Vertical Center Of Mass Research Articles

Tall and Fall Versus Drop and Drive Strategy in College Baseball Pitchers for Velocity and Elbow Valgus Torque

Background: Depending on anthropometrics and coaching style, pitchers are taught to pitch with a stride strategy that are traditionally classified as “tall and fall” or “drop and drive” for the purpose of maximizing pitch velocity. Purpose/Hypothesis: The purpose of this study was to determine the effects of stride strategy (tall and fall vs drop and drive) in college baseball pitching on pitch velocity and elbow valgus torque. It was hypothesized that pitch velocity and elbow valgus torque would increase as pitchers aligned more with the tall and fall technique. Study Design: Controlled laboratory study. Methods: Markerless motion capture data were recorded on 64 collegiate pitchers (height, 1.89 ± 0.06 m; weight, 93.06 ± 9.44 kg) during game play at the host institution during the 2023 season. Peak magnitudes of body center of mass (COM) vertical displacement were determined using a straight-line trajectory between peak knee height and lead foot contact and used as a continuous variable. Pitchers were required to throw ≥4 fastballs during their outing to be included in the analysis. Multilevel modeling was used to determine associations between peak magnitudes of positive and negative vertical displacement of COM on pitch velocity and elbow valgus torque. Every fastball throughout the season with biomechanics data for each pitcher was included in the multilevel model. Results: Fastball velocity was mean ± SD 90.68 ± 2.90 mph (40.54 ± 1.29 m/s). Mean maximal negative vertical COM displacement was −0.91 ± 0.47 inches (−0.023 ± 0.012 m), which occurred 18.1% ± 5.75% of the way between peak knee height and stride foot contact. Mean maximal positive vertical COM displacement was 1.73 ± 1.14 inches (0.044 ± 0.029 m), which occurred 65.7% ± 7.8% of the time from peak knee height to stride foot contact. Positive COM displacement (β = 0.54; P < .001) and timing of peak positive COM displacement (β = 1.82; P = .023) reduced interpitcher variance by 9.9% and improved the ability of our model to predict fastball velocity. Negative COM displacement improved the ability of our model to predict ball velocity (β = −0.45; P = .021). Vertical COM displacement did not influence elbow valgus torque. Conclusion: Increasing vertical COM displacement in either the positive or the negative direction resulted in increased fastball velocity but did not result in greater elbow valgus torque. This indicates that the stride method may be used for performance enhancement but is unlikely to influence ulnar collateral ligament injury risk in college baseball pitchers. Clinical Relevance: Clinicians should not use stride mechanics as an injury risk indicator or diagnostic factor in injury etiology for college baseball pitchers.

Walking on Virtual Surface Patterns Leads to Changed Control Strategies.

Inclusive design does not stop at removing physical obstacles such as staircases. It also involves identifying architectural features that impose sensory burdens, such as repetitive visual patterns that are known to potentially cause dizziness or visual discomfort. In order to assess their influence on human gait and its stability, three repetitive patterns-random dots, repetitive stripes, and repetitive waves (Lisbon pattern)-were displayed in a coloured and greyscale variant in a virtual reality (VR) environment. The movements of eight participants were recorded using a motion capture system and electromyography (EMG). During all test conditions, a significant increase in the muscular activity of leg flexor muscles was identified just before touchdown. Further, an increase in the activity of laterally stabilising muscles during the swing phase was observed for all of the test conditions. The lateral and vertical centre of mass (CoM) deviation was statistically evaluated using a linear mixed model (LMM). The patterns did cause a significant increase in the CoM excursion in the vertical direction but not in the lateral direction. These findings are indicative of an inhibited and more cautious gait style and a change in control strategy. Furthermore, we quantified the induced discomfort by using both algorithmic estimates and self-reports. The Fourier-based methods favoured the greyscaled random dots over repetitive stripes. The colour metric favoured the striped pattern over the random dots. The participants reported that the wavey Lisbon pattern was the most disruptive. For architectural and structural design, this study indicates (1) that highly repetitive patterns should be used with care in consideration of their impact on the human visuomotor system and its behavioural effects and (2) that coloured patterns should be used with greater caution than greyscale patterns.

Impact of step width on trunk motion and gait adaptation in elderly women with knee osteoarthritis.

Step width during walking can provide important information about aging and pathology. Although knee osteoarthritis (OA) is a common disease in elderly women, little is known about how different step widths influence gait parameters in patients with knee OA. To address this, we investigated the differences between narrower and wider step width on the center of mass (CoM) and gait biomechanics of elderly women with knee OA. Gait and CoM data were measured using a three-dimensional motion capture system and anthropometric data were acquired via standing full-limb radiography. Thirty elderly women with knee OA were divided into two groups depending on the average step width value (0.16 m). Specifically, the narrower step width group included those with a below average step width (n= 15) and the wider step width group included those with an above average step width (n= 15). The differences between the two groups were analyzed using an independentt-test. Walking speed, step length, knee and ankle sagittal excursion, and medial-lateral CoM range were significantly greater in the narrower group. In contrast, the medial-lateral CoM velocity, medial-lateral ground reaction force (GRF), and foot progression angle were significantly higher in wider group. The external knee adduction moment, vertical GRF, and vertical CoM did not differ between the groups. Our data indicate that step width in women with knee OA is associated with trunk motion and gait patterns. People with a narrower step might improve their gait function by increasing trunk frontal control to maintain gait stability. In contrast, in those with a wider step, greater toe out angle and shorter step length might be a compensatory adaptation to reduce knee loading.

Comparing the Effects of an Off-Ice Sprint-Change of Direction Task on Trunk Kinematics and Gait Laterality in Collegiate Ice Hockey Players

Laterality preferences are intrinsic in most physical activities, and ice hockey is one domain wherein these preferences might influence performance. Biomechanical laterality between dominant and nondominant (or preferred and nonpreferred) limbs is believed to be an advantageous attribute that is linked with skilled performance. Yet little is known about the implications of motor asymmetries for skilled performers in dynamic, time-constrained, team-based activities in an off-ice environment. This can be extended to when player position is considered, notably for those playing in a defensive or an offensive position. In this study, fourteen semi-professional collegiate male ice hockey players (age: 21.87 ± 2.98 years; BMI: 25.26 ± 3.21 kg/m) performed a randomized repeated 15 m sprint-change of direction task. Assessments of lower limb laterality were carried out as participants commenced the 15 m sprint change of direction task in both a right and left foot rear setback position. Biomechanical laterality between right and left rear foot setback positions was inferred by an ActiGraph GTx3 triaxial accelerometer that was located on the participants’ spinous process, representing the trunk centre of mass (CoM). Overall, ANOVA results indicated significant differences across all sprint split times between the right and left foot rear setback positions, with times significantly quicker when players commenced in a right rear foot setback position (p &lt; 0.001). ANOVA revealed significant differences in trunk CoM acceleration between in a right and left rear setback position, specifically during the initial 0–10 m sprint split, with offensive players observed to have lesser trunk anteroposterior and vertical CoM acceleration (p = 0.05) and during the final 5 m sprint split (p = 0.002, d = 0.7), despite overall smaller effect sizes seen in the left foot rear setback position. It appears that starting with the foot in a right rear setback position results in quicker 15 m performance times and concurrent lower magnitudes of trunk CoM acceleration. Although we demonstrated that offensive players were quicker and displayed less trunk CoM acceleration, we recommend that future studies use a greater number of participants for inter-limb symmetry in these movement tests.

Relationship among the COM Motion, the Lower Extremity and the Trunk during the Squat.

Squatting is a common motion in activities of daily living and is frequently used in training programs. Squatting requires a shift of the body in both vertical and anterior-posterior directions. Postural control during squatting is considered a mixed strategy; however, details and roles of the trunk and lower limb joints are unclear. The purpose of this study was to investigate the relationship among the kinematics of the lower limb, the trunk and the center of mass (COM) descent during squatting. Twenty-six healthy young adults performed repeated parallel squats. Lower limb joint and trunk angles and the COM were analyzed using a 3D motion analysis system. We evaluated the relationship between the kinematics and the squat depth by performing correlation analysis and multiple linear regression analysis. The ankle was the first to reach its maximum angle, and the remaining joints reached their maximum angles at the maximum squat depth. The knee joint motion and the squat depth were significantly correlated and there was a correlation between the hip and the ankle joint motion and the anteroposterior displacement of the COM during squatting. Multivariate linear regression analysis indicated that squat depth was predicted by both the knee and ankle motion and that anteroposterior displacement of the COM was predicted by the hip, ankle, and knee joint motion. The knees contributed to the vertical COM motion during squatting, while the hips contributed to the COM motion in the anteroposterior direction. On the other hand, the ankles contributed to COM motions in both the vertical and anteroposterior directions during squatting.

Influence of Perturbation’s Type and Location on Treadmill Gait Regularity

Background: This study aimed to investigate how —external perturbations caused by a treadmill belt’s acceleration (Acc) and deceleration (Dec) during the Initial-Contact (Initial), Mid-Stance (Mid), and Pre-Swing (ToeOff) phases affect gait regularity in young adults. Methods: Twenty-one healthy young females walked on a treadmill in a virtual environment (Motek GRAIL), in which four unexpected perturbations were applied to the left belt at the Initial, Mid, and ToeOff stages. Sample entropy (SampEn) was calculated for the center of mass (CoM) displacements for six perturbation scenarios in three directions—anterior–posterior (AP), medial–lateral (ML), and vertical (vert)—with SampEn vector lengths (m) ranging from 2 to 10. Results: The CoM displacement exhibited its highest regularity (low SampEn values) in the AP and vert directions during Dec–ToeOff, across all m values. Similarly, this pattern was observed in the ML direction, but exclusively for m = 2 and 4. The least-regular CoM trajectories (high SampEn values) were for Dec–Mid in the AP direction, across all m values. This trend persisted in the ML direction only for m = 2 and 4. However, the most irregular CoM displacements in the ML direction occurred during Dec–ToeOff for the remaining m values. Vertical CoM displacements exhibited the highest irregularities during Dec–Initial for m ≥ 4. Conclusions: Evaluating the regularity of CoM displacements using SampEn can be a useful tool for assessing how gait perturbations are handled.

Neuromechanical stabilisation of the centre of mass during running

BackgroundStabilisation of the centre of mass (COM) trajectory is thought to be important during running. There is emerging evidence of the importance of leg length and angle regulation during running, which could contribute to stability in the COM trajectory The present study aimed to understand if leg length and angle stabilises the vertical and anterior-posterior (AP) COM displacements, and if the stability alters with running speeds. MethodsData for this study came from an open-source treadmill running dataset (n = 28). Leg length (m) was calculated by taking the resultant distance of the two-dimensional sagittal plane leg vector (from pelvis segment to centre of pressure). Leg angle was defined by the angle subtended between the leg vector and the horizontal surface. Leg length and angle were scaled to a standard deviation of one. Uncontrolled manifold analysis (UCM) was used to provide an index of motor abundance (IMA) in the stabilisation of the vertical and AP COM displacement. ResultsIMAAP and IMAvertical were largely destabilising and always stabilising, respectively. As speed increased, the peak destabilising effect on IMAAP increased from −0.66(0.18) at 2.5 m/s to −1.12(0.18) at 4.5 m/s, and the peak stabilising effect on IMAvertical increased from 0.69 (0.19) at 2.5 m/s to 1.18 (0.18) at 4.5 m/s. ConclusionTwo simple parameters from a simple spring-mass model, leg length and angle, can explain the control behind running. The variability in leg length and angle helped stabilise the vertical COM, whilst maintaining constant running speed may rely more on inter-limb variation to adjust the horizontal COM accelerations.

Change in sensory integration and regularity of postural sway with the suspensory strategy during static standing balance.

The suspensory strategy, a method for controlling postural balance in the vertical direction of the center of mass (COM), is considered by the elderly as a means of balance control. The vertical COM control might alter the sensory integration and regularity of postural sway, which in turn impacts balance. However, to date, this was not confirmed. Thus, this study aimed at investigating the influence of the suspensory strategy achieved through knee flexion on the static standing balance. Nineteen participants were monitored at knee flexion angles of 0°, 15°, and 65°. Time-frequency analysis and sample entropy were employed to analyze the COM data. Time-frequency analysis was utilized to assess the energy content across various frequency bands and corresponding percentage of energy within each frequency band. The outcomes of time-frequency are hypothesized to reflect the balance-related sensory input and sensory weights. Sample entropy was applied to evaluate the regularity of the COM displacement patterns. Knee flexion led to a decreased COM height. The highest energy content was observed at 65° knee flexion, in contrast with the lowest energy observed at 0° in both the anterior-posterior (AP) and medial-lateral (ML) directions. Additionally, the ultra-low-frequency band was more pronounced at 65° than that at 0° or 15° in the ML direction. Furthermore, the COM amplitudes were notably higher at 65° than those at 0° and 15° in the AP and ML directions, respectively. The sample entropy values were lower at 65° and 15° than those at 0° in the ML direction, with the lowest value observed at 65° in the vertical direction. The suspensory strategy could enhance the sensory input and cause sensory reweighting, culminating in a more regular balance control. Such suspensory strategy-induced postural control modifications may potentially provide balance benefits for people with declining balance-related sensory, central processing, and musculoskeletal system functions.

Association of Changes in Hip and Knee Kinematics During a Single-Leg Squat With Changes in Patient-Reported Outcomes at 6 Months and 1 Year After Hip Arthroscopy

Background: Previous studies have demonstrated alterations in squat kinematics in patients with femoroacetabular impingement syndrome (FAIS). Little is known about the effects of arthroscopic hip surgery on biomechanics during a single-leg squat (SLS) in these patients. Purpose/Hypothesis: The purpose of this study was to determine if (1) lower extremity dynamic range of motion (ROM) during an SLS task improves after hip arthroscopy for FAIS and (2) correlations exist between changes in patient-reported outcomes (PROs) and changes in lower extremity dynamic ROM during an SLS after hip arthroscopy for FAIS. It was hypothesized that dynamic hip ROM would improve after hip arthroscopy and that hip dynamic ROM would be associated with changes in PRO scores at both 6 months and 1 year. Study Design: Descriptive laboratory study. Methods: Patients with FAIS performed 3 SLSs that were analyzed using a 20-camera motion capture system. Dynamic ROMs were calculated in 3 planes for the hip, knee, ankle, and pelvic segments. Squat depth was calculated as the change in vertical center of mass during the squat cycle. PROs including the Hip Outcome Score–Activities of Daily Living (HOS-ADL), Hip Outcome Score–Sports (HOS–Sports), International Hip Outcome Tool–12, and visual analog scale for pain scores were collected preoperatively and at the time of postoperative testing. Paired-samples t tests were used to compare kinematic variables pre- and postoperatively. Correlations were used to compare changes in PROs with changes in kinematics. All statistical analysis was performed using SPSS Version 26. Results: Fifteen patients were tested preoperatively and at a mean of 9 months postoperatively. All PRO measures improved postoperatively at 6 months and 1 year. Squat depth and sagittal plane hip and knee dynamic ROMs were significantly improved postoperatively. Positive correlations existed between changes in (1) hip ROM with the 6-month HOS-ADL score (r = 0.665) and (2) knee ROM with the 6 month (r = 0.590) and 1-year (r = 0.565) HOS–Sports scores. Conclusion: Dynamic sagittal plane hip and knee ROMs improve after hip arthroscopy for FAIS. These improvements demonstrate strong correlations with improvements in some but not all postoperative PROs. Clinical Relevance: The current study sought to better understand the role of dynamic movement in the diagnosis and treatment of FAIS. These findings indicate that dynamic ROM and squat depth can, similarly to PROs, serve as biomarkers for patient function both before and after hip arthroscopic surgery.

Individual muscle contributions to the acceleration of the centre of mass during gait in people with mild-to-moderate hip osteoarthritis

BackgroundPeople with mild-to-moderate hip osteoarthritis (OA) exhibit hip muscle weakness, alterations in hip kinematics and kinetics and hip contact forces during gait compared to healthy controls. However, it is unclear if those with hip OA use different motor control strategies to coordinate the motion of the centre of mass (COM) during gait. Such information could provide further critical assessment of conservative management strategies implemented for people with hip OA. Research questionDo muscle contributions to the acceleration of the COM during walking differ between individuals with mild-to-moderate hip OA and controls? MethodsEleven individuals with mild-to-moderate hip OA and 10 healthy controls walked at a self-selected speed while whole-body motion and ground reaction forces were measured. Muscle forces during gait were obtained using static optimisation and an induced acceleration analysis was performed to determine individual muscle contributions to the acceleration of the COM during single-leg stance (SLS). Between-group comparisons were made using independent t-tests via Statistical Parametric Modelling. ResultsThere were no between-group differences in spatial-temporal gait parameters or three-dimensional whole-body COM acceleration. The rectus femoris, biceps femoris, iliopsoas and gastrocnemius muscles in the hip OA group contributed less to the fore-aft accelerations of the COM (p < 0.05), and more to the vertical COM acceleration with the gluteus maximus (p < 0.05), during SLS, compared to the control group. SignificanceSubtle differences exist in the way people with mild-to-moderate hip OA use their muscles to accelerate the whole-body centre of mass during the SLS phase of walking relative to healthy controls. These findings improve understanding of the complex functional consequences of hip OA and enhance our understanding of how to monitor the effectiveness of an intervention on biomechanical changes in gait in people with hip OA.

Effects of load increase on lower extremity kinetic and kinematic variables in the back squat exercise.

Squats are one of the most widely used weight training methods worldwide, and the single most ubiquitous with regard to multi-joint resistance training. The objective of the present study was to investigate kinematic and kinetic changes in the lower extremities as a result of load increases during a back squat exercise, and to propose an association between back squats and lower extremity injuries. Eight individuals with experience of back squat training were recruited. The subjects performed back squats with loads of 25%, 50%, 100%, and 125% of their body weight. During the performance, the center of pressure (COP) sway; vertical center of mass (COM) velocity; joint moment; joint range of motion (ROM) of flexion/extension and adduction/abduction; and rotation of the ankle, knee, and hip joints were measured. The participants' lower extremity joint ROM, vertical COM velocity, and COP variability did not change significantly with changes in weight loading. However, the moments applied to the lower extremity joints differed according to changes in barbell weight. The moments of plantar flexion (f= 54.362, p< 0.001), dorsiflexion (f= 8.475, p< 0.001), knee flexion (f= 12.013, p< 0.001), knee extension (f= 8.581, p< 0.001), hip flexion (f= 5.111, p< 0.001), and hip extension (f= 11.053, p< 0.001) increased in the sagittal plane (flexion/extension). There was also a significant increase in ankle eversion (f= 5.612, p= 0.004), hip abduction (f= 3.242, p= 0.037), and adduction (f= 5.846, p= 0.003) in the frontal plane (adduction/abduction). Among the moment variables in the transverse plane (rotation), there were significant differences in ankle internal rotation (f= 7.043, p= 0.001) and hip external rotation (f= 11.070, p< 0.001). As the barbell load increased, posture and performance were maintained, but rotational moments of the joints differed. It is expected that the joint directions that showed significant differences in this study are likely to be vulnerable to the risk of injury when an excessive load is applied to the body. Examples include the hip adduction moment, hip external rotation moment, and ankle internal rotation moment, and apply regardless of the increase in the rotational moments of joints from load increases.

Muscle Contributions to Take-Off Velocity in the Long Jump.

A key determinant of long jump performance is the ability to increase the vertical velocity of the center of mass (COM) while minimizing the loss in forward velocity (running speed) during the take-off phase, but exactly how this occurs is not fully understood. We combined a three-dimensional musculoskeletal model of the body with dynamic optimization theory to simulate the biomechanics of the long jump take-off and determine the contributions of the individual leg muscles to jump performance. The body was modeled as a 29-degree-of-freedom skeleton actuated by a combination of muscles and net joint torques. A dynamic optimization problem was solved to reproduce full-body motion and ground-force data recorded from experienced subelite jumpers. The optimization solution then was analyzed to determine each muscle's contribution to the ground-force impulse and hence the change in velocity of the COM during the take-off phase. The hip, knee, and ankle extensors dominated the change in velocity of the COM during take-off. Vasti (VAS) generated the highest support impulse and contributed one-third (33%) of the increase in vertical COM velocity generated by all the muscles. Soleus (SOL) and gluteus maximus (GMAX) also developed substantial support impulses and contributed 24% and 16% of the increase in vertical COM velocity, respectively. VAS also generated the highest braking impulse and contributed approximately one-half (55%) of the loss in forward COM velocity generated by all the muscles, whereas SOL and GMAX made much smaller contributions (12% and 7%, respectively). VAS, SOL, and GMAX contributed nearly three-quarters (73%) of the increase in vertical COM velocity at take-off, suggesting that these muscles ought to be prioritized in strength training programs aimed at improving long jump performance.

Young adults use whole-body feedback and ankle proprioception to perceive small locomotor disturbances

To prevent a fall when a disturbance to walking is encountered requires sensory information about the disturbance to be sensed, integrated, and then used to generate an appropriate corrective motor response. Prior research has shown that feedback of whole-body motion (e.g., center-of-mass kinematics) drives this corrective response. Here, we hypothesized that young adults also use whole-body motion to perceive locomotor disturbances. 15 subjects performed a locomotor discrimination task in which the supporting leg was slowed during stance every 8–12 steps to emulate subtle slips. The perception threshold of these disturbances was determined using a psychometrics approach and found to be 0.08 ± 0.03 m/s. Whole-body feedback was examined through center-of-mass (CoM) kinematics and whole-body angular momentum (WBAM). Perturbation-induced deviations of CoM and WBAM were calculated in response to the two perturbation levels nearest each subject's perception threshold. Consistent with our hypothesis, we identified significantly higher perturbation induced deviations for perceived perturbations in sagittal-plane WBAM, anteroposterior CoM velocity, and vertical CoM velocity and acceleration. Because whole body motion is not sensed directly but instead arises from the integration of various sensory feedback signals, we also explored local sensory feedback contributions to the perception of locomotor disturbances. Local sensory feedback was estimated through kinematic analogues of vision (head angle), vestibular (head angular velocity), proprioception (i.e., sagittal hip, knee, and ankle angles), and somatosensation (i.e., anterior-posterior & mediolateral center-of-pressure, COP). We identified significantly higher perturbation induced deviations for perceived perturbations in sagittal-plane ankle angle. These results provide evidence for both whole-body feedback and ankle proprioception as important for the perception of subtle slip-like locomotor disturbances in young adults. Our interpretation is ankle proprioception is a dominant contributor to estimates of whole-body motion to perceive locomotor disturbances.

Contribution of lower extremity muscles to center of mass acceleration during walking: Effect of body weight

Overweight or obesity is known to be associated with altered activations of lower extremity muscles. Such changes in muscular function may lead to the development of mobility impairments or joint diseases. However, little is known about how individual lower extremity muscles contribute to the whole-body center of mass (COM) control during walking and the effect of body weight. This study examined the contribution of individual lower extremity muscle force to the COM accelerations during walking in overweight and non-overweight individuals. Musculoskeletal simulations were performed for the stance phase of walking with data collected from 11 overweight and 13 non-overweight adults to estimate lower extremity muscle forces and their contributions to the COM acceleration. Mean time-series data from each parameter were compared between body size groups using Statistical Parametric Mapping. Compared to the non-overweight group, the overweight group revealed a greater gastrocnemius contribution to the mediolateral (p = 0.006) and vertical (p < 0.001) COM accelerations during mid-stance, and had a lower vastus contribution to the anteroposterior COM acceleration (p < 0.001) during pre-swing. Increased contributions from the large posterior calf muscles to the mediolateral COM acceleration may be related to efforts to alleviate COM sway in overweight individuals.

Projected frontal area and its components during front crawl depend on lung volume.

We examined the influence of lung volume on the vertical body position, trunk inclination, and projected frontal area (PFA) during swimming and the inter-relationships among these factors. Twelve highly trained male swimmers performed a 15 m front crawl with sustained maximal inspiration (INSP), maximal expiration (EXP), and intermediate (MID) at a target velocity of 1.20 m·s-1 . Using our developed digital human model, which allows inverse kinematics calculations by fitting individual body shapes measured with a three-dimensional photonic image scanner to individually measured underwater motion capture data, vertical center of mass (CoM) position, trunk inclination, and PFA were calculated for each complete stroke cycle. In particular, the PFA was calculated by automatic processing of a series of parallel frontal images obtained from a reconstructed digital human model. The vertical CoM position was higher with a larger lung-volume level (p < 0.01). The trunk inclination was smaller in INSP and MID than in EXP (p < 0.01). PFA was smaller with a larger lung-volume level (p < 0.01). Additionally, there was a significant interaction of vertical CoM position and trunk inclination with PFA (p=0.006). There was a negative association between PFA and vertical CoM position, and a positive association between PFA and trunk inclination less than the moderate vertical CoM position (each p < 0.05). These results obtained using our methodology indicate that PFA decreases with increasing lung volume due to an increase in vertical CoM position, and additionally due to a decrease in trunk inclination at low-to-moderate lung-volume levels.

Optimizing Template Models to Quantifiably Assess Center of Mass Kinematic Reconstruction.

The center of mass (COM) plays a fundamental role in human ambulation, but the redundant nature of the human body adds complexity to mathematically modeling its dynamics. Template models like the Bipedal Spring Loaded Inverted Pendulum (B-SLIP) and the Virtual Pivot Point (VPP) address this complexity by removing the redundancy while retaining desired salient characteristics, such as the COM evolution. However, template models for the COM during human walking have mostly been used for qualitative analysis due to issues such as overestimation of COM vertical displacement. This paper considers a quantifiable template-based analysis of human walking by using an optimization framework to set the model parameter values for matching both explicitly and implicitly considered gait characteristics. Furthermore, it is shown that allowing the leg stiffness of the B-SLIP and VPP model to vary throughout the gait cycle better matches vertical COM trajectories with 54%-63% error reduction. These optimized template models show promise in retaining ground reaction force (GRF) information, which is not explicitly considered during the optimization process. Future work looks to incorporate these optimized trajectories as a reference for control of a lower-limb knee-ankle prosthesis.

Vertical body position during front crawl increases linearly with swimming velocity and the rate of its increase depends on individual swimmers

ABSTRACT Vertical body position during swimming is assumed to closely affect drag. It is consequently associated with swimming velocity; however, the association between swimming velocity and vertical body position has not yet been sufficiently established. Here, we aimed to clarify how vertical body position increases with front crawl velocity and whether there are inter-individual differences in velocity effect. Eleven college-level male swimmers performed a 15 m front crawl with sustained forced maximal inspiration at various swimming velocities. The body’s centre of mass (CoM) was estimated from individual digital human models with inertial parameters using inverse kinematics. The horizontal CoM velocity and vertical CoM position from the water surface were averaged for one stroke cycle as respective indexes of swimming velocity and vertical body position. Linear mixed-effects model analysis revealed that there is a positive trend between swimming velocity and vertical CoM position during front crawl across the participants. These results indicate that swimming velocity is associated with vertical body position during front crawl. Additionally, the linear mixed-effects model with random intercepts and slopes was a better fit than that with only random intercepts, indicating that there are inter-individual differences in the rate of increase in vertical body position against swimming velocity.

Pelvic elevation induces vertical kinetic energy without losing horizontal energy during running single-leg jump for distance

ABSTRACT In a running single-leg jump (RSLJ) for distance, the generation of vertical velocity without loss of horizontal velocity during the take-off phase is ideal, but difficult; however, we hypothesized that the pelvic rotation in the frontal plane achieved it. Here we show the effect of each segment rotation on the horizontal and vertical kinetic energies ( and ) of the centre of mass (CoM) during the take-off phase of an RSLJ for distance. We collected kinematic and ground-reaction-force data during RSLJs for distance by nine male long jumpers, involving an approximately 20-m approach in an outdoor field. We determined the components of the and changes due to each segment movement. Elevation of the pelvic free-leg side increased (0.53±0.16 J/kg, 9±3% of the total change). Pelvic axial rotation decreased , while pelvic elevation did not affect it (0.01±0.02 J/kg, no significant difference from zero). In contrast, forward rotations of the stance-leg shank and thigh decreased while simultaneously increasing . The results showed that pelvic elevation increased the vertical CoM velocity without causing a loss in horizontal velocity, although the lower-limb segments’ effects on the vertical and horizontal velocities exhibited a trade-off, as previously speculated. RSLJs for distance have been frequently assumed as sagittal movements. However, our findings highlight the importance of three-dimensional pelvic movement, particularly in the frontal plane, for controlling both the vertical and horizontal velocities. Highlights l We show the effect of each segment rotation on the horizontal and vertical kinetic energies ( and ) of the centre of mass during the take-off phase of a running single-leg jump for distance. l Elevation of the pelvic free-leg side increased but did not decrease , while the forward rotations of the stance-leg thigh and shank decreased , while simultaneously increasing . l We highlight the importance of pelvic movement in the frontal plane for controlling both the vertical and horizontal velocities with single-leg stance.

Mind your step: Target walking task reveals gait disturbance in individuals with incomplete spinal cord injury

BackgroundWalking over obstacles requires precise foot placement while maintaining balance control of the center of mass (CoM) and the flexibility to adapt the gait patterns. Most individuals with incomplete spinal cord injury (iSCI) are capable of overground walking on level ground; however, gait stability and adaptation may be compromised. CoM control was investigated during a challenging target walking (TW) task in individuals with iSCI compared to healthy controls. The hypothesis was that individuals with iSCI, when challenged with TW, show a lack of gait pattern adaptability which is reflected by an impaired adaptation of CoM movement compared to healthy controls.MethodsA single-center controlled diagnostic clinical trial with thirteen participants with iSCI (0.3–24 years post injury; one subacute and twelve chronic) and twelve healthy controls was conducted where foot and pelvis kinematics were acquired during two conditions: normal treadmill walking (NW) and visually guided target walking (TW) with handrail support, during which participants stepped onto projected virtual targets synchronized with the moving treadmill surface. Approximated CoM was calculated from pelvis markers and used to calculate CoM trajectory length and mean CoM Euclidean distance TW-NW (primary outcome). Nonparametric statistics, including spearman rank correlations, were performed to evaluate the relationship between clinical parameter, outdoor mobility score, performance, and CoM parameters (secondary outcome).ResultsHealthy controls adapted to TW by decreasing anterior–posterior and vertical CoM trajectory length (p < 0.001), whereas participants with iSCI reduced CoM trajectory length only in the vertical direction (p = 0.002). Mean CoM Euclidean distance TW-NW correlated with participants’ neurological level of injury (R = 0.76, p = 0.002) and CoM trajectory length (during TW) correlated with outdoor mobility score (R = − 0.64, p = 0.026).ConclusionsThis study demonstrated that reduction of CoM movement is a common strategy to cope with TW challenge in controls, but it is impaired in individuals with iSCI. In the iSCI group, the ability to cope with gait challenges worsened the more rostral the level of injury. Thus, the TW task could be used as a gait challenge paradigm in ambulatory iSCI individuals.Trial registration Registry number/ ClinicalTrials.gov Identifier: NCT03343132, date of registration 2017/11/17.

Animate Prime Movers: A Prototype Based Methodology for Estimation of Renewable Power Production

The world is shifting towards renewable energy sources most notably solar and wind power. Besides these two, there are other sources of renewable power which are relatively less exploited. Among these, a rather unexplored field is that of animate prime movers. The current paper intends to present hardware prototype based methodology for evaluation of the potential of generatable power from an exercising animate prime mover – which in the current case is a male caprine subject. MATLAB environment has been used for an attempt to track the center of mass (COM) motion of the subject subsequent to its movement on a retrofitted treadmill. These COM motion trajectories can be used to evaluate the potential of generatable power – wherein the vertical COM motion upon the treadmill with an incline is compared with the corresponding COM motion on the machine when it is flat, and thus the power expended for vertical propulsion of the body is evaluated. This power is potentially generatable if the machine is kept flat and an energy harvesting mechanism is attached to it. Furthermore, the paper includes a relevant literature review section for this relatively unorthodox field.