COM Velocity Research Articles

Evaluation of Core Stability and Foot Kinematics of Taekwondo Athletes

To score in taekwondo competition requires faster kicking. Among the factors that influence kicking velocity, core stability is important, but the relationship between core stability and kicking velocity in taekwondo is unclear. The aim of this study was to investigate the association between core stability and foot segmental COM velocity at the moment of kick. A total of 13 taekwondo instructors (gender: male, height: 172.6±7.3 cm, weight: 64.3±11.78 kg, age: 29±4 years) participated in this study. The center of mass velocity of the left foot segment at the moment of the kick and the level of core stability was measured using the Sahrmann core stability test. During the Naraechagi, the velocity of the foot segment COM relative to the laboratory origin at the moment of the aerial phase kick was positively correlated in the forward and backward directions X-axis. Moderate correlation in the left and right direction Z-axis. Very strong correlation in the up and down direction Y-axis. Through the current experiment, we found a strong correlation between core stability and kicking speed in the forward and backward and up and down directions. Therefore, we believe that adding core stability training to taekwondo training has the potential to increase kicking speed.

Kinematic Measures for Recovery Strategy Identification following an Obstacle-Induced Trip in Gait

This study aimed to identify the kinematic measures determining balance outcome following an over-ground trip perturbation. 117 healthy older adults who experienced laboratory-induced trips were divided into loss of balance (LOB) and no LOB groups. The LOB group contained 27 fallers and 34 non-fallers, and the no LOB group contained 21 participants using cross-over strategy and 35 participants using obstacle-hit strategy. A 2-class hierarchical regression model for balance loss showed that margin of stabilty could determine the balance outcomes (LOB or not) with an overall accuracy of 92.7%. The 4-class model for recovery strategies showed that the combination of margin of stability, trunk angle, and COM velocity could determine 81.9% of strategies. Our findings would enhance intervention development for populations at risk of trip-induced falls.

Association of balance control mechanisms with brain structural integrity in older adults with mild cognitive impairment

BackgroundOlder adults with mild cognitive impairment (OAwMCI) exhibit subtle balance control and gait deficits which are predominantly associated with structural brain pathologies such as impaired white matter integrity and reduced gray matter volume. However, the relationship between balance recovery mechanisms and neural substrates in OAwMCI remains unknown. This study thus aimed to explore the associations of volitional (self-initiated) and reactive balance (in response to an external perturbation) control with structural brain integrity. MethodsTen OAwMCI (MoCA 18-25/30; greater than 55 years) were examined on the limits of stability test (volitional balance via Equitest), stance perturbation test (reactive balance via ActiveStep treadmill) and underwent magnetic resonance imaging. Forward movement (frequently performed functional activity of daily living) was quantified by maximum excursion (maximum ability to shift one’s center of gravity toward the theoretical limit [MXE-%])and directional control (amount of movement exhibited towards the target proportional to the movement away from the target [DCL-%]) on the limits of stability test. Slip-like (prevalent type of accidental falls) perturbations were quantified by postural stability (shortest distance of the COM motion state, i.e., its position and velocity, to the theoretical boundary) on the ActiveStep treadmill. White matter integrity was quantified by fractional anisotropy (FA, movement of water molecules directionality) and gray matter volume measured in mm3. ResultsFor volitional balance control, reduced forward MXE was significantly (p < 0.05) associated with lower FA in left (R2 = 0.56) and right (R2 = 0.60) corticospinal tract, left (R2 = 0.49) and right (R2 = 0.51) corticothalamic tract, left (R2 = 0.70) and right (R2 = 0.57) frontopontine tract, right (R2 = 0.67) cingulum, anterior commissure (R2 = 0.82), and corpus callosum (R2 = 0.62). Reduced forward DCL was significantly (p < 0.05) associated with reduced gray matter volume in the left (R2 = 0.75) and right (R2 = 0.81) cerebellum, brainstem (R2 = 0.64), right (R2 = 0.49) thalamus. For reactive balance control, reduced postural stability (p < 0.05) was significantly associated with reduced FA in the left (R2 = 0.75) and right (R2 = 0.64) corticospinal tract, left (R2 = 0.67) and right (R2 = 0.65) frontopontine tract. Reduced postural stability was significantly (p < 0.05) associated with reduced gray matter volume in the brainstem (R2 = 0.72) and right cerebellum (R2 = 0.70). ConclusionOur results indicate that structural brain integrity influences stability control in OAwMCI for both volitional and reactive balance tasks, which may share some common cortico-subcortical motor pathways and relay centers. Results also show that the integrity of descending pathways from cortical attentional centers could influence stability control for both tasks.

Maximal Strength in Relation to Force and Velocity Patterns During Countermovement Jumps.

To investigate the associations between maximal strength and GRF and COM velocity patterns during CMJ. Nineteen female college lacrosse players performed 3 maximal-effort CMJs and isometric midthigh pull. GRF and COM velocity time series data from the CMJ were time normalized and used as inputs to principal-components analyses. Associations between isometric midthigh pull peak force and CMJ principal-component scores were investigated with a correlational analysis. Isometric midthigh pull peak force was associated with several GRF and COM velocity patterns. Correlations indicated that stronger players exhibited a GRF pattern characterized by greater eccentric-phase rate of force development, greater peak GRF, and a unimodal GRF profile (P = .016). Furthermore, stronger athletes exhibited a COM velocity pattern characterized by higher velocities during the concentric phase (P = .004). Maximal strength is correlated to specific GRF and COM velocity patterns during CMJ in female college lacrosse athletes. Since maximal strength was not correlated with discrete CMJ variables, the patterns extracted via principal-components analyses may provide information that is more beneficial for performance coaches and researchers.

Stability region derived by center of mass for older adults during trivial movements

BackgroundIt is important to understand the dynamic stability mechanisms of the elderly in performing different body movements, as it may be related to fall prevention. Research questionHow construct time-independent region of stability as bench-marked for elderly people during trivial movements? MethodsIn this paper, we propose to construct time-independent region of stability (RoS) and characterize age-related differences using center of mass velocity (CoMv) and acceleration (CoMa) synchronically during left stand, right stand, left kick, right kick, walk, sit-to-stand. Twenty-nine subjects participated in the experiments. Six Vicon MX motion capture cameras and two AMTI OR6 Series Force Plate recorded the movements of elderly and young people. Statistical analyses and derivation formulas of RoS were proposed. ResultsThe normalized CoMv and CoMa for elderly group was found to be significantly difference to the young group when doing left stand, right kick, left kick. In addition, the normalized CoMa of elderly group demonstrated significantly larger than that of young group for left stand (−0.310 ± 0.142; −0.484 ± 0.186), right kick (−0.347 ± 0.118; −0.473 ± 0.161), walk (−0.388 ± 0.086; −0.433 ± 0.108). However, the normalized CoMa of elderly group demonstrated significantly smaller than young group for right stand (0.373 ± 0.166; 0.490 ± 0.197), left kick (0.365 ± 0.140; 0.466 ± 0.185), sit-to-stand (0.297 ± 0.151; 0.326 ± 0.148), that suggesting age-related differences in momentum control. SignificanceThe velocity and acceleration of CoM could provide a better understanding of human momentum control, which would better reveal the underlying mechanism of body instability and gait imbalance.

Acute Effects of Handheld Loading on Standing Broad Jump in Youth Athletes.

The study aimed to investigate the acute effects of handheld loading on standing broad jump (SBJ) performance and biomechanics. Fifteen youth male athletes (mean age: 14.7 ± 0.9 years; body mass: 59.3 ± 8.0 kg; height: 1.73 ± 0.07 m) volunteered to participate in the study. Participants were assigned to perform SBJ with and without 4 kg dumbbells in a random order. Kinematic and kinetic data were collected using 10 infrared high-speed motion-capture cameras at a 250 Hz sampling rate and two force platforms at a 1000 Hz sampling rate. A paired t-test was applied to all variables to determine the significance between loading and unloading SBJs. Horizontal distance (p < 0.001), take-off distance (p = 0.001), landing distance (p < 0.001), horizontal velocity of center of mass (CoM; p < 0.001), push time (p < 0.001), vertical impulse (p = 0.003), and peak horizontal and vertical ground reaction force (GRF; p < 0.001, p = 0.017) were significantly greater in loading SBJ than in unloading SBJ. The take-off vertical velocity of CoM (p = 0.001), take-off angle (p < 0.001), peak knee and hip velocity (p < 0.001, p = 0.007), peak ankle and hip moment (p = 0.006, p = 0.011), and peak hip power (p = 0.014) were significantly greater in unloading SBJ than in loading SBJ. Conclusions: Acute enhancement in SBJ performance was observed with handheld loading. The present findings contribute to the understanding of biomechanical differences in SBJ performance with handheld loading and are highly applicable to strength and conditioning training for athletes.

Compensatory postural responses to backward loss of balance in patients with cerebellar disease

BackgroundImpaired control of balance and coordinated reactions are a primary deficit of cerebellar dysfunction. As compared to other neurological patients with balance impairments, there has been little research assessing the characteristics of compensatory responses associated with falls in patients with cerebellar disease (CD). Research questionThe aim of this study was to examine the effects of cerebellar disease on compensatory balance control in response to postural perturbation. Do CD patients increase the number of steps when responding to instability because of inappropriate initial step reactions or poor control of trunk motion or both? MethodsIn this explorative study, 10 patients suffering from degenerative cerebellar ataxia and 10 age-matched healthy controls were examined. The balance recovery reactions were assessed using a lean-and-release postural perturbation method. Spatiotemporal characteristics of stepping movement and COM variables associated with torso motion were analyzed using 3D motion capture system. ResultsCD patients took multiple steps whereas matched controls generally took single steps to recover balance following perturbation. The characteristics of the initial step at the time of the fall revealed that foot reaction time, foot response time, and step distance of the initial step were similar between CD patients and matched controls. However, CD patients exhibited a shorter foot-to−COM distance, higher COM velocity, and less trunk flexion with which to attenuate their body momentum after the landing of the first step than did matched controls. SignificanceAlthough initial step responses were probably adequate, poor control of torso motion appears to be a particular problem that causes multiple-step reactions in CD patients. This observation would help to guide the development of tailored fall intervention strategies in CD patients aimed at promoting their recovery capacity in response to a pronounced balance challenge.

Characteristics of Voluntary-induced Stepping Response in Persons with Stroke compared with those of healthy Young and Older Adults

BackgroundImpairment of protective steps to recover balance from external perturbation is evident after stroke. Voluntary-induced stepping response (VSR) can be used to practice protective steps by instructing an individual to voluntarily lean their whole body forward until they perceive a loss of balance and automatically induce a step. However, to improve protective stepping performance, detailed characteristics of VSR in healthy persons are required. Research questionWhat is the difference in VSR between healthy and persons with stroke? MethodsAn observational study was conducted in 30 participants, (10 young, 10 older, and 10 persons with stroke). All participants performed VSR for 10 trials. Step length, step width, step duration, CoM position, CoM velocity, trunk-hip displacement, and strategies of response were recorded using a motion capture system and analysed using Matlab software. Statistical analysis was performed using One-way ANOVA and Chi-square. ResultsOn average, participants with stroke had shorter step lengths and step durations than young and older adults. Step width of older adults and participants with stroke was wider than that of young adults (p < 0.05). While multiple steps and losing balance were reported more frequently in participants with stroke than the others, the percentage of trials in which participants grasped the handrails was not significantly different between older adults and participants with stroke. CoM position, CoM velocity, and trunk-hip displacement at foot liftoff were significantly smaller in older adults and participants with stroke than young adults (p < 0.05). Participants with stroke tended to use trunk bending rather than trunk leaning strategies to generate VSR in contrast to healthy participant. The prevalence of the trunk bending strategy was also greater in older adults than young adults. SignificanceValues obtained from healthy groups can be used as guidelines to set realistic goals during VSR training to improve protective steps in patients with stroke.

Directional Control Mechanisms in Multidirectional Step Initiating Tasks.

Typical anticipatory postural adjustments (APAs) in forward gait or step initiation tasks to prepare for possible disturbances caused by prime voluntary movements and to accelerate the body forward have been previously reported. However, it is not clear how wide the variations in step directions are differentiated and controlled in non-forward step initiation tasks during the APA phase. The main goal of this study is to explain the directional control mechanisms by investigating the APA of step initiation tasks in forward, diagonal, lateral, and posterior directions. The center of pressure (COP) trajectories and related muscle (soleus, tibialis anterior, and gluteus medius of both lower limbs) activities during the APA of step initiation tasks in nine different directions were analyzed in six healthy young males. Posterior shifts of COP during APA decreased as the direction became more lateral (0° to 90°). For posterior step initiations, COP moved anteriorly from the initial position to accelerate the center of mass of the whole body (COM) backward. Lateral shifts of COP toward the stepping foot during APA decreased as the stepping direction became more lateral (from 0° to 45° and from 180° to 113°) while it plateaued to about zero in the direction from 45° to 113°. Both anteroposterior and lateral displacements of COP in APA were nonlinearly modulated to each direction, but they were linearly related to the anteroposterior and mediolateral component of the velocities of COM at the take-off of the stance foot. Thus, the scaling of APA, reflected in the anteroposterior and lateral displacements of COP and the temporal sequence of selected muscle activities, was based on the anteroposterior and mediolateral components of the take-off velocity of COM that ultimately controls the direction of steps.

Optimal Standing Jump Trajectory Generation for Biped Robots

One of the disadvantages of biped robots is the slow movement. Jumping or running can be the solution to this. This paper describes an optimal jump trajectory generation method for biped robots. In order to conveniently create a jumping trajectory, the center of mass trajectory of the robot was divided into vertical and horizontal directions. The vertical trajectory was designed to maintain the desired flight time by considering a capacity of a actuator and the impact force at landing. The horizontal trajectory was designed to conform to the desired horizontal COM velocity at takeoff while maintaining the desired zero moment point by using preview control. We also considered the friction force between the robot and the ground and the region of motion of the robot. This process was defined as a nonlinear optimization problem, and the optimal jump trajectory was obtained. The trajectory was verified by simulation and standing jump experiment of an actual humanoid robot.

A Design of Assist Controllers Based on the CoM Velocity of Attachment for Digging Operation of a Hydraulic Excavator

A Design of Assist Controllers Based on the CoM Velocity of Attachment for Digging Operation of a Hydraulic Excavator

Characterizing the demands of backward balance loss and fall recovery during stair descent to prevent injury

Understanding the demands of balance recovery on stairs is important for developing strategies to prevent falls on stairs. This study characterized recovery strategies and whole-body movement following unexpected backward balance loss during stair descent in twelve young adults. Following balance loss, peak downward COM velocity was approximately double that experienced during non-perturbation stair descent. Participants used several balance recovery strategies: harness reliance (n = 1), no grasping reaction (n = 3), and grasping some environmental feature (n = 8). Of the five participants who used the handrail, four demonstrated grasping errors. Peak resultant handrail forces ranged from 24.2N to 238.3N. The results highlight the challenge of balance recovery during stair descent, showing that some people will use any available surface to arrest a fall. Our findings serve as a benchmark to understand the impact of stair-related interventions on fall recovery.

Combined Resistance and Stretching Exercise Training Benefits Stair Descent Biomechanics in Older Adults.

IntroductionStair descent is a physically demanding activity of daily life and common risk for falls. Age-related deteriorations in ankle joint capacities make stair descent particularly challenging for older adults in built environments, where larger rise steps are encountered. Exercise training may allow older adults to safely cope with the high biomechanical demands of stair descent. However, little is known about the demands of increased rise stairs for older adults, nor the impact of exercise.AimWe investigated whether the effects of lower-limb resistance training would alter joint kinetics and movement strategies for older adults when descending standard rise, and increased rise stairs.MethodsFifteen older adults descended a four-step stair adjusted to standard rise (170 mm), and increased rise (255 mm) on separate visits. Between these two visits, randomly allocated participants underwent 16 weeks of either: resistance exercise training (n = 8) or habitual activity (n = 7). Kinetic data were measured from step-mounted force plates, and kinematic data from motion-capture cameras. Training involved twice-weekly sessions of lower-limb resistance exercises (three sets of ∼8 repetitions at ∼80% three-repetition maximum), and static plantarflexor stretching (three, 45 s holds per leg).ResultsStandard stairs – Peak ankle joint moments increased (p < 0.002) and knee joint moments decreased (p < 0.01) during descent after exercise training. Peak centre of pressure-centre of mass (CoP-CoM) separations increased in posterior (p = 0.005) and medio-lateral directions (p = 0.04) after exercise training. Exercise training did not affect CoM descent velocity or acceleration. Increased rise stairs – Required greater ankle, knee, and hip moments (p < 0.001), peak downward CoM velocity and acceleration (p = 0.0001), and anterior-posterior CoP-CoM separation (p = 0.0001), but lower medial-lateral CoP-CoM separation (p < 0.05), when compared to standard stair descent. Exercise training did not affect joint kinetics or movement strategies.DiscussionExercise training increased the maximum joint ROM, strength and force production of the ankle, and enabled a greater ankle joint moment to be produced in single-leg support (lowering phase) during standard stair descent. Descending increased rise stairs raised the task demand; exercise training could not overcome this. Future research should prioritize the ankle joint in stair descent, particularly targeting plantarflexor torque development across stairs of varying riser heights.

Parameters of the crossing points between center of pressure and center of mass signals are potential markers of postural control efficiency

Posturographic signals were recorded for 384 subjects of different ages and with old persons with gait disturbances. Four conditions were used: Eyes Open/Closed vs. Head Normal/Bent Back. ‘Center of Pressure’ (CoP) signals were decomposed into ‘Center of Mass’ (CoM) and the remaining difference between Center of Pressure and Center of Mass (CoPM). The Zero-Crossing points in which the Center of Mass and Center of Pressure paths cross each other have been extracted. Velocity of CoM, velocity of CoPM and acceleration of CoPM in Zero-Crossing points were analyzed to be potential markers of balance efficiency. Three factors causing the deterioration of balance quality were analyzed: closing eyes, bending the head back and patient age. The influence of the given factors was measured using the significance p of the t-Student test and Cohen's d effect size and applied to differences for the logarithms of three of the mentioned above variables measured without and with the given deteriorating factor. In the majority of comparisons, the proposed new parameters of balance quality possessed higher statistical power to detect deteriorated balance quality than the standard parameters: standard deviation of the signal and ellipse area covering 90% of the signal envelope. Most valuable are the velocity and acceleration of CoPM for the medio-lateral direction. Logarithms of the analyzed parameters are proposed to be used in analyses because they possess normal or close to normal distribution and they are less sensitive to single high values occurring often in measurements.

Physical Factors Differentiate Pain-free Return To Play And Return With Knee Symptoms 9 Months After ACL Reconstruction

PURPOSE: The aim of this study was to identify strength, power and biomechanical differences between male athletes who made a pain free return to play (RTP) and those that did not at 9 month post ACL reconstruction. METHODS: Nine months after ACLR 158 males athletes who had returned to pre-injury sport participation (64 reporting knee symptoms/94 reporting none) carried out strength testing using isokinetic dynamometry on quadriceps and hamstrings and 3D biomechanical analysis of single countermovement jump, single leg drop jump and planned and unplanned 90° change of direction (CoD) as well as an IKDC questionnaire. Differences in IKDC, strength and jump height measures on the ACLR side and in limb symmetry index (LSI) between groups were analysed with statistical parametric mapping (SPM, 0D unpaired t-test). The odds ratio for making a pain free RTP if LSI >90% was also calculated for the strength and jump variables independently and collectively. Biomechanical differences in the jump and CoD tests on the ACLR side and in symmetry between groups was analysed with SPM (1d, unpaired t-test). Effect size was calculated using Cohen’s D for all analyses. RESULTS: There was a large effect size (ES) difference in IKDC score between groups (89 +/- 6 with no pain; 80 +/- 8 with pain; ES 1.1). There were medium effect size differences in quadriceps strength on ACLR side (ES 0.42) and LSI (0.45) with an odds ratio of 2.7. There were similar differences in SLDJ height on ACLR side (ES 0.3) and LSI (0.37) with an odds ratio of 3.5. The odds of making a pain free RTP when LSI >90% on all tests was 6.8. There were no biomechanical differences between groups on the jump tests. There were biomechanical differences on the more demanding CoD tests with differences on the on the ACLR side and symmetry in foot rotation angle, knee extension moment and hip rotation angle (ES 0.51 to 0.61) in the unplanned CoD and in symmetry of posterior and vertical ground reaction force and COM velocity at initial contact (ES 0.5 to 0.58) in the unplanned CoD with greater asymmetry in the painful group. CONCLUSION: This study demonstrates strength, power and biomechanical differences in those that RTP with knee symptoms after ACLR with those achieving >90% LSI in all 4 strength and jump tests almost 7 times more likely to make a pain free RTP.

Older adults exhibit variable responses in stepping behaviour following unexpected forward perturbations during gait initiation

With the socioeconomic burden associated with falls expected to rise as the average age of the Canadian population increases, research is needed to elucidate the nature of postural responses generated by older adults (OA) following a posture-destabilizing event. This knowledge is even more imperative for novel and difficult tasks, such as gait initiation (GI), a task known to pose a postural threat to stability for OA. A common technique to regain stability following an unexpected perturbation is reactive stepping. A deficiency in the execution of a reactive control strategy following a destabilizing event may be the cause of many unexpected falls in OA. The purpose of this study is to explore age related changes in the nature of these responses during a challenging GI task combined with an unexpected forward perturbation of the support surface. A total of 18 young adults (YA) and 16 OA performed 36 trials containing 20 unexpected perturbations. We calculated step width, length, time and COM velocity in the first unperturbed step and the second perturbed step. Results revealed that, during unperturbed GI, OA had a reduced forward velocity and took shorter, faster steps. Following forward perturbations, OA altered stepping patterns, perhaps to reduce single support duration, via reduced base of support and shorter step length compared to YA. Additionally, OA executed both forward and backwards directed steps however YA only generated forward steps. Regression analyses revealed that reduced forward velocity was predictive of step direction; which is possibly an unfavorable motor control strategy as OA who walk slower generated a posterior directed step immediately following the perturbation. This strategy is of concern as rapid responses by the trail limb are required to recover successfully, and these alterations may be associated with an elevated risk of falls.

Kinematic and kinetic analysis of the goalkeeper’s diving save in football

ABSTRACTKinetics and full body kinematics were measured in ten elite goalkeepers diving to save high and low balls at both sides of the goal, aiming to investigate their starting position, linear and angular momentum, and legs' contribution to end-performance. Our results showed that goalkeepers adopted a starting position with a stance width of 33 ± 1% of leg length, knee flexion angle of 62 ± 18° and hip flexion angle of 63 ± 18°. The contralateral leg contributed more than the ipsilateral leg to COM velocity (p < 0.01), both for the horizontal (2.7 ± 0.1 m·s−1 versus 1.2 ± 0.1 m·s−1) and for the vertical component (3.1 ± 0.3 m·s−1 versus 0.4 ± 0.2 m·s−1). Peak horizontal and peak angular momenta were significantly larger (p < 0.01) for low dives than for high dives with a mean difference of 55 kg·m·s−1 and 9 kg·m2·s−1, respectively. In addition, peak vertical momentum was significantly larger (p < 0.01) for high dives with a mean difference between dive heights of 113 kg·m·s−1. Coaches need to highlight horizontal lateral skills and exercises (e.g. sideward push-off, sideward jumps), with emphasis on pushing-off with the contralateral leg, when training and assessing goalkeeper’s physical performance.

Foot Placement Modulation Diminishes for Perturbations Near Foot Contact.

Whenever a perturbation occurs during walking we have to maintain our balance using the recovery strategies that are available to us. Foot placement adjustment is often considered an important recovery strategy. However, because this strategy takes time it is likely a poor option if the foot is close to contact at the instant a perturbation occurs. The main goal of this study is to gain a better understanding of how humans deal with balance perturbations during walking if foot placement adjustments are constrained by time. Ten healthy subjects walked on an instrumented treadmill and received mediolateral and anteroposterior pelvis perturbations at various instances during the single support phase. The results show that foot placement modulation in the first recovery step following anteroposterior perturbations is fairly invariant of the perturbation magnitude and direction, regardless of the onset instance. For mediolateral perturbations, foot placement adjustments strongly modulate with the perturbation magnitude and direction, but these effects diminish when the perturbation onset is closer to the instant of foot contact. For most perturbations the first recovery step was consistent across subjects for all onset instances. However, in the second step various strategies arose that were not consistent across subjects, nor within subjects, especially for perturbations applied close to foot contact. Despite these different strategies, the COP location following foot contact strongly related to the COM velocity throughout these strategies. The results show that humans have various ways to compensate for limited availability of a foot placement strategy, with strategy selection highly dependent on the instant during the gait phase at which the perturbation is applied.

Kinematic analysis to improve the completeness of YANG Hak Seon technique: A case study

Purpose The purpose of the study was to perform a comparative analysis of the YANG Hak Seon technique carried out by "K" athlete with the kinematical data of "Y" athlete and propose a method to improve the YANG Hak Seon technique of "K" athlete Method The subject recruited for the study was a male athlete from Korean national team (Age: 21, height: 1.65 m, body weight: 59.6 kg, and career: 11 years). Four high - speed cameras were used to analyze the 3D motion of the YANG Hak Seon technique performed by "K" athlete. The variables selected for analysis were the velocity of COM, displacement of COM, the rotational &amp; torsional angle of the trunk and rotational &amp; torsional angular velocity of the trunk. The results obtained were compared to the preexisting data of the "Y" athlete (data set from the published research) Results Firstly, the horizontal displacement of the YANG Hak Seon technique of the "K" athlete was observed to be shorter along with lower vertical displacement during landing compared to “Y” athlete. In addition, the overall horizontal velocity was low and vertical velocity was not generated which rises during the BC (board contact) phase. Although the rotational angular velocity of the trunk was lower during the BC, HC (horse contact) phase and LD (landing) phase, torsional angular velocity was higher during the LD Conclusion In order to improve the completeness of the YANG Hak Seon technique of the K player, it is necessary to enter with a fast and low posture on the footplate during the initial phase. In the BC phase, it is essential to raise the COM simultaneously while landing on the footplate and increase the rotational angular velocity of the trunk.

Effects of constrained trunk movement on frontal plane gait kinematics

Previously it has been shown that constraining step width in gait coincides with decreased trunk displacements. Conversely, external stabilization of the upper body in gait coincides with decreased step width, but this may in part be due to changes in passive dynamics of the leg. In the present study, trunk kinematics during gait were constrained without external stabilization by using an orthosis, to investigate whether step width and dynamic gait stability in the ML direction are changed in relation to trunk kinematics. Nine healthy young adults walked on a treadmill at three different speeds with no intervention and while wearing a thoracolumbar orthosis. Based on marker trajectories, trunk COM displacement, body COM displacement and velocity, step width, and margin-of-stability in ML direction were calculated. The results showed that the orthosis significantly reduced trunk and body COM displacements. As hypothesized, the restriction of trunk movement coincided with significantly decreased step width, while the margin-of-stability was not affected. These findings indicate that, when trunk movements are constrained, humans narrow step width, while maintaining a constant margin-of-stability. In conclusion, the present results in combination with previous work imply that in gait a reciprocal coupling between trunk kinematics and foot placement in the frontal plane subserves control of stability in the frontal plane.