Average Angular Velocity Research Articles

The Effect of Fatigue-Induced Changes in Eggbeater-Kick Kinematics on Performance and Risk of Injury.

To investigate the effects of fatigue on the vertical force and kinematics of the lower limbs during maximal water polo eggbeater kicking. Twelve male water polo players maintained as high a position as possible while performing the eggbeater kick with the upper limbs raised out of the water until they were unable to keep the top of the sternum (manubrium) above water. Data comprising 27 complete eggbeater-kick cycles were extracted corresponding to 9 cycles of the initial nonfatigued (0%), 50% time point (50%), and final fatigued (100%) periods of the trial. Vertical force, foot speed, and hip-, knee-, and ankle-joint angles were calculated. Mean vertical force (0%, 212.2 N; 50%, 184.5 N; 100%, 164.3 N) progressively decreased with time. Speed of the feet (0.4 m/s), hip abduction (2.9°), and flexion (3.6°) decreased with fatigue, while hip internal rotation (3.6°) and ankle inversion (4°) increased with fatigue. Average angular velocity decreased for all joint motions. Eggbeater-kick performance decreases with fatigue. Inability to maintain foot speeds and hip and ankle actions with progressing fatigue diminishes the ability of the player to produce vertical force during the cycle. Increased internal rotation of the hip when fatigued and the large eversion/abduction of the ankle during the cycle may be predisposing factors for the prevalence of patellofemoral pain syndrome observed among eggbeater-kick performers. Appropriate training interventions that can limit the effects of fatigue on performance and injury risk should be considered.

Measurement of Lumbar Spine Functional Movement in Low Back Pain.

Individuals with low back pain (LBP) present with alterations or limitations of spinal mobility. The identification of simple clinical methods for evaluating functional movement of the spine is necessary to allow quantification of the degree of movement impairment and permit monitoring of patient improvement with rehabilitation. This study evaluated movement of the spine in 20 patients with chronic nonspecific LBP compared with 19 pain-free participants using a novel measurement device that permits the dynamic assessment of spinal movement in a rapid and subject-specific manner. Two flexible sensor strips were fixed paravertebrally to the spine with each sensor strip measuring angles in 12 predetermined, adjacent, 25-mm-long segments. Maximum range of motion (ROM) and average angular velocity (AAV) of lumbar and pelvic movement were measured within identical angular and temporal frames during the descending and ascending phase of active lumbar flexion, extension, rotation, and lateral flexion following a standard choreography. Participants with LBP completed a number of questionnaires including the Tampa Scale of Kinesiophobia, Pain Catastrophizing Scale, and Spielberger State-Trait Anxiety Inventory. Across all movements, the individuals with LBP displayed 10% to 15% less ROM (P<0.05) and 15% to 30% less AAV (P<0.05) at both the pelvis and lumbar regions compared with controls. ROM as well as AAV, in most cases, were negatively correlated (R=-0.49 to -0.75) with the Tampa Scale of Kinesiophobia, Pain Catastrophizing Scale, and Spielberger State-Trait Anxiety Inventory in the LBP group (all P<0.05) especially during the initial descending phase of movement. This study provide support for the utility of this device for quantifying movement impairments in individuals with fairly low levels of LBP and general functional limitations. The results show that velocity measurements rather than ROM show the greatest differences in individuals with LBP compared with asymptomatic participants. Impaired lumbar and pelvis movement was correlated to the individuals with LBP's degree of anxiety, fear, and catastrophizing.

Experimental optimization of power-function-shaped drive pulse for stick-slip piezo actuators

Motion of a stick-slip piezo actuator is generally controlled by the parameters related to its mechanical design and characteristics of the driving pulses applied to piezoceramic shear plates. The goal of the proposed optimization method is to find the driving pulse parameters leading to the fastest and the most reliable actuator operation. In the paper the method is tested on a rotary stick-slip piezo actuating system utilized in an atomic force microscope.The optimization is based on the measurement of the actuator response to driving pulses of different shapes and repetition frequencies at various load forces. To provide it, a computer controlled testing system generating the driving pulses, and detecting and recording the corresponding angular motion response of the actuator by a position sensitive photo detector (PSPD) in real time has been developed. To better understand and interpret the experimental results, supportive methods based on a simple analytical model and numerical simulations were used as well.In this way the shapes of the single driving pulses and values of the load force providing the biggest actuator steps were determined. Generally, the maximal steps were achieved for such a combination of the pulse shapes and load forces providing high velocities at the end of the sticking mode of the actuator motion and, at the same time, lower decelerations during the slipping mode.As for the multiple driving pulses, the pulse shapes and values of repetition frequency ensuring the sticking mode of the actuator motion during the pulse rise time together with the maximum average angular rotor velocity were specified. In this way the effective and stable operation conditions of the actuator were provided.In principle, the presented method can be applied for the testing and optimization of any linear or angular stick-slip actuator.

Research on the dynamics of single-acting crank pump with damless hydro turbine drive

The research of the dynamic model of single-acting crank pump with damless hydro turbine drive has been made in the present work. Compiled dynamic and mathematical models of single-acting crank pump with damless hydro turbine drive have been constructed. The equations of motion have been solved using analytical and numerical methods and their results have been compared. The characteristics of the damless hydro turbine with the load of the crank pump have been evaluated depending on the radius of the rotor and on the speed of the watercourse. It has been revealed that the average angular velocity of rotation of hydro turbine in a stationary mode is the angular velocity of the hydro turbine at idle and does not depend on the mode of piston pumps. Average speed depends only on the parameters of a hydro turbine and the flow velocity of the watercourse. The results obtained in the course of theoretical research can be successfully used for the design of hydro turbine as a drive for single-acting crank pump. DOI: http://dx.doi.org/10.5755/j01.mech.20.6.7432

Compression- and shear-driven jamming of U-shaped particles in two dimensions

We carry out numerical simulations of soft, U-shaped, frictionless particles in $d=2$ dimensions in order to explore the effects of complex particle shape on the jamming transition. We consider both cases of uniform compression-driven and shear-driven jamming as packing fraction $\phi$ and compression or shear rate is varied. Upon slow compression, jamming is found to occur when the isostatic condition is satisfied. Under driven steady state shearing, jamming occurs at a higher packing fraction $\phi_J$ than observed in compression. A growing relaxation time and translational correlation length is found as $\phi$ increases towards $\phi_J$. We consider the orientational ordering and rotation of particles induced by the shear flow. Both nematic and tetratic ordering are found, but these decrease as $\phi$ increases to $\phi_J$. At the jamming transition, the nematic ordering further decreases, while the tetratic ordering increases, but the orientational correlation lengths remain small throughout. The average angular velocity of the particles is found to increase as $\phi$ increases, saturating to a plateau just below $\phi_J$, but then increasing again as $\phi$ increases above $\phi_J$.

Ambulatory assessment of shoulder abduction strength curve using a single wearable inertial sensor.

The aim of the present article was to assess the reliability of strength curves as determined from tridimensional linear accelerations and angular velocities measured by a single inertial measurement unit (IMU) fixed on the upper arm during a shoulder abduction movement performed holding a 1 kg dumbbell in the hand. Within-subject repeatability of the task was assessed on 45 subjects performing four trials consisting of one maximal shoulder abduction-adduction movement. Intraclass correlation coefficient (ICC) was computed on the average movement angular velocity (VEL) and range of movement (ROM) across the four trials. Within-subject repeatability of torque curves was assessed in terms of waveform similarities by computing the coefficient of multiple determination (CMD). Accuracy of the estimated ROM was assessed using an isokinetic dynamometer. High ICC values of ROM (0.955) and VEL (0.970) indicated a high within-subject repeatability of the task. A high waveform similarity of torque curves was also found between trials (CMD = 0.867). Accuracy with respect to isokinetic dynamometer in estimating ROM was always <1 degree (p = 0.37). This study showed the effectiveness of using a single wearable IMU for the assessment of strength curve during isoinertial movements in a way that complies with the needs of clinicians in an ambulatory setting.

Age-related difference in postural control during recovery from posterior and anterior perturbations.

Decreased reactive postural responses in elderly adults may place them at increased risk for falls and related injuries. The first step in addressing the high rate of falls in the elderly population is to determine a baseline for postural response in healthy young and healthy elderly individuals. To determine these age-related differences in reactive postural responses during recovery from posterior and anterior perturbations, we used the tether-release method in conjunction with a motion analysis system to evaluate overall movement latencies, overall movement amplitude and velocity, and joint-specific amplitude and velocity in healthy young (n = 10, mean age=25 ± 5) and healthy elderly participants (n = 10, mean age = 67 ± 6). During posterior perturbations, healthy elderly participants had increased recovery time (P = 0.01) and ratio of center of mass to step length (P = 0.013) when compared with young participants. Elderly participants also had decreased step length (P = 0.006), peak COM velocity (P = 0.01), peak knee flexion angle (P = 0.002), and decreased hip (P = 0.005) and knee (P = 0.0005) average angular velocity when compared with young participants. We conclude that these movement deficiencies at the hip and knee limited the length of the recovery step. With this restricted step, elderly participants could not achieve adequate mechanical advantage to counteract the displacement of their COM using a single step. During anterior perturbations, elderly participants did not exhibit any significant differences compared to young participants in overall movement variables. This understanding of postural responses in healthy individuals is clinically relevant to the development of rehabilitation programs for individuals at high fall risk.

Limits of Stability and Adaptation to Wearing Rocker Bottom Shoes

Stability and balance are fundamental during static and dynamic activities. The effects of wearing rocker bottom sole (RBS) shoes on the limits of stability (LOS) and adaptation to wearing RBS shoes need to be investigated. The objectives of this study were to evaluate the LOS when wearing RBS shoes, and to evaluate if people improve their stability while wearing RBS shoes over time. Eleven female subjects with no lower extremity impairments participated in the study. The LOS were tested at baseline and weeks 3 and 6 using a Neurocom SMART EquiTest equipment. Center of pressure (CoP) was determined using force plates, and the center of gravity (CoG) position was estimated from the CoP measures and subjects' anthropometry. Subjects performed a series of tasks that involved leaning in different directions so as to move the vertical projection of their CoG. End-point excursions of the CoG floor projection were calculated as a percentage of the distance between the starting position and the target. Considering the body as an inverted pendulum, we recorded the average angular velocity of the inverted pendulum during the movements and quantified directional control as a percentage of movement toward versus away from the target. Shoe types were compared using paired t tests, and sessions were compared using repeated measures ANOVA. The angular velocities of the inverted pendulum (ie, CoG velocity) were not significantly different between shoe conditions in the front and back directions at baseline (4 ± 3 with RBS vs 5 ± 2 deg/sec with regular shoes, and 4 ± 1 vs 6 ± 4 deg/sec). Front directional control of the CoG was significantly worse with RBS shoes at weeks 3 and 6 ( P < .015). Front end-point excursions were also lower with RBS shoes both at baseline and week 6 ( P < .014). There were no significant changes over time. The findings indicate that the LOS were negatively affected by wearing RBS shoes and that people do not improve their stability while wearing these shoes even after a 6-week period of use. This study shows that wearing RBS shoes increase instability and the instability remains even after wearing these shoes for six weeks.

Looking and homing: how displaced ants decide where to go

We caught solitary foragers of the Australian Jack Jumper ant, Myrmecia croslandi, and released them in three compass directions at distances of 10 and 15 m from the nest at locations they have never been before. We recorded the head orientation and the movements of ants within a radius of 20 cm from the release point and, in some cases, tracked their subsequent paths with a differential GPS. We find that upon surfacing from their transport vials onto a release platform, most ants move into the home direction after looking around briefly. The ants use a systematic scanning procedure, consisting of saccadic head and body rotations that sweep gaze across the scene with an average angular velocity of 90° s(-1) and intermittent changes in turning direction. By mapping the ants' gaze directions onto the local panorama, we find that neither the ants' gaze nor their decisions to change turning direction are clearly associated with salient or significant features in the scene. Instead, the ants look most frequently in the home direction and start walking fast when doing so. Displaced ants can thus identify home direction with little translation, but exclusively through rotational scanning. We discuss the navigational information content of the ants' habitat and how the insects' behaviour informs us about how they may acquire and retrieve that information.

A measurement system for the bicycle crank angle using a wireless motion sensor attached to the crank arm

In this study, we propose a system for measuring the rotational angle of a bicycle crank arm. This system consists of a wireless motion sensor with bi-axial acceleration and angular velocity sensors attached to the crank arm. Rotational angles measured by the motion sensor were compared with data from a motion capture system. We found the RMS (root-mean-square) error for the bicycle crank angle was 0.339 ± 0.115 degrees (mean ± SD), and the angular velocity RMS error normalized by the average angular velocity was 0.655 ± 0.217 %. Using the proposed motion sensor system, we were able to measure the rotational angle and angular velocity of the bicycle crank to the same accuracy and high frequency as the motion capture system. Furthermore, we demonstrate it is possible to precisely obtain the rotational crank angle to evaluate fluctuations of crank angular velocity.

Effects of dopamine replacement therapy on lower extremity kinetics and kinematics during a rapid force production task in persons with Parkinson disease

Postural instability appears to be a dopamine resistance motor deficit in persons with Parkinson disease (PD); however, little is known about the effects of dopamine replacement on the relative biomechanical contributions of individual lower extremity joints during postural control tasks. To gain insight, we examined persons with PD using both clinical and laboratory measures. For a clinical measure of motor severity we utilized the Unified Parkinson Disease Rating Scale motor subsection during both OFF and ON medication conditions. For the laboratory measure we utilized data gathered during a rapid lower extremity force production task. Kinematic and kinetic variables at the hip, knee, and ankle were gathered during a counter movement jump during both OFF and ON medication conditions. Sixteen persons with PD with a median Hoehn and Yahr severity of 2.5 completed the study. Medication resulted in significant improvements of angular displacement for the hip, knee, and ankle. Furthermore, significant improvements were revealed only at the hip for peak net moments and average angular velocity compared to the OFF medication condition. These results suggest that dopamine replacement medication result in decreased clinical motor disease severity and have a greater influence on kinetics and kinematics proximally. This proximally focused improvement may be due to active recruitment of muscle force and reductions in passive restraint during lower extremity rapid force production.

The smoothness of unconstrained head movements is velocity-dependent

Non-smooth, irregular movements reported in persons with neck pain have been suggested to signify motor impairment. However, irregular movements are additionally observed during slow movements in healthy participants. We therefore examined whether the smoothness of head movements is related to the movement speed in 26 healthy participants. Six unconstrained small and large amplitude head movements were completed in the sagittal plane at three different self-chosen speeds. Kinematic variables were calculated from position data and overall smoothness of the movement was assessed by the normalized jerk cost (NJC). Relationship between NJC and average movement angular velocity was analyzed using a mixed factor model. Movement duration, angular velocity, NJC and number of submovements differed significantly between speed conditions for all movement directions and amplitudes (all p<.05). We found a strong relationship between the average angular velocity and NJC across all movement directions and amplitudes (all p<.0001). Large amplitude movements showed higher NJC for a given movement velocity than small amplitude movements (p<.001). We have shown that the smoothness of head movements is strongly related to the movement velocity, thus fast movements are smooth while slow movements are jerky. In addition, movements of larger amplitude are less smooth than movements of smaller amplitude.

FRI0472-HPR Assessment of postural control, strenght of lower limbs and pain in individuals with and without fibromyalgia

BackgroundFibromyalgia (FM) is a syndrome characterized by chronic widespread musculoskeletal pain and the presence of tender points associated with sleep disturbance, fatigue, chronic headaches and psychiatric disorders, factors that may...

The remarkable agreement between the oscillation and wandering characteristics of solutions of differential systems

Lyapunov-type oscillation and wandering indicators are defined for solutions of systems of differential equations; these are the average frequency of zeros for the projection of a solution onto some line and the average angular velocity of rotation of a solution about the origin in some basis, respectively. An integral equality relating these indicators is obtained. The indicators introduced are shown to coincide if, prior to averaging, the oscillation indicators are minimized over all possible lines, and the wandering indicators over all possible bases.Bibliography: 17 titles.

Experimental and Numerical Study of the Motion of a Liquid Pouring from a Beverage Can

The motion of a liquid pouring from a beverage can is experimentally and numerically studied. First, we measure pouring motion for sixteen examinees and find that the can motion in pouring consists of three stages; tipping stage, filling stage, and returning stage. In each stage, the angular velocity of a can is nearly constant, and its average velocity is obtained. A liquid flow from a can rotating at the average angular velocity is visualized with high-speed cameras and is also numerically simulated with the Volume of Fluid (VOF) method. At the beginning of pouring, the liquid from a can opening is once blocked by the rim of a upper lid and then flows over the rim. It falls from the can forming a V-shaped surface, which converges few centimeters below the rim expanding the liquid surface in the direction perpendicular to the V-shaped surface. This results in a wavy pattern of the liquid surface. The computational result agrees with the experiment.

2P1-F02 昆虫の匂い源探索行動における行動パラメタに対する定位性能の評価(バイオロボティス(2))

In robotics, chemical plume tracing has been a challenging problem since odor distribution is very complex. Male silkworm moths have the ability to search for females by tracing their pheromone plumes. To investigate the moth's brain adaptability to modify its behavior, we identified the brain as a dynamic model by using a brain-machine hybrid system, which was composed of a moth's brain and a robotic body. As a result, the brain has the ability to keep the angular velocity responses constant. Then we evaluated by computer simulations whether the localization performance was related to the angular velocity, which was one of the behavior parameters. In conclusion, adjusting the angular velocity of robots to the average angular velocity of moths potentially improves the localization performance.

A Simplified Model of the Internal Combustion Engine

This project further investigates a model of a simplified internal combustion engine considered by Kranc in 1977. Using Euler’s method for ordinary differential equations, we modeled the interaction between the engine’s flywheel and thermodynamic power cycle. Approximating with sufficiently small time intervals (0.001 seconds over a period of 12 seconds) reproduced Kranc’s results with the engine having an average angular velocity of 72/sec.

1P1-F07 フレキシブルな噴射管を有するウォーターポンプジェット推進機構を持つ小型遊泳ロボット(フレキシブルロボット・メカニズム)

In this paper, we propose a swimming robot driven by a water jet pump with an active exible nozzle for steering. The proposed robot is of 220[mm] in length and consists of a slim body for entering a narrow space. Experimental results using a prototype of the proposed swimming robot show that the robot not only can swim forward at the average velocity of 0.44[m/s] corresponding about 2[BL/s](body length per second), but also can turn underwater at the average angular velocity of 156[deg/s] with a small turning radius of 160[mm].

탄소나노튜브 인솔 착용에 따른 드롭 착지 동작의 생체역학적 분석

The purpose of this study was to determine the biomechanical effect of wearing carbon nanotube-based insole on cushioning and muscle tuning during drop landing. Twenty male university students(age: <TEX>$21.2{\pm}1.5yrs$</TEX>, height: <TEX>$175.4{\pm}4.7cm$</TEX>, weight: <TEX>$70.2{\pm}5.8kg$</TEX>) who have no musculoskeletal disorder were recruited as the subjects. Average axial strain, average shear strain, inversion angle, linear velocity, angular velocity, vertical GRF and loading rate were determined for each trial. For each dependent variable, a one-way analysis of variance(ANOVA) with repeated measures was performed to test if significant difference existed among different three conditions(p<.05). The results showed that Average axial strain of line 4 was significantly less in CNT compared with EVA and PU during IP phase. The average shear strain was less in CNT compared with EVA and PU during other phases. The inversion angle was increased in CNT compared with EVA and PU during all phase. In linear velocity, angular velocity, vertical GRF and loading rate, there were no significant difference between the three groups. This result seems that fine particle of carbon nanotube couldn't make geometric form which can absolve impact force by increasing density through eliminating voids of forms. Thus, searching for methods that keep voids of forms may play a pivotal role in developing of insole. This has led to suggestions of the need for further biomechanical analysis to these factors.

Differences in Human Cervical Spine Kinematics for Active and Passive Motions of Symptomatic and Asymptomatic Subject Groups

Most musculoskeletal disorders of the head and neck regions cannot be identified through imaging techniques; therefore clinician-conducted assessments (passive motions) are used to evaluate the functional ability of these regions. Although active motions do not require interaction with a clinician, these movements can also provide diagnostic indicators of dysfunction. The purpose of this research was to determine whether kinematic measures differed between active and passive movements of participants in symptomatic and asymptomatic groups. Data obtained on cervical lateral flexion range of motion (ROM), coupled axial rotation, and the angular velocity of lateral flexion were statistically analyzed and demonstrated differences between active and passive motions for symptomatic and asymptomatic subjects. Active motions had higher angular velocities (P&lt; .001) and larger ROMs, with greater lateral flexions (P&lt; .05). The asymptomatic group produced a larger average lateral flexion of 7.9° at an average angular velocity of 2 deg/s greater than the symptomatic group. Trends with regard to group assignment were the same for active and passive motions. This work demonstrates the potential for using kinematic measures of active and passive motions to develop an objective standard for diagnoses of cervical dysfunction and supports validity of the clinician-based analysis to distinguish between participant groups.