The purpose of this study was to determine the influence of loading direction on the structural response of the human clavicle subjected to three-point bending. A total of 20 clavicles were obtained from 10 unembalmed fresh-frozen postmortem human subjects ranging from 45 to 92 years of age. The right and left clavicles from each subject were randomly divided into two test groups. One group was impacted at 0° from the transverse plane, and the second group was impacted at 45° angle from the transverse plane. There was no statistically significant difference in peak force (p = .22), peak moment (p = .30), or peak displacement (p = .44) between specimens impacted at 0° versus 45° from the transverse plane. However, there was a significant difference in the structural stiffness (p = .01) and peak strain (p < .01) between specimens impacted at 0° versus 45° from the transverse plane. The peak strain, however, must be evaluated with caution because of the variation in fracture location relative to the strain gauge. Due to the controlled matched data set, the differences in the structural stiffness with respect to loading direction can be attributed to the complex geometry of the clavicle and not material differences.
Andrew R. Kemper, Joel D. Stitzel, Craig McNally, H. Clay Gabler and Stefan M. Duma
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.
Jeffrey J. Brault, Theodore F. Towse, Jill M. Slade and Ronald A. Meyer
Short-term creatine supplementation is reported to result in a decreased ratio of phosphocreatine (PCr) to total creatine (TCr) in human skeletal muscle at rest. Assuming equilibrium of the creatine kinase reaction, this decrease in PCr:TCr implies increased cytoplasmic ADP and decreased Gibbs free energy of ATP hydrolysis in muscle, which seems contrary to the reported ergogenic benefits of creatine supplementation. This study measured changes in PCr and TCr in vastus lateralis muscle of adult men (N = 6, 21–35 y old) during and 1 day after 5 d of creatine monohydrate supplementation (0.43 g·kg body weight−1·d−1) using noninvasive 31P and 1H magnetic-resonance spectroscopy (MRS). Plasma and red-blood-cell creatine increased by 10-fold and 2-fold, respectively, by the third day of supplementation. MRS-measured skeletal muscle PCr and TCr increased linearly and in parallel throughout the 5 d, and there was no significant difference in the percentage increase in muscle PCr (11.7% ± 2.3% after 5 d) vs. TCr (14.9% ± 4.1%) at any time point. The results indicate that creatine supplementation does not alter the PCr:TCr ratio, and hence the cytoplasmic Gibbs free energy of ATP hydrolysis, in human skeletal muscle at rest.
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.
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.
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.
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.
Samantha L. Winter and John H. Challis
For a physiologically realistic range of joint motion and therefore range of muscle fiber lengths, only part of the force-length curve can be used in vivo; i.e., the section of the force–length curve that is expressed can vary. The purpose of this study was to determine the expressed section of the force–length relationship of the gastrocnemius for humans. Fourteen male and fourteen female subjects aged 18–27 performed maximal isometric plantar flexions in a Biodex dynamometer. Plantar flexion moments were recorded at five ankle angles: −15°, 0°, 15°, 30°, and 40°, with negative angles defined as dorsiflexion. These measurements were repeated for four randomly ordered knee angles over two testing sessions 4 to 10 days apart. The algorithm of Herzog and ter Keurs (1988a) was used to reconstruct the force–length curves of the biarticular gastrocnemius. Twenty-four subjects operated over the ascending limb, three operated over the descending limb, and one operated over the plateau region. The variation found suggests that large subject groups should be used to determine the extent of normal in vivo variability in this muscle property. The possible source of the variability is discussed in terms of parameters typically used in muscle models.
Timothy R. Derrick, Graham E. Caldwell and Joseph Hamill
A modified mass-spring-damper model was used to simulate the vertical ground reaction forces of a human runner as stride length was altered. Spring stiffness values were selected by an optimizing routine that altered model parameters to match the model ground reaction force curve to a runner’s actual ground reaction force curve. A mass in series with a spring was used to simulate the behavior of body structures that produce the active portion of the ground reaction force. A second mass in series with a spring-damper system was used to simulate the behavior of those components that cause the impact portion of the ground reaction force. The stiffness of the active spring showed a 51% decrease as subjects increased their stride length. The stiffness value of the impact spring showed a trend opposite that of the active spring, increasing by 20% as strides lengthened. It appears that the impact stiffness plays a role in preventing the support leg from collapsing in response to the increased contact velocities seen in the longer strides.
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.