Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 94
Filtrar
1.
Sci Total Environ ; 948: 174793, 2024 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-39019266

RESUMEN

The present study explores the intricacies of CALIPSO Level 3 optimized Aerosol Optical Depth (AOD) and Dust Aerosol Optical Depth (DAOD) products. Hence, the study focused on regions in the Middle East and North Africa (MENA) across different seasons from January 2007 to December 2020. The study utilizes a refined 1° × 1° grid resolution to analyze horizontal distribution patterns, seasonal variations, and the interplay of various aerosol constituents. The Middle East (ME) stands out with intensified AOD during transitional periods, and the Saharan-Sahel Dust (SSD) belt exhibits higher DAOD during specific seasons. Regions with significant industrialization and human activities exhibit high non-dust AOD values, while major dust sources like the SSD and the Arabian Desert showed high DAOD values in the spring and summer seasons. The study reveals seasonal variations in AOD and DAOD, with different regions showing distinct characteristics influenced by topographic and environmental factors. Observational evidence on the vertical distribution of dust layers is crucial for modeling studies to assess the impact of airborne dust particles on radiation and clouds. However, there are challenges in assimilating dust into atmospheric models due to limited ground measurements near dust sources. Further, the statistical metrics highlight regional and seasonal variations in DAOD, Dust Center of Mass, and Dust Top Height. The analysis extends to particle depolarization ratio, aerosol classification, spatial deviation in dust composition, AOD, and cloud properties (e.g., cloud optical thickness and cloud fraction). This has been influenced by several factors such as atmospheric circulation patterns, temperature, humidity, and land cover changes. Trends in AOD and DAOD over timescale indicate regional variations in aerosol concentrations. The study offers valuable insights into the complex atmospheric phenomena shaping the examined regions over the 13 years.

2.
Gait Posture ; 113: 224-231, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-38954928

RESUMEN

BACKGROUND: Individuals with myelomeningocele (MMC) present with neurological and orthopaedic deficiencies, requiring orthoses during walking. Orthoses for counteracting dorsiflexion may restrict activities such as rising from a chair. RESEARCH QUESTION: How are sit-to-stand (STS) movements performed with ankle joint-restricted ankle-foot orthoses (AFO) and knee-ankle-foot orthoses with a free-articulated knee joint (KAFO-F)? METHODS: Twenty-eight adults with MMC, mean age 25.5 years (standard deviation: 3.5 years), were divided into an AnkleFree group (no orthosis or a foot orthosis) and an AnkleRestrict group (AFOs or KAFO-Fs). Study participants performed the five times STS test (5STS) while their movements were simultaneously captured with a three-dimensional motion system. Centre of mass (CoM) trajectories and joint kinematics were analysed using statistical parametric mapping. RESULTS: The AnkleRestrict group performed the STS slower than the AnkleFree group, median 8.8 s (min, max: 6.9, 14.61 s) vs 15.0 s (min, max: 7.5, 32.2 s) (p = 0.002), displayed reduced ankle dorsiflexion (mean difference: 6°, p = 0.044) (74-81 % of the STS cycle), reduced knee extension (mean difference: 14°, p = 0.002) (17-41 % of the STS cycle), larger anterior pelvic tilt angle (average difference: 11°, p = 0.024) (12-24 % of the STS cycle), and larger trunk flexion angle (on average 4°, p = 0.029) (6-15 % of the STS cycle). SIGNIFICANCE: The differences between the AnkleFree and AnkleRestrict groups in performing the STS seem consistent with the participants functional ambulation: community ambulation in the AnkleFree group, and household and nonfunctional ambulation with less hip muscle strength in the majority of the AnkleRestrict group. No differences in the 5STS CoM trajectories or the kinematics were found with respect to the AFO and KAFO-Fs groups. Because orthoses are constructed to enable walking, the environment needs to be adjusted for activities in daily living such as the STS movement.


Asunto(s)
Articulación del Tobillo , Ortesis del Pié , Meningomielocele , Humanos , Fenómenos Biomecánicos , Meningomielocele/fisiopatología , Meningomielocele/rehabilitación , Adulto , Masculino , Femenino , Articulación del Tobillo/fisiopatología , Zapatos , Adulto Joven , Sedestación , Posición de Pie , Articulación de la Rodilla/fisiopatología , Aparatos Ortopédicos , Caminata/fisiología
3.
J Microsc ; 295(2): 140-146, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-38372408

RESUMEN

Atomic electric fields in a thin GaN sample are measured with the centre-of-mass approach in 4D-scanning transmission electron microscopy (4D-STEM) using a 12-segmented STEM detector in a Spectra 300 microscope. The electric fields, charge density and potential are compared to simulations and an experimental measurement using a pixelated 4D-STEM detector. The segmented detector benefits from a high recording speed, which enables measurements at low radiation doses. However, there is measurement uncertainty due to the limited number of segments analysed in this study.

4.
Gait Posture ; 109: 153-157, 2024 03.
Artículo en Inglés | MEDLINE | ID: mdl-38309126

RESUMEN

BACKGROUND: Exploring the use of minimum marker sets is important for balancing the technical quality of motion capture with challenging data collection environments and protocols. While minimum marker sets have been demonstrated to be appropriate for evaluation of some motion patterns, there is limited evidence to support model choices for abrupt, asymmetrical, non-cyclic motion such as balance disturbance during a bathtub exit task. RESEARCH QUESTION: How effective are six models of reduced complexity for the estimation of centre of mass (COM) displacement and velocity, relative to a full-body model. METHODS: Eight participants completed a bathtub exit task. Participants received a balance perturbation as they crossed the bathtub rim, stepping from a soapy wet bathtub to a dry floor. Six reduced models were developed from the full, 72-marker, 12 segment 3D kinematic data set. Peak displacement and velocity of the body COM, and RMSE (relative to the full-body model) for displacement and velocity of the body COM were determined for each model. RESULTS: Main effects were observed for peak right, left, anterior, posterior, upwards and downwards motion, and peak left, anterior, posterior, upwards and downwards velocity. Time-varying (RMSE) was smaller for models including the thighs than models not containing the thighs. In contrast, inclusion of upper arm, forearm, and hand segments did not improve model performance. The model containing the sacrum marker only consistently performed the worst across peak and RMSE metrics. SIGNIFICANCE: Findings suggest a simplified centre of mass model may adequately capture abrupt, asymmetrical, non-cyclic tasks, such as balance disturbance recovery during obstacle crossing. A reduced kinematic model should include the thighs, trunk and pelvis segments, although models that are more complex are recommended, depending on the metrics of interest.


Asunto(s)
Brazo , Pelvis , Humanos , Movimiento (Física) , Extremidad Superior , Mano , Fenómenos Biomecánicos , Equilibrio Postural
5.
J Biomech ; 165: 112018, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38412623

RESUMEN

Balance studies usually focus on quantities describing the global body motion. Assessing such quantities using classical marker-based approach can be tedious and modify the participant's behaviour. The recent development of markerless motion capture methods could bypass the issues related to the use of markers. This work compared dynamic balance related quantities obtained with markers and videos. Sixteen young healthy participants performed four different motor tasks: walking at self-selected speed, balance loss, walking on a narrow beam and countermovement jumps. Their movements were recorded simultaneously by marker-based and markerless motion capture systems. Videos were processed using a commercial markerless pose estimation software, Theia3D. The centre of mass position (CoM) was computed, and the associated extrapolated centre of mass position (XCoM) and whole-body angular momentum (WBAM) were derived. Bland-Altman analysis was performed and root mean square difference (RMSD) and coefficient of correlation were computed to compare the results obtained with marker-based and markerless methods. Bias remained of the magnitude of a few mm for CoM and XCoM positions, and RMSD of CoM and XCoM was around 1 cm. RMSD of the WBAM was less than 10 % of the total amplitude in any direction, and bias was less than 1 %. Results suggest that outcomes of balance studies will be similar whether marker-based or markerless motion capture system are used. Nevertheless, one should be careful when assessing dynamic movements such as jumping, as they displayed the biggest differences (both bias and RMSD), although it is unclear whether these differences are due to errors in markerless or marker-based motion capture system.


Asunto(s)
Captura de Movimiento , Movimiento , Humanos , Movimiento (Física) , Caminata , Programas Informáticos , Fenómenos Biomecánicos
6.
J Biomech ; 157: 111703, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37451207

RESUMEN

Stepping strategies following external perturbations from different directions is investigated in this work. We analysed the effect of the perturbation angle as well as the level of awareness of individuals and characterised steps out of the sagittal plane between Loaded Side Steps (LSS), Unloaded Medial Steps (UMS) and Unloaded Crossover Steps (UCS). A novel experimental paradigm involving perturbations in different directions was performed on a group of 21 young adults (10 females, 11 males, 20-38 years). Participants underwent 30 randomised perturbations along 5 different angles with different levels of awareness of the upcoming perturbations (with and without wearing a sensory impairment device) for a total of 1260 recorded trials. Results showed that logistic models based on the minimal values of the Margin of Stability (MoS) or on the minimal values of the Time to boundary (Ttb) performed the best in the sagittal plane. However, their accuracy stayed above 79% regardless of the perturbation angle or level of awareness. Regarding the effect of the experimental condition, evidences of different balance recovery behaviours due to the variation of perturbation angles were exposed, but no significant effect of the level of awareness was observed. Finally, we proposed the Distance to Foot boundary (DtFb) as a relevant quantity to characterise the stepping strategies in response to perturbations out of the sagittal plane.


Asunto(s)
Pie , Equilibrio Postural , Femenino , Humanos , Masculino , Adulto Joven , Fenómenos Biomecánicos , Pie/fisiología , Equilibrio Postural/fisiología , Adulto
7.
J Biomech ; 156: 111675, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37329641

RESUMEN

Estimating the position of the whole-body centre of mass (CoM) based on skin markers and anthropometric tables requires tracking the pelvis and lower body, which is impossible for wheelchair users due to occlusion. In this work, we present a method to track the user's whole-body CoM using visible markers affixed to the user and wheelchair where the user remains seated in their wheelchair, by expressing the pelvis and lower body segments in wheelchair coordinates. The accuracy of this method was evaluated on the anterior-posterior (AP) and medial-lateral (ML) axes by comparing the projected CoM to the centre of pressure measured by four force plates, for 11 able-bodied participants adopting 9 static postures that include extreme reaching postures. The estimation accuracy was within 33 mm (AP) and 9 mm (ML), with a precision within 23 mm (AP) and 12 mm (ML). Tracking the whole-body CoM during wheelchair propulsion will allow researchers to better understand the dynamics of propulsion, which may help devise new approaches to increase the energy transfer from the arms to the ground and reduce the risks of developing musculoskeletal disorders.


Asunto(s)
Captura de Movimiento , Silla de Ruedas , Humanos , Brazo , Postura , Fenómenos Biomecánicos
8.
Clin Biomech (Bristol, Avon) ; 107: 106005, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37302301

RESUMEN

BACKGROUND: The control of the center of mass is essential for a stable and efficient gait. Post-stroke patients present several impairments, which may compromise the control of the center of mass during gait in the sagittal and frontal planes. This study aimed to identify changes in the vertical and mediolateral behavior of the center of mass during the single stance phase of post-stroke patients using the statistical parametric mapping analysis. It also aimed to identify alterations in the center of mass trajectories regarding the motor recovery stages. METHODS: Seventeen stroke patients and 11 neurologically intact individuals were analyzed. The statistical parametric mapping approach was used to identify changes in the center of mass trajectories between stroke and healthy groups. The trajectories of the center of mass of post-stroke individuals were compared according to their motor recovery status. FINDINGS: A near-flat vertical trajectory of the center of mass was indenfitifed in the stroke group compared to their healthy counterparts, especially on the paretic side. The center of mass trajectories in both directions (vertical and mediolateral) presented substantial alteration at the end of the single stance phase in the stroke group. The trajectory of the center of mass of the stroke group was symmetrical in the mediolateral direction between the sides. The trajectories of the center of mass presented similar pattern irrespective of the motor recovery status. INTERPRETATION: The statistical parametric mapping approach showed to be suitable for determining gait changes in post-stroke individuals, irrespective of their motor recovery stage.


Asunto(s)
Trastornos Neurológicos de la Marcha , Rehabilitación de Accidente Cerebrovascular , Accidente Cerebrovascular , Humanos , Caminata , Marcha , Accidente Cerebrovascular/complicaciones , Trastornos Neurológicos de la Marcha/etiología , Fenómenos Biomecánicos
9.
J Sci Med Sport ; 26(6): 328-334, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37271700

RESUMEN

OBJECTIVES: Swimming intra-cycle velocity fluctuation has often been assessed using the coefficient of variation, which requires a mathematical assumption of a positive linear relationship between the velocity mean and standard deviation. As this assumption has never been tested, the current study aimed to investigate the within-participant relationship between the mean and standard deviation of the intra-cycle velocity. DESIGN: Cross-sectional study. METHODS: The intra-trial mean and standard deviation of one stroke cycle centre of mass velocity (vCMmean and vCMSD, respectively) were obtained from 80 front crawl trials (10 participants × eight swimming speeds) using whole-body three-dimensional motion analysis. The linear mixed-effect model and intra-class correlation analysis were used to test the linear relationship between vCMmean and vCMSD (n = 80) and the absolute agreement between vCMmean and vCMSD relative to those during the fastest trial (n = 70). RESULTS: Neither the linear regression model (95 % confidence interval range of the fixed effect of vCMmean: -0.003-0.031) nor the intra-class correlation coefficient (ICC = 0.07; p = 0.26) verified linear relationships between vCMmean and vCMSD, which violated the background assumption of coefficient of variation calculation. CONCLUSIONS: When investigating the intra-cycle velocity fluctuation, the coefficient of variation should not be used alone. Researchers and practitioners should always interpret/report the obtained results together with the mean and standard deviation to avoid misleading conclusions and feedback because the coefficient of variation obtained from one cycle velocity data is likely biased by mean velocity.


Asunto(s)
Natación , Humanos , Estudios Transversales , Fenómenos Biomecánicos
10.
Sensors (Basel) ; 22(19)2022 Sep 27.
Artículo en Inglés | MEDLINE | ID: mdl-36236420

RESUMEN

In ice hockey, the butterfly style/stance is a technique distinguished by the goalkeepers (goalie) dropping to their knees to block attempts to score. Although this goalie style has been around for many years, comparisons between on and off-ice attire has not been undertaken. Therefore, this preliminary study compared differences in torso acceleration and energy expenditure by way of the Metabolic Equivalent of Task (MET) during off-ice and on-ice butterfly stances/saves. Seven participants each performed 8 on-ice butterfly saves/stances whilst wearing full hockey attire followed by 8 off-ice butterfly stances without wearing full hockey attire whilst torso acceleration was collected. The off-ice movement significantly increased vertical torso acceleration (p < 0.01, d > 0.90) with increased MET, compared to on-ice motion. Despite no significant difference in anteroposterior and mediolateral torso kinematics, vector magnitudes were significantly greater (p < 0.01, d > 0.90) when the stance was performed off-ice. The increased vertical acceleration observed when goalies performed the movement off-ice could be due to a failure to maintain adequate posture without the support of the external load. The results of this study may help inform off-ice training interventions for ice hockey goalkeeping.


Asunto(s)
Hockey , Aceleración , Fenómenos Biomecánicos , Humanos , Movimiento , Torso
11.
J Biomech ; 144: 111345, 2022 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-36283145

RESUMEN

Rocker-profile design shoes are commonly used in clinical settings. Such footwear reduces in-shoe pressure over the forefoot area during the gait, and depending on the rocker-profile type (i.e., toe-only, heel negative, or double rocker), affects lower limb kinematics, kinetics, and muscle electromyographic activity. However, whether wearing rocker-profile shoes influence the dynamics of the body centre of mass (BCoM) is unknown. We used a mathematical procedure combining Lissajous contours and Fourier analysis to describe the 3D trajectory of the BCoM in walking with rocker-profile (RollingSole) and flat (Control) shoes at 0.97, 1.25, and 1.53 m s-1 in 30 participants. Harmonics amplitude and phase were compared using linear and circular statistics, respectively. External (Wext), kinematic internal (Wint,k) and total (Wtot) mechanical works, and the mechanical energy fraction recovered from a pendular exchange of potential and kinetic energy were also calculated. RollingSole shoes yielded greater Wext (1-9 %; P < 0.05) and fractional pendular energy exchange (1-8 %; P < 0.01), with lower Wint,k (2-5 %; P < 0.05) and unchanged Wtot (P ≥ 0.30). RollingSole shoes led also to a greater mean height of the BCoM (1-3 %; P < 0.01), and amplitude of the anteroposterior and vertical symmetric, and mediolateral 2nd-to-5th harmonics (1-30 %; P < 0.01). No differences between shoes were found for the harmonics phase (P ≥ 0.14). Our results indicate that RollingSole shoes enhanced an inverted pendulum-like behaviour of the BCoM during walking with no alterations in total mechanical work. This may result from the combination of rocker-profile design and greater BCoM height (through thicker soles) with such shoes, increasing recovery of mechanical energy in step-to-step transitions and mid-stance.


Asunto(s)
Zapatos , Caminata , Humanos , Diseño de Equipo , Caminata/fisiología , Marcha/fisiología , Fenómenos Biomecánicos
12.
Anim Front ; 12(3): 45-53, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35711501
13.
Clin Biomech (Bristol, Avon) ; 93: 105595, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-35247709

RESUMEN

BACKGROUND: Retraining stepping reactions in people post-stroke is vital. However, the relationship between the stimulus and resulting stepping performance in people post-stroke is unknown. We explored relationships between stepping stimulus and stepping reactions initiated by either paretic or non-paretic legs of people post-stroke and controls. Relationships were examined in the context of clinical measures of balance. METHODS: Centre of mass dynamics were measured during self-initiated destabilizing leaning stimuli that required stepping reactions by paretic and non-paretic legs of people post-stroke (n = 10) and controls (n = 10) to recover balance. Step characteristics of the first two steps of stepping reactions were measured. Correlations were calculated between clinical measures of balance and mobility and the centre of mass and step characteristics. FINDINGS: Steps were shorter and slower with decreased centre of mass fore-aft and downward displacement and velocity when initiated by paretic and non-paretic legs compared with controls. However, increase in centre of mass displacement and velocity in the fore-aft and downward direction tended to be associated with a greater increase in step length and speed when stepping reactions were initiated by the paretic and non-paretic legs compared with controls. Time to step initiation in response to onset of falling stimulus did not differ between groups. Strong positive correlations were found between clinical balance and mobility scores and centre of mass and step dynamics in fore-aft and vertical directions. INTERPRETATION: These results support objective measurement of centre of mass to quantify the stimulus influencing step dynamics and stepping performance during retraining interventions following stroke.


Asunto(s)
Equilibrio Postural , Accidente Cerebrovascular , Fenómenos Biomecánicos , Humanos , Pierna , Equilibrio Postural/fisiología , Accidente Cerebrovascular/complicaciones
14.
J Biomech ; 135: 111015, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-35259658

RESUMEN

Horizontal jumps are discrete, fast, over-ground movements requiring coordination of the centre of mass (CoM) and base of support and are routinely assessed in sports settings. There is currently no biomechanics-based system to aid in their quick and objective large-scale assessment. We describe a practical system combining a single low-cost depth-sensing camera and point-cloud processing (PCP) to capture whole-body CoM and foot kinematics. Fourteen participants performed 10 single-leg horizontal jumps for distance. Foot displacement, CoM displacement, CoM peak velocity and CoM peak acceleration in the anterior-posterior direction of movement were compared with a reference 15-segment criterion model, captured concurrently using a nine-camera motion capture system (Vicon Motion Systems, UK). Between-system Pearson's correlations were very-large to near-perfect (n = 140; foot displacement = 0.99, CoM displacement = 0.98, CoM peak velocity = 0.97, CoM peak acceleration = 0.79), with mean biases being trivial-small (-0.07 cm [0.12%], 3.8 cm [3.5%], 0.03 m·s-1 [1.6%], 0.42 m·s-2 [7%], respectively) and typical errors being trivial-small for displacement (foot: 0.92 cm [0.8%]; CoM: 3.8 cm [3.4%]) and CoM peak velocity (0.07 m·s-1 [4.3%]), and large for CoM peak acceleration (0.72 m·s-2 [15%]). Limits of agreement were -1.9 to 2.0 cm for foot displacement, -11.3 to 3.6 cm for CoM displacement, -0.17 to 0.12 m·s-1 for CoM peak velocity and -2.28 to 1.43 m·s-2 for CoM peak acceleration. The practical system captured CoM and foot kinematics during horizontal jumps with acceptable precision. Further work to improve estimates of CoM accelerations and different populations are warranted.


Asunto(s)
Nube Computacional , Pie , Aceleración , Fenómenos Biomecánicos , Humanos , Extremidad Inferior
15.
J Hum Kinet ; 81: 41-52, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-35291642

RESUMEN

Indoor spin cycling has gained popularity as a training modality for triathletes. Part of its appeal is that it can form a component of a structured periodised training program and provide an alternative to outdoor cycling. Indices of physiological components (i.e., the metabolic equivalent, caloric cost, perceived exertion) and changes in the body position can be inferred by wearable technology such as an accelerometer. This pilot study aimed to investigate the relationship between the rating of perceived exertion, heart rate reserve, and the metabolic equivalent between the whole body centre of mass acceleration using a sacrum mounted triaxial accelerometer during 20 minutes of 6 varied power conditions of indoor spin cycling. Compared with other conditions, cycling at a steady state (>152-205 W) resulted in extremely large effects (> 0.9) in mediolateral acceleration and the rating of perceived exertion (p < 0.0001). The relationship between the body position (aerodynamic to drops) induced significant changes in anteroposterior acceleration magnitude (p < 0.0001), although moving from drops to the aerodynamic position was not significant despite a large increase in heart rate reserve and extremely large effects of perceived exertion. The rating of perceived exertion scale and the metabolic equivalent comparative to the whole body centre of mass acceleration magnitude and power displayed a strong correlation (r = 0.865). An individually determined whole body centre of mass accelerations combined with perceived exertion, the metabolic equivalent and heart rate reserve could potentially contribute to improved indoor triathlete spin cycling performance.

16.
Eur J Appl Physiol ; 122(5): 1231-1237, 2022 May.
Artículo en Inglés | MEDLINE | ID: mdl-35235031

RESUMEN

PURPOSE: We have previously observed substantially higher oxygen uptake in soldiers walking on terrain at night than when performing the same walk in bright daylight. The aims of the present study were to investigate the influence of vision on mechanical efficiency during slow, horizontal, constant-speed walking, and to determine whether any vision influence is modified by load carriage. METHODS: Each subject (n = 15) walked (3.3 km/h) for 10 min on a treadmill in four different conditions: (1) full vision, no carried load, (2) no vision, no carried load, (3) full vision with a 25.5-kg rucksack, (4) no vision with a 25.5-kg rucksack. RESULTS: Oxygen uptake was 0.94 ± 0.12 l/min in condition (1), 1.15 ± 0.20 l/min in (2), 1.15 ± 0.12 l/min in (3) and 1.35 ± 0.19 l/min in (4). Thus, lack of vision increased oxygen uptake by about 19%. Analyses of movement pattern, by use of optical markers attached to the limbs and torso, revealed considerably shorter step length (12 and 10%) in the no vision (2 and 4) than full vision conditions (1 and 3). No vision conditions (2 and 4) increased step width by 6 and 6%, and increased vertical foot clearance by 20 and 16% compared to full vision conditions (1 and 3). CONCLUSION: The results suggest that vision has a marked influence on mechanical efficiency even during entrained, repetitive movements performed on an obstacle-free horizontal surface under highly predictable conditions.


Asunto(s)
Metabolismo Energético , Caminata , Fenómenos Biomecánicos , Prueba de Esfuerzo , Marcha , Humanos , Oxígeno
17.
J Exp Biol ; 225(1)2022 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-34982164

RESUMEN

Estimating centre of mass and mass moments of inertia is an important aspect of many studies in biomechanics. Characterising these parameters accurately in three dimensions is challenging with traditional methods requiring dissection or suspension of cadavers. Here, we present a method to quantify the three-dimensional centre of mass and inertia tensor of birds of prey using calibrated computed tomography (CT) scans. The technique was validated using several independent methods, providing body segment mass estimates within approximately 1% of physical dissection measurements and moment of inertia measurements with a 0.993 R2 correlation with conventional trifilar pendulum measurements. Calibrated CT offers a relatively straightforward, non-destructive approach that yields highly detailed mass distribution data that can be used for three-dimensional dynamics modelling in biomechanics. Although demonstrated here with birds, this approach should work equally well with any animal or appendage capable of being CT scanned.


Asunto(s)
Aves , Extremidades , Animales , Fenómenos Biomecánicos , Tomografía , Tomografía Computarizada por Rayos X/veterinaria
18.
Sports Biomech ; 21(6): 669-684, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31762385

RESUMEN

We aimed to quantify the contribution of lower body segment rotations in producing foot velocity during the soccer volley kick. Fifteen male experienced university players kicked a soccer ball placed at four height conditions (0, 25, 50 and 75 cm). Their kicking motion was captured at 500 Hz. The effectiveness of lower body segment rotations in producing forward (Ffv) and upward (Fuv) foot velocity were computed and time integrated. Major contributors for Ffv were a) left hip linear velocity, b) knee extension and c) pelvis retroflexion (the pitch rotation). The contribution of a) become smaller as the ball height increased while those of b) and c) did not change significantly. Moreover, the pelvis clockwise rotation (the yaw rotation) showed apparent contribution only for volley kicking (except 0 cm height). Major contributors for Fuv were 1) knee flexion, 2) hip internal rotation, 3) pelvis clockwise rotation (the roll rotation) and 4) hip flexion. The contributions of 1) and 4) become consistently smaller as the ball height increased, while those of 2) and 3) become larger systematically. Soccer volley kicking was found to have unique adaptations of segmental contributions to achieve higher foot position while maintain foot forward velocity.


Asunto(s)
Fútbol , Fenómenos Biomecánicos , Cadera , Humanos , Rodilla , Extremidad Inferior , Masculino
19.
Gait Posture ; 90: 313-319, 2021 10.
Artículo en Inglés | MEDLINE | ID: mdl-34564004

RESUMEN

BACKGROUND: Genu valgum results in lower limb malalignment and altered joint mechanics. The study aimed to identify the effects of genu valgum on balance control and muscular work at the joints during gait in children. RESEARCH QUESTION: Would bilateral genu valgum affect balance control and muscular work at the joints during gait in children? METHODS: Thirteen children with genu valgum and thirteen healthy peers walked at their preferred speed while the body's motions and ground reaction forces were measured to calculate the inclination angles (IA) and the rates of change of IA (RCIA) of the body's center of mass (COM) relative to the center of pressure (COP), as well as the muscular work done at the joints. An independent t-test was used to compare the variables between groups (α = 0.05). RESULTS: Compared to the controls, the patients showed significantly increased step width with altered frontal IA and RCIA variables (p < 0.05), including increased average IA over single-limb support and increased peak RCIA during double-limb support (p < 0.05). The patients significantly increased posterior RCIA at heel-strike but decreased anterior RCIA at toe-off (p < 0.05). The patients showed increased muscular work at both the hip and knee during single-limb support (p < 0.05). SIGNIFICANCE: The children with genu valgum showed a specific balance control strategy during gait. In the frontal plane, greater hip and knee muscular work was needed to maintain balance under an increased IA, likely owing to increased step width associated with the valgus alignment. In the sagittal plane, less smooth and less stable COM-COP control with increased RCIA at the key gait events indicates faster weight transfer between double-limb and single-limb support. It is suggested that patients with genu valgum, especially in more severe cases, should be monitored for signs of decreased ability and/or muscular strength in maintaining balance during gait.


Asunto(s)
Genu Valgum , Fenómenos Biomecánicos , Niño , Marcha , Humanos , Articulación de la Rodilla , Extremidad Inferior , Caminata
20.
Somatosens Mot Res ; 38(4): 294-302, 2021 12.
Artículo en Inglés | MEDLINE | ID: mdl-34496708

RESUMEN

PURPOSE: Coordinated movements of both lower limbs may be a clinically important indicator of motor control during quiet standing. From a neurological point of view, it is known that extensive coupling of muscles must be coordinated an upright posture. However, movement coordination between the lower limbs is the final motor output, is unknown. In this study, we focussed on the ground reaction force (GRF) vector and clarified the time and frequency characteristics of the force vectors of both lower limbs. MATERIALS AND METHODS: A total of 16 healthy young adults and 18 healthy older adults participated and placed each bare foot on one of two force plates to measure the GRF vectors (i.e., anteroposterior, mediolateral, and vertical) of each lower limb and determine the centre of mass (COM) acceleration in the anteroposterior direction (COMacc). Characteristics of the coordination of both lower limbs during movements were analysed using coherence analysis and cross-correlation function analysis (CCF). RESULTS: The coherence levels of the force vectors of both lower limbs were higher in all three directions and significantly increased in the older adults. CCF analysis showed that the force vectors of both lower limbs were negatively correlated at the zero-time lag. Moreover, a weak correlation was observed between COMacc and coherence values. CONCLUSIONS: The assessment of bilateral lower limb connectivity using force vectors can be used as an evaluation method to reflect changes in the ability to control bipedal standing during ageing.


Asunto(s)
Extremidad Inferior , Equilibrio Postural , Anciano , Envejecimiento , Humanos , Movimiento , Adulto Joven
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA