Amphiphilic Janus Particles Confined in Symmetrical and Janus-Like Slits.

We use Monte Carlo simulations to investigate the behavior of Janus spheres composed of attractive and repulsive parts confined between two parallel solid surfaces. The slits with identical and competing walls are studied. The adsorption isotherms of Janus particles are determined, and the impact of the density in the pore on the morphology is discussed in detail. So far, this issue has not been systematically investigated. New, unique structures are observed along the isotherms, including the bilayer and three-layer structures located at different distances from the walls. We analyze how selected parameters affect the positional and orientational ordering in these layers. In some cases, the particles form highly ordered hexagonal lattices.

The influence of sedentary behaviour on lumbar-pelvic kinematics during squatting and forward bending among physically active students.

Prolonged sitting may involve several mechanisms that make it a risk factor for low back pain. The aim of this study was to investigate lumbar-pelvic kinematics and multifidus muscle (MF) activity during squatting and forward bending in relation to the sedentary behaviour of physically active students. Sixty-three students were divided into two groups according to the time spent in a sitting position during the day: 'high' (>7 h/day); 'low' (≤7 h/day). Lumbar-pelvic ratios, ranges of motion, angular velocities, and MF flexion-relaxation phenomenon were investigated. Data were obtained using the optical motion analysis system, and surface electromyography. The results indicated that lumbar-pelvic ratios during both tasks and velocity of lumbar spine during squatting were significantly greater in the 'high' than in the 'low' sitting group. Muscle activity showed no differences between groups. Prolonged sitting can be considered a factor that slightly, but statistically significantly influences the lumbar-pelvic kinematics in physically active people.Practitioner summary: Lumbar-pelvic kinematics can be altered by prolonged sitting in physically active students. Lumbar-pelvic ratios during squatting and forward bending and lumbar spine velocity during squatting were significantly greater in the 'high' than in the 'low' sitting group. Sedentary behaviour should be considered during an assessment of movement patterns.Abbreviations: BMI: body mass index; ERR: extension-relaxation ratio; FRP: flexion-relaxation phenomenon; FRR: flexion-relaxation ratio; IPAQ: International Physical Activity Questionnaire; LBP: low back pain; METs: metabolic equivalent of tasks; MF: multifidus muscle; PA: physical activity; ROM: range of motion; sEMG: surface electromyography.

Relationship of lumbar-hip kinematics during trunk flexion and sex, body mass index, and self-reported energy expenditure: a cross-sectional analysis.

PURPOSE: Physical activity (PA) is a well-known, simple and effective preventive and therapeutic intervention for low back pain (LBP). In spite of the growing interest in active lifestyles and its benefits, more needs to be known about the relationship between energy expenditure, body mass and lumbar-pelvic kinematics during the forward bending movement in a group of young asymptomatic people who met PA guidelines. Young people can be identified as a future risk group of civilisation diseases and lumbar-hip kinematics can be considered as a predictor of LBP occurrence. The aim of this study was to identify the association of gender, self-reported energy expenditure, body mass index, and lumbar-hip kinematics in young people. METHODS: Sixty-four students at pre-employment stage participated in the study. They declared moderate-to-high PA and activity-induced energy expenditure (AEE) was self-reported. Kinematic data of the lumbar spine, pelvis and hip were collected during forward bending using a 3D motion capture system. RESULTS: Sex was found to be associated with pelvis (ß = -0.38 p = 0.002) and lumbar mobility (ß = 0.49, p < 0.001) during forward bending and BMI was related only to lumbar mobility (ß = -0.41, p = 0.001). Recreation AEE significantly predicted hip flexion mobility (ß = 0.38, p = 0.002). CONCLUSIONS: This study showed that among a sample of physically active young people, BMI, self-reported AEE and sex can partially predict lumbar-hip kinematics during trunk flexion. Recreational PA can be regarded as improving hip mobility and thus making forward bending more effective and less prone to injury.

Altered squat movement pattern in patients with chronic low back pain.

INTRODUCTION AND OBJECTIVE: Low back pain (LBP) is a problem which causes human suffering and entails costs for treatment. Chronic LBP is considered a civilization diseases in developed countries and one of the major public health problem worldwide. Squatting is a part of such daily activities as sitting down, standing up or lifting objects. In this study, hip, knee, and ankle joint motions during squatting are analyzed in the sagittal plane. The aim of the study was to find a relationship between the function of the lower limb during squatting and LBP incidence. MATERIAL AND METHODS: Eleven healthy subjects and eight subjects suffering from low back pain were enrolled in tes study. Participants performed squat while maintaining heel contact with the ground throughout the movement. The participants attempted to make a squat as deep as possible. Kinematic data were captured using a Vicon optical motion capture system. RESULTS: The low back pain group had a greater range of motion of the hip and knee with reference to the ankle joint motion, compared to the control group. There was no statistically significant difference in ankle dorsiflexion between groups. Control group reached maximal ankle dorsiflexion at higher point of descent than LBP group. CONCLUSIONS: The findings support the hypothesis that the strategy of movement is different in subjects with and without back pain. They may suggest that subjects with low back pain in maximal squat use the hip joint and knee joint to a greater extent than subjects without back pain, with comparable ankle dorsiflexion. Clinicians should take into consideration the influence of ankle motion and timing on exercise biomechanics in persons suffering from low back pain.

Sex-dependent differences in single-leg squat kinematics and their relationship to squat depth in physically active individuals.

The purpose of this study is to compare recreationally physically active females and males with regard to spine, pelvis and lower limb joints peak angles in each plane of motion during a single leg squat (SLS). The second aim is to investigate the relationship between kinematics and SLS depth in females and males. Fifty-eight healthy, young adults performed 5 repetitions of a single right leg squat to maximal depth while keeping their balance. Kinematic data were obtained using an optical motion capture system. At the hip, greater adduction and greater internal rotation were observed in females than in males. Females had more extended spines and less outward bended knees throughout the SLS than did men. In males, squat depth was significantly, positively correlated with the maximal angle of the ankle (r = 0.60, p < 0.001), the knee (r = 0.87, p < 0.001), the hip (r = 0.73, p < 0.001) and the pelvis (r = 0.40, p = 0.02) in the sagittal plane. A positive significant correlation was found between SLS depth and maximal angle of the knee (r = 0.88, p < 0.001) and the ankle (r = 0.53, p = 0.01) in the sagittal plane in females. Males and females used different motor strategies at all levels of the kinematic chain during SLS.

How Are Squat Timing and Kinematics in The Sagittal Plane Related to Squat Depth?

The aim of this study was to analyze the relationship of range of motion (ROM) in the sagittal plane and timing parameters during a bodyweight squat to the depth of the squat. Sixty participants (20 females and 40 males) took part in this study. They were instructed to perform a bodyweight squat to the maximal depth position. Kinematic data were obtained using the optical motion capture system. The time for the descent phase of squatting was normalized from 0% (initial position, start of movement) to 100% (squat position-stop of movement). The ROM of ankle, knee, hip, pelvis and spine in the sagittal plane and the normalized time when the maximum joint angles occurred during the descent were analyzed to investigate the relationship between them and the squat depth in males and females. The knee ROM contributed most significantly, from all joints to squatting depth in both females and males (r = 0.92, p < 0.001). The squat depth was related to lumbar, hip and knee motion in females and to all kinematics parameters in males. Maximal ankle dorsiflexion and pelvis anterior tilt were reached earlier than the maximal angles of knee, hip and spine during squatting. Pelvis and ankle timing was negatively correlated with the squat depth (rs = -0.64, p < 0.001 and rs = -0.29, p = 0.02, respectively). This suggests that pelvis and ankle timing can be important to keeping balance during squatting and can lead to achieving the desired depth.

Bioelectrical Activity of Vastus Medialis and Rectus Femoris Muscles in Recreational Runners with Anterior Knee Pain.

Patellofemoral pain syndrome (PFPS), the most common source of knee pain among physically active individuals, is defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peri-patellar pathology. Differences in the activation and endurance of the quadriceps components, causing an imbalance in the forces controlling patellar tracking during flexion and extension in the knee joint, appear to be the most commonly reported risk factors for PFPS. The aim of this study was to determine the differences in bioelectric activity of vastus medialis and rectus femoris muscles during half knee bend position in runners with PFPS. The sample comprised 20 recreational runners (15 males, 5 females; aged 27 ± 5 years) reporting knee pain and diagnosed with PFPS. The age- and sex-matched control group consisted of recreational runners who did not report knee pain. The myon electromyographic system was used to determine the changes in the electromyographic median frequency during a half squat position. The decrease in the median frequency of vastus medialis and rectus femoris muscles was significantly greater in runners with PFPS in comparison to the control group (p < 0.01 for right and left vastus medialis and right rectus femoris; p < 0.05 for left rectus femoris). There is a relationship between knee pain related to PFPS and the imbalance of bioelectric activity of vastus medialis and rectus femoris muscles. Achieving the muscular balance within the thigh muscles can be an important factor in the rehabilitation process of PFPS.

What factors can affect lumbopelvic flexion-extension motion in the sagittal plane?: A literature review.

Clinicians use forward bending and backward return in routine clinical examinations for evaluating spine mobility. The magnitude and timing of lumbar spine and pelvic contributions have been described in the literature as lumbopelvic rhythm. There is still limited knowledge about the factors which can determinate lumbar and hip mobility and coordination in the sagittal plane. The aim of this study is to demonstrate those factors contributing to the lumbopelvic rhythm and to explain the differences observed between subjects. The studies included in the review present possible explanations of observed lumbar-pelvic motion and/or coordination. They measure movement of the lumbar spine, the pelvis and/or the hip in the sagittal plane. The search was conducted in August 2017. Two databases (PubMed and Web of Science) were searched. The search identified 126 potentially relevant articles (53 in PubMed, 73 in Web of Science). Initial screening based on titles and abstracts retrieved 35 articles. The second stage of selection involved reading the full texts of articles. Twenty-four papers were selected in this stage. After careful bibliographic study, seven papers were added for this review, resulting in a total of 31. This literature review demonstrates those factors contributing to lumbopelvic motion. Age and gender, hamstring muscle tightness, feet position, muscle fatigue, movement speed and external loading as well phase of motion can affect various aspects of lumbopelvic rhythm.