Leg Acceleration Research Articles

The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running

Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

Leg Impact Accelerations And Ground Reaction Forces During Running On A Treadmill And Overground.

PURPOSE: The purpose of the study is to determine the relationship between impact forces and leg accelerations while running on a treadmill and overground. METHODS: Subjects (n=12: 8 males, 4 females; age: 23.9 ± 6.02 y; height: 1.71 m ± 0.11 m; mass: 69.8 ± 14.5 kg) participated in a 1-day test during which ground reaction forces (GRF) and leg accelerations were recorded during overground and treadmill running. All GRF data were collected using an instrumented force treadmill (Bertec, USA) with handrails removed and treadmill surface even with floor surface. To complete overground trials, subjects ran over the treadmill (belt not moving) with speed measured suing timing gates placed before and after the treadmill surface. A wired uniaxial accelerometer was securely placed on the distal medial aspect of the right tibia to measure leg impact acceleration (legpeak). All subjects completed 10 trials for each of 3 speed conditions (preferred speed (PS) ± 0.25 m/s) for each condition (treadmill, overground). Impact force (F1), legpeak, and ratio of F1: legpeak were determined and compared between speeds and modes using repeated measures ANOVAs. RESULTS: None of the variables were influenced by the interaction of speed and mode (Ratio, p=0.701; F1, p=0.778; legpeak , p=0.736). Ratio was not influenced by speed (p=0.281) or mode (p=0.126). F1 was not different between overground and treadmill (p=0.077) but was influenced by speed (p=0.024) increasing on average 8.4% from slow to fast speed. Legpeak was 36.5% greater during overground vs. treadmill (p=0.048) but did not change over speeds (p=0.206). CONCLUSIONS: The consistent ratio between F1 and legpeak during treadmill and overground running seems to indicate the relationship between these parameters is not influenced by mode of running. However, the greater legpeak during overground running and the trend for a greater F1 overground is an indication that subjects may have used different strategies to achieve the same speeds while running overground vs. treadmill.

Dynamics analysis of a novel 5-DoF 3SPU+2SPRR type parallel manipulator

A novel 5-DOF 3SPU+2SPRR type parallel manipulator is proposed. First, the formulae are derived for solving the kinematics parameters of the moving platform. Second, the kinematics of the active legs and connection rod are analyzed, and the formulae for solving velocity and acceleration of the active legs and connection rod are derived. Third, the formulae are derived for solving the dynamic active and constrained forces. Finally, an analytic example is given for solving the dynamics, and the analytic solved results are verified by the mechanism simulation. This paper is aimed at laying a solid theoretical and technical foundation for its prototype manufacture and control.

Validation of HOBO Pendant® data loggers for automated step detection in two age classes of male turkeys: growers and finishers

Activity levels can be used as a predictor of health status, physical condition, feed efficiency, and coping style in animals. Small, portable data loggers have been validated as an inexpensive and effective alternative to video or live observation for automated activity detection in several livestock species. Our study aimed to validate the use of Onset HOBO Pendant® G acceleration data loggers for automated step detection in two age classes of male turkeys: growers and finishers. The loggers were attached to one leg in an elastic harness and programmed to record each turkey’s leg accelerations every 0.1s. For the grower turkeys, the activities of 60 males were recorded in a runway twice per week from 9–11 weeks of age. In the finisher trial, the loggers were attached to eight 14 week old male turkeys to record their stepping activities in a trial pen over 54min. Simultaneous video observation allowed for logger suitability to be determined for reporting walking activity. The 0.1s data points were identified as either: true positives, false positives, false negatives, or true negatives then the logger sensitivity, false discovery rate, specificity, precision, and accuracy were calculated for each turkey run. Over the 309 grower turkey runs, 4364 steps were observed in the video while the loggers detected 4865 steps. The grower logger results showed a mean sensitivity of 96.02±6.82%, specificity of 99.10±0.86%, and an average false discovery rate of 12.41±10.13% for step detection (mean±standard deviation). For the grower turkey loggers, the mean precision and accuracy for step detection were 87.59±10.13% and 98.95±0.77%. For the eight finisher turkeys, a total of 2420 steps were seen by the video and the loggers recorded 2691 data points as steps. The finisher turkey logger data showed a mean sensitivity of 89.58±11.75%, mean false discovery rate of 14.73±10.66%, and average specificity of 99.81±0.19%. The finisher logger results had a mean precision of 85.27±10.66% and a mean accuracy of 99.73±0.13%. Although the loggers showed high sensitivity for detecting turkey steps under research settings, future research should try to reduce the loggers’ susceptibility to background noise, which would improve their performance for application in commercial conditions.

Postural responses to anterior and posterior perturbations applied to the upper trunk of standing human subjects.

This study concerned the effects of brisk perturbations applied to the shoulders of standing subjects to displace them either forwards or backwards, our aim being to characterise the responses to these disturbances. Subjects stood on a force platform, and acceleration was measured at the level of C7, the sacrum and both tibial tuberosities. Surface EMG was measured from soleus (SOL), tibialis anterior (TA), the hamstrings (HS), quadriceps (QUAD), rectus abdominis (RA) and lumbar paraspinal (PS) muscles. Trials were recorded for each of four conditions: subjects’ eyes open (reference) or closed and on a firm (reference) or compliant surface. Observations were also made of voluntary postural reactions to a tap over the deltoid. Anterior perturbations (mean C7 acceleration 251.7 mg) evoked activity within the dorsal muscles (SOL, HS, PS) with a similar latency to voluntary responses to shoulder tapping. Responses to posterior perturbations (mean C7 acceleration −240.4 mg) were more complex beginning, on average, at shorter latency than voluntary activity (median TA 78.0 ms). There was activation of TA, QUAD and SOL associated with initial forward acceleration of the lower legs. The EMG responses consisted of an initial phasic discharge followed by a more prolonged one. These responses differ from the pattern of automatic postural responses that follow displacements at the level of the ankles, and it is unlikely that proprioceptive afferents excited by ankle movement had a role in the initial responses. Vision and surface properties had only minor effects. Perturbations of the upper trunk evoke stereotyped compensatory postural responses for each direction of perturbation. For posterior perturbations, EMG onset occurs earlier than for voluntary responses.Electronic supplementary materialThe online version of this article (doi:10.1007/s00221-015-4442-2) contains supplementary material, which is available to authorized users.

Inertial Measurement Units (IMUs) in Drowning Prevention: An Exploratory Study

The use of inertial measurement unit (IMUs) sensors in competitive swimming movement analysis has become increasingly popular but has not been applied to measuring water competencies related to drowning prevention. This study explored the potential use of IMU sensors in three simulated water competency activities in a pool environment. Participants were a subset (n = 12) of a cohort of students (n = 37) taking part in the Can You Swim in Clothes? project. Participants undertook a swim for speed test over 25 m, a distance swim of 5-min duration, and a flotation test, also for 5 min, wearing swimwear and again in lightweight street clothing while wearing an IMU to measure leg acceleration forces. Results showed that clothing impeded swimming sprint speed and distance but not flotation. Authors suggest further research with regard to IMU placement, appropriate survival activities, and measurement protocols and recommend the need for expanded future IMU use.

Inertial Measurement Units (IMUs) in Drowning Prevention: An Exploratory Study

The use of inertial measurement unit (IMUs) sensors in competitive swimming movement analysis has become increasingly popular but has not been applied to measuring water competencies related to drowning prevention. This study explored the potential use of IMU sensors in three simulated water competency activities in a pool environment. Participants were a subset (n = 12) of a cohort of students (n = 37) taking part in the Can You Swim in Clothes? project. Participants undertook a swim for speed test over 25 m, a distance swim of 5-min duration, and a flotation test, also for 5 min, wearing swimwear and again in lightweight street clothing while wearing an IMU to measure leg acceleration forces. Results showed that clothing impeded swimming sprint speed and distance but not flotation. Authors suggest further research with regard to IMU placement, appropriate survival activities, and measurement protocols and recommend the need for expanded future IMU use.

Controlled In-Plane Locomotion of a Hexapod Using a Single Actuator

This paper presents “1STAR,” which is the first robot that is driven by a single actuator but can be directly commanded to move straight or turn clockwise or counterclockwise. The legged robot relies on a novel actuation gait, which exploits the compliance disparity between alternate stance tripods, to generate rotation by continuously accelerating and decelerating the legs. The direction of turning depends on the configuration of the legs—tripod left or right—and the timing of the acceleration and deceleration. Alternating leg acceleration in successive steps allows for continuous rotation in the desired direction. The turning radius can be varied by changing the timing of the leg acceleration and deceleration without changing the cycle frequency and linear speed. A simplified kinematic motion model of a robot is presented, and a dynamic simulation is performed to analyze the behavior and optimize robot parameters. The locomotion gait is verified experimentally using our newly designed “1STAR” robot.

Modeling of the Propulsion Hydrodynamics for the Water Strider Locomotion on Water Surface

Modeling of the propulsion hydrodynamics of water striders, which was rare performed in previous studies, was developed in this paper. First, kinematical mechanism of the production of dipolar vortex in the wake of striders was illustrated by investigating the dependencies between the velocities on trajectories of the leg and velocity distribution in vortices. Subsequently, topological similarities between the hemispherical vortex and dipolar vortex was demonstrated by comparing their geometries and velocity distributions. Afterwards, velocity dependencies between the leg and flow in vortex further revealed that the translational speed of vortex is roughly determined by leg speed and that peak leg speed is about 2.5 times of the mean leg speed. Hence, the acceleration was formulized based on the peak and mean speeds of the leg. According to Theorem of Momentum and equivalence between the momentums of the water strider and fluid, mean propulsion force was then formulized, which is correlated with the leg acceleration and volume of vortex. It was found that the strider should produce bigger ‘water balls’ (enclosed in vortices) and push them backward with a larger acceleration so that to obtain a greater reaction force for propelling. For the same strider, further derived scaling law tells propulsion force is linearly dependent on leg speed and is parabolic with respective to Weber number. An incisive analysis on experimental data indicated the radius of dipolar vortex is comparable to the length of leg's second tarsal on water. Finally, Young-Laplace equation was yielded for the balance of pressures on upside and underside of water surface. Accordance between reported measurements and predicted values indicates the validity and reasonability of the model.

The acute effect of stretching on the kinematics of instep kicking in soccer

Some previous research indicates that compared to dynamics stretching, static stretching may inhibit the performance of the instep kick, but the effect of these two modes of stretching on soccer players with differing levels of playing experience is not known. Hence, the purpose of this study was to examine the effects of static and dynamic stretching during pre-exercise warm-up on lower extremity kinematics during soccer instep kicking in less and more experienced players. Twenty-four professional male soccer players (12 less experienced and 12 more experienced players) volunteered to participate. Lower extremity joint kinematics of soccer instep kicking were analyzed after static stretching, dynamic stretching, and no-stretching warm-up protocols. The kinematic variables analyzed were the maximum hip angular velocity and maximum knee angular velocity during the leg acceleration phase, and maximum ball velocity after impact phase. Relative to the no-stretching condition, both less and more experienced players had significantly larger hip angular velocity, knee angular velocity, and ball velocity after dynamic stretching than after static stretching. There were no significant differences in joint angular kinematics and ball velocity data between less and more experienced players after static stretching compared to dynamic stretching. This study suggests that dynamic stretching within warm-ups may be more effective than static stretching as a preparation for the instep kick in soccer players.

Kinetostatic analysis of a novel 6-DoF 3UPS parallel manipulator with multi-fingers

A novel 6-DoF 3UPS parallel manipulator (PM) with multi-fingers is proposed and its kinetostatics is studied in the light of its application. First, the proposed PM with multi-fingers is designed, and its structural characteristics are analyzed. Second, some formulae are derived for solving the displacement, linear/angular velocity and acceleration of UPS type composite active leg, the Jacobian and Hessian matrices, and the velocity, statics and acceleration of the 3UPS PM. Third, the kinematics of fingers and the workload applied on the fingers are transformed into the coordination kinematics and the active forces/torques applied onto the active legs of both the proposed PM and the fingers. Fourth, an analytic solving example of the proposed PM with three fingers is given for illustrating the application of the kinetostatic formulae. Fifth, the workspaces of the proposed PM and one finger are constructed. Finally, the analytic solutions are verified by simulation solutions.

Patterns of anterior and posterior muscle chain interactions during high performance long-hang elements in gymnastics

In a prior study with high level gymnasts we could demonstrate that the neuromuscular activation pattern during the “whip-like” leg acceleration phases (LAP) in accelerating movement sequences on high bar, primarily runs in a consecutive succession from the bar (punctum fixum) to the legs (punctum mobile). The current study presents how the neuromuscular activation is represented during movement sequences that immediately follow the LAP by the antagonist muscle chain to generate an effective transfer of momentum for performing specific elements, based on the energy generated by the preceding LAP. Thirteen high level gymnasts were assessed by surface electromyography during high performance elements on high bar and parallel bars. The results show that the neuromuscular succession runs primarily from punctum mobile towards punctum fixum for generating the transfer of momentum. Additionally, further principles of neuromuscular interactions between the anterior and posterior muscle chain during such movement sequences are presented. The findings complement the understanding of neuromuscular activation patterns during rotational movements around fixed axes and will help to form the basis of more direct and better teaching methods regarding earlier optimization and facilitation of the motor learning process concerning fundamental movement requirements.

Kinematics and statics analysis of a novel 5-DoF parallel manipulator with two composite rotational/linear active legs

A novel 5-DoF parallel manipulator (PM) with two composite rotational/linear active legs is proposed and its kinematics and statics are studied systematically. First, a prototype of this PM is constructed and its displacement is analyzed. Second, the formulas are derived for solving the linear/angular velocity and acceleration of UPS composite active leg. Third, the Jacobian and Hessian matrices are derived and formulas for solving the velocity, statics and acceleration of this PM are derived. Third, a reachable work space is constructed using a CAD variation geometric approach. Finally, the kinematics and statics of this PM are illustrated and solved. The solved results are verified by the simulation results.

Neuromuscular onset succession of high level gymnasts during dynamic leg acceleration phases on high bar

In several athletic disciplines there is evidence that for generating the most effective acceleration of a specific body part the transfer of momentum should run in a “whip-like” consecutive succession of body parts towards the segment which shall be accelerated most effectively (e.g. the arm in throwing disciplines). This study investigated the question how this relates to the succession of neuromuscular activation to induce such “whip like” leg acceleration in sports like gymnastics with changed conditions concerning the body position and momentary rotational axis of movements (e.g. performing giant swings on high bar). The study demonstrates that during different long hang elements, performed by 12 high level gymnasts, the succession of the neuromuscular activation runs primarily from the bar (punctum fixum) towards the legs (punctum mobile). This demonstrates that the frequently used teaching instruction, first to accelerate the legs for a successful realization of such movements, according to a high level kinematic output, is contradictory to the neuromuscular input patterns, being used in high level athletes, realizing these skills with high efficiency.Based on these findings new approaches could be developed for more direct and more adequate teaching methods regarding to an earlier optimization and facilitation of fundamental movement requirements.

Specific characteristics of spontaneous movements in preterm infants at term age are associated with developmental delays at age 3 years

The aim of this study was to investigate the relationship between the characteristics of spontaneous movements in preterm infants at term age and developmental delay at 3years of age. We analysed video recordings of the spontaneous movements in the supine position of 124 preterm infants (44 males, 80 females) at 36 to 44weeks postmenstrual age (PMA). The infants were born preterm (22-36wks PMA; birthweight 489-1696g) and had not received a diagnosis of a neurological or developmental disorder by the age of 3years. The recorded spontaneous movements were quantified using six movement indices, which were calculated from two-dimensional trajectories of all limbs. The infants were divided into three developmental groups, normal, borderline, or delayed, based on their developmental quotient as calculated using the Kyoto Scale of Psychological Development 2001 (Kyoto Scale) at 3years of age. Group differences in the movement indices were analysed. In the delayed group, average velocity of arms and legs were significantly lower (p<0.05 and p<0.01 respectively), the numbers of movement units of arms and legs were significantly lower (p<0.05 and p<0.01 respectively), kurtosis of acceleration of arms and legs was significantly higher (p<0.05 in each case), and correlation between limb velocities was higher (p<0.05) than in the normal group. In children who exhibited developmental delay at 3years of age, the spontaneous movements at term age can be described as less active with intermittent occurrences of abrupt and synchronized movements of the limbs. Recognition of these characteristics of spontaneous movements at term age may be used as a predictor for subsequent cognitive and behavioural development in preterm infants.

Effects of Foot Strike on Low Back Posture, Shock Attenuation, and Comfort in Running

Barefoot running (BF) is gaining popularity in the running community. Biomechanical changes occur with BF, especially when initial contact changes from rearfoot strike (RFS) to forefoot strike (FFS). Changes in lumbar spine range of motion (ROM), particularly involving lumbar lordosis, have been associated with increased low back pain. However, it is not known if changing from RFS to FFS affects lumbar lordosis or low back pain. The purpose of this study was to determine whether a change from RFS to FFS would change lumbar lordosis, influence shock attenuation, or change comfort levels in healthy recreational/experienced runners. Forty-three subjects performed a warm-up on the treadmill where a self-selected foot strike pattern was determined. Instructions on running RFS/FFS were taught, and two conditions were examined. Each condition consisted of 90 s of BF with RFS or FFS, order randomly assigned. A comfort questionnaire was completed after both conditions. Fifteen consecutive strides from each condition were extracted for analyses. Statistically significant differences between FFS and RFS shock attenuation (P < 0.001), peak leg acceleration (P < 0.001), and overall lumbar ROM (P = 0.045) were found. There were no statistically significant differences between FFS and RFS in lumbar extension or lumbar flexion. There was a statistically significant difference between FFS and RFS for comfort/discomfort of the comfort questionnaire (P = .007). There were no statistically significant differences between other questions or the average of all questions. Change in foot strike from RFS to FFS decreased overall ROM in the lumbar spine but did not make a difference in flexion or extension in which the lumbar spine is positioned. Shock attenuation was greater in RFS. RFS was perceived a more comfortable running pattern.

Musculoskeletal Attenuation of Impact Shock in Response to Knee Angle Manipulation

Shock waves resulting from the foot-ground impact are attenuated by biological tissues within the body. It has been suggested that the primary site for shock attenuation is the knee joint. The purpose of this study was to determine if knee flexion affects the filtering characteristics of the musculoskeletal system in response to impacts. Impacts were delivered to 10 participants during inline skating on a treadmill at 2.0 m/s. Four knee angle conditions (0, 10, 20, and 30 degrees) were investigated using real-time visual feedback of motion capture data. Shock attenuation between the leg and head was determined using accelerometry. The cutoff frequency of the body was determined by progressive filtering of the leg acceleration until differences between head acceleration and filtered leg acceleration were minimized. A nonlinear increase in shock attenuation (p < .001) and a nonlinear decrease in the cutoff frequency of the body (p < .001) were observed as the knee became more flexed. These results suggest that the knee joint acts as a low-pass filter allowing greater shock attenuation with increased knee flexion. Flexing the knee may shift the shock-attenuating responsibilities away from passive biological tissue toward active muscular contraction.

Entropy analysis of tri‐axial leg acceleration signal waveforms for measurement of decrease of physiological variability in human gait

Disease-related and senescent decrease of physiological variability in biological time-series outputs (e.g., heart rate) has drawn increasing attention as a potential new type of biomarker. In this paradigm, measurement of variability in periodic motion may enable quantitative evaluation of functional limitation in people with musculoskeletal disorders. A novel technique to measure variability of leg motion patterns during level walking was used to study 52 adults with symptomatic knee osteoarthritis (OA), and 57 asymptomatic control subjects over a wide range of age (20-79 years). The hypothesis was that cycle-to-cycle variability in leg motion patterns, indexed by tri-axial acceleration signal entropy, would be lower in those with greater age or with knee symptoms. Leg motions were assessed using portable inertial monitors attached bilaterally just above each ankle. The tri-axial acceleration data were analyzed using a nonlinear variability measurement tool designated as Sample Entropy (SampEn). SampEn data for asymptomatic subjects exhibited a significant negative correlation (r = -0.287, p = 0.0306) with greater age. OA subjects had significantly lower SampEn values (p = 0.0002) than did age-matched asymptomatic subjects who walked at equivalent velocity. This approach holds promise as a basis for valid, inexpensive, and convenient objective evaluation of limitations in human gait function.

Measurement of acceleration while walking as an automated method for gait assessment in dairy cattle

The aims were to determine whether measures of acceleration of the legs and back of dairy cows while they walk could help detect changes in gait or locomotion associated with lameness and differences in the walking surface. In 2 experiments, 12 or 24 multiparous dairy cows were fitted with five 3-dimensional accelerometers, 1 attached to each leg and 1 to the back, and acceleration data were collected while cows walked in a straight line on concrete (experiment 1) or on both concrete and rubber (experiment 2). Cows were video-recorded while walking to assess overall gait, asymmetry of the steps, and walking speed. In experiment 1, cows were selected to maximize the range of gait scores, whereas no clinically lame cows were enrolled in experiment 2. For each accelerometer location, overall acceleration was calculated as the magnitude of the 3-dimensional acceleration vector and the variance of overall acceleration, as well as the asymmetry of variance of acceleration within the front and rear pair of legs. In experiment 1, the asymmetry of variance of acceleration in the front and rear legs was positively correlated with overall gait and the visually assessed asymmetry of the steps (r ≥0.6). Walking speed was negatively correlated with the asymmetry of variance of the rear legs (r=−0.8) and positively correlated with the acceleration and the variance of acceleration of each leg and back (r ≥0.7). In experiment 2, cows had lower gait scores [2.3 vs. 2.6; standard error of the difference (SED)=0.1, measured on a 5-point scale] and lower scores for asymmetry of the steps (18.0 vs. 23.1; SED=2.2, measured on a continuous 100-unit scale) when they walked on rubber compared with concrete, and their walking speed increased (1.28 vs. 1.22m/s; SED=0.02). The acceleration of the front (1.67 vs. 1.72g; SED=0.02) and rear (1.62 vs. 1.67g; SED=0.02) legs and the variance of acceleration of the rear legs (0.88 vs. 0.94g; SED=0.03) were lower when cows walked on rubber compared with concrete. Despite the improvements in gait score that occurred when cows walked on rubber, the asymmetry of variance of acceleration of the front leg was higher (15.2 vs. 10.4%; SED=2.0). The difference in walking speed between concrete and rubber correlated with the difference in the mean acceleration and the difference in the variance of acceleration of the legs and back (r ≥0.6). Three-dimensional accelerometers seem to be a promising tool for lameness detection on farm and to study walking surfaces, especially when attached to a leg.

Kinematics Analysis of Some Linear Legs With Different Structures for Limited-DOF Parallel Manipulators

To solve the velocity and acceleration of legs with different structures is a fundamental and challenging issue for dynamics analysis of parallel manipulators (PMs). In this paper, the kinematics of linear legs with different structures for limited-degree of freedom (DOF) PMs is studied. First, based on kinematics/statics of general limited-DOF PM, the formulas are derived for solving the angular velocity/acceleration of some linear legs with different structures. Second, the velocity and acceleration of the piston/cylinder in the legs are represented by velocity and acceleration of platform in PM. Finally, the solving procedures are illustrated by applying this approach to a 4DOF PM.