Krystyna Gielo-Perczak

Biomechanics of Slips

The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or ‘friction used/achievable’ during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

Human-centred approaches in slipperiness measurement

A number of human—centred methodologies subjective, objective, and combined are used for slipperiness measurement. They comprise a variety of approaches from biomechanically-oriented experiments to psychophysical tests and subjective evaluations. The objective of this paper is to review some of the research done in the field, including such topics as awareness and perception of slipperiness, postural and balance control, rating scales for balance, adaptation to slippery conditions, measurement of unexpected movements, kinematics of slipping, and protective movements during falling. The role of human factors in slips and falls will be discussed. Strengths and weaknesses of human-centred approaches in relation to mechanical slip test methodologies are considered. Current friction-based criteria and thresholds for walking without slipping are reviewed for a number of work tasks. These include activities such as walking on a level or an inclined surface, running, stopping and jumping, as well as stair ascent and descent, manual exertion (pushing and pulling, load carrying, lifting) and particular concerns of the elderly and mobility disabled persons. Some future directions for slipperiness measurement and research in the field of slips and falls are outlined. Human-centred approaches for slipperiness measurement do have many applications. First, they are utilized to develop research hypotheses and models to predict workplace risks caused by slipping. Second, they are important alternatives to apparatus-based friction measurements and are used to validate such methodologies. Third, they are used as practical tools for evaluating and monitoring slip resistance properties of footwear, anti-skid devices and floor surfaces.

Physical neuroergonomics: The human brain in control of physical work activities

One of the important functions of the human brain is voluntary control of movements and motor activities combined with perceptual, cognitive and affective processes. This paper introduces the emerging field of study, named hereby as physical neuroergonomics, that focuses on the knowledge of human brain activities in relation to the control and design of physical tasks. Motor, cognitive and emotional aspects and their inter-relationships in connection to physical ergonomics are considered. A review of recent advances in functional electroencephalography (EEG), with special accent on the time domain analyses of the human brain activity in selected motor tasks, is also presented. The reported studies of isometric elbow-flexion contractions confirmed that the cerebral-cortex system controls the extent of muscle activation and is responsible for smoothing out high-speed motor control processes. Furthermore, the emotional attitudes of the subject to the activity can compel performance beyond acceptable loading through psychological pressure or necessity. The discussed results are important to ones understanding of human limitations and capabilities on a variety of physical tasks, and may ultimately help explain the mechanisms of musculoskeletal injuries at work. These results also underscore the need for a novel approach to workplace studies, i.e. neuroergonomics design.

Measuring Slipperiness - Human Locomotion and Surface Factors

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Ecological models of human performance based on affordance, emotion and intuition

This paper proposes a complementary approach to Rasmussens taxonomy of the human skill-, rule-, and knowledge-based performance models by combining the ecological concept of affordances with the neural concepts of human emotion and intuition. The classical cognitive engineering framework is extended through the neuro-ecological approach, including personal human attributes important in exercising control over the work environment. The proposed affordance-, emotion-, and intuition-based models correspond to the three types of human performance, namely: learning, adaptive and tuning control, respectively. The new framework is not a predictive model of the operator behaviour, but rather it describes the processes of neuro-ecological control of the human environment.

The golden section as a harmonizing feature of human dimensions and workplace design

The purpose of this paper is to present a philosophical aspect of the ecology of human-machine systems by exploring the potential application of the basic pattern referred to as the golden section to workplace design and human body dimensions. Studies of stairway and industrial knife designs confirm that subjects prefer workplace and tool dimensions that are related to their human body segment lengths. In this paper, it is suggested that for each task or equipment there are different body segments which should be considered as a transitional element harmonizing a human body with its workplace. Hence, for a knife design - grip size circumference and blade length, for stairway design - length of foot and height of a riser. The psychophysical assessments affirm an existence of the golden section in workplace/tool design as a preferred design harmonizing an individuals body dimensions with work demands.

Effect of Impeded Medial Longitudinal Arch Drop on Vertical Ground Reaction Force and Center of Pressure During Static Loading

Background: Arch supports commonly used to alleviate foot pain can impede the normal drop of medial longitudinal arch (MLA) thereby altering its function. The purpose of the study was to examine the effect of using arch supports on vertical ground reaction force (GRF) and center of pressure (COP) during simulated midstance while the foot was statically loaded. Materials and Method: Ten healthy young subjects were recruited. Two dimensional (2D) analysis of the MLA was captured for both barefoot (BF) and arch support conditions before and after loading via a custom made weight loading apparatus. The foot was loaded and positioned to simulate the midstance phase of walking. Two-dimensional reflective markers demarcated the MLA and captured with the loaded foot on a force platform. The impeded MLA drop was compared between the unloaded BF, loaded BF and loaded arch support conditions. The vertical GRF, the anterior-posterior and the medial-lateral COP displacements were also measured in response to the impeded MLA by the arch supports. Results: The arch supports impeded the MLA drop (p < 0.05) and shifted the COP toward the medial side (p < 0.05), specifically for the rearfoot (calcaneal segment region), but no changes were determined for the vertical GRF (p > 0.05). Conclusion: The impedance of MLA drop by the arch support altered the pattern of the ML COP shift in the rearfoot region. Clinical Relevance: The use of arch supports may not relieve painful foot conditions that are associated with excessive calcaneal eversion indicated by altering COP shifts in localized foot regions.

Effects of simulated occupational task parameters on balance

The effects of single-handed load holding, length of the base of support, and standing surface condition (narrow and wide construction beams) on balance were investigated in twenty-three healthy men between the ages of 18 and 55 years old. Balance during quiet standing was evaluated from postural sway measurements derived from center of pressure (COP) displacement. These measurements included the range or maximal displacement of the COP in the anteroposterior (AP) and mediolateral (ML) directions, the elliptical area, and mean sway velocity. Holding a load in the hand did not significantly affect postural sway measures (p > 0.05), although the effect of surface condition was significant on all COP measures (p < 0.001). Lengthening the base of support did not affect the ranges or elliptical area, but increased the mean velocity of sway (p = 0.001). Changes in the dimensional characteristics of the surface condition and length of base of support affected postural sway, possibly by requiring adjustments to balance and motor control strategies. Further research is required to determine if these changes are detrimental to maintaining balance and increase the risk of falls for workers in similar environments.

Multidimensional Aspects of Slips and Falls

The study of slips and falls has traditionally focused on body kinematics and tribology. However, this strictly mechanical approach does not allow scientists to assess the importance of each component in relation to the complete system, and thus it lacks integration. The purpose of this chapter is to present and demonstrate the components of a broad analysis for in-depth understanding of slips and falls while walking on level surfaces. In most slip-and-fall studies, balance analysis is simplified and attributed to the point of heel contact. To determine sufficient fall prevention strategies, however, one must analyze balance before the critical moment of lost control. Such an approach requires the sciences of biomechanics, mechanics, anatomy, and neuromuscular control, as well as tribology. Causes of slips and falls are complex, and prevention approaches are often reactive, driven by high-injury trends and lawsuits. Prevention strategies need to be more proactive: Understanding the causes of accidents can...

Nonlinear behavior of the center of pressure in simulated standing on elevated construction beams.

This study investigated the effects of width of construction beams and single-hand load holding task conditions on nonlinear behavior of the foot center of pressure (COP) exerted on the beam. The foot COP, defined as the point of application of the result of vertical forces acting on the surface of foot support, was measured in the lateral direction under simulated standing task conditions. Twelve healthy male subjects were asked to hold a load of 6.8 kg and 11.3 kg while standing on the elevated construction beams with widths of 10 and 22.5 cm (4 and 9 inches, respectively) under low and high foot separation (foot step). The results showed that both beam width and single-hand load carrying conditions had significant effects on the observed nonlinearity of the foot center of pressure exerted on the beam. Standing on the narrow beam resulted in higher level of chaotic behavior of COP compared to the wide beam condition. The nonlinearity of the COP exerted by the forward (left) foot was higher for the narrow beam condition. For both beams, the nonlinearity of the COP exerted by the forward (left) foot was consistently higher than the COP exerted by the backward (right) foot. Furthermore, for both beams, single-handed holding of the 11.3 kg load resulted in higher levels of COP nonlinearity than carrying 6.8 kg or no load at all. The study results indicate that nonlinear dynamics behavior of the forward foot under single-handed high load holding condition may be critical to preserving lateral stability during standing at the construction beams.