Calcolo delle densità con metodo fotogrammetrico di Jensen PDF

## Calcolo delle densità con metodo fotogrammetrico di Jensen - The method consists of scanning the different body segments of the subject with a camera using a 45° inclined mirror, so that both lateral and superior views of the subject's body are present in a single photograph. - This allows for t...

## Calcolo delle densità con metodo fotogrammetrico di Jensen - The method consists of scanning the different body segments of the subject with a camera using a 45° inclined mirror, so that both lateral and superior views of the subject's body are present in a single photograph. - This allows for the measurement of segment lengths and cross-sections. ## 10- FENOMENOLOGIA DELLA LOCOMOZIONE - Posture is the maintenance of an upright position, due to integration of information from the vestibular, somatosensory, and visual systems. - Posture is maintained by the action of postural muscles. - The center of pressure (CoP) and the center of mass (CoM) of the subject need to coincide. - The center of pressure can be measured through the use of force platforms. - The center of mass is calculated through integration of baricenters of various segments. - Posturography is the identification of any deviations in the movement control system related to nervous and sensory system pathologies. ## VARIABILI DI INTERESSE - **CICLO DEL PASSO:** The synchronized movement of the upper and lower limbs during walking is essential for balance. - **Upper limb pendulation:** The upper limbs move in counterphase with the lower limbs. - **Analysis of the gait cycle:** The gait cycle ranges from the initial contact of one foot to the subsequent contact of the same foot. - The simple gait cycle of one limb goes from the initial contact of the contralateral foot to the initial contact of the foot being analyzed. - The stance phase corresponds to the flight phase of the other limb. Both feet are in contact during the double support phase. - The stance phase can be divided into three sub-phases. - The stance and swing phases are affected by pathologies. ## DISTANCE PARAMETERS: REFERENCE VALUES - **Step length:** 0.73 ±.02 m - **Velocity:** 1.39 ±.06 m/s - **Swing velocity:** 3.3.14 m/s - **Stride length:** 1.47 ±.08 m - **Step width:** 0.11.03 m ## TEMPORAL PARAMETERS - **Stance time:** 720 msec RT / 810 msec LT - **Swing time:** 460 msec RT / 470 msec LT - **Stance time (% stride):** 61% RT / 63% LT - **Swing time (% stride):** 39% RT / 37% LT ## ANGLES: ABSOLUTE AND RELATIVE - **Absolute angles:** Define the segment position with respect to the laboratory reference system. - **Relative angles:** Define the angles formed by co-occurring body segments. - Absolute angles are affected by the orientation of movement. ## VERTICAL DISPLACEMENT OF THE ILIAC CRESTS - The vertical movement of the iliac crests is a characteristic of walking. - The speed and amplitude of the displacement of the iliac crests during the different phases of the gait cycle are indicative of a pathological gait. ## INCLINATION OF THE REACTION FORCE VECTOR: SAGITTAL AND FRONTAL PLANE - **Butterfly diagram:** The force vector is analyzed in the sagittal and frontal planes. - The butterfly diagram represents the force vector generated by the heel strike and the push-off phase of the foot. - The vertical component of the force vector has two peaks and one valley. - The antero-posterior and medio-lateral components of the force vector also have a butterfly pattern. - The antero-posterior component of the force vector is dominant in the stance phase. - The medio-lateral component of the force vector is primarily medial. ## COMBINATION OF THE REACTION FORCE COMPONENTS OF THE RIGHT AND LEFT LIMBS - The force vector of the limb in contact with the platform is highlighted in red. - The combined force vector of both limbs is highlighted in blue. - Both limbs are in double support during the double support phase. - The antero-posterior and medio-lateral components of the force vector are zero during double support. - If the reaction force vector is greater than body weight, the acceleration of the body center is upward. - If the reaction force vector is lesser than body weight, the acceleration of the body center is downward. ## DYNAMIC INVERSE PROBLEM - The dynamic inverse problem involves determining internal forces or moments of the body from the known kinematics of the movement. - The external moments are balanced by internal moments. - Internal moments are generated by the muscles acting on the different joints. - Ankle joint moments: Plantarflexion (negative) during the initial stance phase, dorsiflexion (positive) during the rest of the stance. - Knee joint moments: Flexion (positive) during the initial stance phase, extension (negative) during the rest of the stance. - Hip joint moments: Flexion (positive) during the initial stance phase, extension (negative) during the rest of the stance. - The moment at the ankle joint returns 0 at the end of the stance phase. - The moment at the knee joint is not 0 at the end of the stance phase. - The moment at the hip joint is not 0 at the end of the stance phase. ## MOMENTS AND JOINT POWER - Joint power is the product of joint moments and angular velocity. - Positive power corresponds to concentric contraction and negative power corresponds to eccentric contraction. ## PATOLOGICAL CASE - **Case 1:** The subject has extra-rotated right foot. The graphs of moments and power are analyzed. - The ankle moment (dorsi-plantar flexion) for the pathological subject (red) is different from the normal subject: the curve is entirely in plantar flexion because the subject's entire weight is resting on the front of the foot. - The ankle moment (dorsi-plantar flexion) for the pathological subject (red) is different from the normal subject: The subject is not producing any power with the right limb, which demonstrates the limited capacity for propelling with the antero-posterior component of the foot. - The knee joint moment (flexion/extension) for the pathological subjects (red and blue) demonstrates hyperextension of the knee on both sides. - The ankle joint moment (dorsi-plantar flexion) for the pathological subjects (red and blue) demonstrates dorsiflexion on both sides. - The graphs of moments and power show the difference between the right limb and the left limb. ## GRAPHICAL DESCRIPTION OF THE CASE - **Kinematics:** Both the right knee and the left knee are hyperextended. The right ankle and the left ankle are dorsiflexed. - **Dynamics:** During the stance phase, the force vector at the knee is anterior, generating an extension moment. The force vector at the ankle is anterior, generating dorsiflexion moment. These moments are due to the action of the external forces. The internal moment at the knee is in flexion; The internal moment at the ankle is in plantarflexion. - Internal moments are not 0 during the stance phase. - **Power:** The subject exhibits an increased energy absorption at the ankle. ## ELECTROMYOGRAPHY - Electromyography of the rectus femoris reveals an abnormal or excessive extension action, while the normal gait would expect a pressure action. - Electromyography of the rectus femoris demonstrates an increased effort during the stance phase, which contradicts the normal gait pattern. - Electromyography of the rectus femoris demonstrates an improvement three years after surgery. - The gait speed and stance phase are improved. - The kinematic pattern of the hip is normalized. - The kinematic pattern of the knee approaches normalization. - The reflection of the caviglia continues to show an alteration. ## WALKING UP AND DOWN STAIRS - The principles of walking apply to stair climbing and descending. - The additional factor for stairs is changes in potential gravitational energy. ## BIOMECHANICAL ANALYSIS OF POSTURE - Posture is the maintenance of the upright position. - Posturography identifies deviations in the control of movement related to pathologies of the central nervous system. - Posturography takes into account the movement of the center of pressure (CoP), the center of mass (CoM), and other postural stability markers. - The CoP is influenced by factors like breathing and heart rate. - The CoP is controlled by postural muscles. ## STABOLOMETRY - The CoP is determined by the force platform. - The statokinesiogram is the visual representation of the CoP in time. - This movement is a response to continuous changes in the COP which are generated by breathing, heart rate, and voluntary movement. - The CoP's trajectory can be analyzed in terms of its amplitude, standard deviation, and total length. ## CALCULATION OF THE CoM - The CoM can be calculated through double integration or a geometric method. - During double integration, the force measurements from a force plate can be integrated to determine velocity and then position of the CoM. - When using a geometric method, the CoM is determined by weighted average of body segments. ## POSTURAL ANALYSIS: INVERTED PENDULUM MODEL OF WINTER - The inverted pendulum model is a widely used model for understanding postural control. - The model assumes the body is a massless rod, with the center of mass concentrated at the top, and the ankle joint is a frictionless hinge. - The model represents the muscular forces acting on the hip as an actuator. - The COP is a resultant force and not the CoM. - The model emphasizes that the COP controls the CoM through a continuous adjustment mechanism regulated by muscle activity. ## GENERALIZATION OF THE MODEL: FRONTAL PLANE - The frontal plane model considers the action of hip abductors and adductors. - The model includes a muscle actuator for these hip muscles, along with muscle actuators for the inverters and everters of the left and right ankle. - The body weight is distributed on both legs. ## ATTO MOTORIO: INIZIO DEL CAMMINO - The first step initiates the gait cycle, where the weight is shifted to the left leg. - The CoP moves backward and then forward, chasing the CoM. - The initial step generates an inertial force that propels the CoM forward. - The CoP and CoM trajectories are different due to the effect of inertial action. - The CoP controls the CoM based on the principle of the inverted pendulum. ## MODELLI AND STIMA DELLE FORZE INTERNE - Calculating internal forces involves determining the net internal force vector (which is the result of muscle forces, ligament forces, and contact forces). - Internal forces are usually estimated using a dynamic inverse model. - The number of unknown variables is more than the number of equations, therefore the system is indeterminate. - The unknown variables can be determined using invasive techniques such as sensorized prostheses. - The complexity of the problem can be reduced by modeling the system as a single dominant muscle. - Neuromuscular control can also be modeled by using recruitment patterns to determine time-dependent activation patterns of muscles. ## CONCLUSION - The inverted pendulum model is a simplified model, and it is important to consider the true complexity of the musculoskeletal system. - Biomechanical analyses of gait and posture provide insights into the control mechanisms of human movement. ## RIASSUNTO DEL CORSO The course covers the biomechanics of human movement, including: - the physiological basis of movement - the generation of energy - the musculoskeletal system - methodological and theoretical tools to analyze the musculoskeletal system - the biomechanics of movement.