A STRAIN-GAUGE UNIAXIAL LOAD CELL TO EVALUATE MUSCULAR STRENGTH LEVEL IN ISOMETRIC EXERCISE

INTRODUCTION "Muscle strength is defined as the magnitude of the torque exerted by a muscle (or muscles) in a single maximal isometric contraction of unrestricted duration" (Atha, 1981 ). Strength diagnosis (Schmidtbleicher, 1992) by means of strength and power tests is considered as a very useful procedure to identify talents or to control the evolution in the tralning or rehabilitation progress. The results of specific tests provide information about relative deficiencies and they can be used to figure out individual strength training programs. Also, maximum isometric force and the rate of force development seem to be important qualities related to the athletic performance (Wilson and Murphy, 1995). In consequence of this study a strain-gauge uniaxial load cell has been designed and developed to measure in real-time, and store the well established mechanical parameters to evaluate muscular force during isometric exercise. These parameters are: a) the peak value of the force exerted on the load b)the time to reach a predetermined percentage of its maximum value c) the gradient of the force-time curve d) the interval to maintain a determined level of isometric force. The measurement chain includes: i) the load cell which is an lnstrumentated steel ring with a Wheatstone circuit ii) the amplifier iii) a low-pass analogic filter iv) an AID converter v) the personal computer with mathematical processor and the software for signal treatment and results' representation. RESULTS An INSTRON electro-hydraulic testing system has been used to calibrate the measurement chain and to evaluate its performance (r = -.999, pc ,00000). The measurement range of the load cell is up to 3500 N, its precision is k5 N and its sampling rate is 500 Hz. The software permits the representation of the results in real-time providing the possibility for feedback applications. CONCLUSION Convenient technical characteristics recommend the use of this uniaxial load cell to evaluate muscle strength capacity in isometric conditions.. REFERENCES Atha, J. (t981). Strengthening muscle. In D.I. Miller (Ed.) Exercise and Sport Science Reviews, vol. 9, 1-73. Philadelphia Franklin Institute. Shmidtbleicher, D. (1 992). Training for Power events, Strength and Power in Sport. P.V. Komi (Ed.), 381-395, Blackwell. Wilson, G. J.; Murphy A.J. (1 995). Strength Diagnosis: the use of the pre-training test data to determine individual specific strength training. XVth I.S.B. Congress. Book of abstracts, 994-995

From Davydov solitons to decoherence-free subspaces: self-consistent propagation of coherent-product states

The self-consistent propagation of generalized $D_{1}$ [coherent-product] states and of a class of gaussian density matrix generalizations is examined, at both zero and finite-temperature, for arbitrary interactions between the localized lattice (electronic or vibronic) excitations and the phonon modes. It is shown that in all legitimate cases, the evolution of $D_{1}$ states reduces to the disentangled evolution of the component $D_{2}$ states. The self-consistency conditions for the latter amount to conditions for decoherence-free propagation, which complement the $D_{2}$ Davydov soliton equations in such a way as to lift the nonlinearity of the evolution for the on-site degrees of freedom. Although it cannot support Davydov solitons, the coherent-product ansatz does provide a wide class of exact density-matrix solutions for the joint evolution of the lattice and phonon bath in compatible systems. Included are solutions for initial states given as a product of a [largely arbitrary] lattice state and a thermal equilibrium state of the phonons. It is also shown that external pumping can produce self-consistent Frohlich-like effects. A few sample cases of coherent, albeit not solitonic, propagation are briefly discussed.Comment: revtex3, latex2e; 22 pages, no figs.; to appear in Phys.Rev.E (Nov.2001

JOINT CO-ORDINATE SYSTEM AND ATTITUDE VECTOR: INFLUENCE IN THE INTERPRETATION OF MOVEMENTS

INTRODUCTION: A rapid lateral braking movement and a rapid turning movement were recorded with two cameras Photo Sonics 16mm at 200 frames/s. The different Joint Coordinate Systems and the attitude vector has a better behavior in these practical cases as suggested by H. Woltring and has the same anatomical sense that the most usual Joint Coordinate Systems. RESULTS: Four body segments were defined: foot, leg, thigh and hip. Three markers define the 3D position of each segment. The position of the markers was selected following the criteria that the movement of muscles and skin had not a big influence on the measurements. To define the anatomical axes the anthropometrical model proposed by Vaughan et al. (1992) was used with some variations, because of the supposition that some markers belong 'to two body segments at the same time is not correct in the movements studied. CONCLUSIONS: In the two movements studied the angle's curves calculated with the attitude vector have a form similar to those of the curves calculated with JCS-1 and JCS+1 which the Joint Coordinate Systems recommended as standard in Cole et al. (1993) and ISB (1995), but the absolute value of the angles is displaced. It is clear that the selection of the JCS has influence in the angle's value and, in some cases, it can change the description of the movement. The order of rotations in JCS are 123 (+1), 231 (+2), 312 (+3), 132 (-1), 321 (-2),213 (-3). In lateral braking movement JCS+3 changes the hip flexion for hip extension and knee flexion for knee extension. And 71 JCS-3 changes hip adduction for hip abduction and hip internal rotation for hip external rotation. In the turning movement JCS+2 changes hip flexion, hip adduction, knee adduction and ankle supination. JCS+3 changes hip flexion, hip adduction, knee extension and knee internal rotation. JCS-3 changes hip adduction. If only these JCS had been used, the description of movement would have been incongruent. Although the attitude vector has some mathematical advantages, the matter of wh ich is the more anatomical is still open. The attitude vector represents the movement in one helical displacement around an axis The different JCS represent the movement in three ordered helical displacements around three consecutive axes. REFERENCES: Cole, G.K.; Nigg, B.M.; Ronsky, J.L.; Yeadon, M.R. (1993) Application of the Joint Coordinate System to the Three Dimensional Joint Attitude and Movement Representation: A Standardization Proposal. Transactions of the ASME, 115,344-349. ISB (1995) A joint coordinate system for the ankle complex. ISB News'letter, 59, 6-8. Kapandji, IA (1988) Cuaderno 2: Miembro Inferior. Cuadernos de fisiologia articular.(Edited by Masson S.A.). Barcelona. Vaughan, C.L; Davis, B.L.; O'Connor, J.C. (1992) Dynamics of human gait. Human Kinetics Books, Champaign, IIlinois Woltring, H.J. (1994) 3-D attitude representation of human joints: a standardization proposal. J. Biomech. 27

At-home vital bleaching : a comparison of hydrogen peroxide and carbamide peroxide treatments

El blanqueamiento de los dientes vitales que realiza el/la paciente domiciliariamente con férulas bajo supervisión del/de la dentista es una alternativa interesante entre las que integran este tipo de terapéutica odontológica, ya sea, de forma aislada o combinada con alguna de las modalidades de tratamiento en la consulta. En este procedimiento blanqueador se usan peróxidos de baja concentración que se aplican sobre el esmalte dentario mediante una cubeta individualizada especialmente diseñada para ello. El objetivo del presente trabajo es analizar y comparar dos productos blanqueadores comerciales de diferente concentración indicados para esta técnica, VivaStyle (Vivadent) y FKD (Kin); el primero de ellos es un peróxido de carbamida al 10%, mientras que el segundo es un peróxido de hidrógeno al 3,5%. Se analizan los parámetros que deben ser controlados durante la puesta en práctica de este tipo de procedimiento y se presentan 6 casos (3 de ellos tratados con uno de los productos mencionados y los otros 3 con el otro) en los que se constata su capacidad blanqueadora y la aparición y la intensidad de hipersensibilidad postoperatoria. Los resultados obtenidos muestran que ambos productos son eficaces para la función para la que han sido desarrollados. En general, la hipersensibilidad dentaria es mínima

In vivo evaluation of the effects of 10% carbamide peroxide and 3.5% hydrogen peroxide on the enamel surface

Objetivos: El blanqueamiento de los dientes vitales que realiza el/la paciente en su domicilio bajo la supervisión del/de la dentista con férulas individualizadas especialmente diseñadas para ello y peróxidos de baja concentración, es una opción de entre las que integran esta terapéutica odontológica, ya sea, como tratamiento único o combinada con otra modalidad de blanqueamiento en la consulta. El objetivo del presente trabajo es analizar el efecto que producen sobre la superficie del esmalte dos productos blanqueadores indicados para esta técnica. Diseño del estudio: Se emplearon dos productos blanqueadores, el VivaStyle (Vivadent), peróxido de carbamida al 10%, y el FKD (Kin), peróxido de hidrógeno al 3,5%, que se aplicaron mediante férulas sobre los dientes anteriores de 20 pacientes (10 en cada grupo). El tiempo de aplicación de cada producto fue de 2 y 3 horas al día respectivamente durante 28-33 días. Se obtuvieron réplicas de las superficies dentales antes y después del tratamiento, las cuales fueron observadas con un microscopio electrónico de barrido. Resultados: Las imágenes obtenidas muestran la integridad de la superficie dental, con el mantenimiento de las estructuras normales de la superficie del esmalte. Conclusiones: Los resultados obtenidos muestran que ninguno de los dos productos alteran la superficie del esmalte, no observándose, pues, cambios postoperatorios