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Hemiplegia is a neurological disorder that is often detected in children with cerebral palsy. Although many studies have investigated muscular activity in hemiplegic legs, few EMG-based findings focused on unaffected limb. This study aimed to quantify the asymmetric behavior of lower-limb-muscle recruitment during walking in mild-hemiplegic children from surface-EMG and foot-floor contact features. sEMG signals from tibialis anterior (TA) and gastrocnemius lateralis and foot-floor contact data during walking were analyzed in 16 hemiplegic children classified as W1 according to Winter' scale, and in 100 control children. Statistical gait analysis, a methodology achieving a statistical characterization of gait by averaging surface-EMG-based features, was performed. Results, achieved in hundreds of strides for each child, indicated that in the hemiplegic side with respect to the non-hemiplegic side, W1 children showed a statistically significant: decreased number of strides with normal foot-floor contact; decreased stance-phase length and initial-contact sub-phase; curtailed, less frequent TA activity in terminal swing and a lack of TA activity at heel-strike. The acknowledged impairment of anti-phase eccentric control of dorsiflexors was confirmed in the hemiplegic side, but not in the contralateral side. However, a modified foot-floor contact pattern is evinced also in the contralateral side, probably to make up for balance requirements.

Muscle co-contractions are particularly relevant in analyzing children pathologies. To interpret surface electromyography (sEMG) in pathological conditions, reliable normative data in non-pathological children are required for direct comparison. Aim of the study was the quantification of co-contraction activity between quadriceps femoris (QF) and hamstring muscles during walking in healthy children. To this aim, Statistical gait analysis was performed on sEMG signals from rectus femoris (RF), vastus medialis (VM), and lateral hamstrings (LH), in 16401 strides walked by 100 healthy school-age children. Co-contractions were assessed as overlapping period between activation intervals of considered muscles. Results showed full superimpositions of LH with both RF and VL activity from terminal swing, 80-100% of gait cycle, to successive loading response (0-15% of gait cycle), in around 90% of strides, as reported in adults. This indicates that children regularly use a cocontraction activity between QF and hamstring muscles in weight acceptance during walking, supporting the hypothesis of a regulatory role of co-contraction in providing knee joint stability. Concomitant activity of QF and hamstring muscles was detected also during push-off phase (30-50% of gait cycle), showing a large variability intra and inter subjects and a lower occurrence frequency (around 25% of strides). This could be intended for controlling rapid knee flexion and/or stabilizing pelvis during body progression. Present findings represent the first attempt to provide normative sEMG dataset on variability of QF and hamstring muscles co-contractions during child walking, useful for discriminating physiological and pathological behavior and for designing future studies on maturation of gait., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: The purpose of the study was the assessment of activation patterns of the extensor digitorum brevis (EDB) muscle in healthy children, during walking at self-selected speed and cadence., Approach: To this end, statistical gait analysis was performed on surface electromyographic (sEMG) signals of the EDB, in a large number (hundreds) of strides per subject. sEMG data from the tibialis anterior (TA) and gastrocnemius lateralis (GL) were also investigated for comparative purposes., Main Results: Results from 23 healthy children showed a large variability in the number of muscle activations, occurrence frequency, and onset-offset instants across considered strides. The assessment of different modalities of muscle activation allowed the identification of a single activity pattern, common to all the modalities and we were able to characterize the behavior of the EDB during the gait of healthy children. The pattern of EDB activity centered in two main regions of the gait cycle: in the second half of the stance phase (detected in 100% of subjects) and in the final swing phase (50%). Comparison with the TA and GL regions of activity suggested that the EDB and TA worked mainly as antagonist muscles for the ankle joint, while the EDB and GL did not oppose each other in action, but acted in synergy for the control of the ankle joint during walking., Significance: The 'Normality' pattern for the EDB activity reported here represents the first attempt to develop a reference for dynamic sEMG of the EDB in healthy children, enabling us to include the physiological variability of the phenomenon. Present results could be useful for discriminating physiological and pathological behavior in children and for deepening the maturation of the gait.

Natural variability of myoelectric activity during walking was recently analyzed considering hundreds of strides. This allowed assessing a parameter seldom considered in classic surface EMG (sEMG) studies: the occurrence frequency, defined as the frequency each muscle activation occurs with, quantified by the number of strides when a muscle is recruited with that specific activation modality. Aim of present study was to propose the occurrence frequency as a new parameter for assessing sEMG-signal variability during walking. Aim was addressed by processing sEMG signals acquired from Gastrocnemius Lateralis, Tibialis Anterior, Rectus Femoris and Biceps femoris in 40 healthy subjects in order to: (1) show that occurrence frequency is not correlated with ON/OFF instants (R mean =0.11±0.07; P>0.05) and total time of activation (R mean =0.15±0.08; P>0.05); (2) confirm the above results by two handy examples of application (analysis of gender and age) which highlighted that significant (P<0.05) gender-related and age-related differences within population were detected in occurrence frequency, but not in temporal sEMG parameters. In conclusion, present study demonstrated that occurrence frequency is able to provide further information, besides those supplied by classical temporal sEMG parameters and thus it is suitable to complement them in the evaluation of variability of myoelectric activity during walking., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The research purpose was to quantify the co-contraction patterns of quadriceps femoris (QF) vs. hamstring muscles during free walking, in terms of onset-offset muscular activation, excitation intensity, and occurrence frequency. Statistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH), in 16315 strides walked by 30 healthy young adults. Results showed full superimpositions of MH with both VL and RF activity from terminal swing, 80 to 100% of gait cycle (GC), to the successive loading response (≈0-15% of GC), in around 90% of the considered strides. A further superimposition was detected during the push-off phase both between VL and MH activation intervals (38.6±12.8% to 44.1±9.6% of GC) in 21.9±13.6% of strides, and between RF and MH activation intervals (45.9±5.3% to 50.7±9.7 of GC) in 32.7±15.1% of strides. These findings led to identify three different co-contractions among QF and hamstring muscles during able-bodied walking: in early stance (in ≈90% of strides), in push-off (in 25-30% of strides) and in terminal swing (in ≈90% of strides). The co-contraction in terminal swing is the one with the highest levels of muscle excitation intensity. To our knowledge, this analysis represents the first attempt for quantification of QF/hamstring muscles co-contraction in young healthy subjects during normal gait, able to include the physiological variability of the phenomenon., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this paper a graphical user interface (GUI) built in MATLAB® environment is presented. This interactive tool has been developed for the analysis of superficial electromyography (sEMG) signals and in particular for the assessment of the muscle activation time intervals. After the signal import, the tool performs a first analysis in a totally user independent way, providing a reliable computation of the muscular activation sequences. Furthermore, the user has the opportunity to modify each parameter of the on/off identification algorithm implemented in the presented tool. The presence of an user-friendly GUI allows the immediate evaluation of the effects that the modification of every single parameter has on the activation intervals recognition, through the real-time updating and visualization of the muscular activation/deactivation sequences. The possibility to accept the initial signal analysis or to modify the on/off identification with respect to each considered signal, with a real-time visual feedback, makes this GUI-based tool a valuable instrument in clinical, research applications and also in an educational perspective.

"In vivo" studies reported that the co-activation of gastrocnemius and quadriceps femoris (QF) muscles produces ACL strain values greater than those caused by an isolated activation of either muscle. Aim of this study was to assess the co-activation of gastrocnemius (lateral head, GL) and vastus lateralis (VL) in healthy and young adults during walking. To this purpose the Statistical Gait Analysis was performed, that allows a characterization of gait considering hundreds of strides belonging to the same walking trial. Three GL/VL co-activations were detected during a single gait cycle: in foot-contact phase, from 6.8±8.5% to 22.9±23.3% of gait cycle, (FC co-activation), in push-off phase, from 33.0±11.9% to 41.5±13.4% (PO co-activation), and in swing phase, from 86.5±6.7% to 93.2±5.9% (SW co-activation). FC co-activation was the most recurrent (in 100% of the strides, P<;0.001) and longest (16% of gait cycle) one. Thus, the ACL strain due to the co-activation between GL and VL is longer and more frequently during FC phase, than in all the others gait phases. Moreover, the position of the knee and the amount of the weight-bearing on knee, achieved in this gait phase, suggested that FC co-activation is the one that produces a highest strain value of anterior cruciate ligament (ACL). These findings could help to better understand risk factors of the ACL injuries and to design more focused preventive and rehabilitative strategies.

The surface electromyogram (SEMG) is a signal noninvasively (through electrodes located on the body surface) acquired for evaluating the electrical activity produced by skeletal muscles. In thoracic acquisitions, SEMG is typically affected by the electrocardiographic (ECG) signal, representing the electrical activity of the heart. SEMG and ECG power spectra mainly fall within 5-450 Hz and 0.05-50 Hz, respectively. Consequently, SEMG and ECG components overlap in the 5-50 Hz range. Although removing SEMG low spectral components, high-pass linear filtering (LF) with a cut-off frequency of 20 Hz remains the standard technique to clean SEMG from ECG. Thus, the aim of the present study was to propose the Segmented Beat Modulation Method (SBMM) as a tool to clean SEMG from ECG without removing SEMG components below 20 Hz. A SEMG recording was first acquired from the left rectus abdominis of a subject, and then filtered using both SBMM and LF. Filtered SEMGs obtained with the two techniques were compared. Results indicate that SBMM eliminates ECG interference from SEMG better than LF, since the latter procedure maintains ECG components between 20 and 50 Hz. In addition, after ECG removal by SBMM, SEMG showed a significant amount of spectral components (up to 20%) in the low-frequency range. Maintaining such low-frequency components, which go lost when applying LF, is desirable since they likely associate to the firing rates of the active motor units. In conclusion, SBMM represents a useful tool to clean SEMG from ECG without loss of frequency components.

Purpose: The study was designed to assess the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) in healthy school-age children during gait at self-selected speed and cadence, in terms of variability of onset-offset muscular activation and occurrence frequency., Methods: Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatio-temporal and sEMG-based parameters over numerous strides, was performed in 100 healthy children, aged 6-11 years. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL., Results: On average, 165±27 strides were analyzed for each child, resulting in approximately 16,500 strides. Results showed that GL and TA act as pure agonist/antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 19.2±10.4% of strides. In the remaining strides, statistically significant (p<0.05) co-contractions appear in early stance (46.5±23.0% of the strides), mid-stance (28.8±15.9%), pre-swing (15.2±9.2%), and swing (73.2±22.6%). This significantly increased complexity in muscle recruitment strategy beyond the activation as pure ankle plantar/dorsiflexors, suggests that in healthy children co-contractions are likely functional to further physiological tasks as balance improvement and control of joint stability., Conclusions: This study represents the first attempt for the development in healthy children of a normative dataset for GL/TA co-contractions during gait, achieved on an exceptionally large number of strides in every child and in total. The present reference frame could be useful for discriminating physiological and pathological behavior in children and for designing more focused studies on the maturation of gait., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The study was designed to assess the natural variability of the activation modalities of vastus medialis (VM) and vastus lateralis (VL) during walking at a self-selected speed and cadence of 30 young, healthy, females. This was achieved by conducting statistical gait analysis on the surface electromyographic signals from hundreds of strides for each subject. Results revealed variability in the number of activations, occurrence frequency, and onset-offset instants across the thousands of strides analyzed. However, despite the variability, there was one activation occurrence which remained consistent across subjects for both VM and VL. This occurred from terminal swing to the following loading response (observed in 100% of strides). A second, less frequent, activation occurred between mid-stance up to pre-swing (observed in 39.3±22.4% of strides for VM and in 35.1±20.6% for VL). No significant differences (p>0.05) were observed in the onset-offset instants or in the occurrence frequency, which suggest a simultaneous recruitment of VM and VL. This "normality" pattern represents the first attempt at developing a reference frame for vastii sEMG activity during walking, that is able to include the physiological variability of the phenomenon and control the confounding effects of age and gender., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The study was designed to assess the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) in healthy young adults during gait at self-selected speed and cadence, in terms of variability of onset-offset muscular activation and occurrence frequency. Statistical gait analysis (SGA), a recent methodology performing a statistical characterization of gait by averaging spatio-temporal and EMG-based parameters over numerous strides, was performed in twenty-four healthy young adults. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results showed that GL and TA act as pure agonist/antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 21.3 ± 8.2% of strides. In the remaining strides, statistically significant (p < 0.05) co-contractions appear in early stance (29.2 ± 1.7%), mid-stance (32.1 ± 18.3%) and swing (62.2 ± 2.0%). This significantly increased complexity in muscle recruitment strategy beyond the activation as pure ankle plantar/dorsiflexors, suggests that co-contractions are likely functional to further physiological tasks as foot inversion, balance improvement, control of ankle stability and knee flexion. This study represents the first attempt for the development in healthy young adults of a "normality" reference frame for GL/TA co-contractions, able to include the physiological variability of the phenomenon and eliminate the confounding effect of age., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Soleus muscle flap as coverage tissue is a possible surgical solution adopted to cover the wounds due to open fractures. Despite this procedure presents many clinical advantages, relatively poor information is available about the loss of functionality of triceps surae of the treated leg. In this study, a group of patients who underwent a soleus muscle flap surgical procedure has been analyzed through the heel rise test (HRT), in order to explore the triceps surae residual functionalities. A frequency band analysis was performed in order to assess whether the residual heads of triceps surae exhibit different characteristics with respect to both the non-treated lower limb and an age-matched control group. Then, an in-depth analysis based on a machine learning approach was proposed for discriminating between groups by generalizing across new unseen subjects. Experimental results showed the reliability of the proposed analyses for discriminating between-group at a specific time epoch and the high interpretability of the proposed machine learning algorithm allowed the temporal localization of the most discriminative frequency bands. Findings of this study highlighted that significant differences can be recognized in the myoelectric spectral characteristics between the treated and contralateral leg in patients who underwent soleus flap surgery. These experimental results may support the clinical decision-making for assessing triceps surae performance and for supporting the choice of treatment in plastic and reconstructive surgery. Graphical Abstract The Graphical abstract presents the scope of the proposed analysis of myoelectric signals of soleus and gastrocnemius muscles of patiens groups during Hell Rise Test, highlighting the applied methods and the obtained results. [ABSTRACT FROM AUTHOR]

The present work proposes an interactive software tool for surface electromyography signal processing and analysis, focused on the assessment of muscular activations during walking and easy-to-use also for users without signal treatment knowledge. The tool is based on two logical steps: first, an automatic detection of muscle activations is provided; then, the user can tune the value of each processing parameter, with a real-time visual feedback. A stride-to-stride evaluation of muscular recruitment and a co-contraction recognition are available, together with the computation of an average myoelectric activation pattern. The tunable signal processing tailors the analysis to any considered application, allowing to extract information from low-quality signals. A muscle activity characterisation from the single stride to the whole walking trial is also provided. Beyond gait analysis and muscles activation timing identification, this tool could be valuable also in an educational scenario, considering the interactive characteristics of the graphical user interface. [ABSTRACT FROM AUTHOR]

The present study was designed to achieve a comprehensive analysis of gender-related differences in the myoelectric activity of lower limb muscles during normal walking at self-selected speed and cadence, in terms of muscle activation patterns and occurrence frequencies. To this aim, statistical gait analysis (SGA) of surface EMG signal from tibialis anterior (TA), gastrocnemius lateralis (GL), rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL) was performed in 11 female (F-group) and 11 male (M-group) age-matched healthy young adults. SGA is a recent methodology performing a statistical characterization of gait, by averaging spatio-temporal and sEMG-based parameters over numerous strides. Findings showed that males and females walk at the same comfortable speed, despite the significantly lower height and higher cadence detected in females. No significant differences in muscle onset/offset were detected between groups. The analysis of occurrence frequencies of muscle activity showed no significant differences in BF and RF, between groups. Conversely, in F-group, compared with M-group, GL, TA and VL showed a significantly higher occurrence frequency in the modalities with a high number of activations, and a significantly lower occurrence frequency in the modalities with a low number of activations. These findings indicate a propensity of females for a more complex recruitment of TA, GL and VL during walking, compared to males. The observed differences recommend the suitability of developing electromyographic databases, separated for males and females. [ABSTRACT FROM AUTHOR]

Background: In this paper, squat named by Authors unconstrained because performed without constrains related to feet position, speed, knee maximum angle to be reached, was tested as motor task revealing differences in functional performance after knee arthroplasty. It involves large joints ranges of motion, does not compromise joint safety and requires accurate control strategies to maintain balance. Methods: Motion capture techniques were used to study squat on a healthy control group (CTR) and on three groups, each characterised by a specific knee arthroplasty design: a Total Knee Arthroplasty (TKA), a Mobile Bearing and a Fixed Bearing Unicompartmental Knee Arthroplasty (respectively MBUA and FBUA). Squat was analysed during descent, maintenance and ascent phase and described by speed, angular kinematics of lower and upper body, the Center of Pressure (CoP) trajectory and muscle activation timing of quadriceps and biceps femoris. Results: Compared to CTR, for TKA and MBUA knee maximum flexion was lower, vertical speed during descent and ascent reduced and the duration of whole movement was longer. CoP mean distance was higher for all arthroplasty groups during descent as higher was, CoP mean velocity for MBUA and TKA during ascent and descent. Conclusions: Unconstrained squat is able to reveal differences in the functional performance among control and arthroplasty groups and between different arthroplasty designs. Considering the similarity index calculated for the variables showing statistically significance, FBUA performance appears to be closest to that of the CTR group. Level of evidence: III a. [ABSTRACT FROM AUTHOR]

EMG-based differences between females and males during walking are generally acknowledged in adults. Aim of the study was the quantification of possible gender differences in myoelectric activity of gastrocnemius lateralis (GL) and tibialis anterior (TA) during walking in school-age children. Gender-related comparison with adults was also provided to get possible novel insight in maturation of gait. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over hundreds of strides, was performed in100 healthy school-age children (C-group) and in 33 healthy young adults (YA-group). On average, 301±110 consecutive strides were analyzed for each subject. In C-group, no significant differences (p>0.05) were observed between females and males in GL and TA, considering mean onset/offset instants of activation and occurrence frequency. Stratifying the C-group for age, small differences between females and males in occurrence frequency of GL arose in oldest children. In YA-group, females showed a significant propensity for a more complex recruitment of TA and GL (higher number of activations during gait cycle, quantified by occurrence frequency) compared to males. These outcomes suggest that gender-related differences in sEMG parameters do not characterize the recruitment of GL and TA during child walking in early years (6-8 years), start occurring when adolescence is approaching (10-12 years), and are acknowledged in both ankle muscles only in adults. Present findings seem to support previous studies on maturation of gait which indicate adolescence as the time-range where gait is completing its maturation path. [ABSTRACT FROM AUTHOR]