Home Effects of sampling rate on automated fatigue recognition in surface EMG signals
Article Open Access

Effects of sampling rate on automated fatigue recognition in surface EMG signals

  • Lorenz Kahl , Marcus Eger and Ulrich G. Hofmann EMAIL logo
Published/Copyright: September 12, 2015
Download Article (PDF)
Become an author with De Gruyter Brill
Author Information Explore this Subject
Current Directions in Biomedical Engineering
From the journal Current Directions in Biomedical Engineering Volume 1 Issue 1

Abstract

This study investigated the effects different sampling rates may produce on the quality of muscle fatigue detection algorithms. sEMG signals were obtained from isometric contractions of the arm. Subsampled signals resulting in technically relevant sampling rates were computationally deduced from the original recordings. The spectral based fatigue recognition methods mean and median frequency as well as spectral moment ratio were included in this investigation, as well as the sample and the fuzzy approximate entropy. The resulting fatigue indices were evaluated with respect to noise and separability of different load levels. We concluded that the spectral moment ratio provides the best results in fatigue detection over a wide range of sampling rates.

Keywords: EMG; muscle fatigue; sample rate; MNF; MDF; spectral moment ratio; sample entropy; fuzzy approximate entropy; FES; physiotherapy; neuroprosthesis

1 Introduction

It is part of common knowledge that excessive bodily exercise will lead to muscle fatigue, easily assessed as the muscles’ inability to continuously deliver a constant force. Both physiotherapy and Functional Electro-Stimulation (FES), the noninvasive stimulation of de-innervated muscles, have gone to great lengths to develop stimulation patterns to avoid early muscle fatigue, yet to provide optimal therapeutic outcome. Insofar, it is of great interest to objectively assess muscular fatigue and adjust training accordingly. Muscular fatigue can be detected by subtle changes in electromyographic recordings from the affected muscle. An overview of known fatigue detection algorithms can be found in Gonzalez-Izal et al. [5]. Our investigation compared the performance of different reported fatigue detection algorithms depending on the sampling rate of the input sEMG (surface EMG) signal. We considered algorithms based on mean (MNF) and median (MDF) frequencies as well as the spectral moment ratio (SMR), sample (SampEn) and fuzzy approximate entropy (fApEn). These algorithm’s performance was evaluated based on sEMG signals with technically most relevant sampling rates between 256 and 1024 Hz.

2 Methods

The investigations are based on sEMG recordings from upper arm’s biceps muscles while pulling against a constant force. The experiment was conducted with 12 healthy volunteers (age between 17 and 56, 6 female and 6 male). Written consent to take part in the experiment was obtained from the volunteers prior to the start of the experiment.

2.1 Experimental setup

Each subject was requested to pull a rope attached to his/her wrist with a bent arm and the elbow leaning flat on a support. The experiment was conducted with the subject sitting upright in front of a table fitted with pulleys to enable isotonic lifting of a defined weight (see Fig. 1 a). The block and pulley construction exerted a constant force on the biceps muscles, once the prepared weight was lifted off the ground.

Figure 1 Setup of the experiment. The block and pulley construction with the seated subject is shown in (a). (b) visualizes the position of the electrodes on the arm.
Figure 1

Setup of the experiment. The block and pulley construction with the seated subject is shown in (a). (b) visualizes the position of the electrodes on the arm.

For calibration purposes the volunteer was asked to pull against a spring scale with his/her maximal achievable effort. That way the maximum voluntary contraction (MVC) was determined. Afterwards the subjects were granted a resting period of at least 30 minutes.

Then the subject was requested to lift a weight of 20% of his/her previously determined MVC for 3 minutes. This trial was intended to produce a non-fatiguing sEMG recording. In this case all subjects persevered the maximum duration of 3 minutes.

After another resting period of at least 30 minutes the subject was requested to pull with 60% of his/her MVC to produce a fatiguing sEMG recording. Each volunteer was told to be free to let go the load and relax when feeling exhausted. Subjects were able to sustain the load between 60 seconds until the end of the trial after 3 minutes. The average duration of the 60% MVC trial was 135 seconds.

sEMG was recorded from eight self-adhesive electrodes (Covidien Kendall, H124SG) placed on the upper arm on top of the biceps (see Fig. 1 b). They were placed in two rows (first row electrodes 1-4, second row electrodes 5-8). Electrodes 3 and 7 were placed above the thickest point of the biceps and electrodes 1 and 4 were placed on the distal end of the upper arm. Electrodes were attached next to each other without gap in between. The centers of adjacent electrodes were thus (in accordance with their diameter) 24 mm apart.

Recordings were made with a Porti amplifier (TMSI, Oldenzaal, Netherlands). The amplifier included a 22 bit analog digital converter and was operated with a sampling rate of 1024 Hz. The common electrode of the amplifier was connected on the back side of the upper arm, opposite to the other electrodes, on top of the triceps muscle.

2.2 Signal processing

Raw values provided by the amplifier were imported into a PC for offline analysis. All further steps of signal processing were conducted in R [3]. In a first step 28 differential channels representing all possible combinations of two from eight electrodes were calculated. To remove a possible baseline offset, all differential channels were filtered with a high pass filter (3rd order Butterworth IIR filter with 2Hz corner frequency).

Downsampled sEMG signals were derived from the original 1024 Hz signal to investigate the effect of sampling rate limitations. The resampled sEMG signals had sampling rates of 256, 384, 512, 640, 768 and 896 Hz. The re-sampling was carried out by bandlimited interpolation [8] as implemented by the resample method from the R signal package.

Fatigue was quantified based on the high pass filtered sEMG signal as well as the derived resampled sEMG signals by the following, briefly described fatigue evaluation algorithms. The evaluation was performed epoch-wise with an epoch size of one second. A new epoch was started every 128 ms, resulting in eight epochs overlapping at each point in time and in fatigue tracings with 8 Hz sampling rate.

2.2.1 Frequency based fatigue algorithms

Frequency based fatigue algorithms quantify the spectral compression that is connected to the reduction of the conduction velocity occurring in fatiguing muscles as explained by Lindström et al. [6]. These algorithms are based on the epoch-wise estimated power spectral density (PSD). The PSD was estimated by the FFT based Welch method with eight sub segments, no overlapping and the Hamming window function.

An alternative PSD estimation was obtained by the Burg algorithm [2]. The Burg algorithm is a parametric PSD estimation method. In a first step parametric PSD estimators determine a linear filter. This filter is designed in a way that it would transform white noise into a signal with the same spectral shape as the original signal to be analyzed. In case of the Burg algorithm filter coefficients of an autoregressive filter and a gain are calculated. The order of the filter was adaptively determined by the Akaike Information Criterion as implemented by the R function ar.burg(). In a second step the PSD estimation was calculated from the autoregressive filter coefficients.

The mean (also known as central) frequency MNF=f0fs/2f⋅PSD(f)dff0fs/2PSD(f)df as well as the median frequency (MDF) were calculated as described in Merletti and Parker [1]. MDF is defined as∫0MDFPSD(f)df∫MDFfs/sPSD(f)df.

Furthermore the PSD estimation was evaluated with the spectral moment ratio (SMR) reported as new spectral index in [4]. Instead of using fixed frequency bands with fixed boundaries as with the old H/L ratio [9], Dimitrov and colleagues used the ratio of the spectral moments of the orders -1 and 5. The spectral moment of order k is defined as Mk=∫0fs/2fk⋅PSD(f)df. Finally the spectral moment ratio was calculated as SMR=lnM−1M5. We decided to use the natural logarithm of the ratio to circumvent changes by several orders of magnitude.

2.2.2 Entropy based fatigue algorithms

Entropy estimation is a nonlinear method that might be used as a fatigue indicator. One possible entropy calculation method is the sample entropy (SampEn) as introduced by Richman and Moorman [7]. Xie et al. [10] suggested an improved algorithm named fuzzy approximate entropy (fApEn) as a fatigue indicator.

Sample entropy is defined by Richman and Moorman [7] as negative natural logarithm of the conditional probability that two sequences similar for m points remain similar at the next point m+1. Two vectors are considered similar if their distance according to the uniform norm is below a threshold r. The sample entropy is calculated epoch-wise. Each epoch is first normalized to have zero mean and a standard deviation of one. The sample entropy was calculated for vector length m = 1, 2, 3, 4, 5, 6, 7 and thresholds of r = 0.3, 0.4, 0.5, 0.6, 0.7. A value of vector length of one in combination with r = 0.3 and a vector length of two in combination with r = 0.7 proved satisfactory. The sample entropy was calculated using code available from http://www.physionet.org/physiotools/sampen/c/.

The fuzzy approximate entropy is calculated in a similar manner. In contrast to the sample entropy the mean of each part vector is subtracted prior to comparison under the uniform norm. Moreover instead of the simplification to a binary state threshold, a fuzzy function u(d,r)=exp(−d2r) is applied on the distance d. In case of the fuzzy approximate entropy a vector length of two and a threshold of r = 0.6 were used.

2.3 Evaluation of quality

The performance of the fatigue methods were compared with respect to two criteria. The first criterion of a good fatigue detection algorithm is to demonstrate little noise in case of a fatigue producing load. The second criterion is that it will provide a good discrimination of different degrees of fatigue, assuming that these are resulting from the different load levels.

To account for the first criterion the fatigue index’ noise was quantified by calculating the coefficient of determination R2 following the suggestion of Xie et al. [10]. The coefficient of determination states how much of a signal can be described by a line with constant slope. The closer R2 is to one, the better. This analysis is based on the first 60 s of the 60% MVC load case. Figure 2 illustrates an example. An average R2 value was evaluated for each combination of fatigue algorithm and sampling rate across all subjects and electrode channels.

Figure 2 The top panel shows exemplary sEMG recordings from the 20% MVC load case (green) and the 60% MVC load case (red). The corresponding fatigue signals (spectral moment ratio) are displayed below. The vertical lines indicate the beginning and ending of the first 60 seconds considered for evaluation.
Figure 2

The top panel shows exemplary sEMG recordings from the 20% MVC load case (green) and the 60% MVC load case (red). The corresponding fatigue signals (spectral moment ratio) are displayed below. The vertical lines indicate the beginning and ending of the first 60 seconds considered for evaluation.

To investigate how well different degrees of fatigue can be discriminated the results of the different load levels were analyzed. This analysis is based on the assumption that different load levels will lead to different degrees of fatigue. A best fit linear slope was calculated for the first 60 s of all fatigue signals for both the 20% and 60% MVC load cases. See Figure 2 for an example. The slope of this line corresponds to the change of the underlying fatigue signal in the first 60 s of the contraction. For each combination of sampling rate and fatigue algorithm a separabilty value Δ=|μ(δ60−δ20)σ(δ60−δ20)| (defined as the ratio of the mean and the standard deviation of the differences in between the 20% and the 60% MVC load) was calculated across electrode channels and subjects. The bigger the delta, the better.

3 Results

Figure 3a shows the average coefficient of determination for the 60% MVC load case. In general the coefficient of determination rises with larger sampling rates. In case of the frequency based methods the spectral moment ratio shows the largest R2 values followed by mean and median frequency. All three PSD evaluation methods show larger coefficients of determination if they are based on Burg spectral estimation compared to the classical FFT based Welch algorithm. Both entropy algorithms suffer a strong decrease of the average coefficient of determination for small sampling rates.

Figure 3 Results of the various fatigue algorithms plotted against the sampling rate. (a) visualizes the coeflcients of determination R2. Separability values are shown in (b).
Figure 3

Results of the various fatigue algorithms plotted against the sampling rate. (a) visualizes the coeflcients of determination R2. Separability values are shown in (b).

Figure 3b shows the values quantifying the separability of the different load levels. In the field of frequency based algorithms the spectral moment ratio lies closely above the mean frequency followed by the median frequency. In contrast to the evaluation of the coefficient of determination the results of the Burg spectral estimation are very close to those based on the Welch method. The results of the entropy based methods are again more sensitive to smaller sampling rates than the frequency based methods.

4 Conclusion

The results show that the fatigue detection quality of all tested algorithms is sensitive to the sampling rate of the input sEMG signal. At the three tested frequency based methods the median frequency yielded the worst results. Above a sampling rate of 640 Hz the results are not improving for both investigated spectral estimations and in respect to both R2 and. It seems quite reasonable that this effect is connected to the characteristic of the median to be robust against outliers. Small portions of the frequency compression in higher bands are attenuated similar to outliers. In contrast the results of the mean frequency are slightly improving for sampling rates larger than 640 Hz. The SENIAM recommendations [1] suggest a sampling rate of 1 kHz or larger for general sEMG applications. The results show that this recommendation seems reasonable for mean and median frequency based fatigue detection.

At low sampling rates the results of the spectral moment ratio are comparable to the mean frequency. Towards higher sampling rates the advantage of the spectral moments method above the mean frequency becomes more and more obvious. It seems that the intention of the smooth weighting function to take the spectral compression also for higher frequencies into account is effective and that the algorithm needs a high sampling rate to display this strength. This is in accordance with the fact that Dimitrov et al. [4] used a sampling rate of even 2 kHz.

Kammeyer and Kroschel [2] showed that the Burg algorithm can yield a very good spectral estimation even for small epoch sizes if the autoregressive model is suitable to the data. The results suggest that this is the case for the investigated sEMG data as the Burg algorithm leads to higher R2 values in case of all three PSD based evaluation methods possibly caused by Burg’s lower estimation variance.

The results also show that the entropy based fatigue methods are more sensitive against a reduction of the sampling rate than the frequency based methods. In case of the sample entropy the choice of the best parameters strongly depends on the sampling rate whereas this is not the case with the fuzzy approximate entropy. The fatigue detection quality based on fApEn showed also best results at a sampling rate of 1024 Hz. This is in accordance with the 1 kHz sampling rate used by Xie et al. [10].

Funding: This work was funded by Drägerwerk AG & Co. KGaA, Lübeck.

Author’s Statement

  1. Conflict of interest: Authors state no conflict of interest. Material and Methods: Informed consent: Informed consent has been obtained from all individuals included in this study. Ethical approval: The research related to human use has been complied with all the relevant national regulations, institutional policies and in accordance the tenets of the Helsinki Declaration, and has been approved by the authors’ institutional review board or equivalent committee.

References

[1] Merletti R, Parker PA, eds. Electromyography : physiology, engineering, and noninvasive applications. IEEE Press series in biomedical engineering. Wiley-Interscience [u.a.], Hoboken, 2004.10.1002/0471678384Search in Google Scholar

[2] Kammeyer KD, Kroschel K. Digitale Signalverarbeitung. Vieweg + Teubner, 7 edn., 2009.Search in Google Scholar

[3] R Core Team. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria, 2013.Search in Google Scholar

[4] Dimitrov GV, Arabadzhiev TI, Mileva KN, Bowtell JL, Crichton N, Dimitrova NA Muscle fatigue during dynamic contractions assessed by new spectral indices. Medicine & Science in Sports & Exercise 11(0195-9131):1971–1979, 2006.10.1249/01.mss.0000233794.31659.6dSearch in Google Scholar PubMed

[5] Gonzalez-Izal M, Malanda A, Gorostiaga E, Izquierdo M Electromyographic models to assess muscle fatigue. J Electromyogr Kinesiol 22(4):501–512, 2012.10.1016/j.jelekin.2012.02.019Search in Google Scholar PubMed

[6] Lindström L, Magnusson R, Petersen I Muscular Fatigue and Action Potential Conduction Velocity Changes Studied with Frequency Analysis of EMG Signals. Electromyography 4:341–356, 1970.Search in Google Scholar

[7] Richman JS, Moorman JR Physiological time-series analysis usind approximate entropy and sample entropy. Am J Physiol Heart Circ Physiol 278:H2039 – H2049, 2000.10.1152/ajpheart.2000.278.6.H2039Search in Google Scholar PubMed

[8] Smith JO, Gossett P A flexible sampling-rate conversion method. In Acoustics, Speech, and Signal Processing, IEEE Intern. Conf. on ICASSP ’84., vol. 9, 112–115. 1984.Search in Google Scholar

[9] Stulen FB, De Luca CJ Frequency Parameters of the Myoelectric Signal as a Measure of Muscle Conduction Velocity BME-28, No 7:515–523, 1981.10.1109/TBME.1981.324738Search in Google Scholar PubMed

[10] Xie HB, Guo JY, Zheng YP Fuzzy approximate entropy analysis of chaotic and natural complex systems: detecting muscle fatigue using electromyography signals. Ann Biomed Eng 38(4):1483–1496, 2010.10.1007/s10439-010-9933-5Search in Google Scholar PubMed

Published Online: 2015-9-12
Published in Print: 2015-9-1

© 2015 by Walter de Gruyter GmbH, Berlin/Boston

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Articles in the same Issue

  1. Research Article
  2. Development and characterization of superparamagnetic coatings
  3. Research Article
  4. The development of an experimental setup to measure acousto-electric interaction signal
  5. Research Article
  6. Stability analysis of ferrofluids
  7. Research Article
  8. Investigation of endothelial growth using a sensors-integrated microfluidic system to simulate physiological barriers
  9. Research Article
  10. Energy harvesting for active implants: powering a ruminal pH-monitoring system
  11. Research Article
  12. New type of fluxgate magnetometer for the heart’s magnetic fields detection
  13. Research Article
  14. Field mapping of ballistic pressure pulse sources
  15. Research Article
  16. Development of a new homecare sleep monitor using body sounds and motion tracking
  17. Research Article
  18. Noise properties of textile, capacitive EEG electrodes
  19. Research Article
  20. Detecting phase singularities and rotor center trajectories based on the Hilbert transform of intraatrial electrograms in an atrial voxel model
  21. Research Article
  22. Spike sorting: the overlapping spikes challenge
  23. Research Article
  24. Separating the effect of respiration from the heart rate variability for cases of constant harmonic breathing
  25. Research Article
  26. Locating regions of arrhythmogenic substrate by analyzing the duration of triggered atrial activities
  27. Research Article
  28. Combining different ECG derived respiration tracking methods to create an optimal reconstruction of the breathing pattern
  29. Research Article
  30. Atrial and ventricular signal averaging electrocardiography in pacemaker and cardiac resynchronization therapy
  31. Research Article
  32. Estimation of a respiratory signal from a single-lead ECG using the 4th order central moments
  33. Research Article
  34. Compressed sensing of multi-lead ECG signals by compressive multiplexing
  35. Research Article
  36. Heart rate monitoring in ultra-high-field MRI using frequency information obtained from video signals of the human skin compared to electrocardiography and pulse oximetry
  37. Research Article
  38. Synchronization in wireless biomedical-sensor networks with Bluetooth Low Energy
  39. Research Article
  40. Automated classification of stages of anaesthesia by populations of evolutionary optimized fuzzy rules
  41. Research Article
  42. Effects of sampling rate on automated fatigue recognition in surface EMG signals
  43. Research Article
  44. Closed-loop transcranial alternating current stimulation of slow oscillations
  45. Research Article
  46. Cardiac index in atrio- and interventricular delay optimized cardiac resynchronization therapy and cardiac contractility modulation
  47. Research Article
  48. The role of expert evaluation for microsleep detection
  49. Research Article
  50. The impact of baseline wander removal techniques on the ST segment in simulated ischemic 12-lead ECGs
  51. Research Article
  52. Metal artifact reduction by projection replacements and non-local prior image integration
  53. Research Article
  54. A novel coaxial nozzle for in-process adjustment of electrospun scaffolds’ fiber diameter
  55. Research Article
  56. Processing of membranes for oxygenation using the Bellhouse-effect
  57. Research Article
  58. Inkjet printing of viable human dental follicle stem cells
  59. Research Article
  60. The use of an icebindingprotein out of the snowflea Hypogastrura harveyi as a cryoprotectant in the cryopreservation of mesenchymal stem cells
  61. Research Article
  62. New NIR spectroscopy based method to determine ischemia in vivo in liver – a first study on rats
  63. Research Article
  64. QRS and QT ventricular conduction times and permanent pacemaker therapy after transcatheter aortic valve implantation
  65. Research Article
  66. Adopting oculopressure tonometry as a transient in vivo rabbit glaucoma model
  67. Research Article
  68. Next-generation vision testing: the quick CSF
  69. Research Article
  70. Improving tactile sensation in laparoscopic surgery by overcoming size restrictions
  71. Research Article
  72. Design and control of a 3-DOF hydraulic driven surgical instrument
  73. Research Article
  74. Evaluation of endourological tools to improve the diagnosis and therapy of ureteral tumors – from model development to clinical application
  75. Research Article
  76. Frequency based assessment of surgical activities
  77. Research Article
  78. “Hands free for intervention”, a new approach for transoral endoscopic surgery
  79. Research Article
  80. Pseudo-haptic feedback in medical teleoperation
  81. Research Article
  82. Feasibility of interactive gesture control of a robotic microscope
  83. Research Article
  84. Towards structuring contextual information for workflow-driven surgical assistance functionalities
  85. Research Article
  86. Towards a framework for standardized semantic workflow modeling and management in the surgical domain
  87. Research Article
  88. Closed-loop approach for situation awareness of medical devices and operating room infrastructure
  89. Research Article
  90. Kinect based physiotherapy system for home use
  91. Research Article
  92. Evaluating the microsoft kinect skeleton joint tracking as a tool for home-based physiotherapy
  93. Research Article
  94. Integrating multimodal information for intraoperative assistance in neurosurgery
  95. Research Article
  96. Respiratory motion tracking using Microsoft’s Kinect v2 camera
  97. Research Article
  98. Using smart glasses for ultrasound diagnostics
  99. Research Article
  100. Measurement of needle susceptibility artifacts in magnetic resonance images
  101. Research Article
  102. Dimensionality reduction of medical image descriptors for multimodal image registration
  103. Research Article
  104. Experimental evaluation of different weighting schemes in magnetic particle imaging reconstruction
  105. Research Article
  106. Evaluation of CT capability for the detection of thin bone structures
  107. Research Article
  108. Towards contactless optical coherence elastography with acoustic tissue excitation
  109. Research Article
  110. Development and implementation of algorithms for automatic and robust measurement of the 2D:4D digit ratio using image data
  111. Research Article
  112. Automated high-throughput analysis of B cell spreading on immobilized antibodies with whole slide imaging
  113. Research Article
  114. Tissue segmentation from head MRI: a ground truth validation for feature-enhanced tracking
  115. Research Article
  116. Video tracking of swimming rodents on a reflective water surface
  117. Research Article
  118. MR imaging of model drug distribution in simulated vitreous
  119. Research Article
  120. Studying the extracellular contribution to the double wave vector diffusion-weighted signal
  121. Research Article
  122. Artifacts in field free line magnetic particle imaging in the presence of inhomogeneous and nonlinear magnetic fields
  123. Research Article
  124. Introducing a frequency-tunable magnetic particle spectrometer
  125. Research Article
  126. Imaging of aortic valve dynamics in 4D OCT
  127. Research Article
  128. Intravascular optical coherence tomography (OCT) as an additional tool for the assessment of stent structures
  129. Research Article
  130. Simple concept for a wide-field lensless digital holographic microscope using a laser diode
  131. Research Article
  132. Intraoperative identification of somato-sensory brain areas using optical imaging and standard RGB camera equipment – a feasibility study
  133. Research Article
  134. Respiratory surface motion measurement by Microsoft Kinect
  135. Research Article
  136. Improving image quality in EIT imaging by measurement of thorax excursion
  137. Research Article
  138. A clustering based dual model framework for EIT imaging: first experimental results
  139. Research Article
  140. Three-dimensional anisotropic regularization for limited angle tomography
  141. Research Article
  142. GPU-based real-time generation of large ultrasound volumes from freehand 3D sweeps
  143. Research Article
  144. Experimental computer tomograph
  145. Research Article
  146. US-tracked steered FUS in a respiratory ex vivo ovine liver phantom
  147. Research Article
  148. Contribution of brownian rotation and particle assembly polarisation to the particle response in magnetic particle spectrometry
  149. Research Article
  150. Preliminary investigations of magnetic modulated nanoparticles for microwave breast cancer detection
  151. Research Article
  152. Construction of a device for magnetic separation of superparamagnetic iron oxide nanoparticles
  153. Research Article
  154. An IHE-conform telecooperation platform supporting the treatment of dementia patients
  155. Research Article
  156. Automated respiratory therapy system based on the ARDSNet protocol with systemic perfusion control
  157. Research Article
  158. Identification of surgical instruments using UHF-RFID technology
  159. Research Article
  160. A generic concept for the development of model-guided clinical decision support systems
  161. Research Article
  162. Evaluation of local alterations in femoral bone mineral density measured via quantitative CT
  163. Research Article
  164. Creating 3D gelatin phantoms for experimental evaluation in biomedicine
  165. Research Article
  166. Influence of short-term fixation with mixed formalin or ethanol solution on the mechanical properties of human cortical bone
  167. Research Article
  168. Analysis of the release kinetics of surface-bound proteins via laser-induced fluorescence
  169. Research Article
  170. Tomographic particle image velocimetry of a water-jet for low volume harvesting of fat tissue for regenerative medicine
  171. Research Article
  172. Wireless medical sensors – context, robustness and safety
  173. Research Article
  174. Sequences for real-time magnetic particle imaging
  175. Research Article
  176. Speckle-based off-axis holographic detection for non-contact photoacoustic tomography
  177. Research Article
  178. A machine learning approach for planning valve-sparing aortic root reconstruction
  179. Research Article
  180. An in-ear pulse wave velocity measurement system using heart sounds as time reference
  181. Research Article
  182. Measuring different oxygenation levels in a blood perfusion model simulating the human head using NIRS
  183. Research Article
  184. Multisegmental fusion of the lumbar spine a curse or a blessing?
  185. Research Article
  186. Numerical analysis of the biomechanical complications accompanying the total hip replacement with NANOS-Prosthetic: bone remodelling and prosthesis migration
  187. Research Article
  188. A muscle model for hybrid muscle activation
  189. Research Article
  190. Mathematical, numerical and in-vitro investigation of cooling performance of an intra-carotid catheter for selective brain hypothermia
  191. Research Article
  192. An ideally parameterized unscented Kalman filter for the inverse problem of electrocardiography
  193. Research Article
  194. Interactive visualization of cardiac anatomy and atrial excitation for medical diagnosis and research
  195. Research Article
  196. Virtualizing clinical cases of atrial flutter in a fast marching simulation including conduction velocity and ablation scars
  197. Research Article
  198. Mesh structure-independent modeling of patient-specific atrial fiber orientation
  199. Research Article
  200. Accelerating mono-domain cardiac electrophysiology simulations using OpenCL
  201. Research Article
  202. Understanding the cellular mode of action of vernakalant using a computational model: answers and new questions
  203. Research Article
  204. A java based simulator with user interface to simulate ventilated patients
  205. Research Article
  206. Evaluation of an algorithm to choose between competing models of respiratory mechanics
  207. Research Article
  208. Numerical simulation of low-pulsation gerotor pumps for use in the pharmaceutical industry and in biomedicine
  209. Research Article
  210. Numerical and experimental flow analysis in centifluidic systems for rapid allergy screening tests
  211. Research Article
  212. Biomechanical parameter determination of scaffold-free cartilage constructs (SFCCs) with the hyperelastic material models Yeoh, Ogden and Demiray
  213. Research Article
  214. FPGA controlled artificial vascular system
  215. Research Article
  216. Simulation based investigation of source-detector configurations for non-invasive fetal pulse oximetry
  217. Research Article
  218. Test setup for characterizing the efficacy of embolic protection devices
  219. Research Article
  220. Impact of electrode geometry on force generation during functional electrical stimulation
  221. Research Article
  222. 3D-based visual physical activity assessment of children
  223. Research Article
  224. Realtime assessment of foot orientation by Accelerometers and Gyroscopes
  225. Research Article
  226. Image based reconstruction for cystoscopy
  227. Research Article
  228. Image guided surgery innovation with graduate students - a new lecture format
  229. Research Article
  230. Multichannel FES parameterization for controlling foot motion in paretic gait
  231. Research Article
  232. Smartphone supported upper limb prosthesis
  233. Research Article
  234. Use of quantitative tremor evaluation to enhance target selection during deep brain stimulation surgery for essential tremor
  235. Research Article
  236. Evaluation of adhesion promoters for Parylene C on gold metallization
  237. Research Article
  238. The influence of metallic ions from CoCr28Mo6 on the osteogenic differentiation and cytokine release of human osteoblasts
  239. Research Article
  240. Increasing the visibility of thin NITINOL vascular implants
  241. Research Article
  242. Possible reasons for early artificial bone failure in biomechanical tests of ankle arthrodesis systems
  243. Research Article
  244. Development of a bending test procedure for the characterization of flexible ECoG electrode arrays
  245. Research Article
  246. Tubular manipulators: a new concept for intracochlear positioning of an auditory prosthesis
  247. Research Article
  248. Investigation of the dynamic diameter deformation of vascular stents during fatigue testing with radial loading
  249. Research Article
  250. Electrospun vascular grafts with anti-kinking properties
  251. Research Article
  252. Integration of temperature sensors in polyimide-based thin-film electrode arrays
  253. Research Article
  254. Use cases and usability challenges for head-mounted displays in healthcare
  255. Research Article
  256. Device- and service profiles for integrated or systems based on open standards
  257. Research Article
  258. Risk management for medical devices in research projects
  259. Research Article
  260. Simulation of varying femoral attachment sites of medial patellofemoral ligament using a musculoskeletal multi-body model
  261. Research Article
  262. Does enhancing consciousness for strategic planning processes support the effectiveness of problem-based learning concepts in biomedical education?
  263. Research Article
  264. SPIO processing in macrophages for MPI: The breast cancer MPI-SNLB-concept
  265. Research Article
  266. Numerical simulations of airflow in the human pharynx of OSAHS patients
https://doi.org/10.1515/cdbme-2015-0021
Keywords for this article
EMG; muscle fatigue; sample rate; MNF; MDF; spectral moment ratio; sample entropy; fuzzy approximate entropy; FES; physiotherapy; neuroprosthesis
Creative Commons
BY-NC-ND 3.0

Articles in the same Issue

  1. Research Article
  2. Development and characterization of superparamagnetic coatings
  3. Research Article
  4. The development of an experimental setup to measure acousto-electric interaction signal
  5. Research Article
  6. Stability analysis of ferrofluids
  7. Research Article
  8. Investigation of endothelial growth using a sensors-integrated microfluidic system to simulate physiological barriers
  9. Research Article
  10. Energy harvesting for active implants: powering a ruminal pH-monitoring system
  11. Research Article
  12. New type of fluxgate magnetometer for the heart’s magnetic fields detection
  13. Research Article
  14. Field mapping of ballistic pressure pulse sources
  15. Research Article
  16. Development of a new homecare sleep monitor using body sounds and motion tracking
  17. Research Article
  18. Noise properties of textile, capacitive EEG electrodes
  19. Research Article
  20. Detecting phase singularities and rotor center trajectories based on the Hilbert transform of intraatrial electrograms in an atrial voxel model
  21. Research Article
  22. Spike sorting: the overlapping spikes challenge
  23. Research Article
  24. Separating the effect of respiration from the heart rate variability for cases of constant harmonic breathing
  25. Research Article
  26. Locating regions of arrhythmogenic substrate by analyzing the duration of triggered atrial activities
  27. Research Article
  28. Combining different ECG derived respiration tracking methods to create an optimal reconstruction of the breathing pattern
  29. Research Article
  30. Atrial and ventricular signal averaging electrocardiography in pacemaker and cardiac resynchronization therapy
  31. Research Article
  32. Estimation of a respiratory signal from a single-lead ECG using the 4th order central moments
  33. Research Article
  34. Compressed sensing of multi-lead ECG signals by compressive multiplexing
  35. Research Article
  36. Heart rate monitoring in ultra-high-field MRI using frequency information obtained from video signals of the human skin compared to electrocardiography and pulse oximetry
  37. Research Article
  38. Synchronization in wireless biomedical-sensor networks with Bluetooth Low Energy
  39. Research Article
  40. Automated classification of stages of anaesthesia by populations of evolutionary optimized fuzzy rules
  41. Research Article
  42. Effects of sampling rate on automated fatigue recognition in surface EMG signals
  43. Research Article
  44. Closed-loop transcranial alternating current stimulation of slow oscillations
  45. Research Article
  46. Cardiac index in atrio- and interventricular delay optimized cardiac resynchronization therapy and cardiac contractility modulation
  47. Research Article
  48. The role of expert evaluation for microsleep detection
  49. Research Article
  50. The impact of baseline wander removal techniques on the ST segment in simulated ischemic 12-lead ECGs
  51. Research Article
  52. Metal artifact reduction by projection replacements and non-local prior image integration
  53. Research Article
  54. A novel coaxial nozzle for in-process adjustment of electrospun scaffolds’ fiber diameter
  55. Research Article
  56. Processing of membranes for oxygenation using the Bellhouse-effect
  57. Research Article
  58. Inkjet printing of viable human dental follicle stem cells
  59. Research Article
  60. The use of an icebindingprotein out of the snowflea Hypogastrura harveyi as a cryoprotectant in the cryopreservation of mesenchymal stem cells
  61. Research Article
  62. New NIR spectroscopy based method to determine ischemia in vivo in liver – a first study on rats
  63. Research Article
  64. QRS and QT ventricular conduction times and permanent pacemaker therapy after transcatheter aortic valve implantation
  65. Research Article
  66. Adopting oculopressure tonometry as a transient in vivo rabbit glaucoma model
  67. Research Article
  68. Next-generation vision testing: the quick CSF
  69. Research Article
  70. Improving tactile sensation in laparoscopic surgery by overcoming size restrictions
  71. Research Article
  72. Design and control of a 3-DOF hydraulic driven surgical instrument
  73. Research Article
  74. Evaluation of endourological tools to improve the diagnosis and therapy of ureteral tumors – from model development to clinical application
  75. Research Article
  76. Frequency based assessment of surgical activities
  77. Research Article
  78. “Hands free for intervention”, a new approach for transoral endoscopic surgery
  79. Research Article
  80. Pseudo-haptic feedback in medical teleoperation
  81. Research Article
  82. Feasibility of interactive gesture control of a robotic microscope
  83. Research Article
  84. Towards structuring contextual information for workflow-driven surgical assistance functionalities
  85. Research Article
  86. Towards a framework for standardized semantic workflow modeling and management in the surgical domain
  87. Research Article
  88. Closed-loop approach for situation awareness of medical devices and operating room infrastructure
  89. Research Article
  90. Kinect based physiotherapy system for home use
  91. Research Article
  92. Evaluating the microsoft kinect skeleton joint tracking as a tool for home-based physiotherapy
  93. Research Article
  94. Integrating multimodal information for intraoperative assistance in neurosurgery
  95. Research Article
  96. Respiratory motion tracking using Microsoft’s Kinect v2 camera
  97. Research Article
  98. Using smart glasses for ultrasound diagnostics
  99. Research Article
  100. Measurement of needle susceptibility artifacts in magnetic resonance images
  101. Research Article
  102. Dimensionality reduction of medical image descriptors for multimodal image registration
  103. Research Article
  104. Experimental evaluation of different weighting schemes in magnetic particle imaging reconstruction
  105. Research Article
  106. Evaluation of CT capability for the detection of thin bone structures
  107. Research Article
  108. Towards contactless optical coherence elastography with acoustic tissue excitation
  109. Research Article
  110. Development and implementation of algorithms for automatic and robust measurement of the 2D:4D digit ratio using image data
  111. Research Article
  112. Automated high-throughput analysis of B cell spreading on immobilized antibodies with whole slide imaging
  113. Research Article
  114. Tissue segmentation from head MRI: a ground truth validation for feature-enhanced tracking
  115. Research Article
  116. Video tracking of swimming rodents on a reflective water surface
  117. Research Article
  118. MR imaging of model drug distribution in simulated vitreous
  119. Research Article
  120. Studying the extracellular contribution to the double wave vector diffusion-weighted signal
  121. Research Article
  122. Artifacts in field free line magnetic particle imaging in the presence of inhomogeneous and nonlinear magnetic fields
  123. Research Article
  124. Introducing a frequency-tunable magnetic particle spectrometer
  125. Research Article
  126. Imaging of aortic valve dynamics in 4D OCT
  127. Research Article
  128. Intravascular optical coherence tomography (OCT) as an additional tool for the assessment of stent structures
  129. Research Article
  130. Simple concept for a wide-field lensless digital holographic microscope using a laser diode
  131. Research Article
  132. Intraoperative identification of somato-sensory brain areas using optical imaging and standard RGB camera equipment – a feasibility study
  133. Research Article
  134. Respiratory surface motion measurement by Microsoft Kinect
  135. Research Article
  136. Improving image quality in EIT imaging by measurement of thorax excursion
  137. Research Article
  138. A clustering based dual model framework for EIT imaging: first experimental results
  139. Research Article
  140. Three-dimensional anisotropic regularization for limited angle tomography
  141. Research Article
  142. GPU-based real-time generation of large ultrasound volumes from freehand 3D sweeps
  143. Research Article
  144. Experimental computer tomograph
  145. Research Article
  146. US-tracked steered FUS in a respiratory ex vivo ovine liver phantom
  147. Research Article
  148. Contribution of brownian rotation and particle assembly polarisation to the particle response in magnetic particle spectrometry
  149. Research Article
  150. Preliminary investigations of magnetic modulated nanoparticles for microwave breast cancer detection
  151. Research Article
  152. Construction of a device for magnetic separation of superparamagnetic iron oxide nanoparticles
  153. Research Article
  154. An IHE-conform telecooperation platform supporting the treatment of dementia patients
  155. Research Article
  156. Automated respiratory therapy system based on the ARDSNet protocol with systemic perfusion control
  157. Research Article
  158. Identification of surgical instruments using UHF-RFID technology
  159. Research Article
  160. A generic concept for the development of model-guided clinical decision support systems
  161. Research Article
  162. Evaluation of local alterations in femoral bone mineral density measured via quantitative CT
  163. Research Article
  164. Creating 3D gelatin phantoms for experimental evaluation in biomedicine
  165. Research Article
  166. Influence of short-term fixation with mixed formalin or ethanol solution on the mechanical properties of human cortical bone
  167. Research Article
  168. Analysis of the release kinetics of surface-bound proteins via laser-induced fluorescence
  169. Research Article
  170. Tomographic particle image velocimetry of a water-jet for low volume harvesting of fat tissue for regenerative medicine
  171. Research Article
  172. Wireless medical sensors – context, robustness and safety
  173. Research Article
  174. Sequences for real-time magnetic particle imaging
  175. Research Article
  176. Speckle-based off-axis holographic detection for non-contact photoacoustic tomography
  177. Research Article
  178. A machine learning approach for planning valve-sparing aortic root reconstruction
  179. Research Article
  180. An in-ear pulse wave velocity measurement system using heart sounds as time reference
  181. Research Article
  182. Measuring different oxygenation levels in a blood perfusion model simulating the human head using NIRS
  183. Research Article
  184. Multisegmental fusion of the lumbar spine a curse or a blessing?
  185. Research Article
  186. Numerical analysis of the biomechanical complications accompanying the total hip replacement with NANOS-Prosthetic: bone remodelling and prosthesis migration
  187. Research Article
  188. A muscle model for hybrid muscle activation
  189. Research Article
  190. Mathematical, numerical and in-vitro investigation of cooling performance of an intra-carotid catheter for selective brain hypothermia
  191. Research Article
  192. An ideally parameterized unscented Kalman filter for the inverse problem of electrocardiography
  193. Research Article
  194. Interactive visualization of cardiac anatomy and atrial excitation for medical diagnosis and research
  195. Research Article
  196. Virtualizing clinical cases of atrial flutter in a fast marching simulation including conduction velocity and ablation scars
  197. Research Article
  198. Mesh structure-independent modeling of patient-specific atrial fiber orientation
  199. Research Article
  200. Accelerating mono-domain cardiac electrophysiology simulations using OpenCL
  201. Research Article
  202. Understanding the cellular mode of action of vernakalant using a computational model: answers and new questions
  203. Research Article
  204. A java based simulator with user interface to simulate ventilated patients
  205. Research Article
  206. Evaluation of an algorithm to choose between competing models of respiratory mechanics
  207. Research Article
  208. Numerical simulation of low-pulsation gerotor pumps for use in the pharmaceutical industry and in biomedicine
  209. Research Article
  210. Numerical and experimental flow analysis in centifluidic systems for rapid allergy screening tests
  211. Research Article
  212. Biomechanical parameter determination of scaffold-free cartilage constructs (SFCCs) with the hyperelastic material models Yeoh, Ogden and Demiray
  213. Research Article
  214. FPGA controlled artificial vascular system
  215. Research Article
  216. Simulation based investigation of source-detector configurations for non-invasive fetal pulse oximetry
  217. Research Article
  218. Test setup for characterizing the efficacy of embolic protection devices
  219. Research Article
  220. Impact of electrode geometry on force generation during functional electrical stimulation
  221. Research Article
  222. 3D-based visual physical activity assessment of children
  223. Research Article
  224. Realtime assessment of foot orientation by Accelerometers and Gyroscopes
  225. Research Article
  226. Image based reconstruction for cystoscopy
  227. Research Article
  228. Image guided surgery innovation with graduate students - a new lecture format
  229. Research Article
  230. Multichannel FES parameterization for controlling foot motion in paretic gait
  231. Research Article
  232. Smartphone supported upper limb prosthesis
  233. Research Article
  234. Use of quantitative tremor evaluation to enhance target selection during deep brain stimulation surgery for essential tremor
  235. Research Article
  236. Evaluation of adhesion promoters for Parylene C on gold metallization
  237. Research Article
  238. The influence of metallic ions from CoCr28Mo6 on the osteogenic differentiation and cytokine release of human osteoblasts
  239. Research Article
  240. Increasing the visibility of thin NITINOL vascular implants
  241. Research Article
  242. Possible reasons for early artificial bone failure in biomechanical tests of ankle arthrodesis systems
  243. Research Article
  244. Development of a bending test procedure for the characterization of flexible ECoG electrode arrays
  245. Research Article
  246. Tubular manipulators: a new concept for intracochlear positioning of an auditory prosthesis
  247. Research Article
  248. Investigation of the dynamic diameter deformation of vascular stents during fatigue testing with radial loading
  249. Research Article
  250. Electrospun vascular grafts with anti-kinking properties
  251. Research Article
  252. Integration of temperature sensors in polyimide-based thin-film electrode arrays
  253. Research Article
  254. Use cases and usability challenges for head-mounted displays in healthcare
  255. Research Article
  256. Device- and service profiles for integrated or systems based on open standards
  257. Research Article
  258. Risk management for medical devices in research projects
  259. Research Article
  260. Simulation of varying femoral attachment sites of medial patellofemoral ligament using a musculoskeletal multi-body model
  261. Research Article
  262. Does enhancing consciousness for strategic planning processes support the effectiveness of problem-based learning concepts in biomedical education?
  263. Research Article
  264. SPIO processing in macrophages for MPI: The breast cancer MPI-SNLB-concept
  265. Research Article
  266. Numerical simulations of airflow in the human pharynx of OSAHS patients
Sign up now to receive a 20% welcome discount
Institutional Access
How does access work?
Have an idea on how to improve our website?
Please write us.
© 2025 De Gruyter Brill
Downloaded on 17.9.2025 from https://www.degruyterbrill.com/document/doi/10.1515/cdbme-2015-0021/html
Scroll to top button