Lower Body Movements Research Articles

Resistance exercise training and invitro skeletal muscle oxidative capacity in older adults.

Whether resistance exercise training (RET) improves skeletal muscle substrate oxidative capacity and reduces mitochondrial production of reactive oxygen species in older adults remains unclear. To address this, 19 older males (≥60 years) were randomized to a RET (n = 11) or to a waitlist control group (n = 8) that remained sedentary for 12 weeks. RET was comprised of three upper body and four lower body movements on resistance machines. One set of 8–12 repetitions to failure of each movement was performed on three nonconsecutive days/week. Improvements in chest press and leg press strength were assessed using a three‐repetition maximum (3 RM). Body composition was assessed via dual energy X‐ray absorptiometry. Muscle biopsies were obtained from the vastus lateralis muscle at baseline and at both 3 weeks and 12 weeks. Palmitate and pyruvate oxidation rates were measured from the 14 CO 2 produced from [1‐14C] palmitic acid and [U‐14C] pyruvate, respectively, during incubation of muscle homogenates. PGC‐1α, TFAM, and PPAR δ levels were quantified using qRT‐PCR. Citrate synthase (CS) and β‐HAD activities were determined spectrophotometrically. Mitochondrial production of reactive oxygen species (ROS) were assessed using the Amplex Red Hydrogen Peroxide/Peroxidase assay. There were no significant changes in body weight or body composition following the intervention. Chest press and leg press strength (3RM) increased ~34% (both P < 0.01) with RET. There were no significant changes in pyruvate or fatty acid oxidation or in the expression of target genes with the intervention. There was a modest increase (P < 0.05) in β HAD activity with RET at 12 weeks but the change in CS enzyme activity was not significant. In addition, there were no significant changes in ROS production in either group following RET. Taken together, the findings of this study suggest that 12 weeks of low volume RET does not increase skeletal muscle oxidative capacity or reduce ROS production in older adults.

Relationship between trunk and foot accelerations during walking in healthy adults

Understanding upper body and lower body segment relationships may be an important step in assessing stability during gait. This study explored the relationship between acceleration patterns at the trunk and at the foot during treadmill walking at self-selected pace in healthy adults. Forty healthy subjects walked on a treadmill for 3 minutes at self-selected speed. Root mean square (RMS) and approximate entropy (ApEn) were derived from the acceleration time series at the trunk and at the foot in the frontal and sagittal plane. RMS of accelerations at the trunk were strongly correlated with RMS values at the foot in the sagittal plane (r=0.883, p<0.01) and in the frontal plane (r=0.811, p<0.01). ApEn values at the trunk were moderately correlated with ApEn values at the foot in the sagittal plane (r=0.603, p<0.01) only. These results show that acceleration variability at the foot is related to acceleration variability at the trunk, specifically that increased variability at the foot is tied to increased variability at the trunk in healthy adults. Portable inertial sensors can potentially be used in any environment including a laboratory, clinic, or at home to measure lower and upper body segment motion, and assessing relationships between upper and lower body motion may provide a more comprehensive evaluation of overall stability.

Comparison of Biomechanical Characteristics for the Skill Level in Cycle Pedaling

Objective: This study aimed to compare biomechanical data between elite and beginner cyclists during cycle pedaling by performing a comparative analysis and to provide quantitative data for both pedaling performance enhancement and injury prevention. Methods: The subjects of this study included 5 elite cyclists (age: <TEX>$18{\pm}0years$</TEX>, body mass: <TEX>$64.8{\pm}9.52kg$</TEX>, height: <TEX>$173.0{\pm}4.80cm$</TEX>) and 5 amateur cyclists (age: <TEX>$20{\pm}0years$</TEX>, mass: <TEX>$66.6{\pm}2.36kg$</TEX>, height: <TEX>$175.6{\pm}1.95cm$</TEX>). The subjects pedaled on a stationary bicycle mounted on rollers of the same gear (front: 50 T and rear: 17 T = 2.94) and cadence of 90. The saddle height was adjusted to fit the body of each subject, and all the subjects wore shoes with cleats. In order to obtain kinematic data, 4 cameras (GR-HD1KR, JVC, Japan) were installed and set at 60 frames/sec. An electromyography (EMG) system (Telemyo 2400T, Noraxon, USA) was used to measure muscle activation. Eight sets of data from both the left and right lower extremities were obtained from 4 muscles (vastus medialis oblique [VMO], vastus lateralis oblique [VLO], and semitendinosus [Semitend], and lateral gastrocnemius [Gastro]) bilaterally by using a sampling frequency of 1,500 Hz. Five sets of events (<TEX>$0^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$180^{\circ}$</TEX>, <TEX>$270^{\circ}$</TEX>, and <TEX>$360^{\circ}$</TEX>) and 4 phases (P1, P2, P3, and P4) were set up for the data analysis. Imaging data were analyzed for kinematic factors by using the Kwon3D XP computer software (Visol, Korea). MyoResearch XP Master Edition (Noraxon) was used for filtering and processing EMG signals. Results: The angular velocity at <TEX>$360^{\circ}$</TEX> from the feet was higher in the amateur cyclists, but accelerations at <TEX>$90^{\circ}$</TEX> and <TEX>$180^{\circ}$</TEX> were higher in the elite cyclists. The amateur cyclists had greater joint angles at <TEX>$270^{\circ}$</TEX> from the ankle and wider knee joint distance at <TEX>$0^{\circ}$</TEX>, <TEX>$180^{\circ}$</TEX>, and <TEX>$360^{\circ}$</TEX> than the elite cyclists. The EMG measurements showed significant differences between P2 and P4 from both the right VLO and Semitend. Conclusion: This study showed that lower body movements appeared to be different according to the level of cycle pedaling experience. This finding may be used to improve pedaling performance and prevent injuries among cyclists.

Exploration of the validity of the two-dimensional sagittal plane assumption in modeling the standing long jump

Most previous standing long jump studies have been based on the assumption of two-dimensional sagittal plane motion with bilateral symmetry. The purpose of this study was to investigate the validity of this assumption. Standing long jump trials were collected using six adult male participants. Each participant stood with a foot on each of two force plates and performed eight standing long jumps for maximal distance. Inverse dynamics analyses were performed for two-dimensional (2D) and three-dimensional (3D) models, and joint moments, powers, and work values were compared. The differences between these models with respect to the validity of the common planar jumping assumption were analyzed. Good agreement was observed between 2D and 3D methods for the lower body, with minimal differences in sagittal plane moments, power, and work for the ankle, knee, and lower back. There were significant, but relatively small differences in the sagittal plane kinematics and kinetics at the hip. For the upper body, the results contradicted the sagittal plane assumption in that significant moments and power were generated about the abduction/adduction axis of the shoulder and a similar amount of work was performed about both abduction/adduction and flexion/extension axes of the shoulder. The elbow also showed significant differences in power and work. These results indicate that an assumption of planar motion should be sufficient for many studies of the standing long jump that only examine lower body movement. However, for studies that include upper body motion, diagnosing injury risk, or investigating gender differences, a 3D model may be more appropriate.

UWB-Aided Inertial Motion Capture for Lower Body 3-D Dynamic Activity and Trajectory Tracking

This paper introduces a novel method for simultaneous 3-D trajectory tracking and lower body motion capture (MoCap) under various dynamic activities such as walking and jumping. The proposed method uses wearable inertial sensors fused with an ultrawideband localization system using a cascaded Kalman filter-based sensor fusion algorithm, which consists of a separate orientation filter cascaded with a position/velocity filter. In addition, to further improve the joint angle tracking accuracy, anatomical constraints are applied to the knee joint. Currently, available self-contained inertial tracking methods are not only drift-prone over time but also their accuracy is degraded under fast movements with unstable ground contact states due to the lack of external references. However, our experimental results, which benchmark the system against a reference camera-based motion tracking system, show that the proposed fusion method can accurately capture the dynamic activities of a subject without drift. The results show that the proposed system can maintain similar accuracies between fast and slow motions in lower body MoCap and 3-D trajectory tracking. The obtained accuracies of the system for 3-D body localization and knee joint angle tracking for fast motions were less than 5 cm and 2.1°, respectively.

Kinematic Model-Based Pedestrian Dead Reckoning for Heading Correction and Lower Body Motion Tracking.

In this paper, we present a method for finding the enhanced heading and position of pedestrians by fusing the Zero velocity UPdaTe (ZUPT)-based pedestrian dead reckoning (PDR) and the kinematic constraints of the lower human body. ZUPT is a well known algorithm for PDR, and provides a sufficiently accurate position solution for short term periods, but it cannot guarantee a stable and reliable heading because it suffers from magnetic disturbance in determining heading angles, which degrades the overall position accuracy as time passes. The basic idea of the proposed algorithm is integrating the left and right foot positions obtained by ZUPTs with the heading and position information from an IMU mounted on the waist. To integrate this information, a kinematic model of the lower human body, which is calculated by using orientation sensors mounted on both thighs and calves, is adopted. We note that the position of the left and right feet cannot be apart because of the kinematic constraints of the body, so the kinematic model generates new measurements for the waist position. The Extended Kalman Filter (EKF) on the waist data that estimates and corrects error states uses these measurements and magnetic heading measurements, which enhances the heading accuracy. The updated position information is fed into the foot mounted sensors, and reupdate processes are performed to correct the position error of each foot. The proposed update-reupdate technique consequently ensures improved observability of error states and position accuracy. Moreover, the proposed method provides all the information about the lower human body, so that it can be applied more effectively to motion tracking. The effectiveness of the proposed algorithm is verified via experimental results, which show that a 1.25% Return Position Error (RPE) with respect to walking distance is achieved.

Gender-Based Differences in Trunk and Shoulder Biomechanical Changes Caused by Prolonged Repetitive Symmetrical Lifting

OCCUPATIONAL APPLICATIONS This study indicates that males and females altered their lifting technique equivalently over time, as they fatigued. Time-dependent changes in lifting mechanics were dependent on the phase of the lifting task. At the initiation of the lift from the floor, participants adapted to increasing trunk fatigue by altering their lower body movements to help maintain a more upright trunk posture. When placing the load on the chest height shelf, participants seemed to adapt to growing upper extremity fatigue by holding the load closer to the body, using more elbow flexion, and less upper arm extension. As a result of this adaptation, participants began to use more forward lean. Therefore, as participants fatigued, they seemed to sacrifice balance (more leaning) in order to preserve muscular capability, which was diminishing with fatigue. This suggests that fatigued lifters may not only be at an increased risk of suffering from an overexertion injury, but they may also be more likely to suffer a slip or fall.TECHNICAL ABSTRACT Background: People working in repetitive manual materials handling jobs are at an increased risk of developing spine and shoulder injuries. To address this concern, it is important to understand how different factors, such as gender, can affect the loading on the body when performing high risk repetitive lifting tasks. Purpose: The purpose of this study was to determine if males and females altered their lifting mechanics in similar ways when exposed to a prolonged fatiguing bout of lifting. Method: Thirty-one participants (n = 15 female) performed a repetitive lifting task for 75 minutes. Isometric shoulder and trunk strength were measured pre- and post-lifting, while upper body kinematics were recorded throughout. Results: Exposure time had a similar effect on lifting kinematics for males and females. At the lift origin, participants transitioned over time toward a posture that had a mean (SD) of 7.2° (2.6°) less torso flexion. At the lift destination, participants transitioned toward a posture with 5.9° (1.7°) less shoulder flexion and 10.1° (2.3°) more elbow flexion. Such changes were consistent with a goal of trying to bring the load closer to the torso. Additionally, isometric strength decreased following the 75-minute lifting protocol by 7.9 (1.2) Nm and 52.4 (10.9) Nm at the shoulder and trunk, respectively. Conclusions: Both males and females adapted their kinematics similarly over time, during repetitive lifting. This study suggests that kinematic adaptions may be driven by participants' consideration of the changing relative demands on their body (e.g., increasing fatigue). The presence of kinematic adaptions, in both males and females, invites the opportunity to consider movement analysis methods as a screening tool for detecting fatigue in the workplace. The ability to recognize and address fatigue earlier may help ergonomists in reducing overexertion-based work related injuries.

The Influence of Motor Imagery on Postural Sway: Differential Effects of Type of Body Movement and Person Perspective

The present study examined the differential effects of kinesthetic imagery (first person perspective) and visual imagery (third person perspective) on postural sway during quiet standing. Based on an embodied cognition perspective, the authors predicted that kinesthetic imagery would lead to activations in movement-relevant motor systems to a greater degree than visual imagery. This prediction was tested among 30 participants who imagined various motor activities from different visual perspectives while standing on a strain gauge plate. The results showed that kinesthetic imagery of lower body movements, but not of upper body movements, had clear effects on postural parameters (sway path length and frequency contents of sway). Visual imagery, in contrast, had no reliable effects on postural activity. We also found that postural effects were not affected by the vividness of imagery. The results suggest that during kinesthetic motor imagery participants partially simulated (re-activated) the imagined movements, leading to unintentional postural adjustments. These findings are consistent with an embodied cognition perspective on motor imagery.

Biomechanical Analysis of Straight and Cross Stroke on Smash &amp; Drop Motion in Women Badminton Player

Purpose: The purpose of this study is to analyze the kinematic and the kinetic variables of smash and drop motions in women of college badminton teams by dividing motions into straight and cross ones. Furthermore, its has another purpose that badminton instructors, coaches and leaders can training with scientific and effective ways. Methods: In order to analyze the players smash and drop motions, four video cameras recorded their play. We calculated swing time, racket head velocity, joint angle, joint angular velocity by analyzing motion data by Kwon3D XP program and the displacement of ground reaction force(GRF) from captured force data. Results & Conclusion: First, the motion of straight smash motion is faster than straight drop motion and cross drop motion is faster than the cross smash motion statically. Second, the speed of racket head velocity was shown faster in smash action. In order to play the smash action, shuttle cock must be made a maximum speed of impact on the racket with accurate overhead swing; to play the drop shot action, it must be made a similar performing action as smash but it should reduce the swing speed. Third, in order to play the strong and delicate techniques, the racket should be played gradually from the highest point of the back swing to impact by the angle of trunk, the shoulder joint angle, elbow joint angle, wrist joint angle. Finally, although there was no significant difference in the maximum size of left and right, front and backward, the upper and lower ground reaction force of stroke of badminton, the lower body movement by step is the important factor in badminton motion.

선수용 사이클 웨어의 착용 실태 조사 - 국내 남자 고등학교 사이클 선수를 중심으로 -

This study investigates the actual domestic and overseas cyclewear wearing conditions for male high school cyclists. The study results provide factors and degree of dissatisfaction as basic data for cyclewear development. This study was conducted on 35 male high school cyclists (freshman to seniors) by a questionnaire and interview method. Study results were: Male high school cyclists considered functionality as most important when they bought cyclewear and the brand they most often bought was a cheap domestic brand. Dissatisfaction with the crotch, thigh circumference and minimum leg circumference was higher than other parts during wearing. A cyclist is more sensitive to wear because they require more lower body motion than other parts. Cyclewear should be: less transformed even by frequent laundering, made of breathable material and use a sewing technique that minimizes air resistance and increases fit the body. Functional pads ergonomically designed with high tactile materials should be developed to prevent 'saddle sore' and groin soreness region that happens because of a lower body bending posture when cycling. A follow-up study is recommended to further develop excellence in cyclewear functionality and dimension suitability for male high school cyclists through the size system.

Energy Cost and Enjoyment of Active Videogames in Children and Teens: Xbox 360 Kinect.

New active videogames (AVGs) may provide youth an alternative to traditional play. The purpose of this study was to compare the physical activity energy expenditure (PAEE), intensity, and enjoyment of AVGs with those of seated videogames (SVGs). Youth (8-17 years old) volunteered to play a random selection of six (two SVGs, four AVGs) videogames for 6-10 minutes each. Prior to participation, height, weight, and resting metabolic rate (RMR) were measured. A portable metabolic analyzer was worn during the games to measure total energy expenditure, and PAEE was calculated as (total energy expenditure - measured RMR). An accelerometer was worn on the right hip to measure intensity in counts/minute and steps/minute. Youth were classified as child (8-12 years old) versus teen (13-17 years old), healthy weight (body mass index [BMI] <85th percentile) versus overweight (BMI ≥85th percentile), and male versus female. A three-way mixed-model analysis of variance was used to compare differences in PAEE (metabolic equivalents [METs] and kcal/minute) with sex, weight status, and age group as main effects, including Bonferroni's adjustment. Most AVGs were moderate to vigorous intensity (4.6±0.1 METs; range, 2.8-6.6 METs), where steps/minute (lower-body movement) was positively related to PAEE (R(2)=0.68). All SVGs were classified as light intensity (1.7±0.0 METs). PAEE (kcal/minute) was significantly higher during AVGs and for teens, males, and overweight youth. There was no significant difference in enjoyment between AVGs and SVGs. AVGs elicited sufficient energy cost to be a suitable alternative for traditional play and may contribute to the recommended dose of physical activity, particularly in teens, males, and overweight youth.

Lower body motion analysis to detect falls and near falls on stairs

Purpose We present a methodology to automatically detect falls on stairs, an application of computer vision and machine learning techniques with major real-world importance. Falls on the stairs, in particular, are a common cause of injury among older adults. Comprehending the conditions under which accidents take place could significantly aid in the prevention of falls, support independent living, and improve quality of life.t.

Impact of firefighter gear on lower body range of motion

Purpose – The purpose of this paper is to investigate the incremental impact of firefighter’s personal protective equipment (PPE) on lower body range of motion (ROM) while walking to suggest areas of design improvement for enhanced mobility and safety. Design/methodology/approach – Eight male and four female firefighters participated in the study. Lower body ROM was assessed while they walked in four different configurations of PPE, including turnout ensemble, a self-contained breathing apparatus (SCBA) and boots. The impact of each added PPE item, and gender differences were statistically analyzed. Findings – Wearing firefighter turnout ensemble and SCBA reduced ROM in the lower body in the sagittal and transverse planes. A significant reduction in ROM for anterior-posterior movement at the ankle and the ball of the foot was found while wearing rubber boots with turnout ensemble and SCBA. This puts firefighters at higher risk of experiencing foot injuries and physical strains. A significant increase in medial-lateral movement of the foot while wearing rubber boots may increase risk of ankle sprains. A greater reduction in ROM at the ankle and the ball of the foot for female firefighters may imply greater risk for women compared to men, while wearing boots. Practical implications – Reducing the inflexibility and bulkiness of boots is critical to improve firefighter’s lower body mobility and safety. Originality/value – This study implemented 3-D motion capture technology to analyze how wearing firefighting gear impacted lower body motion. It provides quantitative evidence to recommend ergonomic boot re-design.

Physical activity assessment in the general population; instrumental methods and new technologies.

The objective measurement of human movement and the quantification of energy expenditure due to physical activity is an identified need in both research and the clinical setting. Validated and well-defined reference methods (double labelled water, direct calorimetry, indirect calorimetry) are expensive and mostly limited to the laboratory setting. Therefore, in the last years, several objective measurement devices have been developed which are appropriate for field studies and clinical settings. There is no gold standard among them, as all have limitations. Pedometers are small, non-expensive, count the steps taken and give information on total physical activity, but not about physical activity patterns and behaviour. Accelerometers are expensive, save information about frequency and intensity of physical activity, but not about type of physical activity. Both pedometers and accelerometers only save information about lower body movement, but reliability about the estimation of energy expenditure is limited. Heart rate monitoring relates intensity to energy expenditure, but gives no information about physical activity. GPS watches are portable, relatively inexpensive, non-invasive and provide distance, speed, and elevation with exact time and location, but are maybe limited for the assessment of brief higher speed movement and energy expenditure. Combined motion sensors combine accelerometry with the measurement of physiological variables and share advantages of single devices and are more precise. Manufacturer software which applies activity-specific algorithms for the calculation of energy expenditure can affect energy expenditure results. Most of the devices estimate energy expenditure more accurately at light to moderate intensities; underestimation increases at very light and higher intensity activities.

Hybrid learning model and MMSVM classification for on-line visual imitation of a human with 3-D motions

In this paper, the on-line visual imitation of humanoid robot (HR) for human’s 3-D motions is developed. At the beginning, the 3-D motional sequences of a human is captured by a stereo vision system (SVS), which skeleton algorithm can capture and estimate the 3-D coordinates of fifteen main joints. Since the dynamic balance of the HR is not considered, the proposed on-line visual imitation is divided into two parts, lower body (LB) and upper body (UB). Eleven stable motions of LB with the developed feature vector based on the 3-D coordinates of head, left and right feet are classified by the proposed modified multi-class support vector machine (MMSVM). To confirm the effectiveness of MMSVM, it is also compared with the SVM based on error correcting output codes (ECOC). The imitation of UB is based on the inverse kinematics (IK) of two pairs of (hand, elbow). To enhance one-to-one mapping and to reduce the modeling complexity of IK, two arms of UB are partitioned into eight subwork spaces, and each one is approximated by a pre-trained hybrid learning model. The comparisons between hybrid learning model based and ordinary IKs are also made. Combining the classified motion of LB with the operated IK motion of UB accomplishes the task of imitating the 3-D motions of a human. Finally, the corresponding experiments are presented to validate the effectiveness and practicality of the proposed method.

3D 아바타 동작의 선택 제어를 통한 감정 표현

In this paper, an intuitive emotional expression of the 3D avatar is presented. Using the motion selection control of 3D avatar, an easy-to-use communication which is more intuitive than emoticon is possible. 12 pieces different emotions of avatar are classified as positive emotions such as cheers, impressive, joy, welcoming, fun, pleasure and negative emotions of anger, jealousy, wrath, frustration, sadness, loneliness. The combination of lower body motion is used to represent additional emotions of amusing, joyous, surprise, enthusiasm, glad, excite, sulk, discomfort, irritation, embarrassment, anxiety, sorrow. In order to get the realistic human posture, BVH format of motion capture data are used and the synthesis of BVH file data are implemented by applying the proposed emotional expression rules of the 3D avatar.

Joint Kinetics While Walking on an Irregular Sloped Surface

Occupations, such as railroad work, which requires the worker to perform job functions on irregular surfaces are physically taxing. Previous research and epidemiology have suggested a potential link between walking surface characteristics and injury. However, to date few studies have investigated the impact of irregular surfaces, flat or sloped, on gait dynamics. The current study investigated gait dynamics on a sloped irregular surface in twenty healthy adult men. The participants walked along 2 distinct sloped surfaces [No Ballast (NB), and Mainline Ballast (MB)]. Lower body motion, ground reaction forces, and electromyographic (EMG) signals from lower extremity muscles were collected. Three dimensional joint moments were calculated at the hip, knee and ankle during the down slope step on the walking surfaces. Parameters of interest were moment ranges. Results showed joint moment ranges were generally larger for MB compared to that of NB in the down slope leg. The results suggested walking on ballast increases joint moments at the ankle and knee of the down slope leg during walking on an irregular sloped surface.

스테레오 카메라를 이용한 지능형 보행보조로봇의 개발

용자 보행 추종 성능을 실험적으로 검증하였다. Abstract: This paper describes the development of a walking assistive robot for effective self-rehabilitation for elderly people facing an inconvenience in walking. The main features of the developed robot are enhanced safety and mobility using the baby walker and electric wheelchair mechanisms and an accurate walking tracking control algorithm using potentiometers and stereo cameras. Specifically, a pelvis supporter is designed to prevent the user from falling down and reduce the burden on their legs, and electric motors are used for easy locomotion with low effort. Next, the walking intention and direction of the user are automatically recognized by using potentiometers attached at the pelvis supporter so that the robot can track the user, and the rapidity and accuracy of the tracking were increased by applying a lower-body motion analysis algorithm with stereo cameras. Finally, the user-tracking performance of the developed robot was experimentally verified through stepwise walking assistance experiments.

Promoting Children's Health with Digital Games: A Review of Reviews.

Effective, evidence-based, and interesting methods are needed for children's health promotion. Digital games can be such a method, but there is need for a summary of the evidence on the effectiveness of digital games in promoting children's health. The aim of this review of reviews was to evaluate the quality of systematic reviews, to summarize the evidence in systematic reviews and reviews related to the effectiveness of digital games in children's health promotion, and to identify gaps in knowledge. A systematic literature search was conducted in May-August 2013 from relevant databases, and 1178 references were found. In total, 15 systematic reviews and reviews met the inclusion criteria. Most of the systematic reviews were found to be medium quality on the AMSTAR checklist. Most commonly, systematic reviews and reviews evaluated active videogames. According to the results, evidence of the highest level and quality seems to support an increase in physical activity to light to moderate levels and energy expenditure, especially when playing active videogames that require both upper and lower body movements. In addition, sedentary games were shown to have potential in children's health education, especially in supporting changes in asthma- and diabetes-related behavior and in dietary habits. However, there are still several gaps in the knowledge. There is a need for further high-quality systematic reviews and research in the field of health games.

Temporal Characteristics of High-Frequency Lower-Limb Oscillation during Freezing of Gait in Parkinson's Disease.

A cardinal feature of freezing of gait (FOG) is high frequency (3–8 Hz) oscillation of the legs, and this study aimed to quantify the temporal pattern of lower-body motion prior to and during FOG. Acceleration data was obtained from sensors attached to the back, thighs, shanks, and feet in 14 Parkinson's disease patients performing timed-up-and-go tasks, and clinical assessment of FOG was performed by two experienced raters from video. A total of 23 isolated FOG events, defined as occurring at least 5 s after gait initiation and with no preceding FOG, were identified from the clinical ratings. The corresponding accelerometer records were analyzed within a 4 s window centered at the clinical onset of freezing. FOG-related high-frequency oscillation (an increase in power in the 3–8 Hz band >3 SD from baseline) followed a distal to proximal onset pattern, appearing at the feet, shanks, thighs, and then back over a period of 250 ms. Peak power tended to decrease as the focus of oscillation moved from feet to back. There was a consistent delay (mean 872 ms) between the onset of high frequency oscillation at the feet and clinical onset of FOG. We infer that FOG is characterized by high frequency oscillation at the feet, which progresses proximally and is mechanically damped at the torso.