EMG Power Spectrum and Integrated EMG of Ankle Planterflexors during Stepwise and Ramp Contractions.

Abstract

The aim of this study was to investigate whether the median frequencies (MF) of the electromyogram (EMG) and the integrated EMG (IEMG) of histochemically differentiated ankle plantarflexors, the gastrocnemius and soleus, were force dependent. Bipolar intramuscular wire electrodes were used to measure EMG of the soleus (SO), medial head of gastrocnemius (GM), and lateral head of gastrocnemius (GL) during ramp (single ongoing contractions) with the force increasing linearly from 0 to 100% of maximum voluntary contraction (MVC) and stepwise (steady force levels) ankle plantarflexion at 10, 20, 30, 40, 60, and 80% MVC. EMG and force were measured simultaneously. Power spectral analysis of these signals was performed to calculate MF on 1024-point by fast Fourier transform (FFT) technique. IEMG value of each muscle was also obtained at the same levels of force. While IEMG of three heads of triceps surae in both stepwise and ramp contractions increased significantly with increasing force, MF values of GL during stepwise contraction increased significantly (20, 40, 60, 80% MVC). These results suggest that the sensitivity of EMG power spectrum might be influenced by the proportion of fast twitch muscle fibers, which histochemically corresponds to type II fibers.

Surface Electromiography (Semg) in the Assessment and Treatment of Pelvic Floor Muscles: The Importance of Signal Normalization and Procedure Standardization for Interpretation and Biofeedback

“…As was reported by some authors [4,20], using the Glazer Protocol in the evaluation of pelvic floor muscles related functional disorders, e.g. urinary incontinence, pelvic pain, or sexual disorders it is possible to observe the shifts to the left in sEMG median frequency.…”

“…They have concluded that pelvic floor muscles training with sEMG biofeedback may influence mainly the bioelectric signal spectral frequency. Therefore the improvement in muscles contractile capabilities visible as changes in sEMG spectral frequencies may lead to pelvic floor muscles functional improvement [20].…”

Task Dependent Motor Strategy of Human Triceps Surae Muscle

“…Moreover, unlike the SO, a monoarticular muscle, the GM and GL are biarticular ones that cross the knee joint, hence the angle of the knee joint affects their contributions to plantar flexion torque. In addition to these difference, our previous study suggests that GL may have greater proportion of fast-fatigable twitch muscle fibers than GM 10) . Given these differences in the triceps muscles, their strategies in voluntary movements may differ [11][12][13][14] .…”

“…However, the increase in the IEMG value is commonly believed to due to increases in the amplitude and density of EMG signals resulting from the mutual influences of recruitment and firing rate. For this reason, many studies have used ramp contraction, defined as the generation of a single ongoing force from 0 to MVC 10,[21][22][23][24][25][26] . To our knowledge, however, there have been no investigations on the activities of the prime mover at ramp contractions of various durations under an isometric condition and variable muscle length conditions.…”

“…We hypothesized that activities of the triceps surae would be more clearly defined by three parameters of the constituent muscles, namely, duration of contraction, length of muscle, and plantar flexion performance. To look into this hypothesis, the present study investigated the behavior IEMG of each head of the triceps surae muscle during various ramp contraction durations (5, 10, 15 and 20 s), at three different knee joint angles (0 deg and flexed at 30 deg and 90 deg), across different ankle plantar flexion levels of force (10,20,30,40,50, 60 and 70% MVC).…”