Comparative evaluation of techniques for the harmonic analysis of human motion data

Four mathematical techniques for the estimation of the Fourier coefficients of pseudoperiodic non-exact discrete functions were submitted to comparative evaluation. These techniques were devised within the following basic procedures: (1) numerical harmonic analysis applied either directly or after redistribution of the data points through some interpolation procedure, so that they be evenly spaced in time and exactly fit on cycle period; (2) fitting of the empirical data with an analytical model followed by the calculation of the Fourier integrals of this model. The evaluation was carried out with special reference to the use of these techniques for processing human motion photogrammetric data. The following criteria were used: (1) accuracy of the Fourier coefficient estimates, (2) capability of yielding information about this accuracy, (3) a priori information needed regarding the statistical properties of the experimental error, (4) factors concerning implementation in digital computers. Practical information was obtained for the non-specialist user with regard to the choice of one technique among the several possible in particular circumstances.     

The surface electromyographic evaluation of the Functional Reach in elderly subjects

This study proposes a comprehensive assessment of myoelectric activity of the main muscles involved in the Functional Reach (FR) test, in 24 elderly subjects. A specific protocol for the surface electromyography (sEMG) signal acquisition during FR-test was developed. Results show that anterior muscles activate following a caudo-cranial order. Tibialis Anterior (TA) is the first to be activated (−18.0 ± 16.3% of the FR-period), together with Rectus Femoris (−10.4 ± 17.9%). Then, Rectus Abdominis (19.7 ± 24.7%) and Sternocleidomastoideus (19.9 ± 15.6%) activate after the FR-start. Hamstrings, Soleus, and L4-level Erectores Spinae (posterior muscles) activate after the FR-start in this order (11.4 ± 16.8%, 17.7 ± 16.6%, and 35.2 ± 29.0%, respectively) and remain active until the movement end. The analysis of the kinematic strategies adopted by subjects revealed an association between TA-activation patterns and two kinematic strategies (hip/mixed strategy), quantified by an increase (p < 0.05) of TA-activity duration in subjects adopting the hip strategy (89.9 ± 34.5) vs. subjects adopting the mixed strategy (27.0 ± 16.8). This suggests that TA sEMG activity could be able to discriminate among kinematic strategies, providing different information on balance control. Thus, the present analysis represents the first attempt to quantify the sEMG activity during FR-test in elderly subjects, providing an early contribution in building a reference frame for balance assessment in clinical context.     

Kinematic and electromyographic analysis of the Nordic Hamstring Exercise

The Nordic Hamstring Exercise (NHE) has been introduced as a training tool to improve the efficiency of eccentric hamstring muscle contraction. The aim of this study was to perform a biomechanical analysis of the NHE. Eighteen participants (20.4 ± 1.9 years) performed two sets of five repetitions each of the NHE and maximal eccentric voluntary contraction (MEVC) of the knee flexors on an isokinetic dynamometer whilst knee angular displacement and electrical activity (EMG) of biceps femoris were measured. EMG was on average higher during the NHE (134.3% of the MEVC). During the forward fall of the NHE, the angle at which a sharp increase in downward velocity occurred varied between 47.9 and 80.5 deg, while the peak knee angular velocity (pVelocity) varied between 47.7 and 132.8 deg s^?1. A significant negative correlation was found between pVelocity and peak EMG (r = ?0.62, p < 0.01) and EMG at 45 deg (r = ?0.75, p < 0.01) expressed as a percentage of peak MEVC EMG. Some of the variables analyzed exhibited good to excellent levels of intra- and inter-session reliability. This type of analysis could be used to indirectly monitor the level of eccentric strength of the hamstring muscles while performing the NHE and potentially any training- or injury-related changes.     

Identification and classification of involuntary leg muscle contractions in electromyographic records from individuals with spinal cord injury

Involuntary muscle contractions (spasms) are common after human spinal cord injury (SCI). Our aim was to compare how well two raters independently identified and classified different types of spasms in the same electromyographic records (EMG) using predefined rules. Muscle spasms were identified by the presence, timing and pattern of EMG recorded from paralyzed leg muscles of four subjects with chronic cervical SCI. Spasms were classified as one of five types: unit, tonic, clonus, myoclonus, mixed. In 48 h of data, both raters marked the same spasms most of the time. More variability in the total spasm count arose from differences between muscles (84%; within subjects) than differences between subjects (6.5%) or raters (2.6%). Agreement on spasm classification was high (89%). Differences in spasm count, and classification largely occurred when EMG was marked as a single spasm by one rater but split into multiple spasms by the other rater. EMG provides objective measurements of spasm number and type in contrast to the self-reported spasm counts that are often used to make clinical decisions about spasm management. Data on inter-rater agreement and discrepancies on muscle spasm analysis can both drive the design and evaluation of software to automate spasm identification and classification.     

An electromyographic analysis of two handwriting grasp patterns

BackgroundHandwriting is a fundamental skill needed for the development of daily-life activities during lifetime and can be performed using different forms to hold the writing object. In this study, we monitored the sEMG activity of trapezius, biceps brachii, extensor carpi radialis brevis and flexor digitorum superficialis during a handwriting task with two groups of subjects using different grasp patterns.Subjects and methodsTwenty-four university students (thirteen males and eleven females; mean age of 22.04 ± 2.8 years) were included in this study. We randomly invited 12 subjects that used the Dynamic Tripod grasp and 12 subjects that used the Static Tripod grasp.ResultsThe static tripod group showed statistically significant changes in the sEMG activity of trapezium and biceps brachii muscles during handwriting when compared to dynamic tripod group’s subjects. No significant differences were found in extensor carpi radialis brevis and flexor digitorum superficialis activities among the two groups.ConclusionThe findings in this study suggest an increased activity of proximal muscles among subjects using a transitional grasp, indicating potential higher energy expenditure and muscular harm with the maintenance of this motor pattern in handwriting tasks, especially during the progression in academic life.     

Characteristics and analysis of uterine electromyographic activity in pregnant cows

The electromyographic activity of the cow uterus in the last trimester of pregnancy was investigated. The investigation was performed on 12 animals and the electrical activity was recorded in the last trimester of pregnancy during 11 different periods until the delivery. The duration of the action potential bursts (APB) recorded during the first 7 periods, was small. It did not exceed 2 seconds. A significant increase, however, was recorded at 7 to 9 days before the labor and it involved all the investigated areas in the uterus. The number of APB of the gravid horn was significantly higher than that recorded at other locations in the uterus with the exception of the day of delivery. A significant correlation was found between the number of APB and the level of magnesium in blood serum. The levels of 17-beta estradiol and progesterone were similar during all studied periods with the exception of the last week, in which a dramatic fall in estradiol level and a significant increase in the progesterone concentration were observed. The results showed that it is possible to distinguish three different phases of electric activity in the cow uterus during the last trimester of pregnancy. The features of these phases were discussed.     

An electromyographic analysis of hindlimb function in Alligator during terrestrial locomotion

The neuromuscular control of the hindlimb of American alligators (Alligator mississippiensis) walking on a treadmill was analyzed using simultaneous electromyography (EMG) and cineradiography. EMG and kinematic data were integrated with myological information to discern the interplay of muscles mediating hip and knee movement during the high walk. Twelve muscles, subdivided into 23 individual heads, cross the hip joint of Alligator. Activity patterns of 12 heads of 11 hip muscles and one knee muscle were recorded and quantified. An additional five heads from four muscles were recorded in single individuals. During the stance phase, the caudofemoralis longus prevents hip flexion and actively shortens to retract the femur through an arc of 60–80°. At the same time, the adductor femoris 1 and pubo-ischio-tibialis control femoral abduction. The knee is extended 30–40° during stance by contraction of the femoro-tibialis internus. These stance phase muscles often produce discontinuous, periodic EMG signals within their normal burst profile. In late stance and early swing, the ilio-fibularis and the pubo-ischio-tibialis are responsible for flexing the knee. The limb is protracted by the pubo-ischio-femoralis internus 2 and pubo-ischio-femoralis externus 2, which flex the hip. The ilio-femoralis abducts the limb during swing to suspend it above the tread. The role of the ambiens 1, which is active in midswing, is unclear. The ilio-tibialis 2, flexor-tibialis externus and flexor-tibialis internus 2 yield sporadic, low amplitude EMGs; these muscles are recruited at a very low level, if at all, during the slow high walk. Although EMGs do not conclusively delineate muscle function, activity patterns are particularly helpful in elucidating the complex interaction of muscular heads in this system. J. Morphol. 234:197–212, 1997. © 1997 Wiley-Liss, Inc.     

Objective evaluation of wind chill index by records of frostbite in the Antarctica

Investigations in the Antarctic show that the onset of freezing of exposed skin under natural field conditions is closely correlated to a wind chill index of 1,400, calculated according to the Siple-Passel formula,and provide evidence of the validity of the wind chill formula in this range. Experimental frostbites of isolated fingers exposed to antarctic climatic conditions, however, demonstrate a closer correlation with atmospheric cooling calculated by a different formula. This may be accounted for by differences in cooling rate in relation to body diameter.

---

Zusammenfassung Untersuchungen in der Antarktis zeigen, dass der Beginn des Erfrieren einer exponierten Hautstelle unter natürlichen Bedingungen eine enge Beziehung zu einem Wind-Kälte-Index von 1.400 nach der Formel von Siple-Passel und damit die Gültigkeit der Wind-Kälte-Formel in diesem Bereich unter Beweis stellt.Versuche mit Frostbeulen an isolierten Fingern, die den antarktischen Klimabedingungen ausgesetzt waren, zeigten dagegen eine engere Beziehung zur Kälte der Luft,die nach einer anderen Formel berechnet wurde.Dies mag seinen Grund in Unterschieden des Ausmasses der Abkühlung je nach dem Durchmesser des untersuchten Körperteils haben.

---

Resume Des recherches faites dans l'Antarctique montrent que le début des gelures d'une partie de peau nue est, dans des conditions naturelles,en rapport étroit avec un index vent-froid. Cet index, calculé selon la formule de Siple-Passel,est de 1.400 et prouve que cette formule est valable dans ces conditions. Des essais faits avec des engelures à des doigt isolés, mais exposées aux conditions climatiques de l'Antarctique montrent par contre une relation plus étroite avec le froid de l'air, calculé selon une autre formule. Ces différences sont probablement dues à l'importance de la réfrigération qui dépend, elle, du diamètre de la partie du corps examinée.

---

---

Paper presented during the Fourth Int. Biometeorological Congress,New Brunswick, N.J., 26 August–2 September 1966.     

Automated analysis of prerecorded evoked electromyographic activity from rat muscle

An automated microprocessor-based data acquisition and analysis system has been developed specifically to quantify electromyographic (EMG) activity induced by the convulsant agent catechol in the anaesthetized rat. The stimulus and EMG response are recorded on magnetic tape. On playback, the stimulus triggers a digital oscilloscope and, via interface circuitry, a BBC B microcomputer. The myoelectric activity is digitized by the oscilloscope before being transferred under computer control via a RS232 link to the microcomputer. This system overcomes the problems of dealing with signals of variable latency and allows quantification of latency, amplitude, area and frequency of occurrence of specific components within the signal. The captured data can be used to generate either signal or superimposed high resolution graphic reproductions of the original waveforms. Although this system has been designed for a specific application, it could easily be modified to allow analysis of any complex waveform.     

Application of three-way principal component analysis to the evaluation of two-dimensional maps in proteomics

Three-way PCA has been applied to proteomic pattern images to identify the classes of samples present in the dataset. The developed method has been applied to two different datasets: a rat sera dataset, constituted by five samples of healthy Wistar rat sera and five samples of nicotine-treated Wistar rat sera; a human lymph-node dataset constituted by four healthy lymph-nodes and four lymph-nodes affected by a non-Hodgkin's lymphoma. The method proved to be successful in the identification of the classes of samples present in both of the groups of 2D-PAGE images, and it allowed us to identify the regions of the two-dimensional maps responsible for the differences occurring between the classes for both rat sera and human lymph-nodes datasets.     

The graph theoretical analysis of the SSVEP harmonic response networks

Steady-state visually evoked potentials (SSVEP) have been widely used in the neural engineering and cognitive neuroscience researches. Previous studies have indicated that the SSVEP fundamental frequency responses are correlated with the topological properties of the functional networks entrained by the periodic stimuli. Given the different spatial and functional roles of the fundamental frequency and harmonic responses, in this study we further investigated the relation between the harmonic responses and the corresponding functional networks, using the graph theoretical analysis. We found that the second harmonic responses were positively correlated to the mean functional connectivity, clustering coefficient, and global and local efficiencies, while negatively correlated with the characteristic path lengths of the corresponding networks. In addition, similar pattern occurred with the lowest stimulus frequency (6.25 Hz) at the third harmonic responses. These findings demonstrate that more efficient brain networks are related to larger SSVEP responses. Furthermore, we showed that the main connection pattern of the SSVEP harmonic response networks originates from the interactions between the frontal and parietal–occipital regions. Overall, this study may bring new insights into the understanding of the brain mechanisms underlying SSVEP.     

生态风险分析在农田肥力评价中的应用

生态风险分析属于生态学研究的热点问题之一。本文探讨了生态风险的内涵,定义了生态系统的风险：生态系统的风险是其生态因子所导致的不良事件发生的概率及其后果的严重程度。研究了农田生态系统产生的生态风险——土壤肥力退化风险,将生态风险的理论引进农田生态系统的风险评价中．建立了风险评价指标体系．构建了土壤肥力风险评价的实用数学模型,给出了一种度量土壤肥力风险的简单、合理的科学方法．并就具体实例进行了分析研究。计算结果表明,在评价地区所选的24个样区中,生态风险很大者占样区总数的12．5％,生态风险较大的占33．3％．生态风险一般的占37．5％．风险较小的占16．7％。其中风险很大和较大的一些样区,应是所论样区中土壤改良治理的重点样区。就各样区不同土壤肥力因子存在的风险也给出了定量结果。以上风险分析结果,为土壤肥力风险评价和土壤改良治理提供了定量依据。