A biomechanical analysis of the farmers walk, and comparison with the deadlift and unloaded walk

This study compared the biomechanical characteristics of the farmers walk, deadlift and unloaded walk. Six experienced male strongman athletes performed farmers' walks and deadlifts at 70% of their 1RM deadlift. Significant differences (p < 0.05) were apparent at knees passing with the farmers lift demonstrating greater trunk extension, thigh angle, knee flexion and ankle dorsiflexion. Significantly greater mean vertical and anterior forces were observed in the farmers lift than deadlift. The farmers walk demonstrated significantly greater peak forces and stride rates and significantly shorter stride lengths, ground contact times, and swing times than unloaded walk. Significantly greater dorsiflexion, knee flexion, thigh angle, and significantly lesser trunk angle at foot strike were also observed in the farmers walk. The farmers lift may be an effective lifting alternative to the deadlift, to generating more anterior-propulsive and vertical force with less stress to the lumbar spine due to the more vertical trunk position

Canard-like phenomena in piecewise-smooth Van der Pol systems

We show that a nonlinear, piecewise-smooth, planar dynamical system can exhibit canard phenomena. Canard solutions and explosion in nonlinear, piecewise-smooth systems can be qualitatively more similar to the phenomena in smooth systems than piecewise-linear systems, since the nonlinearity allows for canards to transition from small cycles to canards ``with heads." The canards are born of a bifurcation that occurs as the slow-nullcline coincides with the splitting manifold. However, there are conditions under which this bifurcation leads to a phenomenon called super-explosion, the instantaneous transition from a globally attracting periodic orbit to relaxations oscillations. Also, we demonstrate that the bifurcation---whether leading to canards or super-explosion---can be subcritical.Comment: 17 pages, 11 figure

Systems level circuit model of C. elegans undulatory locomotion: mathematical modeling and molecular genetics

To establish the relationship between locomotory behavior and dynamics of neural circuits in the nematode C. elegans we combined molecular and theoretical approaches. In particular, we quantitatively analyzed the motion of C. elegans with defective synaptic GABA and acetylcholine transmission, defective muscle calcium signaling, and defective muscles and cuticle structures, and compared the data with our systems level circuit model. The major experimental findings are: (i) anterior-to-posterior gradients of body bending flex for almost all strains both for forward and backward motion, and for neuronal mutants, also analogous weak gradients of undulatory frequency, (ii) existence of some form of neuromuscular (stretch receptor) feedback, (iii) invariance of neuromuscular wavelength, (iv) biphasic dependence of frequency on synaptic signaling, and (v) decrease of frequency with increase of the muscle time constant. Based on (i) we hypothesize that the Central Pattern Generator (CPG) is located in the head both for forward and backward motion. Points (i) and (ii) are the starting assumptions for our theoretical model, whose dynamical patterns are qualitatively insensitive to the details of the CPG design if stretch receptor feedback is sufficiently strong and slow. The model reveals that stretch receptor coupling in the body wall is critical for generation of the neuromuscular wave. Our model agrees with our behavioral data(iii), (iv), and (v), and with other pertinent published data, e.g., that frequency is an increasing function of muscle gap-junction coupling.Comment: Neural control of C. elegans motion with genetic perturbation

A biomechanical analysis of the heavy sprint-style sled pull and comparison with the back squat

This study compared the biomechanical characteristics of the heavy sprint-style sled pull and squat. Six experienced male strongman athletes performed sled pulls and squats at 70% of their 1RM squat. Significant kinematic and kinetic differences were observed between the sled pull start and squat at the start of the concentric phase and at maximum knee extension. The first stride of the heavy sled pull demonstrated significantly (

An Investigation of the Relationships Between the Teaching Climate, Students’ Perceived Life Skills Development and Well-Being Within Physical Education

Background: Both education policies and curriculum documents identify the personal development of students as a key objective of modern education. Physical education in particular has been cited as a subject that can promote students&rsquo; life skills development and psychological well-being. However, little research has investigated the processes by which physical education may be related to students&rsquo; development of life skills and their psychological well-being.&nbsp; Purpose: Using Benson and Saito&rsquo;s (2001) framework for youth development theory and research, this study explored the relationships between the teaching climate, students&rsquo; perceived life skills development within physical education, and their psychological well-being.&nbsp; Participants and setting: Participants were 294 British physical education students (Mage = 13.70, range = 11&ndash;18 years) attending six secondary schools in Scotland and England. On average, these male (n = 204) and female (n = 90) students took part in physical education classes for 2.35 hours per week.&nbsp; Data collection: The data were collected via a survey which assessed perceived teacher autonomy support, participants&rsquo; perceived life skills development within physical education (teamwork, goal setting, time management, emotional skills, interpersonal communication, social skills, leadership, and problem solving and decision making), and their psychological well-being (self-esteem, positive affect, and satisfaction with life).&nbsp; Data analyses: The preliminary analysis used descriptive statistics to assess how participants scored on each of the study variables and correlations to assess the relationships between all variables. The main analysis sought to test Benson and Saito&rsquo;s (2001) framework using a series of mediation models which were tested via non-parametric bootstrapping analysis.&nbsp; Findings: This study demonstrated that students perceived they were developing the following life skills through physical education: teamwork, goal setting, time management, emotional skills, interpersonal communication, social skills, leadership, and problem solving and decision making. Overall, the results supported Benson and Saito&rsquo;s (2001) framework for youth development theory and research. In all analyses, perceived teacher autonomy support was positively related to participants&rsquo; perceived life skills development within physical education and their psychological well-being. Participants&rsquo; total life skills development was related to all three psychological well-being indicators &ndash; providing support for the &lsquo;pile-up&rsquo; effect (Benson 2006). Total life skills development also mediated the relationships between perceived teacher autonomy support and participants&rsquo; psychological well-being.&nbsp; Conclusion: The findings suggest that perceived teacher autonomy support, along with total life skills development, are related to participants&rsquo; psychological well-being. Interpretation of the results suggest that physical education teachers should integrate autonomy supportive behaviors into their teaching (e.g., provide choice in activities and encourage students to ask questions) as they are associated with young people&rsquo;s development of multiple life skills and their psychological well-being

Magnetic characterization of the frustrated three-leg ladder compound [(CuCl2tachH)3Cl]Cl2

We report the magnetic features of a new one-dimensional stack of antiferromagnetically coupled equilateral copper(II) triangles. High-field magnetization measurements show that the interaction between the copper triangles is of the same order of magnitude as the intra-triangle exchange although only coupled via hydrogen bonds. The infinite chain turns out to be an interesting example of a frustrated cylindrical three-leg ladder with competing intra- and inter-triangle interactions. We demonstrate that the ground state is a spin singlet which is gaped from the triplet excitation.Comment: 6 pages, 9 figures, revised version submitted to Phys. Rev. B. More information at http://obelix.physik.uni-osnabrueck.de/~schnack