Search Results

You are looking at 61 - 70 of 4,073 items for :

Clear All
Restricted access

Alan Hreljac, Rodney T. Imamura, Rafael F. Escamilla, W. Brent Edwards and Toran MacLeod

The primary purpose of this project was to examine whether lower extremity joint kinetic factors are related to the walk–run gait transition during human locomotion. Following determination of the preferred transition speed (PTS), each of the 16 subjects walked down a 25-m runway, and over a floor-mounted force platform at five speeds (70, 80, 90, 100, and 110% of the PTS), and ran over the force platform at three speeds (80, 100, and 120% of the PTS) while being videotaped (240 Hz) from the right sagittal plane. Two-dimensional kinematic data were synchronized with ground reaction force data (960 Hz). After smoothing, ankle and knee joint moments and powers were calculated using standard inverse dynamics calculations. The maximum dorsiflexor moment was the only variable tested that increased as walking speed increased and then decreased when gait changed to a run at the PTS, meeting the criteria set to indicate that this variable influences the walk–run gait transition during human locomotion. This supports previous research suggesting that an important factor in changing gaits at the PTS is the prevention of undue stress in the dorsiflexor muscles.

Restricted access

Saunders N. Whittlesey, Richard E.A. van Emmerik and Joseph Hamill

Many studies have assumed that the swing phase of human walking at preferred velocity is largely passive and thus highly analogous to the swing of an unforced pendulum. In other words, while swing-phase joint moments are generally nonzero during swing, it was assumed that they were either zero or at least negligibly small compared to gravity. While neglect of joint moments does not invalidate a study by default, it remains that the limitations of such an assumption have not been explored thoroughly. This paper makes five arguments that the swing phase cannot be passive, using both original data and the literature: (1) Computer simulations of the swing phase require muscular control to be accurate. (2) Swing-phase joint moments, while smaller than those during stance, are still greater than those due to gravity. (3) Gravity accounts for a minority of the total kinetics of a swing phase. (4) The kinetics due to gravity do not have the pattern needed to develop a normal swing phase. (5) There is no correlation between pendular swing times and human walking periods in overground walking. The conclusion of this paper is that the swing phase must be an actively controlled process, and should be assumed to be passive only when a study does not require a quantitative result. This conclusion has significant implications for many areas of gait research, including clinical study, control theory, and mechanical modeling.

Restricted access

Kathryn E. Keenan, Saikat Pal, Derek P. Lindsey, Thor F. Besier and Gary S. Beaupre

Cartilage material properties provide important insights into joint health, and cartilage material models are used in whole-joint finite element models. Although the biphasic model representing experimental creep indentation tests is commonly used to characterize cartilage, cartilage short-term response to loading is generally not characterized using the biphasic model. The purpose of this study was to determine the short-term and equilibrium material properties of human patella cartilage using a viscoelastic model representation of creep indentation tests. We performed 24 experimental creep indentation tests from 14 human patellar specimens ranging in age from 20 to 90 years (median age 61 years). We used a finite element model to reproduce the experimental tests and determined cartilage material properties from viscoelastic and biphasic representations of cartilage. The viscoelastic model consistently provided excellent representation of the short-term and equilibrium creep displacements. We determined initial elastic modulus, equilibrium elastic modulus, and equilibrium Poisson’s ratio using the viscoelastic model. The viscoelastic model can represent the short-term and equilibrium response of cartilage and may easily be implemented in whole-joint finite element models.

Restricted access

Andrea N. Lay, Chris J. Hass, D. Webb Smith and Robert J. Gregor

Sloped walking surfaces provide a unique environment for examining the bio-mechanics and neural control of locomotion. While sloped surfaces have been used in a variety of studies in recent years, the current literature provides little if any discussion of the integrity, i.e., validity, of the systems used to collect data. The goal of this study was to develop and characterize a testing system capable of evaluating the kinetics of human locomotion on sloped surfaces. A ramped walkway system with an embedded force plate was constructed and stabilized. Center of pressure and reaction force data from the force plate were evaluated at 6 ramp grades (0, 5, 15, 25, 35, and 39%). Ground reaction force data at 0% grade were effectively the same as data from the same force plate when mounted in the ground and were well within the range of intrasubject variability. Collectively, data from all tests demonstrate the fidelity of this ramp system and suggest it can be used to evaluate human locomotion over a range of slope intensities.

Restricted access

Carla Filomena Silva and P. David Howe

This paper is a call to Adapted Physical Activity (APA) professionals to increase the reflexive nature of their practice. Drawing upon Foucault’s concept of governmentality (1977) APA action may work against its own publicized goals of empowerment and self-determination. To highlight these inconsistencies, we will draw upon historical and social factors that explain the implicit dangers of practice not following policy. We propose that APA practitioners work according to ethical guidelines, based upon a capabilities approach (Nussbaum, 2006, 2011; Sen, 2009) to counteract possible adverse effects of APA practitioner action. A capabilities approach is conducive to the development of each individual’s human potential, by holistically considering the consequences of physical activity (i.e., biological, cultural, social, and psychological dimensions). To conclude, this paper will offer suggestions that may lead to an ethical reflection aligned with the best interest of APA’s users.

Restricted access

Lilian Pichot, Gary Tribou and Norm O’Reilly

Successful sponsorship activities in sport often rely on the integration of relationship marketing, internal marketing, external corporate promotion, and strategic management. Although traditional marketing objectives such as brand integration and consumer targeting remain key components of promotional activities in sport, the use of sport sponsorship in today’s environment increasingly implicates personnel issues in the both the sponsor and the sponsee. In fact, sport sponsorship has become a useful tool for some sponsors and sponsees who seek to motivate and involve their employees more in company activities. Therefore, the focus of this commentary is on the internal-communication and human-resources management functions involved in sport sponsorship decisions. The use of mini-case analyses and a dual-perspective (external and internal objectives) approach allows for informed discussion, and suggestions are made for future research.

Restricted access

Robert Chen and Kaviraja Udupa

Several techniques that involve transcranial magnetic stimulation (TMS) can be used to measure brain plasticity noninvasively in humans. These include paired-associative stimulation (PAS), repetitive transcranial magnetic stimulation (rTMS) and theta burst stimulation (TBS). Some of these techniques are based the principle of use dependent plasticity or are designed to mimic protocols used to induce long-term potentiation or depression in animal studies. These studies have been applied to certain neurological and psychiatric disorders to investigate their pathophysiology. For example, PAS induced plasticity is enhanced in dystonia and stroke but is reduced in Huntington’s disease and schizophrenia. Furthermore, TMS may be used to modulate brain plasticity and has therapeutic potential in neurological and psychiatric disorders such as stroke, Parkinson’s disease, dystonia and depression.

Restricted access

Anneliese Goslin

South African society is a complex mix of first- and third-world components. Urgent socio-economic and political problems must be addressed to avoid chaos. Sport may be a key factor in bringing about change. Sport training strategies should form an integral part of affirmative action and sport development programs in South Africa. The overall aim of this research was to develop a structured scientific approach to the training and development of human resources in South African sport. The research was conducted in four phases over a 2-year period. The aims of the respective phases were to determine the current standard and scope of sport management in black developing townships, to compile a profile of competencies and training needs of sport managers, to develop an in-service training model for the aforementioned sport managers, and to design a comprehensive sport development strategy for South African sport. Research methodologies included questionnaires on general and functional managerial variables and training needs, content analysis of job descriptions, and personal interviews. Results revealed an insufficient standard of sport management in developing townships. A competency-based training and development model was proposed and positioned in an overall strategy for sport development in South Africa.

Restricted access

Jeffrey Graham and Sylvia Trendafilova

This case challenges future sport managers to consider the importance of organizational structure and the impact structure has on job performance and motivation. In the case, students are presented with a university ticket sales department with a traditionally tall bureaucratic organizational structure. In 2014, the department struggled with poor performance, high turnover, and low levels of employee morale. However, the department took drastic steps and adopted an organizational structure that is based on the idea of self-managed teams. Now in 2016 the department is undergoing a thorough evaluation to see whether the organizational change made two years ago has had a positive impact. Even though the case uses a fictional university (i.e., Western Field University), the issues and challenges involved in changing an organizational structure, motivating employees, and leading change stem from real-world situations. The case contains ticket sales data, employee turnover information, and sample quotes from employees that aid in the analysis. This case is intended for use in human resource management classes, but it also has implications for organizational behavior or leadership courses.

Restricted access

Kohei Watanabe, Motoki Kouzaki and Toshio Moritani

In some muscles, nonuniform surface electromyography (EMG) responses have been demonstrated within a muscle, meaning that the electrode location could be critical in the results of surface EMG. The current study investigated possible region-specific EMG responses within the human biceps femoris (BF) muscle. Surface EMG was recorded from various regions along the longitudinal axis of the BF muscle with 20 electrodes. Ten healthy men performed maximal isometric contractions of hip extension and knee flexion, which involve the BF muscle. The ratio of the EMG amplitude between hip extension and knee flexion tasks (HE/KF) was calculated and compared among the regions. There were no significant differences in HE/KF among the regions along the BF muscle (P > .05). This suggests that the entire superficial region of the BF muscle is equally regulated in the 2 different tasks. We suggest that the electrode location is not critical in estimating the activation properties and/or functional role of the superficial region, which corresponds with approximately 50% of the muscle length of the BF muscle, using surface EMG during maximal contraction.