Torque-angle Curve Research Articles

Characterization and Dataset Compilation of Torque–Angle Curve Behavior for M2/M3 Screws

This research explores the torque–angle behavior of M2/M3 screws in automotive applications, focusing on ensuring component reliability and manufacturing precision within the recommended assembly specification limits. M2/M3 screws, often used in tight spaces, are susceptible to issues like stripped threads and inconsistent torque, which can compromise safety and performance. The study’s primary objective is to develop a comprehensive dataset of torque–angle measurements for these screws, facilitating the analysis of key parameters such as torque-to-seat, torque-to-fail, and process windows. By applying Gaussian curve fitting and Gaussian process regression, the research models and simulates torque behavior to understand torque dynamics in small fasteners and remarks on the potential of statistical methods in torque analysis, offering insights for improving manufacturing practices. As a result, it can be concluded that the proposed stochastics methodologies offer the benefit of fail-to-seat ratio improvement, allow inference, reduce the sample size needed in incoming test studies, and minimize the number of destructive test samples needed.

Foot torsional stiffness exhibits gender differences but shows no correlation with medial longitudinal arch height

Although foot mobility tends to be greater in females, sex-based differences in foot torsional stiffness have not been investigated. It is also unclear whether assessing the medial longitudinal arch (MLA) height reflects foot torsional stiffness. This study included 52 healthy adults (26 females and 26 males) with an average age of 24.6 years. The arch height index was used to assess MLA height. To calculate foot torsional stiffness, a custom-built torque meter and a three-dimensional motion analysis system were employed. The forefoot was passively rotated from the maximum eversion to the maximum inversion at a rate of 2.5°/s. The forefoot’s resistance torque and rotation angle relative to the rearfoot were recorded. Foot torsional stiffness was defined by establishing the slope of the regression line from 10° eversion to 10° inversion of the torque–angle curve, with the slope subsequently normalized by body weight. Gender differences in foot torsional stiffness and the correlation between MLA height and foot torsional stiffness were investigated. Foot torsional stiffness was significantly lower in females than in males (0.00237 ± 0.00061Nm/°･kg vs 0.00368 ± 0.00136 Nm/°･kg, p < 0.001, effect size: r = 0.65, statistical power = 0.99). MLA height was not significantly different between sexes. No significant correlations were found between foot torsional stiffness and MLA height in either sex. Foot torsional stiffness and MLA height reflect different mechanical properties of the foot, emphasizing the need for individual assessment and consideration of sex differences.

Mechanical properties of concrete filled steel tube members constrained by carbon fiber reinforced materials under bidirectional coupled loading

Carbon fiber reinforced composite structures have been a research hotspot in recent years, with 9 specimens designed for static tests under bending and torsion loads of CFRP concrete filled steel tubes. The torque angle (T-θ) curve was studied from an experimental perspective. Subsequently, a reasonable finite element model was established using ABAQUS software. In addition, the effects of changes in parameters such as the number of steel concrete strength, bending ratio, and steel ratio on C–CF–CFRP-ST bending and torsion specimens were studied through numerical parameter research. Finally, equations of bearing capacity of CFRP-concrete filled steel tube under coupled bending and torsion are proposed.

Incorporation of compaction effects in the automated generation of 3D woven composites representative volume elements by geometrical modelling

Advanced 3D woven composites have become an enabling technology in many industrial applications due to their proven benefits, particularly the improvement of the out-of-plane mechanical behavior with respect to other reinforcement schemes. The latter property has been shown to be strongly affected by the effects of compaction during manufacturing. The present study proposes an automated framework, based on heuristic procedures, for the generation of representative volume elements (RVEs) of 3D woven composites, allowing to include global and local geometrical features induced by transverse compaction, such as overall thickness reduction, changes in yarn cross-sections and consistent global/local fiber fractions. The methodology is illustrated for three types of reinforcement, namely a plain weave, an angular through-thickness interlock and a 3D orthogonal RVE. The resulting geometries generated by the proposed method compare favourably with typical observations from the literature in a quantitative manner. Finally, the proposed framework is integrated with a previously developed meshing strategy to allow damage studies for a selected architecture (plain weave) under torsional loading, presenting a complete computational chain by building cohesive zone finite element models from compacted RVEs. The torque-angle response curves obtained after the damage simulations show a decrease in stiffness and an increase of damage levels with compaction, which is in line with the expectations.

Six Weeks of Unilateral Flywheel Hip-Extension and Leg-Curl Training Improves Flywheel Eccentric Peak Power but Does Not Enhance Hamstring Isokinetic or Isometric Strength.

This preregistered trial investigated how 6 weeks of unilateral flywheel leg-curl and hip-extension training impact isokinetic, isometric, and flywheel strength and power outcomes. The study involved 11 male university athletes (age 22 [2]y; body mass 77.2 [11.3]kg; height 1.74 [0.09]m) with one leg randomly allocated to flywheel training and one leg to control. Unilateral eccentric and isometric knee-flexion torque and flywheel unilateral leg-curl and hip-extension peak power were tested. Training intensity and volume (3-4 sets of 6 + 2 repetitions) were progressively increased. The intervention enhanced hip-extension concentric (P < .01, d = 1.76, large) and eccentric (P < .01, d = 1.33, large) peak power more than the control (significant interaction effect). Similarly, eccentric (P = .023, d = 1.05, moderate) peak power was enhanced for the leg curl. No statistically significant differences between conditions were found for isokinetic eccentric (P = .086, d = 0.77, moderate) and isometric (P = .431, d = 0.36, small) knee-flexor strength or leg-curl concentric peak power (P = .339, d = 0.52, small). Statistical parametric mapping analysis of torque-angle curves also revealed no significant (P > .05) time-limb interaction effect at any joint angle. Unilateral flywheel hamstring training improved knee-flexor eccentric peak power during unilateral flywheel exercise but not flywheel concentric, isokinetic eccentric, or isometric (long-lever) knee-flexor strength.

Changes in passive hamstring stiffness after primary anterior cruciate ligament reconstruction: A prospective study with comparison of healthy controls

BackgroundThe mechanical properties of knee flexors muscles contribute to reducing anterior cruciate ligament loading. This case-control study evaluated the passive knee flexors stiffness after primary anterior cruciate ligament reconstruction with comparison of healthy controls. MethodsAfter anterior cruciate ligament reconstruction, 88 participants (24.5 [8.6] years, 56,8% males) had two isokinetic tests at 4 and 8 postoperative months with measurement of the passive resistive torque of knee flexors and extensors/flexors strength. In the control group, 44 participants (24.5 [4.3] years, 56,8% males) had one visit with the same procedures. Passive knee flexors stiffness was calculated as the slope of the passive torque-angle curve on the last 10° of knee extension (Nm/°). We investigated the impact of timing and type of surgery (autograft and combined meniscus repair) and persistent knee extension deficits on knee flexors stiffness. FindingsAt 4 and 8 postoperative months, passive knee flexors stiffness was lower on the operated limb than on the non-operated limb (P < 0.001) but both limbs had significant lower values than controls (P < 0.001). Stiffness was positively correlated with knee flexors strength (P < 0.010), and knee flexors stiffness at 4 months was lower in individuals who underwent surgery <6 months from injury (P = 0.040). Knee extension deficit or the type of surgery did not have a significant influence on knee flexors stiffness. InterpretationSimilarly to neuromuscular factors that are traditionally altered after anterior cruciate ligament reconstruction, evaluating passive knee flexors stiffness changes over time could provide supplementary insights into postoperative muscle recovery.

Comparison of Two Design Principles of Unpowered Ankle-Foot Orthoses for Supporting Push-Off: A Case Study.

Ankle propulsion is essential for efficient human walking. In recent years, several working principles have been investigated and applied to ankle-foot orthoses (AFOs) to enhance the work of the plantarflexor muscles and achieve proper propulsion during gait. Comparing the performance and effectiveness of different designs is difficult because researchers do not have a standardized set of criteria and procedures to follow. This leads to a wide range of tests being conducted, with variations in important factors such as walking speed and assistance provided, which greatly affect users' kinematics and kinetics. In this work, we investigate the possibilities and potential benefits of two of the most important design principles for supporting ankle propulsion with unpowered AFOs. To this end, we present and evaluate two AFO prototypes with springs parallel to the Achilles tendon based on: (i) a linear compression spring, and (ii) a customized leaf spring-cam transmission with a non-linear ankle torque-angle curve. The effects of both AFOs are reported for a case study with one healthy participant using both prototypes at two walking speeds under the same experimental conditions. Large reductions in muscular activity were found when the user received assistance, and ankle kinematics were influenced by the different assistance approaches. This case study was intended as a first step to provide insights on how two promising principles can passively support push-off during gait.

The force-length relation of the young adult human tibialis anterior.

Knowledge of the muscle's lengths at which maximum active isometric force is attained is important for predicting forces during movement. However, there is limited information about the in vivo force-length properties of a human muscle that plays crucial roles during locomotion; the tibialis anterior (TA). We therefore aimed to estimate TA's force-length relation from dorsiflexor torque-angle curves constructed from eight women and eight men. Participants performed maximal voluntary fixed-end contractions with their right ankle dorsiflexors from 0° to 30° plantar flexion. Muscle fascicle lengths were estimated from B-mode ultrasound images, and net ankle joint torques were measured using dynamometry. Fascicle forces were estimated by dividing maximal active torques by literature-derived, angle-specific tendon moment arm lengths while assuming a fixed 50% force contribution of TA to the total dorsiflexor force and accounting for fascicle angles. Maximal active torques were higher at 15° than 20° and 30° plantar flexion (2.4-6.4 Nm, p≤0.012), whereas maximal active TA fascicle forces were higher at 15° than 0°, 20° and 30° plantar flexion (25-61 N, p≤0.042), but not different between 15° and 10° plantar flexion (15 N, p=0.277). TA fascicle shortening magnitudes during fixed-end contractions were larger at 15° than 30° plantar flexion (3.9 mm, p=0.012), but less at 15° than 0° plantar flexion (-2.4 mm, p=0.001), with no significant differences (≤0.7 mm, p=0.871) between TA's superficial and deep muscle compartments. Series elastic element stiffness was lowest and highest at lengths 5% shorter and 5% longer than optimum fascicle length, respectively (-30 and 15 N/mm, p≤0.003). TA produced its maximum active force at 10-15° plantar flexion, and its normalized force-length relation had ascending and descending limbs that agreed with a simple scaled sarcomere model when active fascicle lengths from within TA's superficial or deep muscle compartment were considered. These findings can be used to inform the properties of the contractile and series elastic elements of Hill-type muscle models.

Coil Winding Circuit Configurations for Permanent Magnet Synchronous Machines

The article outlines a procedure for drawing up the electric circuits of coil-type armature windings for salient-pole PM electric machines proceeding from the required number of pole pairs (the synchronous rotation frequency) and the number of phases. The procedure implementation algorithm is based on determining the stator teeth number as the one nearest to the number of rotor poles (2p) multiple to the number of phases. In this way, sufficient levels of coil pitch coefficient and winding coefficient are ensured. In accordance with the developed procedure, the coils in the phases can occupy one, two, or four phase zones from the adjacent coils connected into coil groups in a series opposition manner. The algorithm was tested on a few examples of drawing up the connection circuits of synchronous machine windings known from the electrical machinery construction theory and practice, including serially produced ones with the inner stator and for a pilot design of a high-capacity motor. For the latter one, its versions with three- and nine-phase windings for a 32-pole rotor (2p = 32) are compared. Numerical studies of the motor torque for both winding circuit versions carried out using the finite element method have shown that the version with the nine-phase winding produces a 20% higher torque. For one version of a serially produced motor, the winding electric circuit design validity was checked by calculating the torque-angle curves for different current densities. In all examples, formal compliance with the items of the outlined procedure has yielded correct circuit solutions. A criterion for evaluating the PM machine manufacturing complexity has been proposed, which depends on the winding type (distributed or coil-type) and on the number of PMs per magnetic system pole.

Failure response of holed aluminum/glass hybrid composite tubes

It is known that aluminum/composite hybrid tubes of aluminum tube wrapped with a composite material on the outside can offer remarkable performance. This study systematically investigates the effect of stacking sequence on the torque capacity of holed aluminum/composite hybrid tubes. The stacked specimens manufactured by the filament winding method, [±452/Al], [90/±452/Al], and [±452/90/Al], are considered in experimental studies. The tubes were tested for torsional characteristics at a constant angular rotational speed. The experimental studies indicated that although monotonic crack propagation was observed in the aluminum tube with the damage starting from the hole wall at an angle of approximately 45° concerning the specimen axis, the damage in hybrid tubes containing a 90° layer occurs in two phases. This causes a step-like formation in the torque–angle curves. Although the ± 45° reinforcement has a profound effect on torque-carrying, it has been observed that the presence of the 90° composite on the aluminum tube in the reinforced tube improves the effectiveness (torque capacity and stiffness) of the subsequent reinforcement. Accordingly, it is understood that the hybrid structure increases the torque-carrying capacity up to 2.6 times compared to the aluminum tube, corresponding to a 20% increase in specific torque value. The stress components that play an important role in the deformation of the hole wall and damage formation processes have been successfully determined by the finite element method. It was found that there was a consistent relationship between the effect of the stacking sequence on the stress distribution and the experimental results. The results of the study are expected to be useful in terms of providing light and sufficient torque performance in case of possible hole-like discontinuity in-service conditions.

Research and Application of Mechanical State Diagnosis Method of Horizontal Telescopic Type Disconnector

Most transmission parts of the horizontal telescopic type disconnector are directly exposed, resulting in frequent mechanical failures. Its mechanical state is mainly judged by manual operation experience, so it is not easy to achieve rapid and accurate evaluation. In this paper, by establishing the virtual prototype model of the horizontal telescopic type disconnector and building the corresponding test platform, the changing trend of torque in the movement process of the disconnector is analyzed. Compared with the torque-angle curves of the normal state and different mechanical defects’ states, the closing and opening process’s torque increases obviously under the jamming defect. The opening process is torque increases while the closing process’s torque decreases under the spring fatigue defect. The ending torque value of the closing process increases, or there is no typical wave peak in the meshing stage under improper travel defect. There are multiple wave peaks in the meshing stage under the three-phase position asynchrony. With this, the mechanical state diagnosis method of GW23 disconnector based on the torque-angle curve is summarized, and the installation and debugging of the same type of disconnectors in a substation are taken as examples to prove that the rapid and accurate diagnosis of its mechanical state can be realized by using this method in engineering application.

Brachial plexus birth injury and cerebral palsy lead to a common contracture phenotype characterized by reduced functional muscle length and strength.

IntroductionBrachial plexus birth injury (BPBI) and cerebral palsy (CP) both cause disabling contractures for which no curative treatments exist, largely because contracture pathophysiology is incompletely understood. The distinct neurologic nature of BPBI and CP suggest different potential contracture etiologies, although imbalanced muscle strength and insufficient muscle length have been variably implicated. The current study directly compares the muscle phenotype of elbow flexion contractures in human subjects with BPBI and CP to test the hypothesis that both conditions cause contractures characterized by a deficit in muscle length rather than an excess in muscle strength.MethodsSubjects over 6 years of age with unilateral BPBI or hemiplegic CP, and with elbow flexion contractures greater than 10 degrees on the affected side, underwent bilateral elbow flexion isokinetic strength testing to identify peak torque and impulse, or area under the torque-angle curve. Subjects then underwent needle microendoscopic sarcomere length measurement of bilateral biceps brachii muscles at symmetric joint angles.ResultsIn five subjects with unilateral BPBI and five with hemiplegic CP, peak torque and impulse were significantly lower on the affected versus unaffected sides, with no differences between BPBI and CP subjects in the percent reduction of either strength measurement. In both BPBI and CP, the percent reduction of impulse was significantly greater than that of peak torque, consistent with functionally shorter muscles. Similarly, in both conditions, affected muscles had significantly longer sarcomeres than unaffected muscles at symmetric joint angles, indicating fewer sarcomeres in series, with no differences between BPBI and CP subjects in relative sarcomere overstretch.DiscussionThe current study reveals a common phenotype of muscle contracture in BPBI and CP, with contractures in both conditions characterized by a similar deficit in muscle length rather than an excess in muscle strength. These findings support contracture treatments that lengthen rather than weaken affected muscles. Moreover, the discovery of a common contracture phenotype between CP and BPBI challenges the presumed dichotomy between upper and lower motor neuron lesions in contracture pathogenesis, instead revealing the broader concept of “myobrevopathy”, or disorder of short muscle, warranting increased investigation into the poorly understood mechanisms regulating muscle length.

Robust control of a dual-arm space robot for in-orbit screw-driving operation

As large-scale spacecraft like Hubble Space Telescope need in-orbit assembly, there is an increasing need for the in-orbit assembly automatically carried out by space robots. This paper proposes a potential in-orbit screw-driving strategy carried out by a dual-arm space robot. Unlike single-arm space robots, a dual-arm space robot can avoid the translation and rotation of the target during the screw-driving process. For explanation, one arm can be set as the mission arm in the screw-driving process. The other arm can simultaneously provide the opposite contact forces and torques applied to the target. The hybrid position/force control strategy is developed for a dual-arm space robot to precisely deliver the desired contact forces by the end-effectors. Moreover, the base attitude of the space robot is controlled by reaction wheels to reduce the coupled movement between the base and the manipulators. According to a typical screw-driving procedure for automatic assembly, a desired fastening torque–angle curve is designed to ensure that the screw is firmly tightened. A robust Sliding Mode Controller (SMC) is designed to perform well against the uncertainties and disturbances applied to the space robot system. The simulation results show the feasibility of the potential dual-arm in-orbit screw-driving strategy.

Biomechanical Modeling of Brachialis-to-Wrist Extensor Muscle Transfer Function for Daily Activities in Tetraplegia.

A model of the transferred BRA-ECRB muscle-tendon unit was developed to calculate isometric elbow and wrist joint torque as a function of elbow and wrist angles resulting from different BRA reattachment locations from 50 to 80 mm proximal to the wrist joint crease. Using this model, mathematical optimization predicted the optimal location for BRA reattachment in order to perform each of a number of important upper extremity tasks as well as to calculate a global optimum for performing all of the tasks. Analysis of active joint torque showed that the entire elbow torque-angle curve surface shifted "diagonally" toward elbow flexion and wrist extension as the attachment location approached the wrist joint; peak wrist torque was produced at extended wrist angles. Our model predicted that the optimal attachment location for each different task ranged from 54.3 to 74.6 mm proximal to the wrist joint, which is feasible given the anatomy of the muscle-tendon unit. The attachment location to optimize performing all tasks was calculated as 63.5 mm proximal to the wrist joint. This study clearly demonstrates that the BRA, which is underused as a donor in tetraplegia surgery, is an excellent donor muscle to provide wrist extension. Biomechanical simulation further highlighted the need to consider not only donor-muscle appropriateness but the patient's desired function when planning surgical tendon transfers. Quantitative evaluation of the way that surgery affects daily tasks rather than simply matching muscle properties may be a more appropriate approach for surgeons to use when choosing and tensioning donor muscles.

Analysis of double nut installation technology based on new anti loosening performance evaluation test method

Abstract This paper analyzed the torque combination mode of double nut installation, and two common installation methods are tested and verified by using a new anti loosening performance evaluation method. This method can evaluate the anti loosening performance of small size bolts below M5. Through the test, it is found that when the installation torque of upper and lower nuts is different, the anti-loosening performance of double nuts is better than that of upper and lower nuts with the same mounting torque. It is found that there is a certain dispersion in the anti-loosening performance of double nuts, It is analyzed that the reason for this phenomenon is the difference of product quality. It is proposed to evaluate the quality consistency of fastener products through the dispersion degree of torque coefficient K, and a method to determine the installation torque through the angle torque curve is given.

Isokinetic hamstring and quadriceps strength interpretation guideline for football (soccer) players with ACL reconstruction: a Delphi consensus study in the Netherlands

ABSTRACT Strength testing is a key part of rehabilitation and return to sport (RTS) decision making for football players after anterior cruciate ligament reconstruction (ACLR). Isokinetic testing has been the gold standard for strength measurement for decades, but a uniform protocol and clinical implications of test results are lacking. Therefore, this study aimed to 1) develop a uniform protocol for football players based on knowledge and experience from experts in the field of ACL rehabilitation and 2) clarify the clinical interpretation of different isokinetic test outcomes. In a structured Delphi consensus procedure 42 experts (98% full response rate) fulfilled three rounds that involved a survey, content analysis and anonymised feedback report for each round. Surveys addressed the isokinetic protocol, evaluation report and torque–angle curve of the isokinetic test for strength evaluation in football players after ACLR. The final protocol consisted of concentric knee flexion and extension isokinetic testing with 5 repetitions at 60°/sec, 20 repetitions at 180°/sec and 15 repetitions at 300°/sec and 60 seconds rest between sets. All parameters were deemed valuable, with Peak Torque, Max Rep Total Work, Total Work, Range of Motion and Agonist to Antagonist ratio being considered key for clinical interpretation. For qualitative assessment, it was advised to assess the shape, course, volume, potential dips, peak, and build-up to the peak of the parabola. This Delphi consensus study provided a guideline for data collection and clinical interpretation of isokinetic strength testing in football players after ACLR.

Torque-angle curve of the knee flexors in athletes with a prior history of hamstring strain

ObjectivesTo investigate the knee flexor torque-angle curve after hamstring strain injury using different muscle action types and angular velocities. DesignCross-sectional. SettingControlled laboratory. ParticipantsThirteen collegiate athletes injured hamstring strain (21.0 ± 0.8 years; 173.9 ± 6.5 cm; 70.1 ± 10.5 kg). Main outcome measuresConcentric and eccentric knee flexor torque was measured at 60 & 300°/sec. Peak torque and average torque every 10° were determined from torque-angle curve and injured side was compared with non-injured side. ResultsNo significant differences were found in the concentric muscle actions. However, the eccentric peak torque was significantly lower on the injured side at 60°/sec (p = 0.048) and at 300°/sec (p = 0.002). The average eccentric torque was significantly lower on the injured side at 60°/sec from 10° to 20° of knee flexion (p = 0.012–0.018) and at 300°/sec from 10° to 60° of knee flexion (p = 0.005–0.049). ConclusionThe knee flexor torque-angle curve changes with eccentric muscle action after hamstring injury. Eccentric torque declines were close to full knee extension at 60°/sec and a wide range of knee flexion at 300°/sec. The assessment and rehabilitation of eccentric hamstring strength may be important to consider the effect of the angular velocity after hamstring strain injury.

Design of 3D printable prosthetic foot to implement nonlinear stiffness behavior of human toe joint based on finite element analysis

Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function.

Design and evaluation of the SMApp: A stiffness measurement apparatus for ankle–foot orthoses

Ankle–foot orthoses (AFOs) are braces worn by individuals with gait impairments to support ankle motion. AFO rotational stiffness is a key mechanical property that affects gait biomechanics. However, it is unclear how design choices affect AFO stiffness and what specific stiffness ranges impact gait. This stems largely from the absence of commercial devices or established guidelines for measuring AFO stiffness. This paper details the design of the AFO Stiffness Measurement Apparatus (SMApp). The SMApp is a non-destructive, automated system that measures torque and angle as an AFO is moved through a range of motion at a set speed. Using the derived torque–angle curve, we can calculate rotational stiffness, neutral angle and hysteresis of any AFO for speeds up to 37 deg/s. The repeatability of the SMApp was evaluated between and within two operators and three testing sessions using three AFOs cycled 10 times through flexion and extension. We also measured the stiffness of three different AFOs with the SMApp and another published system in a comparative case study. The SMApp had excellent reliability with high intraclass correlation coefficients (ICC ≥0.97) for all measured AFO properties. The standard error of measurement (SEM) and minimum detectable difference (MDD) were comparable to published parameters from other devices for stiffness (SEM ¡ 0.32 N m/°, MDD ¡ 0.88 N m/°) and neutral angle (SEM ¡ 0.30°, MDD ¡ 0.84°). In comparison to a previously described, reliable manual stiffness measurement device, the SMApp measurements had similar stiffness, but different neutral angle values for one of three AFOs. The SMApp can be utilized in future studies for AFO material fatigue testing, to validate finite element models, and to evaluate speed effects on AFO properties.

Association between plantar flexor muscle volume and dorsiflexion flexibility in healthy young males: ultrasonography and magnetic resonance imaging studies

BackgroundAlthough joint flexibility is important for human locomotion, the determinants of joint flexibility are not fully understood. In this study, we examined the relationship between dorsiflexion flexibility and plantar flexor muscle size in healthy young males.Methods and resultsThe dorsiflexion flexibility was assessed using range of motion (ROM) and stiffness during active and passive dorsiflexion. Active ROM was defined as the maximal angle during voluntary dorsiflexion. Passive ROM was defined as the angle at the onset of pain during passive dorsiflexion. Passive stiffness was calculated as the slope of the linear portion of the torque-angle curve between 10º and 20º dorsiflexion of the ankle during passive dorsiflexion. In the first study, the plantar flexor muscle volume (MV) in 92 subjects was estimated on the basis of the lower leg length and plantar flexor muscle thickness, as measured using ultrasonography. The estimated plantar flexor MV correlated significantly with active ROM (r = -0.433), passive ROM (r = -0.299), and passive stiffness (r = 0.541) during dorsiflexion (P = 0.01 for all). In the second study, the plantar flexor MV in 38 subjects was measured using magnetic resonance imaging. The plantar flexor MV correlated significantly with plantar flexor active ROM (r = -0.484), passive ROM (r = -0.383), and passive stiffness (r = 0.592) during dorsiflexion (P = 0.05 for all).ConclusionsThese findings suggest that a larger plantar flexor MV is related to less dorsiflexion flexibility in healthy young males.