Psychometric properties of a questionnaire to assess exercise-related musculoskeletal injuries in older adults attending a community-based fitness facility

Objectives: There currently exists no reliable or validated tool for the assessment of exercise-related injuries in older adults. The purpose was to develop and evaluate the psychometric properties of a questionnaire to measure exercise-related injury in older adults participating in supervised exercise programmes. Design: The study utilised a repeated survey design. Setting: The study took place at one communitybased older-adult exercise facility. Participants: The questionnaire was administered to 110 community-dwelling older adults (45 men, mean age 75±8 years; 65 women, mean age 71±8 years). All participants completed the survey at both time points. Outcome measures: Test–retest reliability of the selfadministered written questionnaire was determined at two-time points. The questionnaire asked participants about their exercise-related injury incurred at the facility in the 12 months. Items included the mechanism, cause and site of injury. The minimum requirement for reliability (κ coefficient) was set at 0.80. Results: 16% (n=18) reported having an injury. Test–retest reliability ranged from 0.76 to 1.00, with all but type of injury (0.76) having κ coefficients greater than 0.80. The lower extremities were the most common site of exercise-related injury. Overexertion movements were the most common cause of injury occurring during strength training exercises. Conclusions: The present questionnaire assessing the 12-month recall in older adults is a reliable measure of exercise-related injuries and information gained indicates that older adults can safely participate in exercise activities.Liza Stathokostas, Olga Theou, Tony Vandervoort, Parminder Rain

Exact Quantum Solutions of Extraordinary N-body Problems

The wave functions of Boson and Fermion gases are known even when the particles have harmonic interactions. Here we generalise these results by solving exactly the N-body Schrodinger equation for potentials V that can be any function of the sum of the squares of the distances of the particles from one another in 3 dimensions. For the harmonic case that function is linear in r^2. Explicit N-body solutions are given when U(r) = -2M \hbar^{-2} V(r) = \zeta r^{-1} - \zeta_2 r^{-2}. Here M is the sum of the masses and r^2 = 1/2 M^{-2} Sigma Sigma m_I m_J ({\bf x}_I - {\bf x}_J)^2. For general U(r) the solution is given in terms of the one or two body problem with potential U(r) in 3 dimensions. The degeneracies of the levels are derived for distinguishable particles, for Bosons of spin zero and for spin 1/2 Fermions. The latter involve significant combinatorial analysis which may have application to the shell model of atomic nuclei. For large N the Fermionic ground state gives the binding energy of a degenerate white dwarf star treated as a giant atom with an N-body wave function. The N-body forces involved in these extraordinary N-body problems are not the usual sums of two body interactions, but nor are forces between quarks or molecules. Bose-Einstein condensation of particles in 3 dimensions interacting via these strange potentials can be treated by this method.Comment: 24 pages, Latex. Accepted for publication in Proceedings of the Royal Societ

Minimum Velocity Dispersion in Stable Stellar Disks. Numerical Simulations

N-body dynamical simulations are used to analyze the conditions for the gravitational stability of a three-dimensional stellar disk in the gravitational field of two rigid spherical components--a bulge and a halo whose central concentrations and relative masses vary over wide ranges. The number of point masses N in the simulations varies from 40 to 500 thousands and the evolution of the simulated models is followed over 10--20 rotation periods of the outer edge of the disk. The initially unstable disks are heated and, as a rule, reach a quasi-stationary equilibrium with a steady-state radial-velocity dispersion $c_r$ over five to eight periods of rotation. The radial behavior of the Toomre stability parameter $Q_T (r)$ for the final state of the disk is estimated. Numerical models are used to analyze the dependence of the gravitational stability of the disk on the relative masses of the spherical components, disk thickness, degree of differential rotation, and initial state of the disk. Formal application of existing, analytical, local criteria for marginal stability of the disk can lead to errors in radial velocity dispersion $c_r$ of more than a factor of 1.5. It is suggested that the approximate constancy of $Q_T \simeq 1.2 -- 1.5$ for $r\simeq (1\div 2)\times L$ (where L is the radial scale of disk surface density), valid for a wide range of models, can be used to estimate upper limits for the mass and density of a disk based on the observed distributions of the rotational velocity of the gaseous component and of the stellar velocity dispersion.Comment: 33 pages, 8 Figs. Published in Astronomy Reports,2003,v.47,p.357 The paper may also be found at http://neptun.sai.msu.su/~zasov/articles/k_z.zi

History, epidemiology and regional diversities of urolithiasis

Archeological findings give profound evidence that humans have suffered from kidney and bladder stones for centuries. Bladder stones were more prevalent during older ages, but kidney stones became more prevalent during the past 100 years, at least in the more developed countries. Also, treatment options and conservative measures, as well as ‘surgical’ interventions have also been known for a long time. Our current preventive measures are definitively comparable to those of our predecessors. Stone removal, first lithotomy for bladder stones, followed by transurethral methods, was definitively painful and had severe side effects. Then, as now, the incidence of urolithiasis in a given population was dependent on the geographic area, racial distribution, socio-economic status and dietary habits. Changes in the latter factors during the past decades have affected the incidence and also the site and chemical composition of calculi, with calcium oxalate stones being now the most prevalent. Major differences in frequency of other constituents, particularly uric acid and struvite, reflect eating habits and infection risk factors specific to certain populations. Extensive epidemiological observations have emphasized the importance of nutritional factors in the pathogenesis of urolithiasis, and specific dietary advice is, nowadays, often the most appropriate for prevention and treatment of urolithiasis

Dynamics of Disks and Warps

This chapter reviews theoretical work on the stellar dynamics of galaxy disks. All the known collective global instabilities are identified, and their mechanisms described in terms of local wave mechanics. A detailed discussion of warps and other bending waves is also given. The structure of bars in galaxies, and their effect on galaxy evolution, is now reasonably well understood, but there is still no convincing explanation for their origin and frequency. Spiral patterns have long presented a special challenge, and ideas and recent developments are reviewed. Other topics include scattering of disk stars and the survival of thin disks.Comment: Chapter accepted to appear in Planets, Stars and Stellar Systems, vol 5, ed G. Gilmore. 32 pages, 17 figures. Includes minor corrections made in proofs. Uses emulateapj.st