Force transmission in a packing of pentagonal particles

We perform a detailed analysis of the contact force network in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The effect of particle shape is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics except for the circular shape of the particles. A counterintuitive finding of this work is that, under steady shearing, the pentagon packing develops a lower structural anisotropy than the disk packing. We show that this weakness is compensated by a higher force anisotropy, leading to enhanced shear strength of the pentagon packing. We revisit "strong" and "weak" force networks in the pentagon packing, but our simulation data provide also evidence for a large class of "very weak" forces carried mainly by vertex-to-edge contacts. The strong force chains are mostly composed of edge-to-edge contacts with a marked zig-zag aspect and a decreasing exponential probability distribution as in a disk packing

A randomized controlled trial to evaluate self-determination theory for exercise adherence and weight control: rationale and intervention description

<p>Abstract</p> <p>Background</p> <p>Research on the motivational model proposed by Self-Determination Theory (SDT) provides theoretically sound insights into reasons why people adopt and maintain exercise and other health behaviors, and allows for a meaningful analysis of the motivational processes involved in behavioral self-regulation. Although obesity is notoriously difficult to reverse and its recidivism is high, adopting and maintaining a physically active lifestyle is arguably the most effective strategy to counteract it in the long-term. The purposes of this study are twofold: i) to describe a 3-year randomized controlled trial (RCT) aimed at testing a novel obesity treatment program based on SDT, and ii) to present the rationale behind SDT's utility in facilitating and explaining health behavior change, especially physical activity/exercise, during obesity treatment.</p> <p>Methods</p> <p>Study design, recruitment, inclusion criteria, measurements, and a detailed description of the intervention (general format, goals for the participants, intervention curriculum, and main SDT strategies) are presented. The intervention consists of a 1-year group behavioral program for overweight and moderately obese women, aged 25 to 50 (and pre-menopausal), recruited from the community at large through media advertisement. Participants in the intervention group meet weekly or bi-weekly with a multidisciplinary intervention team (30 2 h sessions in total), and go through a program covering most topics considered critical for successful weight control. These topics and especially their delivery were adapted to comply with SDT and Motivational Interviewing guidelines. Comparison group receive a general health education curriculum. After the program, all subjects are follow-up for a period of 2 years.</p> <p>Discussion</p> <p>Results from this RCT will contribute to a better understanding of how motivational characteristics, particularly those related to physical activity/exercise behavioral self-regulation, influence treatment success, while exploring the utility of Self-Determination Theory for promoting health behavior change in the context of obesity.</p> <p>Trial Registration</p> <p><b>Clinical Trials Gov. Identifier </b>NCT00513084</p

Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges

Nuclear quantum effects influence the structure and dynamics of hydrogen-bonded systems, such as water, which impacts their observed properties with widely varying magnitudes. This review highlights the recent significant developments in the experiment, theory, and simulation of nuclear quantum effects in water. Novel experimental techniques, such as deep inelastic neutron scattering, now provide a detailed view of the role of nuclear quantum effects in water's properties. These have been combined with theoretical developments such as the introduction of the principle of competing quantum effects that allows the subtle interplay of water's quantum effects and their manifestation in experimental observables to be explained. We discuss how this principle has recently been used to explain the apparent dichotomy in water's isotope effects, which can range from very large to almost nonexistent depending on the property and conditions. We then review the latest major developments in simulation algorithms and theory that have enabled the efficient inclusion of nuclear quantum effects in molecular simulations, permitting their combination with on-the-fly evaluation of the potential energy surface using electronic structure theory. Finally, we identify current challenges and future opportunities in this area of research

Self-regulation and self-control in exercise: The strength-energy model

Self-regulation is an important component of psychosocial theories of exercise behaviour and lack of self-regulatory skills are associated with low adherence to health-related exercise. This review presents a strength-energy model of self-control as an explanation of self-regulation in exercise contexts. The review will provide impetus for original research aimed at understanding exercise behaviour and help develop recommendations for exercise promotion. In the model, self-control is conceptualized as a global but limited resource. Engaging in actions requiring self-control depletes resources leading to self-regulatory failure. Self-control resource depletion is reduced through rest and frequent training on self-control. The expectation of the need to exert self-control in future leads to a conservation of self-control resources. Proposed mechanisms for self-control resource depletion include changes in physiological markers and blood glucose levels. Based on our review, we propose an integrated model of self-regulation incorporating hypotheses from the strength-energy model with those from traditional psychosocial models of exercise behaviour. Recommendations for future research include incorporating hypotheses from the strength-energy model into theories of self-presentation and interpersonal relations in exercise. Practical recommendations aimed at minimising self-control depletion in exercise include the provision of advice on nutrition and recovery, self-control training and motivational and implementation intention strategies

A Classification of Motivation and Behavior Change Techniques Used in Self-Determination Theory-Based Interventions in Health Contexts

While evidence suggests that interventions based on self-determination theory have efficacy in motivating adoption and maintenance of health-related behaviors, and in promoting adaptive psychological outcomes, the motivational techniques that comprise the content of these interventions have not been comprehensively identified or described. The aim of the present study was to develop a classification system of the techniques that comprise self-determination theory interventions, with satisfaction of psychological needs as an organizing principle. Candidate techniques were identified through a comprehensive review of self-determination theory interventions and nomination by experts. The study team developed a preliminary list of candidate techniques accompanied by labels, definitions, and function descriptions of each. Each technique was aligned with the most closely-related psychological need satisfaction construct (autonomy, competence, or relatedness). Using an iterative expert consensus procedure, participating experts (N=18) judged each technique on the preliminary list for redundancy, essentiality, uniqueness, and the proposed link between the technique and basic psychological need. The procedure produced a final classification of 21 motivation and behavior change techniques (MBCTs). Redundancies between final MBCTs against techniques from existing behavior change technique taxonomies were also checked. The classification system is the first formal attempt to systematize self-determination theory intervention techniques. The classification is expected to enhance consistency in descriptions of selfdetermination theory-based interventions in health contexts, and assist in facilitating synthesis of evidence on interventions based on the theory. The classification is also expected to guide future efforts to identify, describe, and classify the techniques that comprise self-determination theory-based interventions in multiple domains

Prevalence and Trends of Symptomatic Pelvic Floor Disorders in U.S. Women

To estimate the prevalence and trends of these pelvic floor disorders in U.S. women from 2005–2010

Evaluation of a standard provision versus an autonomy promotive exercise referral programme: rationale and study design

Background The National Institute of Clinical Excellence in the UK has recommended that the effectiveness of ongoing exercise referral schemes to promote physical activity should be examined in research trials. Recent empirical evidence in health care and physical activity promotion contexts provides a foundation for testing the utility of a Self Determination Theory (SDT) -based exercise referral consultation. Methods/Design Design: An exploratory cluster randomised controlled trial comparing standard provision exercise on prescription with a Self Determination Theory-based (SDT) exercise on prescription intervention. Participants: 347 people referred to the Birmingham Exercise on Prescription scheme between November 2007 and July 2008. The 13 exercise on prescription sites in Birmingham were randomised to current practice (n=7) or to the SDT-based intervention (n=6). Outcomes measured at 3 and 6-months: Minutes of moderate or vigorous physical activity per week assessed using the 7-day Physical Activity Recall; physical health: blood pressure and weight; health status measured using the Dartmouth CO-OP charts; anxiety and depression measured by the Hospital Anxiety and Depression Scale and vitality measured by the subjective vitality score; motivation and processes of change: perceptions of autonomy support from the advisor, satisfaction of the needs for competence, autonomy, and relatedness via physical activity, and motivational regulations for exercise. Discussion This trial will determine whether an exercise referral programme based on Self Determination Theory increases physical activity and other health outcomes compared to a standard programme and will test the underlying SDT-based process model (perceived autonomy support, need satisfaction, motivation regulations, outcomes) via structural equation modelling. Trial registration The trial is registered as Current Controlled trials ISRCTN07682833

The potential psychological benefits of Active Video Games in the rehabilitation of musculoskeletal injuries and deficiencies: A narrative review of the literature

Background: Recent literature suggests that Active Video Games (AVGs) may offer potential psychological benefits during the rehabilitation of musculoskeletal injuries and their corresponding deficiencies. Objectives: To review existing literature regarding the potential psychological benefits of AVGs within the context of rehabilitation from musculoskeletal injury or debilitation. Method: A narrative review of the literature that used the Population, Intervention, Comparison, and Outcomes PICO method was conducted. The literature review included studies that discussed and/or investigated potential psychological benefits of AVGs during musculoskeletal rehabilitation. Of the total 163 papers that were identified, 30 met the inclusion criteria. Results: The Nintendo® WiiTM (Nintendo Co., Ltd, Kyoto, Japan) was the most commonly-used games console that was employed in AVG interventions (15 out of 21), and these studies that investigated potential psychological benefits were typically conducted with elderly populations. These studies reported that using AVGs in musculoskeletal rehabilitation resulted in a number of positive psychological effects (e.g., enjoyment, effects on self). However, most studies lacked a clear theoretical framework, and varied greatly in their designs and methodologies. Conclusion: Despite encouraging findings of AVG use, insufficient evidence exists to reliably verify or refute the potential psychological benefits of AVGs in musculoskeletal rehabilitation. It is recommended that future studies in this area contain a theoretical framework to ensure greater consistency in the methodology used and the execution of the intervention. The potential findings of such investigations may result in the development of optimal, client-tailored rehabilitation programmes