Analysis of dynamic standing foot force patterns in a normal male subject by characterization of microvector weight transfer sequences

Previous foot forceplate analyses in our laboratory have shown that postural sway in a normal male subject induces net weight transfers (microvectors) which have preferred directionalities, and that eye closure is characterized by increases in both the occurrence and magnitudes of these preferred microvectors. The same data generated from 8 x 8 blocks of eyes-open and eyes-closed trials were reanalyzed to examine microvector temporal sequences (i.e., macrovectors). Macrovectors were defined by the number of successive microvectors occurring along the same general direction, (anterior, posterior, right or left). Results suggest that with eye-closure, proprioceptive systems are unable to maintain lateral sway deviations within eyes-open limits. This instability increases lateral macrovector durations while only marginally affecting sagittal macrovector durations.     

The effects of task execution variables on resultant vertical ground reaction force acting on foot sole during squat lifting

The main objective of this study was to investigate the effects of task execution variables on the value and point of application of the resultant vertical ground reaction force acting on the foot sole during squat lifting. This can be of particular importance since it may help to recognize the roles of the foot sole parts in bearing the support force during industrial and labor lifting activities. Twelve healthy men lifted a box with 4, 8 and 12 kg masses at fast and slow speeds. Ground reaction force and center of pressure were measured using two parallel Kistler force-plates. In addition, a Vicon system and a 3D linked segment model were used to define the movement pattern. Significant increases resulted for the peak vertical ground reaction force with the increases in the lift speed (P < 0.05) and box weight (P < 0.05). As well a significant increase resulted for the range of center of pressure location with the increase in the box weight (P < 0.05). Moreover, significant interactions (P < 0.05) between the lift speed and box weight were detected. The front and rear parts of the foot had the most important roles in bearing the support force during the beginning and final phases of movement, respectively. Finally, it was concluded that the value and point of application of vertical ground reaction force are seemingly dependent on the momentum of the subject plus box.     

Asymétries chronométriques, cinétiques et cinématiques de l''initiation de la marche chez un sujet hémiplégique

OBJECTIVE: To investigate the temporal, kinetic and kinematic asymmetry of gait initiation in one subject with hemiplegia with an equinus varus foot. MATERIAL AND METHODS: A kinetic analysis with two AMTI force plates and a kinematic analysis with an ELITE optoelectronic system of gait initiation were performed in one subject with hemiplegia. RESULTS: The duration of the gait initiation phases was asymmetrical. The monopodal phase was shorter when the affected lower limb was supporting than when the healthy one was supporting. The propulsion resulted from the force exerted on the healthy lower limb. The distribution of body weight on the lower limbs was asymmetrical. Body weight support was more important on the healthy side than on the affected side. Maximal extension of the ankle on the hemiplegic side occurred during the swing phase. Ground clearance was increased by elevating the knee higher on the affected side than on the healthy side during the swing phase. Initial contact with the floor was performed with the foot flat on the affected side. CONCLUSION: This preliminary study has shown that gait initiation in one subject with hemiplegia was asymmetrical in kinetics and kinematics. The results concerning kinematics have not been reported previously for gait initiation in subjects with hemiplegia. The study of gait initiation should allow for better understanding postural and movement control strategies developed by patients with hemiplegia.     

基于F-Scan三维动态足底压力分析系统的动静态足底压力分析

背景:有研究表明足的部分解剖区域支撑着人体大部分质量,并调节着人体的平衡,测量这些区域的压强峰值及分布即可获取足、下肢乃至全身的生理、结构及功能等方面的大量信息。目的:观察健康青少年足球运动员自然行走时左右足峰力值、负荷冲量等的动态足底压力分布。方法:采用三维动态足底压力步态分析系统对16~19岁适龄青少年足球运动员进行动态足底压力测试。结果与结论:受试者足底应力-时间曲线呈明显的双峰型,足底10个分析区域峰力均值在足跟外侧最大(P<0.01),右足习惯者第1趾、第1,2跖骨、足跟内外侧区域平均峰力值右足大于左足(P<0.05),而第5跖骨、足弓2个区域平均峰力值左足大于右足(P<0.05)。受试者行走时整足接触阶段、离地阶段负荷中心在第1、2跖骨、足跟内外侧区域,足部最大负荷部位在第1、2跖骨、足跟内外侧区域,男女左右足分布规律基本一致。结果证实,健康青少年足球运动员左右足动态与静态足底压力分布规律存在一致性特征。     

Dynamic characteristics of a sport wheelchair

A single subject performed 36 coast-down trials on a hardwood floor in a sport model wheelchair with velocity ranging from 1.28 to 5.31 m/s (4.6 to 19.1 km/h). A portable computer attached to the wheelchair was used to record the time to the nearest 0.001-second of each half-revolution of a rear wheel. The deceleration during each trial was determined with an average coefficient of variation of 2.6 percent from linear regression of velocity versus time values. A significant relationship (r = 0.97) between deceleration and the square of the velocity was noted in an analysis of the values from the 36 trials. Total drag force and power was calculated as a function of wheelchair velocity from this relationship, indicating that the power output needed to propel the wheelchair increased as a function of the velocity cubed. It is speculated that this noted exponential increase in the energy cost of wheelchair propulsion at higher speeds was due mainly to an increase in air drag.     

Outcome evaluation of ankle osteoarthritis treatments: plantar pressure analysis during relatively long-distance walking

Background

This study aimed to use plantar pressure analysis in relatively long-distance walking for objective outcome evaluation of ankle osteoarthritis treatments, i.e., ankle arthrodesis and total ankle replacement.

Methods

Forty-seven subjects in four groups: three patient groups and controls, participated in the study. Each subject walked twice in 50-m trials. Plantar pressure under the pathological foot was measured using pressure insoles. Six parameters: initial contact time, terminal contact time, maximum force time, peak pressure time, maximum force and peak pressure were calculated and averaged over trials in ten regions of foot. The parameters in each region were compared between patient groups and controls and their effect size was estimated. Besides, the correlations between pressure parameters and clinical scales were calculated.

Findings

We observed based on temporal parameters that patients postpone the heel-off event, when high force in forefoot and high ankle moment happens. Also based on maximum force and peak pressure, the patients apply smoothened maximum forces on the affected foot. In ten regions, some parameters showed improvements after total ankle replacement, some showed alteration of foot function after ankle arthrodesis and some others showed still abnormality after both surgical treatments. These parameters showed also significant correlation with clinical scales in at least two regions of foot.

Interpretation

Plantar pressure parameters in relatively long-distance trials showed to be strong tools for outcome evaluation of ankle osteoarthritis treatments.     

Flat foot functional evaluation using pattern recognition of ground reaction data.

OBJECTIVE: Main purpose of this study was to apply quantitative gait analysis and statistical pattern recognition as clinical decision-making aids in flat foot diagnosis and post-surgery monitoring. DESIGN: Statistical pattern recognition techniques were applied to discriminate between normal and flat foot populations through ground reaction force measurements; ground reaction forces time course was assumed as a sensible index of the foot function. BACKGROUND: Gait analysis is becoming recognized as an important clinical tool in orthopaedics, in pre-surgery planning, post-surgery monitoring and in a posteriori evaluation of different treatment techniques. Statistical pattern recognition techniques have been utilized with success in this field to identify the most significant variables of selected motor functions in different pathologies, and to design classification rules and quantitative evaluation scores. METHODS: Ground reaction forces were recorded during free speed barefoot walks on 28 healthy subjects, and 28 symptomatic flexible flat foot children selected for surgical intervention. A new feature selection algorithm, based on heuristic optimization, was applied to select the most discriminant ground reaction forces time samples. A two-stage pattern recognition system, composed by three linear feature extractors, one for each ground reaction force component, and a linear classifier, was designed to classify the feet of each subject using the selected features. The output of the classifier was used to define a functional score. RESULTS: The classifier assigned the ground reaction force patterns performed by each subject into the right class with an estimated error of 15%, corresponding to an assignment error for each subject's foot of 9%. The most discriminant ground reaction forces time samples selected are in full agreement with the pathophysiology of the symptomatic flexible flat foot. The obtained score was utilized to monitor the 1 and 2 years post-operative functional recovery of two differently treated subgroups of 32 flexible flat foot subjects. CONCLUSIONS: Statistical pattern recognition techniques are promising tools for clinical gait analysis; the obtained score provides important functional information that could be used as a further aid in the clinical evaluation of flat foot and different surgical treatment techniques. RELEVANCE: Symptomatic flexible flat foot surgical decision making is frequently difficult because of the lack of objective criteria to assess functional abnormalities of the foot/ankle complex. Gait analysis and statistical pattern recognition can give us parameters with which to characterize "functional" flat foot. Moreover, we can objectively follow up the recovery of the foot/ankle complex function after surgical treatment.     

Balance performance, force production, and activity levels in noninstitutionalized men 60 to 90 years of age

The purpose of this study was to collect and analyze balance and muscle performance data obtained from 54 men aged 60 to 90 years. Balance was tested using the sharpened Romberg test (SR) and the one-legged stance test (OLST) on each foot with eyes open and eyes closed. A strain-gauge-based quantitative muscle tester (QMT) was used to measure force production. All torque values were normalized as a percentage of body weight. A self-report of activity level also was recorded. The results indicated that OLST scores and normalized torques of the hip flexors, extensors, and abductors had a positive correlation and that SR scores and normalized torques of the hip extensors and right hip abductors had a positive correlation. Subjects who considered themselves to be very active had a significantly higher SR eyes-closed balance time as compared with those who rated themselves as less active. Subjects who considered themselves to be very active also had significantly higher normalized torque values for most muscle groups tested. Negative relationships were shown between age and balance time and between age and force production.     

Foot loading characteristics of different graduations of partial weight bearing

Limited weight bearing of the lower extremity is a commonly applied procedure in orthopaedic rehabilitation after reconstructive forefoot surgery, trauma surgery and joint replacement. The most frequent limitations are given as percentage of body weight (BW) and represent 10 or 50% BW. The extent of foot loading under these graduations of partial weight bearing has not yet been described in detail. The objective of this study was to investigate forces at the foot-sole interface, which occur under graduated limitations of weight bearing. Peak pressure, maximum force, pressure-time integral and force-time integral (Pedar Cable) were assessed for a total of three trials with 10 healthy individuals. The results from limited weight bearing with 10 or 50% BW as taught by an experienced physiotherapist with a bathroom scale were referred to results of a normal gait. The limitation of weight bearing to 10% BW was equal to a bisection of peak pressure and maximum force for the total foot. Halved BW left a remaining 82% of peak pressure and 59% of maximum force for the total foot. We concluded that weight-bearing limitations to 10 and 50% BW lead to discernible differences in foot loading and may be applied to graduate forces of the lower limb for rehabilitation purposes. Foot loading with partial weight bearing exerts the percentage of BW and should be monitored to avoid an exertion of strains on the lower limb.     

Postural vasoconstriction in women during the normal menstrual cycle

1. Postural vasoconstriction in the foot was examined in 15 women during the menstrual, follicular and luteal phases of the menstrual cycle, and in 13 age-matched men on two separate occasions, in a constant-temperature environment (22 degrees C). 2. Skin blood flow was measured using laser Doppler flowmetry with the subject lying down, first with the foot maintained at heart level, then with the foot lowered passively 50 cm below the heart. In six of the women, at the time of experiment, serum oestradiol and progesterone were determined by radioimmunoassay. In four women and three men, foot swelling rate was also measured in the dependent foot using a strain gauge plethysmograph in addition to the postural changes in flow. At each visit, in all subjects, arterial blood pressure, heart rate, body temperature, foot skin temperature and body weight were also recorded. 3. The men showed no significant changes in all the variables assessed. In contrast, in women during the luteal phase diastolic and mean arterial pressures were significantly reduced, whereas heart rate, body temperature, foot skin temperature and body weight were significantly increased, as compared with the follicular and menstrual phases of the cycle. 4. During the follicular phase, when oestradiol concentration was high, there were significant reductions in dependent flow and foot swelling rate associated with a significantly augmented postural fall in flow, whereas during the luteal phase, when both oestradiol and progesterone levels were high, there were significant increases in dependent flow and foot swelling rate associated with a significantly impaired postural fall in flow.(ABSTRACT TRUNCATED AT 250 WORDS)     

A biomechanical analysis of posterior tibial tendon dysfunction,medial displacement calcaneal osteotomy and flexor digitorum longus transfer in adult acquired flat foot

Background

Biomechanical models have been used to study stress in the metatarsals, subtalar motion, lateral column lengthening and subtalar arthroereisis. Posterior tibial tendon dysfunction has been associated with increased loads in the arch of the acquired flat foot. We examine whether a 10 millimeter (mm) medial displacement calcaneal osteotomy and flexor digitorum longus transfer to the navicular reduces these increased loads in the flat foot.

Methods

The response of a normal foot, a foot with posterior tibial tendon dysfunction, and a flat foot to an applied load of 683 Newton was analyzed using a multi-segment biomechanical model. The distribution of load on the metatarsals, the moment about each joint, the force on each of the plantar ligaments and the muscle forces were computed.

Findings

Posterior tibial tendon dysfunction results in increased load on the medial arch, which may cause the foot to flatten. A 10 mm medial displacement calcaneal osteotomy substantially decreases the load on the first metatarsal and the moment at the talo-navicular joint and increases the load on the fifth metatarsal and the calcaneal-cuboid joint. Adding the flexor digitorum longus transfer to the medial displacement calcaneal osteotomy has only a small effect on the flattened foot.

Interpretation

Our biomechanical analysis illustrates that when the foot becomes flat, the force on the talo-navicular joint increases substantially from its value for the normal foot, and that medial displacement calcaneal osteotomy can reduce this increased force back toward the value occurring in the normal foot. This study provides a biomechanical rationale for medial displacement calcaneal osteotomy treatments for posterior tibial tendon dysfunction.     

Where the BOLD signal goes when alpha EEG leaves

Previous studies using simultaneous EEG and fMRI recordings have yielded discrepant results regarding the topography of brain activity in relation to spontaneous power fluctuations in the alpha band of the EEG during eyes-closed rest. Here, we explore several possible explanations for this discrepancy by re-analyzing in detail our previously reported data. Using single subject analyses as a starting point, we found that alpha power decreases are associated with fMRI signal increases that mostly follow two distinct patterns: either 'visual' areas in the occipital lobe or 'attentional' areas in the frontal and parietal lobe. On examination of the EEG spectra corresponding to these two fMRI patterns, we found greater relative theta power in sessions yielding the 'visual' fMRI pattern during alpha desynchronization and greater relative beta power in sessions yielding the 'attentional' fMRI pattern. The few sessions that fell into neither pattern featured the overall lowest theta and highest beta power. We conclude that the pattern of brain activation observed during spontaneous power reduction in the alpha band depends on the general level of brain activity as indexed over a broader spectral range in the EEG. Finally, we relate these findings to the concepts of 'resting state' and 'default mode' and discuss how - as for sleep - EEG-based criteria might be used for staging brain activity during wakefulness.     

Mid foot kinetics characterize structural polymorphism in diabetic foot disease

BACKGROUND: Diabetic foot disease is characterized by progressive foot deformities that lead to amputation and disabling morbidity. The purpose is to investigate the classification of two distinct phenotypes of mid foot structural polymorphism in individuals using plantar kinetic and pressure distribution and tarsal bone density assessments. METHODS: Twenty-two individuals (26 ft) with diabetes mellitus, peripheral neuropathy and at least one mid foot deformity were compared to 29 age-, gender- and race-matched healthy controls (58 ft). Eleven subjects with diabetes mellitus and peripheral neuropathy (11 ft) had lateral deformity; 11 subjects (15 ft) had medial deformity. Each subject had calcaneal bone mineral density and plantar force and pressure assessments walking barefoot over an EMED-ST P-2 platform. FINDINGS: Control subjects had lower mid foot vertical forces and pressures despite significantly higher preferred walking speed. In subjects with diabetes and neuropathy, maximum vertical force was 6-fold greater, force-time integral 9.5-fold greater, peak pressure 6.7-fold higher, pressure-time integral was 9.7-fold greater, contact area 2-fold greater and contact time 1.9-fold higher than controls. Pressure values were larger in involved vs uninvolved (P0.05). During stance in the mid foot, subjects with medial column phenotype showed greater pressure in the medial mask; subjects with lateral column phenotype had greater pressures in the lateral mask (P<0.05). Calcaneal bone density was lower for the deformity foot vs the non-deformity foot; bone mineral density was lower in medial column phenotype vs lateral column phenotype (P=0.02). INTERPRETATION: Diabetic foot disease can be classified as stereotypical, structurally-distinct phenotypes of deformities of the medial and lateral columns of the mid foot. Assessments of pedal bone density and plantar mid foot force and pressure during barefoot walking can characterize the structural polymorphic phenotypes and may assist the foot care specialist in clinical decision making.     

Effects of an aquatic fitness program on the muscular strength and endurance of patients with multiple sclerosis

This study quantified the effects of an aquatic exercise program on muscular strength, endurance, work, and power of patients with multiple sclerosis. Ten individuals with a mean age of 40 years participated in a 10-week aquatic exercise program. Two types of isokinetic dynamometers were used to assess the muscular variables studied. A Cybex II dynamometer was used to measure peak torque, work, and fatigue in the knee flexor and extensor muscles and a biokinetic swim bench was used to measure muscular force, work, fatigue, and power in the upper extremities. Five velocity settings were selected for each of three testing trials (pretrial, midtrial, and posttrial). For the lower extremities, analysis of variance indicated a significant improvement of peak torque for knee extensor muscles from the pretrial to midtrial (p less than .05). Peak torque values from pretrial to midtrial for knee flexors and from midtrial to posttrial for both the knee extensor and flexor muscles indicated a nonsignificant difference at each velocity studied. Fatigue and work values in the lower extremities improved significantly between the pretrial and posttrial (p less than .05). For the upper extremities, an analysis of variance indicated a significant increase in all force measurements from pretrial to posttrial (p less than .05). Power and total work values also improved significantly (p less than .05). No significant difference in fatigue measurements for the upper extremities was found. The results of this investigation indicated that an aquatic exercise program may induce positive changes in muscular strength, fatigue, work, and power in patients with multiple sclerosis.     

Reliability of kinematic measurements of rear-foot motion.

The purpose of this study was to examine the ability of a video-based, computer-interfaced motion analysis system to provide reliable data. Ten subjects with no significant orthopedic or neurological dysfunction and ranging in age from 22 to 45 years (mean = 29.6, SD = 7.8) were tested. Retroreflective markers were placed on the posterior shank and foot of each subject. Footswitches were attached to the plantar forefoot and rear foot. A video camera was placed behind the subject, and video data were collected while the subject walked on a treadmill. One representative gait cycle for each subject was selected and processed 10 times with a video processor and analysis software. Three intraclass correlation coefficients (ICCs) were calculated for variables generated by the analysis software, one for two individual measures and one each for the mean of three and five repeated measures. Except for temporal variables, processing data introduced additional variability into the measurement process, particularly for angular velocity data. Measurement of all variables was highly reliable (ICC values greater than or equal to .95) when based on the mean of at least three repeated measures. Although a single measure of temporal and angular position variables may be considered reliable, we recommend using a mean of three trials for angular velocity variables. Additional research is needed to determine tester and subject variability and validity of the measures.     

Design enhancement of a solid ankle-foot orthosis: real-time contact pressures evaluation

The purpose of our study was to evaluate all contact pressures between the molded ankle-foot orthosis (MAFO) and the subject during activities of daily living. The MAFOs studied are used clinically to reduce plantar contact pressures associated with foot ulcers in adult neuropathic diabetic subjects, alleviating abnormal pressures by redistributing them to low-pressure plantar regions. While effective, MAFOs are often not used by the subject due to weight and comfort issues. An understanding of the contact pressures between the subject and the orthosis is a first step in improving basic MAFO design. Four nonimpaired, young adult males were tested in this study. A right-side MAFO was custom-molded and fitted for each subject by the same orthotist. Real-time pressures were obtained for the entire contact area using the F-Scan pressure measurement system. The data obtained demonstrated high contact pressures along the metatarsals of the foot, around the heel and ankle, and adjacent to the strap attachment sites. No contact pressures were noted along the posterior calf region during any of the activities performed. These data suggest the calf region would be a suitable site for material removal for weight reduction and increased comfort, especially in warm weather. In addition, these data may be useful to orthotists in improving the basic design and to researchers as a starting point for performing complex finite element analysis on the MAFO.     

Effects of self-selected dehydration and meaningful rehydration on anaerobic power and heart rate recovery of elite wrestlers

[Purpose] This study aimed to verify the effects of self-directed weight loss on lower- and upper-body power, fatigue index, and heart rate recovery immediately before a meaningful competition (12 hours of recovery). In addition, this study tested the hypothesis that weight loss provides advantages in strength and power, as the relative power of the wrestlers is higher than that of opponents in the same weight class who do not reduce weight. [Subjects and Methods] Eleven well-trained wrestlers volunteered for the study. At baseline, their mean ± SD age, body mass, and height were 20.45 ± 2.69 years, 74.36 ± 9.22 kg, and 177 ± 5.71 cm, respectively. Repeated-measures one-way analysis of variance was performed to analyze differences. [Results] Rapid weight loss achieved by restriction of energy and fluid intake resulted in exercise-impaired decreases in peak power and increased fatigue index. Moreover, weight loss by dehydration negatively affected cardiovascular stability. [Conclusion] Most of the negative effects of rapid weight loss disappear after a 12-hour recovery period, and relative peak power increases after weight loss.Key words: Power, Dehydration, Rehydration and recovery     

Comparison of functional electrical stimulation to long leg braces for upright mobility for children with complete thoracic level spinal injuries.

OBJECTIVE: To prospectively compare functional electrical stimulation (FES) to long leg braces (LLB) as a means of upright mobility for children with motor-complete thoracic level spinal cord injuries (SCIs). DESIGN: Intrasubject group comparison of two interventions. SETTING: Nonprofit pediatric orthopedic rehabilitation facility specializing in SCI. PATIENTS OR OTHER PARTICIPANTS: Convenience sample of five children between 9 and 18 years old with motor-complete thoracic level SCI. The hip and knee extensors were excitable by electrical stimulation. INTERVENTIONS: The FES system consisted of percutaneous intramuscular electrodes implanted to the hip and knee extensors and a push-button activated stimulator worn about the waist. Standing was accomplished by simultaneous stimulation of all implanted muscles. For foot and ankle stability, either ankle-foot orthoses (AFO) or supramalleolar orthoses were used. The LLB system consisted of a custom knee-ankle foot orthosis (KAFO) for four subjects and a custom reciprocating gait orthosis (RGO) for one subject who required bracing at the hip. For both interventions, either a front-wheeled walker or Lofstrand crutches were used as assistive devices. Each subject was trained in the use of both FES and LLB in seven standardized upright mobility activities: stand and reach, high transfer, toilet transfer, floor to stand, 6-meter walk, stair ascent, and stair descent. MAIN OUTCOME MEASURES: For each mobility activity, five repeated measures of level of independence, using the 7-point Functional Independence Measure (FIM) scale, and time to completion were recorded for each intervention. Subjects were also asked which intervention they preferred. RESULTS: For 94% of comparisons, subjects required equal (70%) or less (24%) assistance using FES as compared with LLB. Six of the seven mobility activities required less time to complete using FES, two activities at significant levels. The FES system was preferred in 62% of the cases, LLB were desired 27% of the time, and there was no preference in 11% of the cases. CONCLUSIONS: The FES system generally provided equal or greater independence in seven mobility activities as compared with LLB, provided faster sit-to-stand times, and was preferred over LLB in a majority of cases. Follow-up evaluations of both modes of upright mobility are needed to compare long-term performance and satisfaction.