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Carlo J. De Luca

This lecture explores the various uses of surface electromyography in the field of biomechanics. Three groups of applications are considered: those involving the activation timing of muscles, the force/EMG signal relationship, and the use of the EMG signal as a fatigue index. Technical considerations for recording the EMG signal with maximal fidelity are reviewed, and a compendium of all known factors that affect the information contained in the EMG signal is presented. Questions are posed to guide the practitioner in the proper use of surface electromyography. Sixteen recommendations are made regarding the proper detection, analysis, and interpretation of the EMG signal and measured force. Sixteen outstanding problems that present the greatest challenges to the advancement of surface electromyography are put forward for consideration. Finally, a plea is made for arriving at an international agreement on procedures commonly used in electromyography and biomechanics.

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Eiji Yamada, Takashi Kusaka, Satoshi Tanaka, Satoshi Mori, Hiromichi Norimatsu and Susumu Itoh

Objective:

To investigate changes in motor-unit activity and muscle oxygenation (MO) during isometric contraction with and without vascular occlusion using surface electromyography (EMG) and near-infrared spectroscopy.

Design and Setting:

MO and EMG of the right vastus medialis muscle were measured during isometric contraction at 30%, 50%, and 70% maximal voluntary contraction (MVC), with and without vascular occlusion.

Participants:

6 healthy men.

Results:

Integrated EMG (IEMG) and mean power frequency were significantly higher with vascular occlusion at 30% and 50% MVC. MO reduction at each load was significantly lower with vascular occlusion. A significant positive correlation was found between IEMG and changes in MO level under both conditions.

Conclusions:

These results suggest that oxygen supply to active muscles was impaired by occlusion and that type II fibers were then preferentially recruited, which suggests that hypertrophy occurs in low-intensity exercise in patients with limitations resulting from advanced age, pain, or postsurgery limitation.

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Guillaume Gaudet, Maxime Raison, Fabien Dal Maso, Sofiane Achiche and Mickael Begon

The aim of this study is to determine the intra- and intersession reliability of nonnormalized surface electromyography (sEMG) on the muscles actuating the forearm during maximum voluntary isometric contractions (MVIC). A subobjective of this study is to determine the intra- and intersession reliability of forearm MVIC force or torque, which is a prerequisite to assess sEMG reliability. Eighteen healthy adults participated at 4 different times: baseline, 1-h post, 6-h post, and 24-h post. They performed 3 MVIC trials of forearm flexion, extension, pronation, and supination. sEMG of the biceps brachii short head, brachialis, brachioradialis, triceps brachii long head, pronator teres, and pronator quadratus were measured. The intraclass correlation coefficient (ICC) on MVIC ranged from 0.36 to 0.99. Reliability was excellent for flexion, extension, and supination MVIC for both intra- and intersession. The ICC on sEMG ranged from 0.58 to 0.99. sEMG reliability was excellent for brachialis, brachioradialis, and pronator quadratus, and good to excellent for triceps brachii, biceps brachii, and pronator teres. This study shows that performing 3 MVICs is sufficient to obtain highly reliable maximal sEMG over 24 h for the main muscles actuating the forearm. These results confirm the potential of sEMG for muscle motor functional monitoring.

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Esther Casas, Arturo Justes and Carlos Calvo

systemic condition at the time of the investigation or surgery in the previous 6 months to the study. The procedure was approved by the ethics committee of the Maz Hospital in accordance with the Declaration of Helsinki. Procedures Surface electromyography (EMG) activity of muscle antagonist pairs upper

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Chi-Whan Choi, Jung-Wan Koo and Yeon-Gyu Jeong

have yet to be established. To determine the validities of the exercises, while conducting 4 different exercises (TSB, BLLS, TLBS, and WSB), 3 target muscles (EO, IO, and QL) were measured using surface electromyography (EMG). The muscles were each independently investigated while performing the 4

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Jerónimo Aragón-Vela, Yaira Barranco-Ruiz, Cristina Casals-Vázquez, Julio Plaza-Díaz, Rafael A. Casuso, Luis Fontana and Jesús F. Rodríguez Huertas

Evaluation of muscular fatigue thresholds in athletes performing short-duration and explosive exercises is difficult because classic parameters do not suffer large variations. Therefore, the aim of this study was to develop a new method to estimate the fatigue threshold in single muscles. Our approach is based on electromyographic data recorded during a maximum incremental strength test until the one repetition maximum is reached. Ten men and 10 women performed a half-squat strength test consisting of five incremental intensities of one repetition maximum. Neither heart rate nor blood lactate concentrations showed significant differences at the various intensities tested. Surface electromyographic activities of vastus lateralis, vastus medialis, and rectus femoris were recorded, finding a break point corresponding to the fatigue threshold occurring in men at 70.74%, 71.48%, and 72.52% of one repetition maximum, respectively. In women, break-point values were 76.66% for vastus lateralis, 76.27% for vastus medialis, and 72.10% for rectus femoris. In conclusion, surface electromyography could be a useful, rapid, and noninvasive tool to determine the fatigue threshold of independent muscles during a maximal half-squat strength test.

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Ji-hyun Lee, Heon-seock Cynn, Sil-ah Choi, Tae-lim Yoon and Hyo-jung Jeong

Context:

Gluteus medius (Gmed) weakness is associated with some lower-extremity injuries. People with Gmed weakness might compensate by activating the tensor fasciae latae (TFL). Different hip rotations in the transverse plane may affect Gmed and TFL muscle activity during isometric side-lying hip abduction (SHA).

Objectives:

To compare Gmed and TFL muscle activity and the Gmed:TFL muscle-activity ratio during SHA exercise with 3 different hip rotations.

Design:

The effects of different hip rotations on Gmed, TFL, and the Gmed:TFL muscle-activity ratio during isometric SHA were analyzed with 1-way, repeated-measures analysis of variance.

Setting:

University research laboratory.

Participants:

20 healthy university students were recruited in this study.

Interventions:

Participants performed isometric SHA: frontal SHA with neutral hip (frontal SHAN), frontal SHA with hip medial rotation (frontal SHA-MR), and frontal SHA with hip lateral rotation (frontal SHA-LR).

Main Outcome Measures:

Surface electromyography measured the activity of the Gmed and the TFL. A 1-way repeated-measures analysis of variance assessed the statistical significance of Gmed and TFL muscle activity. When there was a significant difference, a Bonferroni adjustment was performed.

Results:

Frontal SHA-MR showed significantly greater Gmed muscle activation than frontal SHA-N (P = .000) or frontal SHA-LR (P = .015). Frontal SHA-LR showed significantly greater TFL muscle activation than frontal SHA-N (P = .002). Frontal SHA-MR also resulted in a significantly greater Gmed:TFL muscle-activity ratio than frontal SHA-N (P = .004) or frontal SHA-LR (P = .000), and frontal SHA-N was significantly greater than frontal SHA-LR (P = .000).

Conclusions:

Frontal SHA-MR results in greater Gmed muscle activation and a higher Gmed:TFL muscle ratio.

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Asger R. Pedersen, Peter W. Stubbs and Jørgen F. Nielsen

The aim was to challenge the assumptions of standard statistical analyses of average surface electromyography (sEMG) data as a measurement of response magnitudes following the generation of a reflex. The ipsilateral tibial nerve was stimulated at three stimulation intensities and the response sEMG was measured in the contralateral soleus (cSOL) muscle. The magnitude of the cSOL response was measured at a set time window following ipsilateral tibial nerve stimulation. The averaged and trial-by-trial response magnitudes were assessed and compared. The analysis of the averaged and trial-by-trial response revealed significantly different results as the trial-by trial response magnitudes were log-normally distributed with between subject variance heterogeneity violating assumptions of standard statistical analyses. A statistical model has been suggested for the analysis of the responses. By ignoring trial-by-trial response variability and distribution, erroneous results may occur. This may change the interpretation of the results in some studies.

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Kin Shung, Carlos G. de Oliveira and Jurandir Nadal

The walk–run transition (WRT) is a well-described phenomenon without any known cause; however, mechanical variables related to human gait have been associated with the WRT. This study tested the hypothesis that shock waves in the tibia and 3rd lumbar vertebra in addition to activity of tibialis anterior, vastus lateralis, and erector spinae muscles could be responsible for the WRT. Thirty subjects walked and ran on a treadmill at 80%, 90%, 100%, 110%, and 120% of preferred transition speed. Shock waves were measured with skin-mounted accelerometers and muscle activity by surface electromyography. The influence on the WRT was analyzed with two models. The shock waves and muscle activity tended to a significant increase (p < .05) for both walking and running with increased speed. The only factor that appeared to be involved in the WRT mechanism was the activity of the tibialis anterior; however, this was only confirmed by one of the two models. The use of different models to analyze the same data for the WRT triggers may give different results; thus, a standard model is required to investigate the influence of given factors on biological phenomena.

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Remco J. Baggen, Jaap H. van Dieën, Sabine M. Verschueren, Evelien Van Roie and Christophe Delecluse

Surface electromyography (EMG) is commonly used to measure muscle activation during task performance. It is often used to indirectly estimate individual muscle forces during a contraction 1 instead of measuring force directly (eg, with a dynamometer). This is likely because direct force