Can incline treadmill walking protocol be augmented by visual perturbation for physical therapy use?

Purpose/Hypothesis: Incline treadmill walking (ITW) has been used in different patients receiving physical therapy. Given the critical role of visual information in human locomotion, integrating visual perturbation (VP) to treadmill training could induce the challenge to patients, magnifying the training effects. However, literature regarding how VP influences muscle activation during ITW is limited. Knowledge gaps exist in whether and how the muscle is modulated by the systematically manipulated visual information. We hypothesized that VP could increase muscle activation during ITW, and larger VP could elicit higher muscle activation. Number of subjects: 28 healthy young adults (20-33 years old). Experiment One (EXP1): 12 females, 6 males. Experiment Two (EXP2): 7 females, 3 males. Materials/Methods: A virtual moving corridor was projected in front of the treadmill to display optic flow, and the VP was created by rotating the optic flow. EXP1: The subjects were instructed to walk on the treadmill at the preferred walking speed for 8 conditions (two visual conditions: normal and VP; four inclinations of treadmill: 0,3,6,9-degree) with 2 minutes each. In the normal condition, the optic flow was in concert with the walking speed. In the VP condition, the optic flow rotated for 180˚ at 20˚/s. EXP2: There were 4 conditions on the 9-degree incline treadmill, consisting 360˚ rotating VP at 4 different speeds (10˚, 20˚, 30˚, 60˚/s). All the other settings were the same as EXP1. For both experiments, the surface electromyography (EMG) was used to record the muscle activation of quadriceps, hamstring, tibialis anterior (TA) and gastrocnemius of the right leg. Root-mean-square of the EMG (RMS-EMG) was calculated at the stance phase, swing phase and the total gait cycle. Results: In EXP1, For the TA, the RMS-EMG of VP condition was higher than normal condition (P=0.004) at the stance phase, whereas no significant difference for other gait events. The VP effects were evident for the 12 females. With limited samples in EXP2, the individual descriptive analysis was used and indicated that 6 females and 1 male exhibited higher TA activation at 60˚ VP compared to 10˚ VP at the stance phase. Conclusions: Integrating VP into ITW could elicit specific muscle response. VP increased the TA activation at the stance phase during ITW, and this effect was found dominantly in females. Specifically, higher magnitude of VP could elicit higher TA activation. Clinical Relevance: The effect of ITW regarding muscle activation could be augmented by adding environmental challenges, such as virtual optic flow. VP could be integrated into ITW to elicit specific muscle activation; however, the magnitude of VP needs to be considered based on the expected outcome of training. The gender difference on responding to VP might lead to additional consideration in designing the ITW protocol. Further research is warranted to confirm such unexpected gender discrepancy

科幻．時空．後九七：以「時空」角度論譚劍《人形軟件》的本土回應

譚劍是香港中最重要的科幻作家之一，尤其在倪匡封筆後的科幻邊緣中，他以富有時代意識的科幻寫作，展現後倪匡科幻的獨特面貌。本文分析的《人形軟件》寫就於後九七，除通俗娛樂之外，藉由「空間」與「時間」的切入點，也可見其書寫涉及對香港當時「本土／全球」處境的各種未來想像，當中「本土」並非固定不變，而是能與「全球」的外來文化結合，有著再生成的可能。譚劍就以此賽博龐克科幻，作為未來的預言回應著後九七。 本文可分為四個部分，首個部分先介紹作家，並從香港科幻的邊緣處境開始論述，定位譚劍於香港科幻的位置以及研究意義；第二部分探討在後九七語境下，《人形軟件》以賽博朋克科幻回應香港的方法，以及貼合賽博朋克類型的切入點；第三部分承接上章，以「時空」角度切入文本，從「虛擬香港」、「銅鑼灣911」、「村上病毒」和「來記麵家」四點，看其中對後九七「本土／全球」的想像與預言；第四章為結論，總結全文重點

Gender-Specific Effects on Muscle Activation During Incline Treadmill Walking: A Virtual Perturbation Study For Future Astronauts

Introduction Microgravity-induced muscle atrophy is a critical issue for astronauts in spaceflight [1]. To overcome neuromuscular deconditioning, combining virtual reality (VR) with treadmill training protocol could be a promising countermeasure for astronauts to enhance muscle activities and maximize the training effect [2]. Our previous study [3] found the presence of visual perturbation significantly increased muscle activation while walking on incline treadmill, compared with no visual perturbation; surprisingly, we found females had more pronounced muscle responses than males. Based upon these findings, this study aimed to investigate the effects of different visual rotation speeds and different types of visual perturbation on muscle activation during incline treadmill walking, and how those effects were different between males and females. Methods A total of 20 healthy young adults (10 males and 10 females) participated this study. The normal VR scene was a virtual moving corridor, and its direction and speed were in accordance with the walking speed of the participant on the 9-degree incline treadmill; the participant would feel like walking through an endless corridor. Visual perturbation was created by adding clockwise rotation of the VR in constant or random angular speed. For the constant speed rotation, there were four different rotation speeds at 10°/s, 20°/s, 30°/s, and 60°/s respectively. For the random speed rotation, the rotation speed would change every 360° and was randomly selected at the range of 10°/s and 60°/s. The participant walked in each condition for two minutes. The wireless electromyography sensors were placed at the vastus lateralis (VL), medial hamstring (MH), tibialis anteriors (TA) and lateral gastrocnemius (LG) of the right leg. Multivariate Analysis of Variance (MANOVA) was applied, with the RMS values of VL, MH, TA and LG as the four dependent variables. The analysis was conducted separately for the total gait cycle, and during stance phase and swing phase. Results Increased visual rotation speed of visual perturbation induced higher VL and LG activation; gender had different responses to increased visual rotation speed in VL. The effect of different types of visual perturbation was more pronounced in female, as random speed rotation visual perturbation induced higher MH activation than not only normal VR but also constant speed rotation visual perturbation. Conclusion Integrating visual perturbation into regular treadmill exercise could magnify the training effects to reduce muscle deconditioning for astronauts during spaceflight. The visual rotation speed of visual perturbation should be taken into consideration based on the expected outcome of training. The gender effects revealed different muscle responses between males and females to visual perturbation, which need to be considered and furtherly explored to identify the optimal training countermeasure for astronauts

Housing Price Dispersion: An Empirical Investigation

price dispersion, search models, macroeconomic factor, time aggregation

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

Combining a non-immersive virtual reality gaming with motor-assisted elliptical exercise increases engagement and physiologic effort in children

A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author's publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.Virtual reality (VR) gaming is promising in sustaining children’s participation during intensive physical rehabilitation. This study investigated how integration of a custom active serious gaming with a robot-motorized elliptical impacted children’s perception of engagement (Intrinsic Motivation Inventory), physiologic effort (i.e., exercise speed, heart rate, lower extremity muscle activation), and joint kinematics while overriding the motor’s assistance. Compared to Non-VR condition, during the VR-enhanced condition participants’ perceived engagement was 23% greater (p = 0.01), self-selected speed was 10% faster (p = 0.02), heart rate was 7% higher (p = 0.08) and muscle demands increased. Sagittal plane kinematics demonstrated only a small change at the knee. This study demonstrated that VR plays an essential role in promoting greater engagement and physiologic effort in children performing a cyclic locomotor rehabilitation task, without causing any adverse events or substantial disruption in lower extremity joint kinematics. The outcomes of this study provide a foundation for understanding the role of future VR-enhanced interventions and research studies that weigh/balance the need to physiologically challenge a child during training with the value of promoting task-related training to help promote recovery of walking

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

Chapter 9: Biomechanics

Biomechanics is a discipline. A discipline deals with understanding, predicting, and explaining phenomena within a content domain, and biomechanics is the study of the human body in motion. By applying principles from mechanics and engineering, biomechanists are able to study the forces that act on the body and the effects they produce (Bates, 1991). Hay (1973) describes biomechanics as the science that examines forces acting on and within a biological structure and the effects produced by such forces, whereas Alt (1967) describes biomechanics as the science that investigates the effect of internal and external forces on human and animal bodies in movement and at rest. Each of these definitions describes the essential relationship between humans and mechanics found in biomechanics