Filipa João

The sensitivity of two-dimensional hindlimb joint kinematics analysis in assessing functional recovery in rats after sciatic nerve crush.

Walking analysis in the rat is increasingly used to assess functional recovery after peripheral nerve injury. Here we assess the sensitivity and specificity of hindlimb joint kinematics measures during the rat gait early after sciatic nerve crush injury (DEN), after twelve weeks of recovery (REINN) and in sham-operated controls (Sham) using discriminant analysis. The analysis addressed gait spatiotemporal variables and hip, knee and ankle angle and angular velocity measures during the entire walking cycle. In DEN animals, changes affected all studied joints plus spatiotemporal parameters of gait. Both the spatiotemporal and ankle kinematics parameters recovered to normality within twelve weeks. At this time point, some hip and knee kinematics values were still abnormal when compared to sham controls. Discriminant models based on hip, knee and ankle kinematics displayed maximal sensitivity to identify DEN animals. However, the discriminant models based on spatiotemporal and ankle kinematics data showed a poor performance when assigning animals to the REINN and Sham groups. Models using hip and knee kinematics during walking showed the best sensitivity to recognize the reinnervated animals. The model construed on the basis of hip joint kinematics was the one combining highest sensitivity with robustness and high specificity. It is concluded that ankle joint kinematics fails in detecting minor functional deficits after long term recovery from sciatic nerve crush and extending the kinematic analysis during walking to the hip and knee joints improves the sensitivity of this functional test.

Anatomical Reference Frame versus Planar Analysis: Implications for the Kinematics of the Rat Hindlimb during Locomotion

Functional recovery is the primary goal of therapeutic intervention in neuromuscular rehabilitation. The purpose of this study was to perform a segmental kinematic analysis using both planar angles computation and a tridimensional (3D) reconstruction of the rat hindlimb, regarding the morphology and the movement of each segment. Seven rats were evaluated for natural overground walking, and motion capture of the right hindlimb was collected with an optoeletronic system while the animals walked in the track. 3D biomechanical analyses were carried out and hip, knee, ankle, and metatarsophalangeal joint angular displacements were calculated. For flexion/extension, the knee joint and toe segment were statistically different between planar and 3D analysis, with the toe segment performing less extension at initial contact (IC) and the amplitude during swing phase for the knee being larger. During abduction/adduction, all hip joint parameters

An informational framework to predict reaction of constraints using a reciprocally connected knee model

Researchers have used screw theory to describe the motion of the knee in terms of instantaneous axes of the knee (IAK). However, how geometric change to the dynamic alignment of IAK may affect stance phase of foot loading has not yet been fully explained. We have tested our informational framework through readily accessible benchmark data (Fregly et al. 2012): muscle contraction and ground reaction force are compounded into a wrench that is reciprocal to the IAK and resolved into component wrenches belonging to the reciprocal screw system. This revealed the special screw system that defines the freedom available to the knee and more precisely revealed how to measure this first order of freedom. After this step, we determined the reciprocal screw system, which involves the theory of equilibrium. Hence, a screw system of the first order will have a screw system of the fifth order as its reciprocal. We established a framework the estimation of reaction of constraints about the knee using a process that is simplified by the judicious generation of IAK for the first order of freedom in equilibrium.

An Informational Algorithm as the Basis for Perception-Action Control of the Instantaneous Axes of the Knee

Traditional locomotion studies emphasize an optimization of the desired movement trajectories while ignoring sensory feedback. We propose an information based theory that locomotion is neither triggered nor commanded but controlled. The basis for this control is the information derived from perceiving oneself in the world. Control therefore lies in the human-environment system. In order to test this hypothesis, we derived a mathematical foundation characterizing the energy that is required to perform a rotational twist, with small amplitude, of the instantaneous axes of the knee (IAK). We have found that the joint’s perception of the ground reaction force may be replaced by the co-perception of muscle activation with appropriate intensities. This approach generated an accurate comparison with known joint forces and appears appropriate in so far as predicting the effect on the knee when it is free to twist about the IAK.

Synergistic interaction between ankle and knee during hopping revealed through induced acceleration analysis

The forces produced by the muscles can deliver energy to a target segment they are not attached to, by transferring this energy throughout the other segments in the chain. This is a synergistic way of functioning, which allows muscles to accelerate or decelerate segments in order to reach the target one. The purpose of this study was to characterize the contribution of each lower extremity joint to the vertical acceleration of the bodys center of mass during a hopping exercise. To accomplish this, an induced acceleration analysis was performed using a model with eight segments. The results indicate that the strategies produced during a hopping exercise rely on the synergy between the knee and ankle joints, with most of the vertical acceleration being produced by the knee extensors, while the ankle plantar flexors act as stabilizers of the foot. This synergy between the ankle and the knee is perhaps a mechanism that allows the transfer of power from the knee muscles to the ground, and we believe that in this particular task the net action of the foot and ankle moments is to produce a stable foot with little overall acceleration.

CAN GLOBAL OPTIMIZATION TECHNIQUE COMPENSATE FOR MARKER SKIN MOVEMENT IN RAT KINEMATICS

The motion of the skeletal estimated from skin attached marker-based motion capture(MOCAP) systems is known to be affected by significant bias caused by anatomical landmarks mislocation but especially by soft tissue artifacts (such as skin deformation and sliding, inertial effects and muscle contraction). As a consequence, the error associated with this bias can propagate to joint kinematics and kinetics data, particularly in small rodents. The purpose of this study was to perform a segmental kinematic analysis of the rat hindlimb during locomotion, using both global optimization as well as segmental optimization methods. Eight rats were evaluated for natural overground walking and motion of the right hindlimb was captured with an optoeletronic system while the animals walked in the track. Three-dimensional (3D) biomechanical analyses were carried out and hip, knee and ankle joint angular displacements and velocities were calculated. Comparison between both methods demonstrated that the magnitude of the k...

Efferent Copy and Corollary Discharge Motor Control Behavior Associated with a Hopping Activity

Hoppers respond not only to stimuli from the ground surfaces but also to cues generated by their own behaviors. This leads to desensitization because although the afferent and reafferent signals have distinct causes, they are carried by the same sensory channels. From a behavioral viewpoint, it may be necessary to distinguish between signals from the two causes especially when monitoring changes in the external environment separate from those due to self- movement. We were able to separate afferent sensory stimuli from self-generated, reafferent signals using an action- oriented perception system and dynamic programming approach. This effort addressed the question of how the nerve one-DOF model characterizing the motor control system during hopping, allowing the generation of an estimated ground reaction signal to drive natural shock absorption of the leg.

Biomechanics modeling for functional analysis: Sheep model

The aim of the present manuscript was to provide information on the suitability of using ovine as models for conducting in vivo bone tissue engineering studies, regarding the biomechanical considerations. Despite the need of knowledge of the animal model used for bone tissue research a good planning and study design is equal important. The purpose of this review is to contribute to extrapolation of reliable data for those who pretend to use the ovine model in tissue engineering and regenerative medicine.The aim of the present manuscript was to provide information on the suitability of using ovine as models for conducting in vivo bone tissue engineering studies, regarding the biomechanical considerations. Despite the need of knowledge of the animal model used for bone tissue research a good planning and study design is equal important. The purpose of this review is to contribute to extrapolation of reliable data for those who pretend to use the ovine model in tissue engineering and regenerative medicine.

Diastasis recti during pregnancy and postpartum

Diastasis recti abdominis (DRA) or increased inter-rectus distance (IRD) is characterized by the separation of the rectus abdominis muscles. It has its onset during pregnancy and the first weeks following childbirth. The reliability of the instruments used to assess this condition is unclear. There is scant knowledge on the prevalence and risk factors for development of the condition. There is little evidence on which exercises are most effective in reduction of DRA. The aims of our studies were to establish a reliable method for the assessment of the morphology of the abdominal wall, describe DRA prevalence, risk factors, and evaluate the acute response on the IRD induced by drawing-in and abdominal crunch exercises. The results of three methodological studies showed ultrasound imaging to be a reliable method for measuring IRD. The ultrasound transducer can be held relatively stationary in a clinical setting, to evaluate IRD. DRA is prevalent at 6 months postpartum, with a prevalence rate of 39%. The acute response on IRD produced by drawing-in exercise was a widening of the IRD in postpartum, while the abdominal crunch exercise induced an acute narrowing response of the IRD in pregnancy and in postpartum.

Multimodal MRI Evaluation of Physiological Changes on Leg Muscles due to Fatigue after Intense Exercise

DTI, BOLD and T2 can give us non-invasive information on the functioning of muscles in real time. We used a multimodal approach, that included DTI, BOLD and T2 measurements, to evaluate the physiological changes in several leg muscles, and were able to assess that the soleus and gastrocnemius were the most involved muscles when our volunteers were submitted to intense one legged jump physical exercise conducive to fatigue. DTI, BOLD and T2 can give us non-invasive information on the functioning of muscles in real time. We used a multimodal approach, that included DTI, BOLD and T2 measurements, to evaluate the physiological changes in several leg muscles, and were able to assess that the soleus and gastrocnemius were the most involved muscles when our volunteers were submitted to intense one legged jump physical exercise conducive to fatigue.