Structural, functional, and behavioral plasticity of sensorimotor integration

The general purpose of this dissertation was to analyze structural, functional, and behavioral changes of sensorimotor integration. Study 1 was designed to analyze the effects of altered stretch reflex sensitivity, via vibration, on motor unit behavior. We discovered that altering muscle spindle function resulted in altered MU behavior, with an increase in recruitment thresholds, decrease in firing rates, and reduced motor output; 9% reduction in maximal strength. Study 2's goal was to analyze structural and functional changes associated with aging, their relationships, and how they affect performance. Older adults had smaller CSARF (~5cm2), lower MQRF (~14 au), greater RMAG (~10% MVC), less STR (~101Nm), slower RTD (~554 Nm/s), and poorer balance (~ 0.5 sway index) when compared to the younger. The middle-age group had smaller CSARF (~2 cm2), less STR (~ 39 Nm), slower RTD (~ 415 Nm/s), and poorer performance (~0.29 sway index) when compared to the young group. When comparing the middle-age group to the older group, the older group had smaller CSARF (~3cm2), less STR (~63 Nm) and poorer balance performance in the balance conditions EOSS and ECSS (~0.55 sway index). Variance in STR and RTD were explained by CSARF and RMAG (STR: ~65%; RTD: ~13%). However, most of the variance in RTD was explained by MQRF (~32%). Regarding balance, RMAG was the functional variable explaining most of the variance in EOSS (~30%) condition and CSARF explained most of the variance in ECSS (~99%). Study 3 was designed to identify the determinants behind the age-related changes in antagonist muscle coactivation. The study is still in progress; so far it seems that the variables related to greater coactivation are: cortical agonist-antagonist representation areas overlap, the location of the muscles center of gravity and cortical inhibition. Therefore, age alters many dimensions in the control of voluntary movement; in these studies, we showed the relationship between spindle function and motor unit behavior and output; then we saw discovered significant relationships between sensory variables and motor variables and how they affect performance. In conclusion, to understand the aging process, it is important to analyze plasticity of sensorimotor integration as a whole

Effects of Social Support on Sedentary Student's Readiness to Become Physically Active

The purpose of this study was examine the relationship between social support and sedentary students� readiness to become physically active. Readiness to exercise was measured with the URICA-E2 (University of Rhode Island Continuous Assessment Exercise 2), which groups students in different stages: precontemplation non-believers (PCN), precontemplation believers (PCB) and contemplation (C). For the purpose of this analysis, the higher they scored in the C stage the more ready they were to start exercising; in this stage participants are beginning to consider exercise. 84 completed surveys (n=84) were analyzed, where 69 are female and 15 are male. The different age groups are as follows: 46 were between 18 � 20 years old, 25 were 21 � 23 years old, and 11 were 24 � 29 years old. A pretest/posttest comparison group design was performed. Through the Chi Square analysis it was found that there was no relationship between social support and sedentary students� readiness to become physically active with an x� = 1.71, p 0.10 for the PCN stage. A z test was performed because the eligible number of participants was higher than 50 in the PCB and C stages. The result was z = -1.38, p > 0.10 for the PCB stage and z = -0.68, p > 0.10 for the C stage.Education (PhD

Formulación Del Programa De Prevención De La Deserción: Articulación De Acciones En Un Programa Transversal De Acompañamiento Para La Pontificia Universidad Javeriana

Tras identificar un incremento anual en la deserción de entre el 1% y el 2,4%, se ve la necesidad de formular un Programa que permita articular las acciones y servicios de atención y acompañamiento de la Universidad, con las herramientas para identificar oportunamente los riesgos de deserción. De esta manera, nace el Programa de Prevención de la Deserción (PPD) cuyo propósito es atender a tiempo situaciones de riesgo y vulnerabilidad individual, psicosocial, académico e institucional, que pueden tener incidencia en la deserción estudiantil. El PPD propone, además, fortalecer las acciones y servicios para la prevención de la deserción ya existentes, y promoverlas entre los miembros de la Comunidad Educativa que intervienen en los procesos de formación integral. En el marco de éste mismo, se inició un piloto de acompañamiento estudiantil en la Facultad de Ingeniería, que ha permitido brindar apoyo particular a los estudiantes en etapa inicial. Este piloto, ha permitido, además, formular un Sistema de Alertas Tempranas, para atención oportuna de los riesgos de deserción. El diseño, ejecución y puesta en marcha del Programa tienen como fundamento el Proyecto Educativo Institucional (1992), el Paradigma Pedagógico Ignaciano (1993), las estrategias para el fortalecimiento académico y la integración social de estudiantes (Swail, 2003) y la Guía para la Implementación de Educación Superior del Modelo de Gestión de Permanencia y Graduación Estudiantil en Instituciones de Educación Superior del Ministerio de Educación Nacional (2015)

QUANTIFYING THE RELATIONSHIP BETWEEN CONTRACTION EFFICIENCY AND MUSCLE SIZE ACROSS THE ADULT LIFESPAN

Alejandra Barrera-Curiel1, Ryan J. Colquhoun2, Jesus A. Hernandez-Sarabia1, & Jason M. DeFreitas1 1Oklahoma State University, Stillwater, OK; 2University of South Alabama, Mobile, AL The neuromuscular system undergoes a natural structural and functional degradation associated with aging. Since the size of a muscle affects its stiffness, the age-related reduction in muscle mass may result in decreased contraction speed and efficiency. PURPOSE: To quantify the relationship between muscle size and contraction efficiency, as measured by electromechanical delay (EMD), across the adult lifespan. METHODS: Seventy-five adults between 18 and 84yrs.old were included in this study. Panoramic ultrasound images were taken from each participants’ rectus femoris (RF). Muscle cross-sectional area was defined and measured as the area of interest that included as much muscle as possible (mCSA; cm2). In addition, surface electromyographical (EMG) signals were recorded from the RF while ten tendon taps were delivered to the patellar tendon. EMD was calculated as the time (s) between EMG onset and torque on set during the evoked reflex contractions. Bin widths were utilized to condense data, where subjects were grouped based on their age as follows: 18 –29 yrs. (n = 37), 30 -39 (n = 7), 40 –49 (n = 4), 50 –59 (n = 9), 60 –69 (n = 5) and \u3e70 (n = 4). Polynomial regression(2ndorder) was performed to fit the apparent curvilinear relationship between EMD and mCSA. RESULTS: As can be appreciated in the figure below, EMD slowed and mCSA decreased with age. However, the relationship between EMD and mCSA was not significant (r = -0.57, p-value = 0.55). CONCLUSION: Surprisingly, EMD was not significantly related to mCSA. It is possible that this may be due to the middle-aged groups being underpowered, which led to an outlier bin (40-49 yrs. old). Additionally, are flex contraction was used to measure EMD which might differ from the properties of a voluntary contraction. Further analyses might be needed to study the relationship between EMD and mCSA

DOES IPSILATERAL MOTOR CORTEX ACTIVITY DURING UNILATERAL FATIGUE EXPLAIN THE DEFICITS IN THE NON-FATIGUED LIMB?

Jesus A. Hernandez-Sarabia1, Alejandra Barrera-Curiel1, Micheal J. Luera1, Jason M. DeFreitas1; 1Oklahoma State University, OK Performing unilateral contractions to exhaustion has been shown to lead to force deficits of both the exercised and unexercised limbs. Although limb muscles are controlled by the contralateral hemisphere of the brain, neuroimaging studies have also shown slight activation of the ipsilateral motor cortex during unilateral tasks. However, whether cortical activity of the ipsilateral hemisphere might, in part, be responsible for the force decrements in the non-fatigued limb remains unknown. PURPOSE: To quantify the relationship between changes in maximal voluntary contraction (MVC) of the non-fatigued limb, and oxyhemoglobin (HbO) changes in the ipsilateral motor cortex during a fatiguing task. METHODS: Eleven subjects (M±SD 20.8±1.14 yrs.) performed two maximal voluntary isometric knee extensions of the left leg before (MVCpre) and after fatiguing protocol (MVCpost). The fatiguing protocol consisted of repeated, 50-second long isometric knee extensions with the right leg at 30% MVC until failure. During the fatigue protocol, hemodynamic responses of the motor cortex were recorded at a sampling rate of 5.81 HZ using a continuous-wave functional near infrared spectroscopy system (fNIRS). Raw fNIRS signals were processed and converted to hemoglobin concentrations using HomER2 software, and the peak HbO (HbOpeak) was obtained from the final contraction before failure. MVCpre and MVCpost were used to calculate the percentage of change in maximal force from the fatiguing task (MVCdiff). A Pearson’s correlation between HbOpeak and MVC diff was calculated using SPSS. RESULTS: Paired samples t-test showed a significant difference (p \u3c.05) between MVCpre (828.34±238.8 N) and MVCpost (743.99±227.56 N). Pearson’s correlation between HbOpeak (2.93±1.86E-8) of the ipsilateral motor cortex and MVCdiff (-9.86±12.11 %) of the unexercised leg was not statistically significant (R = -0.368, p = .265). CONCLUSION: We hypothesized that peaks in oxyhemoglobin on the ipsilateral motor cortex during a fatiguing task would explain, to some extent, the force deficits in the unexercised leg. It is worth noting that this study was underpowered for a correlation. However, it is also possible that if the contralateral force deficit is indeed due to neural factors, that it is not cortical in origin

Cross-education: effects of age on rapid and maximal voluntary contractile characteristics in males

Purpose The purpose of this study was to determine the effect of age on the cross-education of rapid and maximal contractile properties for the knee extensors. Methods Young (n = 10; age = 21.1 ± 1.7 years) and older (n = 10; age = 65.3 ± 8.3 years) males performed unilateral isokinetic resistance training (RT) of the knee extensors for 4 weeks. Maximal voluntary isokinetic (45° s−1 and 300° s−1) and isometric testing was conducted for the trained and untrained leg before and after RT. Peak torque (PT) and acceleration were obtained from isokinetic testing as well as torque at 30 ms (TQ30) and 100 ms (TQ100) from the 45° s−1 contraction. PT and rate of torque development were recorded from the isometric contractions. Results Independent of age, isometric PT (10.1%; p = 0.006) as well as PT and acceleration at 300° s−1 (6.7%; p = 0.008 and 4.0%; p = 0.016, respectively) increased in the untrained leg. At 45° s−1, acceleration was increased (3.6%; p = 0.021), but PT remained unchanged (p = 0.227). TQ100 increased similarly between groups (4.5%; p = 0.014), but TQ30 increased only in the older group (9.5%; p = 0.022). Conclusions Cross-education of rapid and maximal contractile parameters can be achieved early during unilateral RT independent of age. These findings indicate the potential for particular unilateral RT protocols to be used for older adults in rehabilitative settings to offset disuse-related reductions in contractile function, which are most dramatic in this population

Measurement of low optical absorption in highly scattering media using the thermal lens effect

In this work we show that the thermal lens effect can be applied to highly scattering and weakly absorbing materials. We apply the thermal lens effect and the z-scan technique to estimate the effective absorption coefficient of a suspension of TiO$_2$ particles with a mean diameter of 220 nm at two wavelengths: 488 nm and 514 nm. From the effective absorption coefficient we estimate the absorption cross section of the particles

Formulación Del Programa De Prevención De La Deserción: Articulación De Acciones En Un Programa Transversal De Acompañamiento Para La Pontificia Universidad Javeriana

Tras identificar un incremento anual en la deserción de entre el 1% y el 2,4%, se ve la necesidad de formular un Programa que permita articular las acciones y servicios de atención y acompañamiento de la Universidad, con las herramientas para identificar oportunamente los riesgos de deserción. De esta manera, nace el Programa de Prevención de la Deserción (PPD) cuyo propósito es atender a tiempo situaciones de riesgo y vulnerabilidad individual, psicosocial, académico e institucional, que pueden tener incidencia en la deserción estudiantil. El PPD propone, además, fortalecer las acciones y servicios para la prevención de la deserción ya existentes, y promoverlas entre los miembros de la Comunidad Educativa que intervienen en los procesos de formación integral. En el marco de éste mismo, se inició un piloto de acompañamiento estudiantil en la Facultad de Ingeniería, que ha permitido brindar apoyo particular a los estudiantes en etapa inicial. Este piloto, ha permitido, además, formular un Sistema de Alertas Tempranas, para atención oportuna de los riesgos de deserción. El diseño, ejecución y puesta en marcha del Programa tienen como fundamento el Proyecto Educativo Institucional (1992), el Paradigma Pedagógico Ignaciano (1993), las estrategias para el fortalecimiento académico y la integración social de estudiantes (Swail, 2003) y la Guía para la Implementación de Educación Superior del Modelo de Gestión de Permanencia y Graduación Estudiantil en Instituciones de Educación Superior del Ministerio de Educación Nacional (2015)