The effect of inclination on lower extremity inter-joint coordination during treadmill walking

Purpose/Hypothesis: Inclined walking is a challenging daily task in comparison with level walking. It requires specific control from central nervous system and exhibits increases in muscle activities and alternations of joint kinematics in lower extremities. However, the knowledge of the inclination effect on the inter-joint coordination is limited. Previous studies have shown the benefits of investigating the inter-joint coordination in patients with Parkinson’s disease, low back pain and hemiplegic gait. This study aimed to evaluate such coordination in healthy young adults during inclined walking. Number of Subjects: 19 healthy young adults (13 females, 6 males; aged 22 – 29 yrs) Materials/Methods: Subjects walked at their comfortable speeds for 2 minutes in four inclined treadmill walking conditions (0%, 5%, 10%, and 15% grade). Three-dimensional kinematics data were captured at 100 Hz by an eight-camera Qualisys motion capture system. To calculate the inter-joint coordination, the phase portraits were created by plotting the specific segment’s angular position versus its angular velocity. The trajectories of these phase portraits were converted from Cartesian coordination to polar coordination to get phase angles. These phase angles were used to calculate the continuous relative phase (CRP) dynamics during a gait cycle between two segments which contained the same joint center. A mean absolute value of the ensemble CRP curve values (MARP) was calculated by averaging the absolute values of all points of the entire ensemble curve. Low MARP indicated that two segments approached to in-phase and vice versa. A two-way repeated ANOVA with Bonferroni correction was used to determine the effect of inclination and the effect of segmental combinations (shank-thigh and foot-shank) on MARP. Results: There was a significant interaction between the effect of inclination and the effect of segmental combinations on MARP (F(3,108) = 85.85, p \u3c 0.001). The MARP of foot-shank combination was lower than that of shank-thigh combination when walking on 0% grade (p \u3c 0.001, approximately 26% less) and on 5% grade (p \u3c 0.001, approximately 28% less). However, the MARP of foot-shank combination was higher than that of shank-thigh combination when walking on 10% grade (p \u3c 0.001, approximately 26% more) and on 15% (p \u3c 0.001, approximately 55% more). Conclusions: When the grade increased to a certain level, the inter-joint coordination changed to a different pattern during treadmill walking. Clinical Relevance: Inclined treadmill walking could be used for lower extremity strengthening, gait training, and cardiopulmonary conditioning. The inclination of walking should challenge the patients properly without increased risk. Our study provided a further understanding of inclination effect on gait pattern and could be used as a reference for clinical decision making. This result suggested that the pattern of the inter-joint coordination changed when the grade was between 5% to 10%. Therefore, for population with a higher fall risk, such as older adults, below 5% grade might be recommended

The use of immersive 360 videos to induce different strategies of postural control

Purpose/Hypothesis: Visual perception is a decision-making process of the central nervous system based on recognitions of relative distances and velocities between objects. With the input from visual perception, an appropriate postural control is applied to maintain balance. Previous studies on how visual perception affects the postural control were only in one direction. Therefore, this study used immersive 360° videos to identify how visual perception affects the postural control in multiple directions. We hypothesized that video with more turns could induce more ML body sway, and video with higher elevation could induce more AP body sway. Number of Subjects: Nineteen healthy young adults (20-31 years; 12 females). Materials/Methods: A Wii Board (Nintendo, Redmond, WA) was used to measure body sway. A smart phone placed in a pair of goggles displayed three 360° videos: 1) a static room (baseline); 2) a roller coaster (MA) at a height of 205 feet with two intense hills, several small hills and one helix; and 3) a roller coaster (PA) at a height of 149 feet with one intense hill, one big loop and one quick corkscrew. Three standing trials on the Wii Board and three sitting trials on the Wii Board placed on a chair were randomly performed. After each trial, subject rated their fear of falling (FOF) by using visual analog scale. Dependent variables were body sway range (distance in AP and ML directions of the center of pressure trajectory) and FOF grading (0-100). Two two-way repeated measures ANOVA were used to examine the interactions between the postural effect (sit/stand) and the visual effect (three videos) on body sway range and FOF. Results: A significant interaction was found in body sway range in AP (p=0.02) and ML directions (p=0.009). The post-hoc comparisons indicated that body sway range was larger in standing than sitting in both directions (pAP=0.008, pML\u3c0.001). Baseline body sway range in AP direction was smaller than in viewing MA (p=0.016) but no difference than in viewing PA (p=0.05). However, in ML direction, baseline body sway range was smaller than in viewing both MA (p=0.01) and PA (p=0.002). Both PA and MA induced higher FOF than baseline (p\u3c0.001), and the FOF was higher in viewing PA than MA (p=0.016). Conclusions: Different 360° videos induced different postural control strategies in AP and ML directions in young adults. The visual perception affected more in ML than AP direction. Based on the active control hypothesis, higher level of imbalance requires higher active control to maintain balance. Increasing FOF indicated that 360° videos could pose an environment with certain postural threat, and rotational roller coaster induced higher FOF than taller roller coaster. Clinical Relevance: Since ML direction is more sensitive to postural threat, ML balance training for patients with compromised balance should be emphasized to reduce falls risk. The immersive 360° video could be a useful tool in generating challenging environments for clinical use and research

Declined Treadmill Walking Eliminates Asymmetric Walking Pattern in Healthy Young Adults

Background: Human locomotion is flexible in any environment, and this fact has been proven when walking on different speeds in each leg on the split-belt treadmill. However, during the split-belt walking, participant’s locomotor behaviors are passively adopted by a motor-driven treadmill. Therefore, how humans actively adjust the flexibility of locomotion is still limited by using the split-belt treadmill. Our current study investigated the flexibility of locomotion by using ankle weight on the dominant leg to induce asymmetric walking pattern when walking on a regular treadmill. We hypothesized that the level of active control would increase to adapt the asymmetric walking in all different kinds of inclinations. Number of Subjects: Twenty healthy young participants (age: 24.7 ± 2.2 years; height: 1.73 ± 0.08 m; mass: 68.92 ± 12.07 kg, 12 females and 8 males) were recruited for this study. Materials/Methods: Six conditions (walking on the level treadmill, 15% inclined treadmill, 15% declined treadmill with/without wearing 4-lb ankle loading on the dominant leg) were randomly assigned to participants. A motion capture system and reflective markers were used to collect data. The markers were placed on the heel and toe of both legs to measure step length symmetric index (SLS) and step time symmetric index (STS). SLS = (SL_non_dominant_leg - SL_dominant_leg)/(SL_non_dominant_leg + SL_dominant_leg); STS = (ST_non_dominant_leg - ST_dominant_leg)/(ST_non_dominant_leg + ST_dominant_leg). A two-way repeated measures ANOVA was used to investigate interaction between effect of unilateral limb loading and the effect of different locomotor conditions on SLS and STS. The significant level was set at 0.05. Results: There was a significant interaction between the effect of ankle loading and the effect of inclinations on SLS and STS (p \u3c 0.0001). The post hoc results indicated that unilateral ankle loading caused the asymmetric walking pattern when walking on the level and inclined treadmill but not on the declined treadmill. This phenomenon could be explained by that participants increased their active control of lower leg during declined treadmill walking to eliminate the effect of unilateral ankle loading by reducing the step length and step time. Conclusions: Walking on the declined surface could induce a higher level of active control than walking on level and an inclined surface. Clinical Relevance: To our best knowledge, this is the first study to demonstrate that walking on the declined surface eliminated the asymmetric walking pattern in young adults. It has been shown that training patients with stroke on a split-belt treadmill reduced their asymmetric walking pattern during overground walking. However, this learning effect disappeared after approximately ten strides or less due to different levels of active control. The current result illustrates the possibility of training on the declined treadmill to regain symmetric walking pattern in patients who walk asymmetrically

Locomotor Sensory Organization Test: How Sensory Conflict Affects the Temporal Structure of Sway Variability During Gait

When maintaining postural stability temporally under increased sensory conflict, a more rigid response is used where the available degrees of freedom are essentially frozen. The current study investigated if such a strategy is also utilized during more dynamic situations of postural control as is the case with walking. This study attempted to answer this question by using the Locomotor Sensory Organization Test (LSOT). This apparatus incorporates SOT inspired perturbations of the visual and the somatosensory system. Ten healthy young adults performed the six conditions of the traditional SOT and the corresponding six conditions on the LSOT. The temporal structure of sway variability was evaluated from all conditions. The results showed that in the anterior posterior direction somatosensory input is crucial for postural control for both walking and standing; visual input also had an effect but was not as prominent as the somatosensory input. In the medial lateral direction and with respect to walking, visual input has a much larger effect than somatosensory input. This is possibly due to the added contributions by peripheral vision during walking; in standing such contributions may not be as significant for postural control. In sum, as sensory conflict increases more rigid and regular sway patterns are found during standing confirming the previous results presented in the literature, however the opposite was the case with walking where more exploratory and adaptive movement patterns are present

Minocycline markedly reduces acute visceral nociception via inhibiting neuronal ERK phosphorylation

<p>Abstract</p> <p>Background</p> <p>Minocycline prevents the development of neuropathic and inflammatory pain by inhibiting microglial activation and postsynaptic currents. But, how minocycline obviates acute visceral pain is unclear. The present study investigated whether minocycline had an any antinociceptive effect on acetic acid-induced acute abdominal pain after intraperitoneal (i.p.) administration of saline or minocycline 1 hour before acetic acid injection (1.0%, 250 μl, i.p.).</p> <p>Results</p> <p>Minocycline (4, 10, or 40 mg/kg) significantly decreased acetic acid-induced nociception (0-60 minutes post-injection) and the enhancement in the number of c-Fos positive cells in the T5-L2 spinal cord induced by acetic acid injection. Also, the expression of spinal phosphorylated extracellular signal-regulated kinase (p-ERK) induced by acetic acid was reduced by minocycline pre-administration. Interestingly, intrathecal introduction of PD98059, an ERK upstream kinase inhibitor, markedly blocked the acetic acid-stimulated pain responses.</p> <p>Conclusions</p> <p>These results demonstrate that minocycline effectively inhibits acetic acid-induced acute abdominal nociception via the inhibition of neuronal p-ERK expression in the spinal cord, and that minocycline may have therapeutic potential in suppressing acute abdominal pain.</p

Enhancing Fundamental Robot-Assisted Surgical Proficiency by Using a Portable Virtual Simulator

Background. The development of a virtual reality (VR) training platform provides an affordable interface. The learning effect of VR and the capability of skill transfer from the VR environment to clinical tasks require more investigation. Methods. Here, 14 medical students performed 2 fundamental surgical tasks—bimanual carrying (BC) and peg transfer (PT)—in actual and virtual environments. Participants in the VR group received VR training, whereas participants in the control group played a 3D game. The learning effect was examined by comparing kinematics between pretraining and posttraining in the da Vinci Surgical System. Differences between VR and playing the 3D game were also examined. Results. Those who were trained with the VR simulator had significantly better performance in both actual PT (P = .002) and BC (P \u3c .001) tasks. The time to task completion and the total distance traveled were significantly decreased in both surgical tasks in the VR group compared with the 3D game group. However, playing the 3D game showed no significant enhancement of fundamental surgical skills in the actual PT task. The difference between pretraining and posttraining was significantly larger in the VR group than in the 3D game group in both the time to task completion (P = .002) and the total distance traveled (P = .027) for the actual PT task. Participants who played the 3D game seemed to perform even worse in posttraining. Conclusions. Training with the portable VR simulator improved robot-assisted surgical skill proficiency in comparison to playing a 3D game

Magnesium Intake in Relation to Systemic Inflammation, Insulin Resistance, and the Incidence of Diabetes

OBJECTIVETo investigate the long-term associations of magnesium intake with incidence of diabetes, systemic inflammation, and insulin resistance among young American adults.RESEARCH DESIGN AND METHODSA total of 4,497 Americans, aged 18–30 years, who had no diabetes at baseline, were prospectively examined for incident diabetes based on quintiles of magnesium intake. We also investigated the associations between magnesium intake and inflammatory markers, i.e., high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), and fibrinogen, and the homeostasis model assessment of insulin resistance (HOMA-IR).RESULTSDuring the 20-year follow-up, 330 incident cases of diabetes were identified. Magnesium intake was inversely associated with incidence of diabetes after adjustment for potential confounders. The multivariable-adjusted hazard ratio of diabetes for participants in the highest quintile of magnesium intake was 0.53 (95% CI, 0.32–0.86; Ptrend < 0.01) compared with those in the lowest quintile. Consistently, magnesium intake was significantly inversely associated with hs-CRP, IL-6, fibrinogen, and HOMA-IR, and serum magnesium levels were inversely correlated with hs-CRP and HOMA-IR.CONCLUSIONSMagnesium intake was inversely longitudinally associated with incidence of diabetes in young American adults. This inverse association may be explained, at least in part, by the inverse correlations of magnesium intake with systemic inflammation and insulin resistance

Identification of multiple rare variants associated with a disease

Identifying rare variants that are responsible for complex disease has been promoted by advances in sequencing technologies. However, statistical methods that can handle the vast amount of data generated and that can interpret the complicated relationship between disease and these variants have lagged. We apply a zero-inflated Poisson regression model to take into account the excess of zeros caused by the extremely low frequency of the 24,487 exonic variants in the Genetic Analysis Workshop 17 data. We grouped the 697 subjects in the data set as Europeans, Asians, and Africans based on principal components analysis and found the total number of rare variants per gene for each individual. We then analyzed these collapsed variants based on the assumption that rare variants are enriched in a group of people affected by a disease compared to a group of unaffected people. We also tested the hypothesis with quantitative traits Q1, Q2, and Q4. Analyses performed on the combined 697 individuals and on each ethnic group yielded different results. For the combined population analysis, we found that UGT1A1, which was not part of the simulation model, was associated with disease liability and that FLT1, which was a causal locus in the simulation model, was associated with Q1. Of the causal loci in the simulation models, FLT1 and KDR were associated with Q1 and VNN1 was correlated with Q2. No significant genes were associated with Q4. These results show the feasibility and capability of our new statistical model to detect multiple rare variants influencing disease risk

Linking Changes in Epithelial Morphogenesis to Cancer Mutations Using Computational Modeling

Most tumors arise from epithelial tissues, such as mammary glands and lobules, and their initiation is associated with the disruption of a finely defined epithelial architecture. Progression from intraductal to invasive tumors is related to genetic mutations that occur at a subcellular level but manifest themselves as functional and morphological changes at the cellular and tissue scales, respectively. Elevated proliferation and loss of epithelial polarization are the two most noticeable changes in cell phenotypes during this process. As a result, many three-dimensional cultures of tumorigenic clones show highly aberrant morphologies when compared to regular epithelial monolayers enclosing the hollow lumen (acini). In order to shed light on phenotypic changes associated with tumor cells, we applied the bio-mechanical IBCell model of normal epithelial morphogenesis quantitatively matched to data acquired from the non-tumorigenic human mammary cell line, MCF10A. We then used a high-throughput simulation study to reveal how modifications in model parameters influence changes in the simulated architecture. Three parameters have been considered in our study, which define cell sensitivity to proliferative, apoptotic and cell-ECM adhesive cues. By mapping experimental morphologies of four MCF10A-derived cell lines carrying different oncogenic mutations onto the model parameter space, we identified changes in cellular processes potentially underlying structural modifications of these mutants. As a case study, we focused on MCF10A cells expressing an oncogenic mutant HER2-YVMA to quantitatively assess changes in cell doubling time, cell apoptotic rate, and cell sensitivity to ECM accumulation when compared to the parental non-tumorigenic cell line. By mapping in vitro mutant morphologies onto in silico ones we have generated a means of linking the morphological and molecular scales via computational modeling. Thus, IBCell in combination with 3D acini cultures can form a computational/experimental platform for suggesting the relationship between the histopathology of neoplastic lesions and their underlying molecular defects