Fatigue Due to Functional Electrical Stimulation Using Random Modulation of Stimulation Parameters

A major limitation of many functional electrical stimulation (FES) applications is that muscles tend to fatigue very rapidly. It was hypothesized that FES-induced muscle fatigue could be reduced by randomly modulating the pulse frequency, amplitude, and pulse width in a range of +/-15%. Seven subjects with spinal-cord injuries participated in this study. FES was applied to quadriceps and tibialis anterior muscles using surface electrodes. Isometric force was measured, and the time for the force to drop by 3 dB (fatigue time) was compared between trials. Four different modes of FES were applied in random order: constant stimulation, randomized frequency, randomized amplitude, and randomized pulse width. There was no significant difference between the fatigue-time measurements for the four modes of stimulation (P=0.329). Therefore, random modulation appeared to have no effect. Based on an observed correlation between maximum force measurements and trial order, we concluded that having 10-min rest periods between trials was insufficient.

Evaluation of an in-shoe pressure measurement system in horses.

To develop an objective, accurate method for quantifying forelimb ground reaction forces in horses by adapting a human in-shoe pressure measurement system and determine the reliability of the system for shod and unshod horses. 6 adult Thoroughbreds. Horses were instrumented with a human in-shoe pressure measurement system and evaluated at a trot (3 m/s) on a motorized treadmill. Maximum force, stance time, and peak contact area were evaluated for shod and unshod horses. Three trials were performed for shod and unshod horses, and differences in the measured values were examined with a mixed model ANOVA for repeated measures. Sensor accuracy was evaluated by correlating measured variables to clinically observed lameness and by a variance component analysis. 4 of 6 horses were determined to be lame in a forelimb on the basis of clinical examination and measured values from the system. No significant differences were observed between shod and unshod horses for maximum force and stance time. A significant decrease in peak contact area was observed for shod and unshod horses at each successive trial. Maximum force measurements provided the highest correlation for detecting lameness (r = 0.91, shod horses; r = 1.0, unshod horses). A variance component analysis revealed that 3 trials provided a variance of 35.35 kg for maximum force (+/- 5.78% accuracy), 0.007 seconds for stance time (+/- 2.5% accuracy), and 8.58 cm2 for peak contact area (+/- 11.95% accuracy). The in-shoe pressure measurement system provides an accurate, objective, and effective method to evaluate lameness in horses.

A functional model system of an hypoxic nerve injury and its evaluation.

Develop an hypoxic peripheral nerve injury model with a controlled injury type and two types of clinically relevant physiological measurements of function during and after recovery. The model, controlling for injury and measurement variables, would have predictable outcomes in function. The functional model could test potential therapeutic interventions with greater sensitivity. Twenty-one rats were used in preliminary studies evaluating peroneal nerve injury types and functional model evaluation. Forty-eight rats were used in a controlled and blinded evaluation of the injury model followed by treatment with hyperbaric oxygen (HBO) as a potential therapeutic intervention and evaluated with functional models. Preliminary studies compared nerve injuries: epineurectomy, epineurectomy with crush and transection with autograft for rate of return of function and final extent of return of function. The gait analysis model was also evaluated and modified to decrease variability. The final study evaluated peroneal epineurectomy and nerve crush injury with serial gait analysis during recovery, final elicited maximum force measurements, and histological analysis. Half of the animals were treated with HBO during recovery (ANOVA or regression statistical analysis were used to determine group differences.). Preliminary studies suggested that the peroneal nerve injury model of an epineurectomy with crush of specified length and a modification of the gait analysis model would yield a useful and predictable injury outcome. The final study resulted in predicted and consistent injury outcomes. In the HBO treatment group, a 12% improvement in function 5 days after HBO treatment was demonstrated (P < .03), but no long-term or histological benefit was seen. A reliable hypoxic nerve injury model has been developed and tested utilizing two functional methods as the primary outcome variables.

Distinct kinetic properties of cardiac myosin isoforms revealed by in vitro studies.

To clarify the physiological significance of myosin isoform redistribution in cardiac adaptation process, we compared the kinetic property of the two cardiac myosin isoforms using in vitro motility assay techniques. Cardiac myosin isoforms V1 and V3 were obtained from ventricular muscle of young rats and hypothyroid rats respectively. On each of these myosin isoforms fixed on a glass coverslip, fluorescently labeled actin filaments were made to slide in the presence of ATP. To measure the force generated by actomyosin interaction, a small latex bead was attached to the barbed end of an actin filament and the bead was captured by the laser optical trap installed in a microscope. The force was determined from the distance between the bead and the trap positions under either auxotonic or isometric conditions. The time-averaged force generated by multiple cross-bridges did not differ significantly between the two isoforms. On the other hand, the unitary force measurement revealed the same level of amplitude but a longer duration for V3 isoform. The same level of time-averaged force is in agreement with not only our previous finding but the results of maximum force measurement in muscle preparations. The difference in kinetic characteristics of the two isoforms could account for the difference in economy of force development and the basis for cardiac adaptation mechanism.

Fatigue of the inspiratory muscle pump in humans: an isoflow approach

A new method is described for measurement of inspiratory muscle endurance in humans that is based on isokinetic principles of muscle testing (i.e., measurement of maximum force during a constant velocity of shortening). Subjects inspired maximally while their lungs were inflated at a constant rate during each breath for 10 min. Inspiratory and expiratory time, flow rate, tidal volume, and end-tidal CO2 were maintained constant. In each subject, maximum inspiratory mouth pressure exponentially decayed over the first few minutes to an apparent sustainable value. Repeated tests in experienced subjects showed high reproducibility of sustainable pressure measurements. To determine the effects of flow, endurance tests were repeated in four subjects at flows of 0.75, 1.0, and 1.25 l/s, with a constant duty cycle. As flow increased, the maximum pressures that could be attained at rest and the maximum sustainable pressures decreased. At each flow, the sustainable pressure remained a constant fraction of the maximum pressure attainable at rest. We interpret the decay in mouth pressure during isoflow endurance tests to directly reflect the loss of net inspiratory muscle force available by maximum voluntary activation of the inspiratory pump.

Changes in web-monitoring forces associated with web reduction in the spider family Uloboridae

Members of the genera Uloborus, Hyptiotes, and Miagrammopes have similar web-monitoring postures, but very different webs and tactics for monitoring them. Orb weavers of the genus Uloborus construct horizontal webs and hang from their hubs, whereas reduced-web uloborids construct vertical webs and monitor them from a single thread. To determine if changes in spider strength accompanied web reduction, resting and maximum force measurements were taken of a developmental series of Hyptiotes cavatus, Uloborus glomosus, Miagrammopes animotus, Miagrammopes pinopus, and an undescribed Costa Rican Miagrammopes using a glass needle strain gauge. Both carapace length and spider weight were used as indexes of spider size. Regression analyses of forces show that H. cavatus exerts the greatest relative force and Miagrammopes species the least. This is consistent with requirements for the operation of each web type: Hyptiotes cavatus tenses its entire triangular web and suddenly releases this tension when a prey strikes its web, whereas a Miagrammopes species jerks a single thread that has captured a prey. Within the genus Miagrammopes, the species with the most highly modified carapace expressed the greatest resting force.

DEVELOPMENT OF THE ARMOUR TENDEROMETER FOR TENDERNESS EVALUATION OF BEEF CARCASSES

AbstractA simple rapid non‐destructive test and apparatus were developed for quantifying tenderness of beef carcasses. A probe with ten 1/2 inch diameter needles mounted on a manifold is pressed manually two inches into the rib eye. Measurements of maximum force during penetration into the cold rib eye on the day after slaughter correlated well with subjective panel tenderness scores on the same meat cooked after one week of aging.