Center Of Mass Displacement Research Articles

Measuring A Rider's Centre Of Mass Displacement During Non-seated Cycling Using A Single Inertial Measurement Unit

Measuring A Rider's Centre Of Mass Displacement During Non-seated Cycling Using A Single Inertial Measurement Unit

Feedforward control for underactuated bipedal walking on compliant continuous steps with varying height

This study develops a feedforward control strategy based on the motion state of center-of-mass (CoM) of a robot for underactuated biped robot stable walking on compliant continuous steps with a known varying height. First, considering ground deformation, a compliant contact model is employed to characterize foot-ground interaction, and a robot–step coupling dynamic model of sagittal and lateral planes are established through decoupling modelling. Second, based on the gait characteristics of human variable-step walking, a feedforward control strategy based on the motion state of CoM is proposed. Varying height step is equivalent to varying slope, an equivalent slope angle and a desired step length can be calculated for each step according to their height. Underactuated bipedal walking control is decoupled into sagittal and lateral master-slave control. The velocity of robot CoM is considered as a system output. It is controlled through the displacement of CoM in a single walking cycle, and thus walking is stabilized. By the proposed method, the walking system is modelled as a polynomial with definite number of degrees and the controlled input is derived through a simple inverse operation on it. Its effectiveness is validated through simulations in an environment with a step varying height of less than 0.032 m. Simulation results show that the proposed method can improve the tracking performance of robot CoM velocity on varying height steps, as compared to a hybrid zero dynamic (HZD)-based controller.

Do Progressive Sensorimotor Training Devices Produce A Graded Increase in Centre of Mass Displacement During Unipedal Balance Exercises in Athletes

Progression of the difficulty of agility exercises in sport is often achieved by changing the stability of the support surface via graded sensorimotor training devices. However, little is known about the challenge imposed to postural equilibrium by these graded devices. This study quantified the instability provided by four sensorimotor training devices typically used to enhance athletic performance; three progressively unstable balance pads (ST1–3) and an oscillatory platform (PM). Twenty-five (13 female, 12 male) young adults (age, 26 ± 3 yr; height, 1.76 ± 0.10 m; and weight, 69 ± 12 kg), completed seven unipedal balance conditions involving stable and progressively unstable surfaces that involved four sensorimotor training devices (ST1-3, PM) and their combination (PM-ST1, PM-ST2). An inertial sensor, mounted over the lumbar spine, was used to monitor Centre of Mass (COM) displacement in each condition. Potential differences in COM displacement between conditions were assessed using a mixed-model analysis of variance. COM displacement differed between training devices; with a progressive, though non-linear, increase in COM displacement from the most (ST1) to the least (ST3) stable balance pad. However, there was no significant difference in COM displacement between the least stable balance pad (ST3) and the oscillatory platform used in isolation (PM) or in combination with balance pads (PM-ST1, PM-ST2). These novel findings have important practical implications for the design of progressive sensorimotor training programs in sport.

Riders Use Their Body Mass to Amplify Crank Power during Nonseated Ergometer Cycling

To date, neither the CoM movement strategies during nonseated cycling nor the limb mechanics that allow this phenomenon to occur have been quantified. Here we estimate how much power can be contributed by a rider's CoM at each instant during the crank cycle by combining a kinematic and kinetic approach to measure CoM movement and joint powers of 15 participants riding in a nonseated posture at three individualized power outputs (10%, 30%, and 50% of peak maximal power) and two different cadences (70 and 120 rpm). The peak-to-peak amplitude of vertical CoM displacement increased significantly with power output and with decreasing cadence. Accordingly, the greatest peak-to-peak amplitude of CoM displacement (0.06 ± 0.01 m) and change in total mechanical energy (0.54 ± 0.12 J·kg) occurred under the combination of high-power output and low cadence. At the same combination of high-power output and low cadence, we found that the peak rate of CoM energy loss (3.87 ± 0.93 W·kg) was equal to 18% of the peak crank power. Consequently, it appears that for a given power output, changes in CoM energy contribute to peak instantaneous power output at the crank, thus reducing the required muscular contribution. These findings suggest that the rise and fall of a rider's CoM acts as a mechanical amplifier during nonseated cycling, which has important implications for both rider and bicycle performance.

Discriminant validity of 3D joint kinematics and centre of mass displacement measured by inertial sensor technology during the unipodal stance task.

The unipodal stance task is a clinical task that quantifies postural stability and alignment of the lower limb joints, while weight bearing on one leg. As persons with knee osteoarthritis (KOA) have poor postural and knee joint stability, objective assessment of this task might be useful. To investigate the discriminant validity of three-dimensional joint kinematics and centre of mass displacement (COM) between healthy controls and persons with knee KOA, during unipodal stance using inertial sensors. Additionally, the reliability, agreement and construct validity are assessed to determine the reproducibility and accuracy of the discriminating parameters. Twenty healthy controls and 19 persons with unilateral severe KOA were included. Five repetitions of the unipodal stance task were simultaneously recorded by an inertial sensor system and a camera-based system (gold standard). Statistical significant differences in kinematic waveforms between healthy controls and persons with severe knee KOA were determined using one-dimensional statistical parametric mapping (SPM1D). Persons with severe knee KOA had more lateral trunk lean towards the contralateral leg, more hip flexion throughout the performance of the unipodal stance task, more pelvic obliquity and COM displacement towards the contralateral side. However, for the latter two parameters the minimum detectable change was greater than the difference between healthy controls and persons with severe knee KOA. The construct validity was good (coefficient of multiple correlation 0.75, 0.83 respectively) and the root mean squared error (RMSE) was low (RMSE <1.5°) for the discriminant parameters. Inertial sensor based movement analysis can discriminate between healthy controls and persons with severe knee KOA for lateral trunk lean and hip flexion, but unfortunately not for the knee angles. Further research is required to improve the reproducibility and accuracy of the inertial sensor measurements before they can be used to assess differences in tasks with a small range of motion.

Impairment of Global Lower Limb Muscle Coactivation During Walking in Cerebellar Ataxias.

The aim of this study was to investigate the time-varying multi-muscle coactivation function (TMCf) in the lower limbs during gait and its relationship with the biomechanical and clinical features of patients with cerebellar ataxia. A total of 23 patients with degenerative cerebellar ataxia (16 with spinocerebellar ataxia, 7 with adult-onset ataxia of unknown etiology) and 23 age-, sex-, and speed-matched controls were investigated. The disease severity was assessed using the Scale for the Assessment and Rating of Ataxia (SARA) in all patients. During walking, simultaneous acquisition of kinematic, kinetic, and electromyography data was performed using a motion analysis system. The coactivation was processed throughout the gait cycle using the TMCf, and the following parameters were measured: synthetic coactivation index, full width at half maximum, and center of activity. Spatiotemporal (walking speed, stance duration, swing duration, first and second double-support durations, step length, step width, stride length, Center of Mass displacement), kinetic (vertical component of GRFs), and energy consumption (total energy consumption and mechanical energy recovered) parameters were also measured. The coactivation variables were compared between patients and controls and were correlated with both clinical and gait variables. A significantly increased global TMCf was found in patients compared with controls. In addition, the patients showed a significant shift of the center of activity toward the initial contact and a significant reduction in energy recovery. All coactivation parameters were negatively correlated with gait speed, whereas the coactivation index and center of activity were positively correlated with both center-of-mass mediolateral displacement values and SARA scores. Our findings suggest that patients use global coactivation as a compensatory mechanism during the earliest and most challenging subphase (loading response) of the gait cycle to reduce the lateral body sway, thus improving gait stability at the expense of effective energy recovery. This information could be helpful in optimizing rehabilitative treatment aimed at improving lower limb muscle control during gait in patients with cerebella ataxia.

The Effect Of Visual Dual-Tasking Interference On Walking In Healthy Young Adults

BackgroundVisual dual-task skills are essential for stable ambulation in everyday life such as walking while reading text. Gait analysis in a virtual environment can provide insight into altered walking performance while visual dual-tasking. Research questionHow visual dual-tasking including cognitive load of reading text and altered optical flow influences walking speed and stability in healthy adults? Also, is there a relationship between the mediolateral centre of mass(CoM) displacement and mediolateral trunk movement? MethodsNineteen able-bodied young adults performed self-selected walking on a treadmill in a virtual environment under the following three conditions; single-task walking, walking while viewing scrolling lines, and walking while reading text scrolling on the screen. Three-dimensional motion analysis was used to measure the effect of dual-tasking on gait velocity, step length, mediolateral CoM displacement, and mediolateral thorax inclination. ResultsThe effect of visual dual-tasking showed significantly increased walking speed and longer step length compared to single-tasking. The cognitive load of reading text while walking had a significant impact on reduced step length variability and greater mediolateral CoM displacement. This was related to the mediolateral thorax inclination. SignificanceA visual dual-task influences gait through altered optical flow and a cognitive load effect. Altered optical flow increased walking speed whilst the visual attention to read text affected foot placement and upright trunk posture, together with greater mediolateral CoM displacement. Thus, dual-tasking of reading text in a virtual environment substantially affected walking stability in healthy young people. This paradigm is therefore useful for assessment of walking stability in daily life and in the clinical setting.

Differences in ground reaction waveforms between elite senior and junior academy sprinters during the block phase and first two steps

The block start and initial steps following block exit are fundamental aspects of sprinting and their development is key to junior athletes’ progression. This study assessed the difference in force production between elite senior (including two sub-10 s 100-m sprinters) and junior academy sprinters during the block phase and the first two steps of a sprint. Thirty-seven male sprinters (17 senior, 20 junior) performed a series of maximal effort 20–40 m acceleration from blocks on an indoor track, with the ground reaction forces produced during the block phase and first two steps measured using force platforms. Senior athletes produced better block-phase performances (average horizontal external power; 15.52 ± 1.48 W/kg, M ± SD) compared with the juniors (12.37 ± 2.21 W/kg; effect size ± 90% confidence interval = 1.28 ± 0.38). However, force production during the initial two steps was comparable across groups. Specifically, senior athletes exhibited higher relative force production and ratio of forces during the early (∼15–35%) block phase and higher anteroposterior forces during the transition from bilateral to unilateral pushing (58–62% of the block phase). Front foot force production was also found to differentiate senior and junior groups at rear block exit (∼55% of the block phase). This may be a required response to the greater centre of mass displacement in order to prevent over-rotation in the senior athletes during the front block pushing phase. Collectively, these results indicate that the progression of junior athletes is non-uniform across the block phase and subsequent two contacts, which should be considered when attempting to progress junior athletes towards senior ranks.

Effects of Breast Motion on Lower-Body Kinematics during Running

We measured the effects of breast motion on lower-body kinematics during overground running. Thirty female participants aged 18–60 years completed two blocks of three trials each of overground running for 25 m at self-selected pace under two conditions: with and without breast support provided by a sports bra. Participants' body movements were analyzed with 18 parameters characterizing breast and lower-body kinematics. Sports bra use reduced breast motion and increased about 83% of the lower-body kinematic parameters, including running velocity; stride length; foot clearance; vertical and lateral center of mass displacement; and thorax, hip, knee, and ankle range of motion (all p < 0.05). Among the changed characteristics, the stride length, center of mass displacements, thorax and knee range of motions correlated negatively (r = –0.25 to –0.46) with the velocity of breast motion. Therefore, the reduction of breast motion may improve lower-body kinematics during running, which may influence sport and leisure performance.

The effects of tai chi chuan exercise training on countermovement jump performance in the elderly

ABSTRACT This study sought to compare the biomechanical parameters of the lower extremities during a countermovement jump in elderly people who are engaged in frequent practice of tai chi chuan (TCG) and in the general population of healthy elderly people (HG). Each group included 12 participants. Ten Vicon Motion System infrared cameras and two Kistler force plates were employed for measurement. The jump height, duration, centre of mass (COM) displacement, joint ROM, and upward velocity were analysed in this study. Motion analysis and force platform data were combined to calculate joint moments and powers during the takeoff phase. The data were analysed using independent sample t-tests. The results showed that the tai chi chuan practitioner group (0.13 m) achieved 44% higher jump heights (p < 0.05). The COM displacement during squatting was lower in the TCG (0.25 m) than in the HG (0.19 m) (p < 0.05). The knee and ankle ROMs of the TCG were higher than those of the HG (p < 0.05). Peak knee moment 23% and peak knee power 32% higher in TCG compared to the HG (p < 0.05), suggesting that frequent practice of tai chi chuan may slow the rate of knee degeneration.

Changes in Gait Kinematic Parameters after Severe Traumatic Brain Injury during Post-Acute Rehabilitation

Changes in gait after traumatic brain injury (TBI) are very important for evaluation, clinical reasoning and forintervention programs. Most studies analyze gait during acute phase, but there is lack of information during post-acute period. The aim of the research was to determine gait biomechanical joint angles and centre of mass displacement changes during post-acute TBI rehabilitation. Participant was a 21-year-old male, after severe TBI, 2 years after trauma. Biomechanical joints angles and centre of mass displacement changes were observed during 3D gait analysis. The subject was asked to walk straight 6 meters, 18 times at his preferred comfortable pace. During walking 1–2 minute breaks were made. Intensive 5 week program was composed of physiotherapy (3 times per week) and yoga (2 times per week). Physiotherapy included stretching, coordination, balance and weight-bearing exercises. Yoga was performed to built core stability, train flexibility and diminish muscle tone. After 5 week rehabilitation statistically significant changes were observed in the centre of mass displacement and in lower extremities and lumbar biomechanics (p &lt; 0.05). After procedures trunk flexion and trunk lateral flexion, lateral pelvic tilt increased, while anterior pelvic tilt decreased (p &lt; 0.05). Hip extension at terminal stance increased, as well while hip adduction in stance phase decreased (p &lt; 0.05). Statistically significant reduction was observed in knee flexion at initial contact, mid-stance and midswing phase (p &lt; 0.05). Prevalent knee flexion at initial contact, observed before rehabilitation, decreased after it (p &lt; 0.05). After the procedure lateral centre of mass displacement decreased and vertical centre of mass displacement increased (p &lt; 0.05). Five weeks of rehabilitation composed of traditional physiotherapy and yoga is effective for gait quality treatment. However, further research is necessary to determine gait biomechanical joint angles and dynamic balance improvements during severe post-acute TBI.Keywords: head injury, walking, balance.

Walking on uneven ground: How do patients with unilateral cerebral palsy adapt?

BackgroundChildren with cerebral palsy experience movement disorders that influence gait stability. It is likely that gait stability further decreases when walking on uneven compared to even ground. Therefore, the aim of this study was to investigate gait on uneven ground in children with unilateral cerebral palsy. MethodsTwenty children with unilateral cerebral palsy and twenty typically developing children performed a three-dimensional gait analysis when walking on even and uneven ground. Spatio-temporal parameters, full-body joint kinematics and centre of mass displacements were compared. FindingsOn uneven versus even ground, both groups showed decreased cadence, increased stance phase and double support time, increased toe clearance height, and increased knee and hip flexion during swing phase. Whereas only the typically developing children walked slower and had increased dorsiflexion and external foot progression during stance phase, only the patients showed increased stride width, increased elbow flexion (affected and non-affected side), and kept the centre of mass more medial when standing on the affected leg. InterpretationPatients and healthy children use similar adaptation mechanisms when walking on uneven ground. Both groups increased the toe clearance height by increasing knee and hip flexion during swing. However, whereas patients enlarge their base of support by increasing stride width, healthy children do so by increasing their external foot progression angle. Furthermore, patients seem to feel more insecure and hold their arms in a position to prepare for falls on uneven ground. They also do not compensate with their non-affected side for their affected side on uneven ground.

Does a novel exergame challenge balance and activate muscles more than existing off-the-shelf exergames?

BackgroundNovel balance-targeting exergames controlled with off-the-shelf hardware, were developed based on current recommendations for balance training in healthy older adults and documented shortcomings of existing games. The aim of this study was to explore the feasibility of these novel exergames as training tool for elderly and, more specifically whether these games can elicit more challenging weight shifts and higher levels of muscle activity compared to existing off-the-shelf exergames. Furthermore, the motivational pull in these new games was studied.MethodsSixteen healthy older adults were recruited to play the novel games and two reference games that were found to be the most challenging ones in terms of weight shifts or muscle activity in previous studies. Weight shifts were expressed relative to participants’ Functional Limits of Stability (FLOS). Muscular challenge of the games was quantified by dividing the signal into 200 ms blocks and determining the average muscle activity within these blocks. The muscle activity was normalized to maximal voluntary contractions (MVC) to categorize the blocks in zones of < 40, 40–60, 60–80 and > 80% MVC. Subsequently, the number of blocks per intensity level and the number of consecutive blocks above 40% were determined. Motivation to play the games was assessed using the Intrinsic Motivation Inventory (IMI) and scores between the games were analyzed using Generalized Estimated Equations (GEE).ResultsThe novel exergames successfully elicited center of mass (COM) displacements with medians of around 80% of FLOS or higher for all directions. Furthermore, the COM displacements in the novel games were larger for each direction than in the reference games, although for one game the sideward left direction reached significance only at the third trial. Compared to the existing games, longer blocks of muscle activation above 40% MVC were found, but overall intensity remained low. IMI scores were high on all subscales, indicating that older adults experienced the games as motivating.ConclusionWe conclude that affordable hardware can be used to create challenging and enjoyable balance training programs using exergames. The exergames that were successful in eliciting challenging weight shifts and muscle activity should now be further studied in longitudinal randomized controlled interventions, to assess effects on balance, muscle strength and eventually fall risk in healthy older adults.

Single IMU Displacement and Orientation Estimation of Human Center of Mass: A Magnetometer-Free Approach

In this article, a self-contained procedure to estimate the vertical, medial–lateral, and anterior–posterior displacement of a single sacrum-worn inertial measurement unit (IMU) is presented, which can be related to the human body center of mass (CoM) displacement during treadmill walking through an adaptation of the sacral marker method. Furthermore, a magnetometer-free custom sensor-fusion algorithm for orientation estimation is proposed alongside a practical alignment procedure to refer relative IMU orientation estimation to a ground-fixed reference frame. Twelve healthy subjects performed two trials of treadmill walking at 3, 4, and 5 km/h for 150 s, with a sacrum-worn IMU. Orientation and displacement estimations were then compared with those obtained from an optoelectronic measurement system. Roll, pitch, and yaw angles showed root mean square error (RMSE) lower than 2° for walking trials at 3, 4, and 5 km/h, with Pearson’s correlation coefficient higher than 0.90 for each angle. Displacement accuracy was evaluated in terms of peak-to-trough distances and RMSE. Mean errors resulted lower than 1 mm for each axis of interest and for each gait speed, with RMSE not higher than 2.5 mm. The proposed off-line algorithm can be used in low-budget and infrastructure-free environments, to achieve reliable CoM displacement estimation during cyclic activities such as treadmill walking.

The effects of back-step footwork on taekwondo roundhouse kick for the counterattack

The roundhouse kick is the most often used kick in Taekwondo sparring matches. In order to execute the effective kicks, footwork is critical. Therefore, the purpose of this study was to biomechanically examine the effects of backstep-footwork on the Taekwondo roundhouse kick for the counterattack. Ten male university Taekwondo athletes executed roundhouse kicks with five counterattack footwork conditions. The duration of the phases of the kick, the center of mass displacement, trunk, right hip, right knee angles, and kicking thigh, shin, foot, and toe velocities were obtained through a three-dimensional video motion analysis. These variables were compared to the conditions using repeated measure analysis of variance, and changed significantly in response to different footwork conditions. It was concluded that as the footwork distance increased, the center of the body became lower, the trunk angle reduced, the kick-leg increased foot speed. Therefore, it would be necessary to make efforts to compensate for the strengths and weaknesses of the various types of kicks that are used to invalidate the opponent's attack and to increase the contribution of each body segment.

A case-control study of gait balance control in veterans with chronic symptoms following mTBI

BackgroundNumerous investigations suggest mild traumatic brain injury (mTBI) may result in persistent gait balance control deficits. Furthermore, military Veterans with symptoms of chronic mTBI often present with physical symptoms that may be associated with impaired gait balance control which may lead to prolonged recovery, difficulty performing activities of daily living, and increased disability. It is therefore important to objectively quantify gait balance deficits in Veterans with chronic mTBI. Research QuestionIs gait balance control impaired in a group of Veterans with chronic symptoms of mTBI when compared to healthy matched Veterans? MethodsEight Veterans with symptoms of chronic mTBI (1 F/7 M) and eight healthy matched Veterans (1 F/7 M) completed a gait balance assessment under single- (ST) and dual-task (DT) conditions. Gait balance control was quantified with whole body center of mass (COM) total medial-lateral (ML) displacement and peak ML velocity, which were calculated from camera-based motion capture. ResultsVeterans with chronic mTBI walked with greater ML COM displacement (approximately 25 % increase) in both ST and DT walking (main effect of group, p = 0.018) when compared to healthy Veterans. The peak ML COM velocity was affected for both groups by performing a concurrent cognitive task (interaction effect, p = .012). Slower ML COM velocities in healthy Veterans suggest the adoption of a conservative balance control strategy, while faster ML COM velocities for Veterans with chronic mTBI may indicate a diminished ability to control ML momentum. SignificanceIncreased frontal plane COM motion under both ST and DT walking was observed in Veterans with chronic mTBI symptoms many years after injury. This suggests gait balance control may be adversely affected during divided attention gait and highlights the need for comprehensive gait analysis in the management of these individuals.

Influence of excess weight on lower-extremity vertical stiffness and metabolic cost of walking

ABSTRACT The purpose was to test whether lower-extremity vertical stiffness and gait mechanics explain differences in energy cost of walking (Cw) between individuals with normal weight (NW) and obesity (OB). Ten OB (33.1 ± 2.0 kg m−2) and 10 NW (24.2 ± 1.3 kg m−2) walked for six minutes on an instrumented treadmill at 1.25 m s−1 while Cw, lower-extremity kinematics, and vertical stiffness (K vert) were measured. NW completed another trial with a loaded vest (NWL) to simulate the BMI of the obese group. Cw was 24% greater in OB (277.5 ± 45.3 J m−1) and 23% greater in NWL (272.7 ± 35.7 J m−1) than NW (211.0 ± 27.0 J m−1, P < 0.005). Mass-specific Cw (Cwkg) wasn’t different between conditions (P = 0.085). Lower-extremity K vert was 40% higher in OB (32.7 ± 5.2 kN m−1) than NW (23.3 ± 4.7 kN m−1, P < 0.001), but neither was different from NWL (27.5 ± 3.4 kN m−1, P > 0.05). Mass-specific K vert (P = 0.081) was similar across conditions. K vert was related to Cw (r = 0.55, P = 0.001). Cwkg wasn’t different between NW or OB, but there was a negative correlation between BMI and Cwkg driven by lower Cwkg in NWL. Cw and K vert covaried in proportion to body mass, but mass-specific K vert was unrelated to Cwkg. Mass-specific K vert was lower in NWL than OB due to NWL’s greater angle of attack, center of mass displacement, and joint range of motion.

Motor adjustments during time-constrained sit-to-walk in people with Parkinson's disease

Sit-to-walk (STW) is a sequential task and a merge of sit-to-stand (STS) and gait initiation that are impaired in people with Parkinson's disease (PD). Performing sequential task under time constraint (e.g., stand up and walk to answer an urgent call) might influence people with PD due to their deficits on internal regulation of continuous, rhythmic and fast movements. It is known the PD behavior during STS and gait initiation tasks are impaired, however, little is known regarding PD behavior on STW. Thus, the aim of this study was to assess the motor behavior of people with PD and healthy older adults during the STW task under time constraint. Fourteen people with idiopathic PD and 14 healthy older adults (OA) participated in this study. They performed the STW task under a time constraint. STW performance (STW total duration, duration of each of the 4 phases of the STW, and the drop in the center of mass (COM) momentum, identified as Fluidity Index - FI), kinematics and kinetics outcomes were assessed throughout the task. The PD group showed increased STW total time and lower FI, longer seat-off (Phase 1) time and first step (Phase 4) when compared to the OA group. Furthermore, the PD group showed more motor impairments (kinematics and kinetics) than the OA group throughout the task from seat-off until heel-off. Also, people with PD exhibited larger mediolateral COM displacement in the standing phase (Phase 2) and greater ground reaction force (GRF) in Phases 1 and 3. We observed that people with PD exhibited more restrictions when compared with healthy older adults on their STW performance, COM and GRF parameters during the STW under time constraint. Some clinical impairments usually observed in people with PD might explain their STW performance such as, motor planning deficits, less automatic motor control and mediolateral balance impairments.

Spike jump biomechanics in male versus female elite volleyball players

ABSTRACT There are well-known biological differences between women and men, especially in technical-coordinative variations that contribute to sex differences in performance of complex movements like the most important offensive action in volleyball, the spike jump. The aim of this study was to investigate sex-dependent performance and biomechanical characteristics in the volleyball spike jump. Thirty female and male sub-elite volleyball players were analysed while striking a stationary ball with maximal spike jump height. Twelve MX13 Vicon cameras with a cluster marker set, two AMTI force plates, surface EMG, and a Full-Body 3D model in Visual3D were used. Main findings include sex differences (P< .05) in jump height (pη2 = .73), approach [speed (pη2 = .61), step length], transition strategy [plant angle, neuromuscular activation (pη2 = .91), horizontal force maxima and impulses], acceleration distances [centre of mass displacement (pη2 = .21), minimal knee and hip angles], use of torso and arms [incline, angular velocity (pη2 = .23)]. Correlations support that the results cannot be explained fully by strength and power differences between sexes but represent the product of technical-coordinative variations. Their relevance is acknowledged for both sexes and numerous performance determinants displayed sex differences. The integration of such attributes into sex-specific training seems promising but its effect requires further investigation.

Diminished Dynamic Physical Performance Is Associated With Orthostatic Hypotension in Geriatric Outpatients.

Orthostatic hypotension (OH), a blood pressure drop after postural change, is a highly prevalent and disabling syndrome in older adults. Yet, the association between physical performance and OH is not clearly established. The aim of this study was to determine whether different types of physical performance are associated with OH in a clinically relevant population of geriatric outpatients. This cross-sectional study included 280 geriatric outpatients (mean age: 82.2 years, standard deviation: 7.1). Orthostatic hypotension was determined using intermittently measured blood pressure and continuously measured blood pressure in a random subgroup of 58 patients. Physical performance was classified into a dynamic type (4-m Walk Test, Chair Stand Test, and Timed Up and Go test) and a static type (standing balance tests, handgrip strength). Associations were analyzed using logistic regression models with adjustments for age, sex, weight, and height. Diminished physical performance on the Chair Stand Test was associated with OH measured intermittently. Diminished physical performance on all dynamic physical domains (4-m Walk Test, Chair Stand Test, and Timed Up and Go test) was associated with OH measured continuously. Static physical performance was not significantly associated with OH. Dynamic physical performance tests with a substantial postural change and center of mass displacement were significantly associated with OH. The influence of physical performance on OH in daily routine activities should be further explored to establish counteracting interventions.