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PubMed1993

Obstacles to and motivation for successful breast-feeding.

This study determined obstetric physiotherapists' perceptions about major obstacles to and methods of motivation for successful breast-feeding by means of the Friedman non-parametric procedure for the two-way analysis of variance. Three categories of obstacles were identified: maternal obstacles, health professionals and society. Maternal obstacles mentioned most were insufficient motivation (25%) and knowledge (24%), anxiety (14%), fatigue (14%), and employment (14%). Obstacles related to health professionals included lack of support for mothers (20%), inappropriate lactation management (19%), lack of knowledge (15%), negative attitudes (5%), and staff shortages (5%). With regard to society, lack of support (27%) and life-styles (29%) were identified as significant obstacles. The two most significantly important methods of motivation were information and education (53%) and contact with other breast-feeders (27%). It is concluded that breast-feeding education efforts can be improved by identifying obstacles to breast-feeding and methods of motivation and that the Friedman test may be a statistical procedure to consider for determining priorities.

Adult↗
PubMed2005

Joint kinetics of the ankle and knee when running over obstacles.

AIM: When running over obstacles of increasing height, heelstrike (HS) runners switch to a forefoot (FF) landing pattern once a critical obstacle height is reached. The primary purpose of this study was to determine whether ankle or knee joint kinetic variables trigger the gait change from a HS to a FF striking pattern as obstacle height increases. METHODS: Ten subjects were filmed from the sagittal plane as they ran at their preferred running speed over a force platform during 6 obstacle height conditions ranging from 10% to 22.5% of standing height, as well as an additional baseline condition with no obstacle (0%). An inverse dynamics approach was utilized to calculate ankle and knee joint kinetics at each condition. RESULTS: Differences in joint kinetics did not occur until a height was reached at which the landing strategy changed from a HS to a FF landing pattern. Most differences occurred at the ankle joint, at which there was a greater maximum plantar flexor moment and a greater amount of energy absorbed when obstacles of sufficient height to require a FF landing pattern were negotiated. CONCLUSIONS: Although no variables were found which met all of the criteria necessary to be considered a determinant of the gait transition, there were variables which distinguished between a HS and FF strike landing pattern as obstacle height increased.

Adult↗
PubMed1995

Computer simulation of the directional displacement of rod-shaped, arc-shaped, and circular objects in an array of obstacles, representing a simple model for the gel electrophoresis of small DNA.

The gel electrophoresis of DNA of identical length but various static conformations was simulated using a two-dimensional model of the movement of rod-shaped, arc-shaped, and circular objects through random arrays of disk-shaped obstacles. At low obstacle density, the displacement rate of these objects decreases from the rod-shaped to the circular to the arc-shaped objects. At high obstacle densities, the displacement rate of circular objects approaches zero. The alignment of the arc-shaped objects along the axis of the directional movement of the objects were retarded in their movement by collisions with the obstacles; the number of collisions of the former, in view of their greater ability to align, was less than that of the latter. Circular objects were exclusively retarded by collisions, while the arc-shaped objects exhibited an additional retarding mechanism, viz. the suspension ("hanging") on the obstacles. When the rigid objects were made flexible, their displacement increased. The increase was most pronounced with the circular objects, allowing them to penetrate at obstacle densities from which the rigid objects were excluded.

Computer Simulation↗
PubMed2004

The presence of an obstacle influences the stepping response during induced trips and surrogate tasks.

Falling is a frequent cause of serious injury in older adults and trips are a dominant cause of falls in this rapidly growing population. Although there are few laboratory protocols that induce actual trips, there are many protocols that utilize surrogate tasks. These surrogate tasks, which are time-critical but do not involve an obstacle, appear to share a number of biomechanical characteristics with stepping responses following a trip. However, although rapid and safe negotiation of the obstacle and restoration of dynamic equilibrium are common requisites for success, we expected that stepping response kinematics during a successful recovery from a trip over a previously unseen obstacle would be substantially different than those of surrogate tasks without an obstacle. Unexpected trips were induced in 13 older men and women by an obstacle, the presence of which the subjects were previously unaware. Selected kinematics of the leading and trailing limb stepping responses during recovery from the induced trip were compared to those of two surrogate tasks that did not involve an obstacle. Multivariate analysis of variance (MANOVA) revealed that step height, step length, peak horizontal velocity, and peak vertical velocity of the leading and trailing limbs were significantly different during recovery from the induced trip compared to the surrogate tasks. These between-task performance differences may limit the extent to which performance of the surrogate tasks accurately and precisely reflect the potential to recover dynamic equilibrium following a trip. Therefore, these findings may be applicable in the design of new or modification of existing interventions to reduce falls in older adults.

Accidental Falls↗
PubMed2006

Intact automatic avoidance of obstacles in patients with visual form agnosia.

In everyday life our reaching behaviour has to be guided not only by the location and properties of the target object, but also by the presence of potential obstacles in the workspace. Recent evidence from neglect and optic ataxia patients has suggested that this automatic obstacle avoidance is mediated by the dorsal, rather than the ventral, stream of visual processing. We tested this idea in two studies involving patients with visual form agnosia resulting from bilateral ventral-stream damage. In the first study, we asked patient DF to reach out and pick up a target object in the presence of obstacles placed at varying distances to the left or right of the target. We found that both DF and controls shifted their trajectories away from the potential obstacles and adjusted their grip aperture in such a way as to minimize risk of collision. In a second study, we asked DF and a second patient, SB, to either reach between, or to bisect the space between, two cylinders presented at varying locations. We found that both patients adjusted their reach trajectories to account for shifts in cylinder location in the reaching task, despite showing significantly worse performance than control subjects when asked to make a bisection judgement. Taken together, these data indicate that automatic obstacle avoidance behaviour is spared in our patients with visual form agnosia. We attribute their ability to the functional intactness of the dorsal stream of visual processing, and argue that the ventral stream plays no important role in automatic obstacle avoidance.

Adult↗
PubMed1998

Characteristics of target-reaching in cats. III. Lifting and protraction with an obstacle in the movement path and after its removal.

Three cats were trained to perform target-reaching to a horizontal tube with food placed at shoulder level, and the kinematic characteristics of the movements were investigated by recording the trajectory of the wrist. From the very onset of training, a vertical obstacle was placed in front of the cats. The obstacle forced the animals to perform movements with an initial phase dominated by limb-lifting to position the wrist above the obstacle, followed by a second phase of protraction towards the tube; in the sagittal plane, the movement paths were segmented with an upwards convexity. After a training period of 1 year (about 7000 movements), the obstacle was removed. All cats then quickly (within a few trials) changed the trajectory so that the main part of protraction now occurred in parallel with limb-lifting during the first half of the movement. The initial slope of the sagittal movement path became less steep and the upwards convexity less pronounced. Such trajectories, which predominated for several experiments after removal of the obstacle, were only slightly different from those observed in control cats not trained with an obstacle. The results are discussed in relation to a previously proposed hypothesis of motor "imprinting" during extensive training in a particular experimental paradigm.

Animals↗
PubMed2005

Comparisons of the joint moments between leading and trailing limb in young adults when stepping over obstacles.

Twenty young healthy adults walked and crossed obstacles of heights of 10%, 20% and 30% of their leg lengths and kinematics and kinetics of their gait analysed. Three-dimensional joint moments of the lower limb were calculated with inverse dynamics analysis. Peak moments and crossing moments (joint moments at the time when the swing foot is above the obstacle) were obtained. Most of the peak moments of the supporting limb joints did not show the same height effects as the corresponding crossing moment components. This suggests that the true effects of obstacle heights on the joint kinetics during obstacle crossing cannot be obtained solely through comparisons of peak moments. For inter-limb comparisons the peak and crossing moments were different, suggesting that the leading and trailing limb adopted different kinetic strategies during obstacle crossing. The findings may help to shed light on further investigation on the motor control strategies of the central nervous system for obstacle crossing.

Adult↗
PubMed2006

Control strategies used by older adults during multiple obstacle avoidance.

The purpose of our study was to determine the methods of control over the center of mass (COM) utilized by older adults when navigating a functional obstacle course. The course included three different types of obstacles placed closely in series requiring subjects to walk around, step over and duck under. Optoelectric cameras were used to record kinematic data as older adults navigated the course under normal and low lighting and different obstacle contrast conditions. Results were compared across lighting conditions and obstacle contrast conditions. Statistical analyses revealed that older adults are able to successfully navigate a functional obstacle course through increases in their trunk motion and a reduction in their average step velocity, via changes in step length or cadence. These adaptations may pose a challenge to the limits of stability of an older adult and place them at a greater risk of falling when avoiding obstacles in their travel path.

Adaptation, Physiological↗
PubMed1997

Obstacles to nutrition labeling in restaurants.

OBJECTIVE: This study determined the major obstacles that foodservices face regarding nutrition labeling. DESIGN: Survey questionnaire was conducted in May 1994. In addition to demographic questions, the directors were asked questions addressing willingness, current practices, and perceived obstacles related to nutrition labeling. SUBJECTS/SETTING: Sixty-eight research and development directors of the largest foodservice corporations as shown in Restaurants & Institutions magazine's list of the top 400 largest foodservices (July 1993). STATISTICAL ANALYSES PERFORMED: P tests were used to determine significance within a group for the number of foodservices that were currently using nutrition labeling, perceived impact of nutrition labeling on sales, and perceived responsibility to add nutrition labels. Regression analysis was used to determine the importance of factors on willingness to label. RESULTS: Response rate was 45.3%. Most companies were neutral about their willingness to use nutrition labeling. Two thirds of the respondents were not currently using nutrition labels. Only one third thought that it was the foodservice's responsibility to provide such information. Several companies perceived that nutrition labeling would have a potentially negative effect on annual sales volume. Major obstacles were identified as menu or personnel related, rather than cost related. Menu-related obstacles included too many menu variations, limited space on the menu for labeling, and loss of flexibility in changing the menu. Personnel-related obstacles included difficulty in training employees to implement nutrition labeling, and not enough time for foodservice personnel to implement nutrition labeling. APPLICATIONS: Numerous opportunities will be created for dietetics professionals in helping foodservices overcome these menu- or personnel-related obstacles.

Food Labeling↗
PubMed2003

Behavioral dynamics of steering, obstacle avoidance, and route selection.

The authors investigated the dynamics of steering and obstacle avoidance, with the aim of predicting routes through complex scenes. Participants walked in a virtual environment toward a goal (Experiment 1) and around an obstacle (Experiment 2) whose initial angle and distance varied. Goals and obstacles behave as attractors and repellers of heading, respectively, whose strengths depend on distance. The observed behavior was modeled as a dynamical system in which angular acceleration is a function of goal and obstacle angle and distance. By linearly combining terms for goals and obstacles, one could predict whether participants adopt a route to the left or right of an obstacle to reach a go (Experiment 3). Route selection may emerge from on-line steering dynamics, making explicit path planning unnecessary.

Adolescent↗
PubMed2000

The Obstacle-Set Method for Representing Muscle Paths in Musculoskeletal Models.

A computational method is introduced for modeling the paths of muscles in the human body. The method is based on the premise that the resultant muscle force acts along the locus of the transverse cross-sectional centroids of the muscle. The path of the muscle is calculated by idealizing its centroid path as a frictionless elastic band, which moves freely over neighboring anatomical constraints such as bones and other muscles. The anatomical constraints, referred to as obstacles, are represented in the model by regular-shaped, rigid bodies such as spheres and cylinders. The obstacles, together with the muscle path, define an obstacle set. It is proposed that the path of any muscle can be modeled using one or more of the following four obstacle sets: single sphere, single cylinder, double cylinder, and sphere-capped cylinder. Assuming that the locus of the muscle centroids is known for an arbitrary joint configuration, the obstacle-set method can be used to calculate the path of the muscle for all other joint configurations. The obstacle-set method accounts not only for the interaction between a muscle and a neighboring anatomical constraint, but also for the way in which this interaction changes with joint configuration. Consequently, it is the only feasible method for representing the paths of muscles which cross joints with multiple degrees of freedom such as the deltoid at the shoulder.

Journal Article↗
PubMed1998

Stepping over obstacles during locomotion: insights from multiobjective optimization on set of input parameters.

In this study we investigate possible objectives that the central nervous system (CNS) may consider in planning a strategy for stepping over an obstacle. A link segment simulation model has been developed based on Lagrangian dynamics, with which muscle force inputs can be optimized to best satisfy the postulated objectives for landing stability, obstacle clearance, and efficiency of the movement. A direct optimization approach with multiobjective criteria based on the kinematic and kinetic characteristics of the swing phase of locomotion is used in the simulation. The role of initial conditions at toe-off and biarticular muscle forces during the swing phase was also investigated. The optimization was performed for both leading limb and the trailing limb during the swing phase. The simulation results demonstrate that the use of biarticular muscles is sufficient to clear a range of obstacles with the trailing limb (obstacle encountered during early swing). Stride length or landing stability objectives need not be specified suggesting a simpler control of trailing limb trajectory by the CNS (one of stride length or landing stability objectives were not necessary). In contrast while the use of biarticular muscles can be sufficient to clear obstacles with the leading limb (obstacle encountered during mid to late swing), a stable landing and smooth toe and knee trajectories are compromised without suitable initial conditions at toe-off. The results suggest that the set of postulated objectives for the lead limb is adequate, although not complete.

Biomechanical Phenomena↗
PubMed2000

Three-dimensional acoustic scattering from a penetrable layered cylindrical obstacle in a horizontally stratified ocean waveguide

In this work, a normal-mode solution is presented for the three-dimensional problem of acoustic scattering from a penetrable horizontally layered cylindrical obstacle in a shallow-water waveguide. The ocean environment around the obstacle is considered horizontally stratified and the bottom is assumed to be rigid. In the general case of depth-dependent sound-speed and density profiles (ssdp) the total acoustic field is calculated numerically, while an analytic solution is obtained in the special case of depth-independent ssdp. Numerical results concerning the transmission loss outside and inside single or double-layered cylindrical structures made of acoustic materials are given for a typical depth-dependent ocean environment. Comparisons with the cases of ideally soft and ideally hard cylindrical obstacles [J. Acoust. Soc. Am. 100, 206-218 (1996)] are also made, illustrating the effect of acoustic properties of the obstacle. An important feature, which clearly emerges from the theoretical analysis and the numerical results, is the necessity of including evanescent modes in the calculations, in order to obtain physically meaningful and numerically accurate results. Furthermore, analytical expressions for the scattering cross section of a (penetrable or impenetrable) cylindrical obstacle are derived in terms of the expansion coefficients of the pressure field, and their behavior as frequency increases is numerically investigated. The solution presented in this paper, although addressing a special geometry, provides a means for handling strong discontinuities in both vertical and horizontal directions, and can serve as a benchmark solution to a problem for which no general numerical model exists, i.e., modeling acoustic scattering from a 3D obstacle in a 3D shallow-water waveguide.

Journal Article↗
PubMed2002

Obstacles to answering doctors' questions about patient care with evidence: qualitative study.

OBJECTIVE: To describe the obstacles encountered when attempting to answer doctors' questions with evidence. DESIGN: Qualitative study. SETTING: General practices in Iowa. PARTICIPANTS: 9 academic generalist doctors, 14 family doctors, and 2 medical librarians. MAIN OUTCOME MEASURE: A taxonomy of obstacles encountered while searching for evidence based answers to doctors' questions. RESULTS: 59 obstacles were encountered and organised according to the five steps in asking and answering questions: recognise a gap in knowledge, formulate a question, search for relevant information, formulate an answer, and use the answer to direct patient care. Six obstacles were considered particularly salient by the investigators and practising doctors: the excessive time required to find information; difficulty modifying the original question, which was often vague and open to interpretation; difficulty selecting an optimal strategy to search for information; failure of a seemingly appropriate resource to cover the topic; uncertainty about how to know when all the relevant evidence has been found so that the search can stop; and inadequate synthesis of multiple bits of evidence into a clinically useful statement. CONCLUSIONS: Many obstacles are encountered when asking and answering questions about how to care for patients. Addressing these obstacles could lead to better patient care by improving clinically oriented information resources.

Clinical Competence↗
PubMed2002

Ineffective disability management by doctors is an obstacle for return-to-work: a cohort study on low back pain patients sicklisted for 3-4 months.

AIMS: To determine obstacles for return-to-work in disability management of low back pain patients sicklisted for 3-4 months. METHODS: A cohort of 467 low back pain patients sicklisted for 3-4 months was recruited. A questionnaire was sent to their occupational physicians (OPs) concerning the medical management, obstacles to return-to-work, and the communication with treating physicians. RESULTS: The OPs of 300 of 467 patients participated in this study. In many cases OPs regarded the clinical waiting period (43%), duration of treatment (41%), and view (25%) of the treating physicians as obstacles for return-to-work. Psychosocial obstacles for return-to-work such as mental blocks, a lack of job motivation, personal problems, and conflicts at work were all mentioned much less frequently by OPs. In only 19% of the patients was there communication between OP and treating physician. Communication almost always entailed an exchange of information, and less frequently an attempt to harmonise the management policy. Surprisingly communication was also limited, when OPs felt that the waiting period (32%), duration of treatment (30%), and view (28%) of treating physicians inhibited return-to-work. Communication was significantly associated with the following obstacles for return-to-work: passivity with regard to return-to-work and clinical waiting period; adjusted odds ratios were 3.35 and 2.23, respectively. CONCLUSIONS: Medical management of treating physicians is often an obstacle for return to work regarding low back pain patients sicklisted for 3-4 months, in the opinion of OPs. Nevertheless communication between OPs and the treating physicians in disability management of these patients is limited. More attention to prevention of absenteeism and bilateral communication is needed in medical courses.

Adolescent↗
PubMed1998

Is backward stepping over obstacles achieved through a simple temporal reversal of forward stepping?

The main purpose of the study was to examine whether backward stepping over obstacles was a simple temporal reversal of kinematic and muscle activation patterns found in forward obstacle avoidance. Obstacle avoidance was used as a probe to represent one aspect of walking over variable terrain. Kinematics, trajectories and muscle activation profiles for forward versus backward stepping over obstacles revealed that the simple reversal of locomotor patterns observed for level walking cannot be applied to obstacle avoidance. However, key kinematic data and limb trajectories for backward leading limb stepping were found to be similar to existing forward trailing limb data. Therefore, it appears that stepping over obstacles requires a complex upper level reorganization of the basic locomotor pattern based on biomechanical and sensory feedback.

Adult↗
PubMed2000

Critical care nurses' perceptions of obstacles and helpful behaviors in providing end-of-life care to dying patients.

BACKGROUND: Little is known about nurses' perceptions of obstacles or helpful behaviors ("helps") in providing end-of-life care in the intensive care setting. OBJECTIVE: To determine the importance of various obstacles and helps in providing end-of-life care as perceived by critical care nurses. METHODS: A questionnaire was mailed to 300 members of the American Association of Critical-Care Nurses. Nurses were asked to rate obstacles and helps in giving end-of-life care, and additional obstacles and/or helps, and answer demographic questions. RESULTS: Six of the top 10 obstacles were related to issues with patients' families that make care at the end of life more difficult, such as the family's not fully understanding the meaning of life support, not accepting the patient's poor prognosis, requesting more technical treatment than the patient wished, and being angry. Added obstacles related mostly to problems with physicians' behavior. Most helps were ways to make dying easier for patients and patients' families, such as agreement among physicians about care, dying with dignity, and families' acceptance of the prognosis. Added helps included allowing music, pets, and so forth into the patient's room. CONCLUSIONS: Nurses have difficulties with patients' families and physicians concerning end-of-life issues, especially when the behaviors remove the nurses from caring for a patient or cause the patient pain or prolong suffering. Nurses do not acknowledge having difficulty providing care to dying patients aside from conflicts that arise because of patients' families and physicians.

Adult↗
PubMed1996

The obstacle course: a tool for the assessment of functional balance and mobility in the elderly.

Many conventional methods employed in the assessment of balance and mobility in the elderly are expensive, difficult to administer, rely heavily on complex technology, or provide limited functional information so essential to the planning and implementation of rehabilitation interventions. The author has developed a functionally oriented obstacle course for use in the rehabilitation setting, to aid in the evaluation of elderly subjects with balance and mobility dysfunction. The obstacle course consists of 12 simulated functional tasks. Qualitative and quantitative individual task and overall scores are given for each obstacle course performance. A description of the design and rationale for the obstacle course is presented. For demonstration purposes, nonexperimental obstacle course performance data from a small group of elderly volunteers is included. With further validation studies, the obstacle course has potential to become a useful tool in the evaluation and rehabilitation of balance and mobility disorders, in order to aid in the prevention of falls and fall-related injuries in the elderly.

Accidental Falls↗