1. Investigación

This study aimed to analyze the position of the lumbopelvic region and lumbar muscle activity in the most common breastfeeding positions. We recorded the curvatures of the lumbar spine and pelvis by means of an electrogoniometer, and the muscle activation levels of the erector spinae with electromyography, in 34 women in erect standing and breastfeeding their children in several positions. Both side lying and clutch-hold positions showed a greater degree of lumbar spine flexion compared to standing. In all sitting postures it was observed that the pelvis was placed in retroversion when compared to standing and side lying. In muscle activity, it was observed that the activation intensity of the right erector in the right side-supported side lying position was significantly lower compared to the rest of breastfeeding postures and standing. Side lying may be a better position to avoid muscle fatigue.

Background: Flexion-relaxation response of the lumbar erector spinae has been previously studied after different interventions such as exercise programs or spinal manipulation, in subjects with chronic low back pain. The objective of the study was to investigate the effects of an isolate myofascial release protocol on erector spinae myoelectric activity and lumbar spine kinematics in chronic low back pain. Methods: Thirty-six participants, with nonspecific chronic low back pain, were randomized to myofascial release group (n=18) receiving four sessions of myofascial treatment, each lasting 40 minutes, and to control group (n=18) receiving a sham myofascial release. Electromyographic and kinematic variables as well as pain and disability questionnaires were analyzed. Findings: There was a bilateral reduction of the flexion relaxation ratio in individuals receiving myofascial release and who did not show myoelectric silence at baseline (right difference M = .34, 95% CI [0.16, 0.33], p ≤ .05 and left difference M = .45, 95% CI [0.16, 0.73], p ≤ .05). There was also a significant reduction in pain in the myofascial release group (difference M = −9.1, 95% CI [−16.3, −1.8], p ≤ .05) and disability (difference M = −5.6, 95% CI [−9.1, −2.1], p ≤ .05), compared with control group. No significant differences between groups were found for the kinematic variables. Interpretation: The myofascial release protocol contributed to the normalization of the flexion- relaxation response in individuals who did not show myoelectric silence before the intervention, and also showed a significant reduction in pain and disability compared with the sham group.

Background. This study aimed to identify which maximum voluntary isometriccontraction (MVIC) and sub-MVIC tests produce the highest activation of the erectorspinae muscles and the greatest reduction in inter-individual variability, to put themforward as reference normalization maneuvers for future studies.Methods. Erector spinae EMG activity was recorded in 38 healthy women during fivesubmaximal and three maximal exercises.Results. None of the three MVIC tests generated the maximal activation level in allthe participants. The maximal activation level was achieved in 68.4% of cases with thetest performed on the roman chair in the horizontal position (96.3±7.3;p<0.01).Of the five submaximal maneuvers, the one in the horizontal position on the romanchair produced the highest percentage of activation (61.1±16.7;p<0.01), and oneof the lowest inter-individual variability values in the normalized signal of a trunkflexion-extension task.Conclusions. A modified Sorensen MVIC test in a horizontal position on a romanchair and against resistance produced the highest erector spinae activation, but not in100% of participants, so the execution of several normalization maneuvers with thetrunk at different inclinations should be considered to normalize the erector spinaeEMG signal. A modified Sorensen test in a horizontal position without resistance isthe submaximal maneuver that produces the highest muscle activation and the greatestreduction in inter-individual variability, and could be considered a good reference testfor normalization.

Introduction: Impact force generates acceleration waves that travel through the body, and possible relationships may be exist between these acceleration waves and injuries. Several studies have analyzed the impact forces on the lower limb in healthy subjects wearing unstable shoes, but there is not accelerometric study analyzing the transmission of these impact forces along the locomotive system. The aim of the present study is to compare the acute effects of wearing unstable shoes (US) vs traditional shoes (TS), on maximum vertical acceleration, impact attenuation, cadence and stride length during gait. Methods: Fourty-three asymptomatic adults participated in the cross-sectional study. Subjects underwent gait analysis with simultaneously collecting heel and tibia peak acceleration, impact magnitude and acceleration rate, as well as shock attenuation and stride parameters (stride length, stride rate). Results: The results showed that wearing US increased cadence (10.99 steps/min; p<0.01), and decreased stride length (0.04 m; p<0.01). Additionally, an increase in maximum tibia peak acceleration, tibia impact magnitude and tibia acceleration rate were reported in the US condition compared to the TS condition, with a decrease of tibia attenuation in the US (p<0.05). Conclusion: Regarding shockwave transmission of ground reaction forces, a lower shock attenuation from the heel to the tibia was reported in the US vs TS condition. Bearing this in mind, it should be pointed that, while it is not yet clear if increased tibia acceleration is harmful to the musculoskeletal system, the US should be used with caution. / Introducción: La fuerza de impacto genera ondas de aceleración que viajan a través del cuerpo, pudiendo existir una relación entre estas ondas y determinados tipos de lesión. Varios estudios han analizado las fuerzas de impacto en el miembro inferior, en sujetos sanos empleando calzado inestable, pero no existen estudios que analicen la transmisión de las aceleraciones a lo largo del aparato locomotor. El objetivo del presente estudio es comparar los efectos agudos del uso de calzado inestable (US) frente al calzado tradicional (TS), sobre la aceleración máxima vertical, la atenuación del impacto, la cadencia y la longitud de la zancada durante la marcha. Método: Cuarenta y tres adultos asintomáticos participaron en el estudio transversal. Los sujetos fueron analizados durante la marcha con la recogida simultánea de la aceleración máxima del talón y la tibia, la magnitud del impacto y la ratio de aceleración, así como la disminución del impacto y determinados parámetros durante la zancada (longitud, frecuencia). Resultados: Los resultados mostraron que el uso de US aumentó la cadencia (10,99 pasos/min; p<0,01) y disminuyó la longitud de la zancada (0,04 m; p<0,01). Adicionalmente, se muestra un aumento en la aceleración máxima, la magnitud del impacto y la ratio de aceleración en la tibia con el calzado US en comparación con la condición de TS, con una disminución en la tibia en los US (p<0.05). Conclusión: La disminución del impacto desde el talón hasta la tibia en la condición de US frente a TS fue menor. Teniendo esto en cuenta, debe señalarse que aunque no está claro si el aumento de la aceleración de la tibia es perjudicial para el sistema musculoesquelético, los US deberían ser empleados con precaución.

Unstable shoe was developed as a walking device to strengthen the lower extremity muscles and reduce joint loading. A large number of studies have reported in asymptomatic adults increased electromyography (EMG) activity throughout the gait cycle in most of the lower limb muscles. However, no previous studies have explored the effects of wearing unstable shoes on trunk muscle activity in patients with chronic low back pain (CLBP). Therefore, the aim of the present study was to compare trunk muscle activity during gait using an unstable shoe and a conventional flat control shoe in patients with CLBP. Thirty-five CLBP patients (51.1±12.4 yrs.; 26±3.8 kg/m2; 9.3±5.2 Roland Morris Disability Questionnaire score) were recruited from the Orthopedic Surgery Service at the Hospital to participate in this cross-sectional study. All participants underwent gait analysis by simultaneously collecting surface electromyography (EMG) data from erector spinae (ES), rectus abdominis (RA), obliquus internus (OI) and obliquus externus (OE) muscles, while walking on a treadmill with flat control shoes and experimental unstable shoes. The results showed significantly higher %EMG activity in ES (mean difference: 1.8%; 95% confidence interval [CI] 1.3 to 2.2), RA (mean difference: 1.5%; 95% CI 0.3 to 2.7), and OI (mean difference: 1.5%; 95% CI 0.2 to 2.8) in the unstable shoes condition compared to the flat shoes condition. Based on these findings, the use of unstable shoes may have potential implications in promoting spine stability, particularly in improving neuromuscular control of trunk muscles in CLBP treatment.

Objective: To investigate the effects that wearing unstable shoes has on disability, trunk muscle activity, and lumbar spine range of motion (ROM) in patients with chronic lower back pain (CLBP). Design: Randomized controlled trial. Setting: Orthopedic Surgery Service. Participants: We randomized 40 adults with nonspecific CLBP either to an unstable shoes group (n = 20) or to the control group (n = 20). Intervention: The participants in the unstable shoes group were advised to wear these shoes for a minimum of six hours a day for four weeks. Control group participants were asked to continue wearing their regular shoes. Outcome measures: Our primary outcome was measurement of back-related dysfunction, assessed using the Roland-Morris Disability Questionnaire. Secondary outcomes included changes in electromyographic (EMG) activity of erector spinae (ES), rectus abdominis (RA), internus obliquus (IO), and externus obliquus (EO) muscles, and changes in lumbar spine ROM. Results: Between-group analysis highlighted a significant decrease in disability in the unstable shoes group compared to the control (−5, 95% confidence interval (CI) = −8.4 to −1.6). Our results revealed a significant increase in the percentage of RA, ES, IO, and EO EMG activity and in lumbar spine ROM in the unstable shoes group compared to the control group. Moreover, our results showed a significant negative correlation between disability and the percentage of ES, RA, and IO muscle activity at the end of the intervention.

The aim of this study was to analyze the position of the lumbopelvic region and the muscle activation of erector spinae and biceps femoris muscles in a group of pregnant women in the third trimester. The hypothesis was that pregnancy-related biomechanical and morphological changes modify the position of the lumbopelvic region and the activation of extensor muscles. The position of the lumbar spine and pelvis in the sagittal plane, and the EMG activity of the erector spinae and biceps femoris muscles, were recorded during standing in 34 nulliparous and 34 pregnant women in the third trimester, and also two months after birth in the group of pregnant women. No significant differences in the position of the lumbar spine or pelvis between the group of pregnant women and nulliparous or postpartum were observed. A significant increase was observed in the EMG activity of the erector spinae (4.6% vs 2.4% and 2.1% in the nulliparous group and postpartum respectively) and the biceps femoris (3.4% vs 1.2% and 1.4%) in pregnant women compared to the other two groups (p <0.01). We conclude that pregnant women in the third trimester show no alterations in lumbopelvic position compared to nulliparous and postpartum women. However, there is an increase of the EMG activity of the trunk extensors. These results indicate that the extensor muscles of the trunk show, in static positions, adaptive responses to the increase of anterior loads during pregnancy.