Neuromechanical Analysis of Anterior Cruciate Ligament Risk Factors in Female Collegiate Soccer Athletes

The anterior cruciate ligament (ACL) acts in an essential role to prevent anterior tibial displacement when experiencing jump-landing forces that are applied to the lower extremity; more than 100,000 injuries per year in the United States in sport activities that often require landing, deceleration-acceleration, cutting and pivoting actions have been reported. The aim of this study was to examine the nature of any lower limb coupling differences between a drop-jump and a side-step cutting actions, assess kinematic and kinetic differences between three tasks, and evaluate the effects of two landing techniques in biomechanical risk factors while performing two unanticipated tasks. Twenty female collegiate soccer athletes from a Division I institution participated in these experiments. Participants performed two unanticipated tasks; sidestep cutting and pivot, combined with two landing techniques. Three-dimensional kinematics and kinetics were recorded. The coupling relations between specific kinematic and kinetic events were assessed using principal component analysis. In addition, the degree of variability between both tasks was assessed using determination of the coefficient of variation (CV). Repeated measures analyses of variance were conducted to assess differences in the kinematic and kinetic parameters between tasks and foot landing techniques (P\u3c0.05). For experiment 1, the results demonstrated that the highly loaded biomechanical variables were different between the movements, showing that the factors are inherently different depending on vertical versus horizontal oriented jump-landing tasks. Experiment II, the pivot task (-41.2 ± 8.8°) had lower knee flexion and increased valgus angle (-7.6 ± 10.1) than the sidestep (-53.9 ± 9.4°, and -2.9 ± 10.0°, respectively) at maximum vertical ground reaction force

Pulvinar thalamic nucleus allows for asynchronous spike propagation through the cortex

We create two multilayered feedforward networks composed of excitatoryand inhibitory integrate-and-fire neurons in the balanced state toinvestigate the role of cortico-pulvino-cortical connections. Thefirst network consists of ten feedforward levels where a Poisson spiketrain with varying firing rate is applied as an input in layerone. Although the balanced state partially avoids spikesynchronization during the transmission, the average firing-rate in the last layer either decays or saturates depending on the feedforwardpathway gain. The last layer activity is almost independent of the inputeven for a carefully chosen intermediate gain. Adding connectionsto the feedforward pathway by a nine areas Pulvinar structure improves the firing-rate propagation to become almost linear amonglayers. Incoming strong pulvinar spikes balance the low feedforwardgain to have a unit input-output relation in the last layer. Pulvinarneurons evoke a bimodal activity depending on the magnitude input: synchronized spike bursts between 20-80 Hz and an asynchronous activityfor very both low and high frequency inputs. In the first regime, spikes of last feedforward layer neurons areasynchronous with weak, low frequency, oscillations in the rate. Here,the uncorrelated incoming feedforward pathway washes out thesynchronized thalamic bursts. In the second regime, spikes in the wholenetwork are asynchronous. As the number of cortical layers increases,long-range pulvinar connections can link directly two or morecortical stages avoiding their either saturation or gradual activityfalling. The Pulvinar acts as a shortcut that supplies theinput-output firing-rate relationship of two separated cortical areaswithout changing the strength of connections in the feedforwardpathway

The Role of Pulvinar in the Transmission of Information in the Visual Hierarchy

Visual receptive field (RF) attributes in visual cortex of primates have been explained mainly from cortical connections: visual RFs progress from simple to complex through cortico-cortical pathways from lower to higher levels in the visual hierarchy. This feedforward flow of information is paired with top-down processes through the feedback pathway. Although the hierarchical organization explains the spatial properties of RFs, is unclear how a non-linear transmission of activity through the visual hierarchy can yield smooth contrast response functions in all level of the hierarchy. Depending on the gain, non-linear transfer functions create either a bimodal response to contrast, or no contrast dependence of the response in the highest level of the hierarchy. One possible mechanism to regulate this transmission of visual contrast information from low to high level involves an external component that shortcuts the flow of information through the hierarchy. A candidate for this shortcut is the Pulvinar nucleus of the thalamus. To investigate representation of stimulus contrast a hierarchical model network of ten cortical areas is examined. In each level of the network, the activity from the previous layer is integrated and then non-linearly transmitted to the next level. The arrangement of interactions creates a gradient from simple to complex RFs of increasing size as one moves from lower to higher cortical levels. The visual input is modeled as a Gaussian random input, whose width codes for the contrast. This input is applied to the first area. The output activity ratio among different contrast values is analyzed for the last level to observe sensitivity to a contrast and contrast invariant tuning. For a purely cortical system, the output of the last area can be approximately contrast invariant, but the sensitivity to contrast is poor. To account for an alternative visual processing pathway, non-reciprocal connections from and to a parallel pulvinar like structure of nine areas is coupled to the system. Compared to the pure feedforward model, cortico-pulvino-cortical output presents much more sensitivity to contrast and has a similar level of contrast invariance of the tuning

La salud de la salud

La intención en el momento de reformar la ley, fue generar una profunda reforma en el sector salud con propósitos de beneficio social, lograr la cobertura universal, estimular la competencia, mejorar los sistemas administrativos y la capacidad gerencial de los hospitales. Sin embargo, su implantación ha resultado un colapso real y una profunda crisis, desde todo punto de vista, en el sector salud. Si bien el espíritu de la ley 100 era crear un verdadero sistema de salud, ésta se transformo y creó un sistema de aseguramiento comercial, en el cual no se contempla la educación, capacitación ni, mucho menos la investigación. Los recursos que vayan a estos dos renglones deben ser considerados inversión y no un gasto, como lo ve el actual SGSSS. Los malos manejos, los intereses personales de algunos de nuestros gobernantes y la corrupción, tienen al borde del abismo el futuro de la salud en Colombi

Predictive Accuracy of the Nelson Equation via BodPod Compared to Commonly Used Equations to Estimate Resting Metabolic Rate in Adults

International Journal of Exercise Science 14(2): 1166-1177, 2021. Indirect calorimetry (IC) is considered the gold standard for assessing resting metabolic rate (RMR). However, many people do not have access to IC devices and use prediction equations for RMR estimation. Equations using fat free mass (FFM) as a predictor have been developed to estimate RMR, as a strong relationship exists between FFM and RMR. One such equation is the Nelson equation which is used by the BodPod (BP). Yet, there is limited evidence whether the Nelson equation is superior to other common equations to predict RMR. To examine the agreement between predicted RMR from common RMR equations and the BP, and RMR measured via IC. Data from 48 healthy volunteers who completed both the BP and IC were collected. Agreement between RMR measured by BP, common regression equations, and indirect caloriometry was evaluated using repeated measures ANOVA, Bland-Altman analysis and root mean square error (RMSE). Predicted RMR values from common equations and BP were significantly different from IC with the exception of the World Health Organization (WHO) equation. Large limits of agreement and RMSE values demonstrate a large amount of error at the individual level. Despite the use of FFM, the Nelson equation does not appear to be superior to other common RMR equations. Although the WHO equation presented the best option within our sample, all equations performed poorly at the individual level. Clinicians should be aware that prediction equations may significantly under- or overestimate RMR compared to IC and when an accurate value of RMR is required, IC is recommended

Mortalidad por Enfermedades Cardiovasculares y su Impacto Económico en Colombia, 2000-2010

Objetivo Establecer el impacto económico de la mortalidad asociada con las enfermedades cardiovasculares en Colombia durante el periodo 2000 – 2010. Materiales y Métodos Se llevó a cabo un estudio ecológico mixto. Se utilizaron las proyecciones de población y los registros de defunciones no fetales de Colombia publicados oficialmente por el Departamento Administrativo Nacional de Estadísticas. De los registros oficiales se extrajo el valor del Salario Mínimo Mensual Legal Vigente -SMMLV- en pesos para determinar el monto de ingresos o consumos mínimos anuales, los cuales fueron convertidos a dólares e indexados al año 2010. Luego, se multiplicó el total de APVP de cada periodo anual por el ingreso mínimo obtenido con anterioridad. Se efectúo la sumatoria de los flujos anuales en dólares para determinar el valor total del costo de los años de vida perdidos en el periodo de estudio y dicho costo se contrastó con el Producto Interno Bruto –PIB- nacional a precios constantes del 2010 convertidos en dólares. La información se analizó en el programa Excel y en el programa EPIDAT. Resultados En Colombia se perdió cerca de 2.785.529 años potenciales de vida que equivalen a USD 7 mil millones, lo cual representó el 4% aproximadamente del PIB obtenido durante el mismo periodo. Conclusiones Los Años Perdidos de Vida Potencial relacionados con las muertes cuyas causales fueron las Enfermedades Cardiovasculares decrecieron y representaron solo el 7% dentro del total de años perdidos asociados a todas las causas de defunciones no fetales

A Functional Agility Short-Term Fatigue Protocol Changes Lower Extremity Mechanics

The purpose of this study was to evaluate the effects of a functional agility fatigue protocol on lower extremity biomechanics between two unanticipated tasks (stop-jump and sidestep). The subjects consisted of fifteen female collegiate soccer athletes (19 ± 0.7 years, 1.67 ± 0.1 m, 61.7± 8 kg) free of lower extremity injury. Participants performed five trials of stop-jump and sidestep tasks. A functional short-term agility protocol was performed, and immediately following participants repeated the unanticipated running tasks. Lower extremity kinematic and kinetic values were obtained pre and post fatigue. Repeated measures analyses of variance were conducted for each dependent variable with an alpha level set at 0.05. Knee position post-fatigue had increased knee internal rotation (11.4 ± 7.5 degrees vs. 7.9 ± 6.5 degrees p = 0.011) than pre-fatigue, and a decreased knee flexion angle (-36.6 ± 6.2 degrees vs. -40.0 ± 6.3 degrees, p = 0.003), as well as hip position post-fatigue had decreased hip flexion angle (35.5 ± 8.7 degrees vs. 43.2 ± 9.5 degrees, p = 0.002). A quick functional fatigue protocol altered lower extremity mechanics of Division I collegiate soccer athletes during landing tasks. Proper mechanics should be emphasized from the beginning of practice/game to aid in potentially minimizing the effects of fatigue in lower extremity mechanics

Landing Technique Affects Knee Loading and Position During Athletic Tasks

Anterior cruciate ligament (ACL) injuries have been reported to occur with the ankle in a dorsiflexed position at initial contact. Few studies have attempted to quantify the biomechanical parameters related with such landing patterns during athletic tasks. Objectives- The purpose of this study was to evaluate the effects that two landing techniques have in lower extremity biomechanics while performing two tasks. Design- Single-group repeated measures design. Methods- Twenty female soccer athletes from a Division 1 institution performed two landing techniques (forefoot and rearfoot) during two unanticipated tasks (sidestep cutting and pivot). Repeated measures analyses of variance were conducted to assess differences in the kinematic and kinetic parameters between landing techniques for each task. Results: The forefoot landing technique had significantly higher internal knee adductor moment than the rearfoot for both the pivot and sidestep cutting task (p \u3c 0.001 and p = 0.003, respectively). For the sidestep cutting task, participants had increased knee valgus angle with the rearfoot, whereas for the pivot they had increased knee valgus with the forefoot landing technique (p \u3c 0.05). Conclusions- The results of this study highlighted that there are inherent differences in biomechanical outcomes between foot-landing techniques. The forefoot landing technique increasingly affects knee adduction moment loading, which can potentially place a higher strain on the ACL. Essentially, the demands of the landing technique on lower extremity biomechanics (e.g., hip and knee) are task dependent

Changes in Lower Extremity Biomechanics Due to a Short-Term Fatigue Protocol

Context: Noncontact anterior cruciate ligament injury has been reported to occur during the later stages of a game when fatigue is most likely present. Few researchers have focused on progressive changes in lower extremity biomechanics that occur throughout fatiguing. Objective: To evaluate the effects of a sequential fatigue protocol on lower extremity biomechanics during a sidestep-cutting task (SS). Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: Eighteen uninjured female collegiate soccer players (age 19.2 ± 0.9 years, height = 1.66 ± 0.5 m, mass 61.6 ± 5.1 kg) volunteered. Intervention(s): The independent variable was fatigue level, with 3 levels (prefatigue, 50% fatigue, and 100% fatigue). Using 3-dimensional motion capture, we assessed lower extremity biomechanics during the SS. Participants alternated between a fatigue protocol that solicited different muscle groups and mimicked actual sport situations and unanticipated SS trials. The process was repeated until fatigue was attained. Main Outcome Measure(s): Dependent variables were hip- and knee-flexion and abduction angles and internal moments measured at initial contact and peak stance and defined as measures obtained between 0% and 50% of stance phase. Results: Knee-flexion angle decreased from prefatigue (-17 degrees ± 5 degrees) to 50% fatigue (-16 degrees ± 6 degrees) and to 100% fatigue (-14 degrees ± 4 degrees) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (-52.9 degrees ± 5.6 degrees) to 50% fatigue (-56.1 degrees ± 7.2 degrees) but decreased from 50% to 100% fatigue (-50.5 degrees ± 7.1 degrees) (F2,34 = 8.282, P = 001). Knee-adduction moment at peak stance increased from prefatigue (0.49 ± 0.23 Nm/kgm) to 50% fatigue (0.55 ± 0.25 Nm/kgm) but decreased from 50% to 100% fatigue (0.37 ± 0.24) (F 2,34 = 3.755, P = 03). Hip-flexion angle increased from prefatigue (45.4 degrees ± 10.9 degrees) to 50% fatigue (46.2 degrees ± 11.2 degrees) but decreased from 50% to 100% fatigue (40.9 degrees ± 11.3 degrees) (F2,34 = 6.542, P= .004). Hip flexion at peak stance increased from prefatigue (49.8 degrees ± 9.9 degrees) to 50% fatigue (52.9 degrees ± 12.1 degrees) but decreased from 50% to 100% fatigue (46.3 degrees ± 12.9 degrees) (F 2,34 = 8.639, P = 001). Hip-abduction angle at initial contact decreased from prefatigue (-13.8 degrees ± 6.6 degrees) to 50% fatigue (-9.1 degrees ± 6.5 degrees) and to 100% fatigue (-7.8 degrees ± 6.5 degrees) (F2,34 = 11.228, P = .001). Hip-adduction moment decreased from prefatigue (0.14 ± 0.13 Nm/kgm) to 50% fatigue (0.08 ± 0.13 Nm/kgm) and to 100% fatigue (0.06 ± 0.05 Nm/ kg) (F2,34 = 5.767, P = .007). Conclusions: The detrimental effects of fatigue on sagittal and frontal mechanics of the hip and knee were visible at 50% of the participants\u27 maximal fatigue and became more marked at 100% fatigue. Anterior cruciate ligament injury-prevention programs should emphasize feedback on proper mechanics throughout an entire practice and not only at the beginning of practice