Across-laboratory reliability of timing parameters of surface EMG activity obtained during gait in three laboratories using standardized measurement technique

Locomotion requires the continuous integration of descending motor commands and sensory inputs from the legs by spinal central pattern generator circuits. Modulation of spinal neural circuits by transspinal stimulation is well documented, but how transspinal stimulation affects corticospinal excitability during walking in humans remains elusive. We measured the motor evoked potentials (MEPs) at multiple phases of the step cycle conditioned with transspinal stimulation delivered at sub- and suprathreshold intensities of the spinally mediated transspinal evoked potential (TEP). Transspinal stimulation was delivered before or after transcranial magnetic stimulation during which summation between MEP and TEP responses in the surface EMG was absent or present. Relationships between MEP amplitude and background EMG activity, silent period duration, and phase-dependent EMG amplitude modulation during and after stimulation were also determined. Ankle flexor and extensor MEPs were depressed by suprathreshold transspinal stimulation when descending volleys were timed to interact with transspinal stimulation-induced motoneuron depolarization at the spinal cord. MEP depression coincided with decreased MEP gain, unaltered MEP threshold, and unaltered silent period duration. Locomotor EMG activity of bilateral knee and ankle muscles was significantly depressed during the step at which transspinal stimulation was delivered but fully recovered at the subsequent step. The results support a model in which MEP depression by transspinal stimulation occurs via subcortical or spinal mechanisms. Transspinal stimulation disrupts the locomotor output of flexor and extensor motoneurons initially, but the intact nervous system has the ability to rapidly overcome this pronounced locomotor adaptation. In conclusion, transspinal stimulation directly affects spinal locomotor centers in healthy humans. NEW & NOTEWORTHY Lumbar transspinal stimulation decreases ankle flexor and extensor motor evoked potentials (MEPs) during walking. The MEP depression coincides with decreased MEP gain, unaltered MEP threshold changes, and unaltered silent period duration. These findings indicate that MEP depression is subcortical or spinal in origin. Healthy subjects could rapidly overcome the pronounced depression of muscle activity during the step at which transspinal stimulation was delivered. Thus, transspinal stimulation directly affects the function of spinal locomotor networks in healthy humans.

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Use of a Shoulder Rest for Playing the Violin Revisited: An Analysis of the Effect of Shoulder Rest Height on Muscle Activity, Violin Fixation Force, and Player Comfort

Medical Problems of Performing Artists ◽

10.21091/mppa.2019.1009 ◽

2019 ◽

Vol 34 (1) ◽

pp. 39-46 ◽

Cited By ~ 1

Author(s):

Laura M Kok ◽

Jim Schrijvers ◽

Marta Fiocco ◽

Barend van Royen ◽

Jaap Harlaar

Keyword(s):

Muscle Activity ◽

Anterior Part ◽

Activity Patterns ◽

Deltoid Muscle ◽

Surface Emg ◽

Emg Activity ◽

Linear Regression Models ◽

Upper Trapezius ◽

Shoulder Muscles ◽

Rest Condition

AIMS: For violinists, the shoulder rest is an ergonomic adaptation to reduce musculoskeletal load. In this study, we aimed to evaluate how the height of the shoulder rest affects the violin fixation force and electromyographic (EMG) activity of the superficial neck and shoulder muscles. METHODS: In professional violinists, four different shoulder rest heights during five playing conditions were evaluated. Outcome variables included the jaw-shoulder violin fixation force and bilateral surface EMG of the upper trapezius (mTP), sternocleidomastoid (mSCM), and left anterior part of the left deltoid muscle (mDTA). Playing comfort was subjectively rated on a visual analogue scale (VAS). Linear regression models were estimated to investigate the influence of the shoulder rest height on muscle activity and violin fixation force as well as the muscle activity of the five evaluated muscles on violin fixation force. RESULTS: 20 professional violinists (4 males, 16 females, mean age 29.4 yrs) participated in this study. The shoulder rest condition had a significant effect on playing comfort (p<0.001), with higher shoulder rest conditions associated with decreased subjective playing comfort. The mean violin fixation force for each shoulder rest condition ranged between 2.92 and 3.39 N; higher shoulder rests were related to a higher violin fixation force (p<0.001). CONCLUSION: In this study, violin fixation force and muscle activity of the left mDTA increased while playing with an increasing height of the shoulder rest. As the shoulder rest influences muscle activity patterns and violin fixation force, adjustment of the shoulder rest and positioning of the violin need to be carefully optimized.

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The effect of toe-tap exercise on abductor hallucis activity and medial longitudinal arch angle in individuals with pes planus

Isokinetics and Exercise Science ◽

10.3233/ies-202107 ◽

2020 ◽

Vol 28 (4) ◽

pp. 415-422

Author(s):

Min-Hyeok Kang ◽

Sang-Min Cha ◽

Jae-Seop Oh

Keyword(s):

Repeated Measures ◽

Plantar Flexion ◽

Surface Emg ◽

Rehabilitation Program ◽

Emg Activity ◽

Electromyographic Activity ◽

Medial Longitudinal Arch ◽

Abductor Hallucis ◽

Pes Planus ◽

Longitudinal Arch

BACKGROUND: Active interventions for pes planus, including short-foot exercises (SF) and toe-spread-out exercises (TSO), aim to continuously support the medial longitudinal arch (MLA) by activating the abductor hallucis (AbdH) muscle. However, compensatory movements, such as ankle supination and/or plantar flexion, often occur during these exercises. OBJECTIVE: To examine the effects of a novel exercise, i.e., the toe-tap (TT) exercise on AbdH activity and MLA angle. METHODS: A total of 16 participants with pes planus participated in this study. Participants performed SF, TSO, and TT exercises. Electromyographic activity of the AbdH and MLA angle during three AbdH contraction exercises were recorded using surface EMG system and digital image analysis program, respectively. The differences in outcome measures among the three exercises were analyzed using one-way repeated-measures analysis of variance. RESULTS: The EMG activity of the AbdH was significantly greater during the TT exercise compared to the SF and TSO exercises. The MLA angle was significantly smaller during the TT exercise compared with the SF and TSO exercises. CONCLUSIONS: These findings suggest that the TT exercise could be effective in activating the AbdH and increasing height of the MLA, as part of a sports rehabilitation program for individuals with pes planus.

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Effects of Sampling Frequency and Sample Window Size on Median Frequency of Surface EMG

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/1071181319631166 ◽

2019 ◽

Vol 63 (1) ◽

pp. 1369-1372

Author(s):

Pramiti Sarker ◽

Gary Mirka

Keyword(s):

Biceps Brachii ◽

Window Size ◽

Elbow Flexion ◽

Surface Emg ◽

Sampling Frequency ◽

Emg Activity ◽

Median Frequency ◽

Surface Electrodes ◽

Emg Signal ◽

Sample Window

Muscle fatigue can be evaluated through the assessment of the downward shift in the median frequency (MDF) of the electromyographic (EMG) signal collected through surface electromyography. Previous research has shown that the value of MDF may be affected by sampling parameters. The purpose of this study was to quantify the combined effect of different sampling frequencies and window sizes on the calculated MDF. A sample of 24 participants performed a simple static elbow flexion exertion (15% MVC) and the EMG activity of the biceps brachii was periodically sampled using surface electrodes for four seconds at a frequency of 4096 Hz as the biceps brachii became fatigued. These collected data were then down-sampled to create a dataset of four window sizes (1s, 2s, 3s, and 4s) and five sampling frequencies (256 Hz, 512 Hz, 1024 Hz, 2048 Hz, and 4096 Hz). Median frequencies were calculated for each combination of sampling frequency and window size and then compared with the 4096 Hz / 4 s condition (considered gold standard) and the errors were calculated. Results suggest the use of a minimum sampling frequency of 512 Hz and a window size of 4s.

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Electromyographic measures of muscle activation and changes in muscle architecture of human elbow flexors during fatiguing contractions

Journal of Applied Physiology ◽

10.1152/japplphysiol.01058.2007 ◽

2008 ◽

Vol 104 (6) ◽

pp. 1720-1726 ◽

Cited By ~ 34

Author(s):

Thorsten Rudroff ◽

Didier Staudenmann ◽

Roger M. Enoka

Keyword(s):

Muscle Activation ◽

Biceps Brachii ◽

Surface Emg ◽

Muscle Architecture ◽

Surface Measurement ◽

Emg Activity ◽

Time To Failure ◽

Elbow Flexors ◽

Emg Amplitude ◽

Rate Of Increase

The study compared changes in intramuscular and surface recordings of EMG amplitude with ultrasound measures of muscle architecture of the elbow flexors during a submaximal isometric contraction. Ten subjects performed a fatiguing contraction to task failure at 20% of maximal voluntary contraction force. EMG activity was recorded in biceps brachii, brachialis, and brachioradialis muscles using intramuscular and surface electrodes. The rates of increase in the amplitude of the surface EMG for the long and short heads of biceps brachii and brachioradialis were greater than those for the intramuscular recordings measured at different depths. The amplitude of the intramuscular recordings from three muscles increased at a similar rate ( P = 0.13), as did the amplitude of the three surface recordings from two muscles ( P = 0.83). The increases in brachialis thickness (27.7 ± 5.7 to 30.9 ± 3.5 mm; P < 0.05) and pennation angle (10.9 ± 3.5 to 16.5 ± 4.8°; P = 0.003) were not associated with the increase in intramuscular EMG amplitude ( P > 0.58). The increase in brachioradialis thickness (22.8 ± 4.8 to 25.5 ± 3.4 mm; P = 0.0075) was associated with the increase in the amplitude for one of two intramuscular EMG signals ( P = 0.007, r = 0.79). The time to failure was more strongly associated with the rate of increase in the amplitude of the surface EMG than that for the intramuscular EMG, which suggests that the surface measurement provides a more appropriate measure of the change in muscle activation during a fatiguing contraction.

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EMG Analysis of Patients with Unilateral Neck Pain

Journal of Sport Rehabilitation ◽

10.1123/jsr.8.1.32 ◽

1999 ◽

Vol 8 (1) ◽

pp. 32-42 ◽

Cited By ~ 1

Author(s):

Robert L. Whalen ◽

Steven P. Konstant ◽

Teddy W. Worrell ◽

Sam Kegerreis

Keyword(s):

Neck Pain ◽

Muscle Activity ◽

Physical Therapist ◽

Surface Emg ◽

High Variability ◽

Emg Activity ◽

Upper Trapezius ◽

Visual Analog Scales ◽

Vas Scores ◽

Emg Electrodes

The purpose of this study was to determine whether differences exist in EMG activity between involved and uninvolved upper trapezius muscles in participants with unilateral neck pain. Thirteen volunteers, seen by a physical therapist, gave informed consent. Surface EMG electrodes were placed on involved and uninvolved upper trapezius muscles. Root mean squared EMG activity was measured. Visual analog scales (VASs) for pain were used for each side. Reliability data indicated high ICC (2,1) but also large SEMs and CVs. EMG activity increased from resting to shrugging to abducting positions. Participants perceived greater pain on the involved side than the uninvolved side. EMG readings for individuals were consistent, however, between participants. EMG had high variability. Although participants' VAS scores were consistent with their reports of unilateral neck pain, surface EMG readings did not support the existence of increased muscle activity on the involved side.

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