Application and effects of neuromuscular electrical stimulation in critically ill patients: Systematic review. In addition, the frequency and pulse duration used during protocol 2 were similar to the 1995; Godfrey et al. The peak power may be directly measured with a photodiode or calculated from pulse energy, pulse duration and pulse shape. Average peak forces produced in response to the 20 Hz testing trains at the pulse duration of the fatiguing trains for protocols 1, 2 and 3, respectively, were 363.2 ± 117.7, 175.0 ± 55.1 and 162.6 ± 53.9 N (prefatigue) and 224.7 ± 68.4, 73.6 ± 24.7 and 41.9 ± 17.1 N (postfatigue). 2002; Wheeler et al. 1996), walk (Agarwal et al. Is high-frequency neuromuscular electrical stimulation a suitable tool for muscle performance improvement in both healthy humans and athletes? Pulse frequency: the number of pulses produced per second, hertz (Hz) or cycles per second (c/s). Clipboard, Search History, and several other advanced features are temporarily unavailable. In addition, in response to testing trains at 600 μs pulse duration, there were no differences in the overall levels of low‐frequency fatigue among the three protocols (Fig. For FES applications, however, because the targeted force is determined by the task requirements, it may not be important to isolate the effects of frequency versus intensity on muscle fatigue and performance, but to determine the combination of frequency and intensity that can generate the targeted muscle force while simultaneously minimizing muscle fatigue. ; Fig. 1). The pre‐ and postfatigue 20 Hz:60 Hz peak force ratios for the three fatigue protocols were compared using two‐way (protocol × fatigue) repeated measures ANOVAs. Pulse Width Modulation is also known as pulse duration modulation (PDM). Our study compared the performance and muscle fatigue produced during repetitive stimulation using three different combinations of frequencies and pulse durations, and found that protocol 1 produced the least muscle fatigue in the motor units recruited by the fatiguing trains (see Fig. Can the Use of Neuromuscular Electrical Stimulation Be Improved to Optimize Quadriceps Strengthening?. (1999) can be explained by greater low‐frequency fatigue and less muscle fatigue than presently observed. Surprisingly, however, the average pulse durations used during protocols 2 (150 ± 22 μs) and 3 (131 ± 24 μs), although significantly different, only varied by 19 μs. For example by increasing the pulse width while decreasing the amplitude. 2005). Development of Stimulator Based on Audio-Visual Feedback Signal. Different combinations of stimulation frequency and intensity can generate a targeted force during functional electrical stimulation (FES). Int J Clin Exp Med. Thus the pulse duration needs to be higher. The width and frequency of the output pulses follow the width and frequency of the TTL input gate. Interleaved neuromuscular electrical stimulation after spinal cord injury. A model for transcutaneous current stimulation: simulations and experiments. As a standardization procedure, the averaged stimulation intensity, the averaged total charge, the initial peak torque, the duty cycle, the contraction duration and the torque-time integral were similar in both protocols. Archives of Physical Medicine and Rehabilitation. Verbal feedback enhances motor learning during post-stroke gait retraining. Pulse Duration (ms) or Pulse Width. Number of times cited according to CrossRef: Advances in neuroprosthetic management of foot drop: a review. Sports Health: A Multidisciplinary Approach. Low‐frequency fatigue is the result of impairment in excitation–contraction coupling that is thought to result from increased levels of intracellular Ca2+ during muscle activation (Westerblad et al. Three different combinations of frequency and pulse duration were used during the three different fatigue protocols, as follows: Protocol 1: Long pulse duration (600 μs) and low frequency The pulse duration of a 300 ms long train was fixed at 600 μs, and the frequency was set to … Evoked EMG versus Muscle Torque during Fatiguing Functional Electrical Stimulation-Evoked Muscle Contractions and Short-Term Recovery in Individuals with Spinal Cord Injury. 2005). 2002c) recently showed that increasing the frequency or number of pulses did not affect the amount of muscle fatigue produced during repetitive isometric contractions if the initial force produced by the stimulation trains was controlled. Has its minimum for ideal transform-limited pulses: Gaussian, \(I(t)\propto \exp\left[-(4\ln 2)t^2/\Delta t^2\right]\):$$\Delta t\cdot \Delta\nu = \frac{2\ln 2}{\pi}\approx0.441.$$ Thus, for FES applications where intensity is increased as the muscle fatigues, a ‘medium’ frequency, similar to the frequency used in protocol 2 of our study, may minimize muscle fatigue. Protocol 2: Medium frequency (30 Hz) and medium pulse duration The frequency of a 300 ms long train was fixed at 30 Hz, and the pulse duration was set to produce 20% MVIC peak force. Table 1 provides detailed information about the subjects' age, sex, MVIC forces, and the stimulation parameters of the fatiguing trains. However, the differences between the results of our present study and those of Godfrey et al. Russ and colleagues (Russ et al. A personal computer equipped with a PCI‐6024E data acquisition board and a PCI‐6602 counter‐timer board was used. Electrical pulses were delivered at 100 Hz (1-ms pulse duration) and 20 Hz (5-ms pulse duration) for the high (HF) and low (LF) frequency protocols, respectively. Eur J Appl Physiol. Since Wavelength (mm) = Propagation speed in tissue … Applied Physiology, Nutrition, and Metabolism. 3A), the last fatiguing train of protocol 1 produced the highest and the last fatiguing train of protocol 3 produced the lowest peak force for this subject (Fig. 1997; Taylor et al. National Center for Biotechnology Information, Unable to load your collection due to an error, Unable to load your delegates due to an error. The term is used within a number of technical disciplines, notably radar. Average peak forces produced in response to the 20 Hz testing trains at the 600 μs pulse duration for protocols 1, 2 and 3, respectively, were 366.2 ± 116.5, 375.7 ± 111.5 and 362.6 ± 110.1 N (prefatigue) and 221.4 ± 68.9, 253.0 ± 72.6 and 230.9 ± 70.3 N (postfatigue). The 20 Hz:60 Hz peak force ratios were calculated at the beginning (prefatigue) and end (postfatigue) of the fatigue protocols both for testing trains at the pulse duration of the fatiguing trains and at the 600 μs pulse duration. A short pulse duration of 0.4 ms with a frequency bandwidth of 5 kHz was set for the resolution of single targets (Kubecka, 1995). The percentage decline in peak forces from the first to last fatiguing trains, percentage decline in peak force between pre‐ and postfatigue 60 Hz testing trains at the pulse duration of the fatiguing trains, and the percentage decline in 60 Hz testing trains at 600 μs pulse duration were compared using one‐way repeated measures ANOVAs. The peak power may be directly measured with a photodiode or calculated from pulse energy, pulse duration and pulse shape. Berger J, Ludwig O, Becker S, Backfisch M, Kemmler W, Fröhlich M. J Sports Sci Med. Linear Frequency Modulated Pulse Waveforms Benefits of Using Linear FM Pulse Waveform. The postfatigue 20 Hz:60 Hz peak force ratios showed significant differences among protocols (F= 50.7; P < 0.01). 1998; Hogan et al. The total energy can be controlled by modulating the pulse width/duration. Since muscle fatigue was the primary focus of our study, it was important to define muscle fatigue in the context of this study. Impact of stimulation frequency on neuromuscular fatigue. A repeated-measures design with 4 stimuli presented in random order was used to test 25 women: (1) 500-microsecond pulse duration, (2) 250-microsecond pulse duration, (3) 500-microsecond pulse duration and low carrier frequency (1 kHz), (4) 250-microsecond pulse duration and high carrier frequency (4 kHz). Each pulse contains 4 cycles. These terms are often confused or used interchangeably, when they are actually three different ways of measuring an electrical signal. Velcro straps were used to stabilize the subjects' upper trunk, waist and thigh. In addition, the frequency and pulse duration used during protocol 2 were similar to the parameters commonly used in clinical FES systems (Taylor et al. The results showed that protocol 1 produced the least decline in peak force in response to the fatiguing trains, as well as the least muscle fatigue and low‐frequency fatigue when the pulse duration was maintained at the level used by the fatiguing trains. A familiar example of PDM is the International Morse Code, used in ship-to-shore communications, amateur radio, and certain other forms of radiotelegraphy. Flow chart showing the experimental protocol for the 4 sessions Please see text for details. BMC Neurol. Protocol 3 showed the most and protocol 1 the least muscle fatigue and low‐frequency fatigue when the pulse duration was maintained at the level used to fatigue the muscle (Fig. There were significant differences in percentage decline in peak force (F= 30.08; P < 0.01) between the first and last fatiguing trains among the three protocols (Fig. Epub 2011 Sep 10. (1999) were of much longer durations (60 min versus 180 s in our study), used much shorter duty cycles (1:15, 1:30 and 1:60 versus 1:2.3 in our study), and produced smaller percentage declines in peak force (22.3 ± 15.1% at 100 Hz versus 51.3 ± 7.5% at 60 Hz in our study). 1979; Garland et al. Pulse duration: the amount of time the current flows in one direction. (1995) tested the rate and amount of fatigue during repetitive stimulation of the human quadriceps muscle with trains at stimulation amplitudes that produced 20, 50 and 80% maximum voluntary isometric contraction (MVIC) forces, and found less decline in force of the fatiguing trains during repetitive stimulation at higher compared to lower stimulation amplitudes. Interestingly, consistent with out present findings, recent studies showed that for healthy subjects and for subjects with spinal cord injury, starting at low frequencies and later switching to high frequencies produced better performance during repetitive non‐isometric contractions than stimulation using either a low or high frequency alone (Kebaetse & Binder‐Macleod, 2004; Kebaetse et al. The combination of frequency and pulse duration that minimizes muscle fatigue and/or maximizes performance during FES may depend on whether or not modulation of frequency or intensity will be used as strategies during repetitive stimulation. Journal of NeuroEngineering and Rehabilitation. Although numerous combinations of frequency and intensity can be used to generate the required muscle force during FES, most clinical FES systems use the minimum frequency that can generate a fused tetanic contraction in the muscle being stimulated and vary the intensity to produce the desired force (Taylor et al. The present findings support the hypothesis that when the same initial peak force is generated using different combinations of frequency and pulse duration, and when the frequency and pulse duration are kept constant throughout repetitive stimulation, repetitive stimulation with a long pulse duration (600 μs) and low frequency (11.5 ± 1.2 Hz; protocol 1) would maximize isometric performance by minimizing muscle fatigue. In pulse duration modulation (PDM), the amplitude of the pulse is kept constant and only the variation in width is noticed. Since ATP utilization by actin–myosin ATPase is proportional to force generation (Boska, 1994; Potma et al. 2005). The duty cycles used to fatigue the muscles (300 ms long trains with 700 ms rest time) were similar to the activation patterns recorded in the quadriceps muscle during normal walking (Pierrynowski & Morrison, 1985). 2): Set stimulation amplitude to generate 50% MVIC peak force During each testing session, after applying the electrodes, the stimulation amplitude was set to produce 50% of the subject's MVIC force using 300 ms long, 60 Hz trains with 600 μs pulse duration. Intracellular Ca2+ concentrations have been shown to be directly related to the stimulation frequency (Chin & Allen, 1996). 1995; Russ et al. For each subject, the MVIC value measured during the first session was used to set the stimulation amplitude for all four sessions. The figure also shows peak forces produced in response to each fatiguing train during the 3 fatigue protocols for a representative subject (C). 5). All 12 subjects were successfully able to complete the MVIC testing during the first session in one or two attempts. Next, the MVIC force was recorded using the burst superimposition technique (Snyder‐Mackler et al. Journal of Orthopaedic & Sports Physical Therapy. If the subject failed to elicit a true MVIC within three repetitions, they were not tested on that day. Effects of an Impulse Frequency Dependent 10-Week Whole-body Electromyostimulation Training Program on Specific Sport Performance Parameters. For this study, we used stimulus pulse duration (PD) to vary the intensity because it was easier to control and provided a more consistent force response from the muscle compared to stimulation amplitude (Grill & Mortimer, 1996). If the electrical stimulation train increased the subject's force output by > 10%, the MVIC test was repeated after a 10 min rest. HD36797 and no. 1988). Thus, we also do not know which stimulation intensity levels can help to minimize fatigue when used for repetitive stimulation during FES. A Grass S8800 stimulator (Grass Instrument Co., Quincy, MA, USA) with a SIU8T stimulus isolation unit was used to deliver the electrical stimulation. Effects of Very High Stimulation Frequency and Wide-Pulse Duration on Stimulated Force and Fatigue of Quadriceps in Healthy Participants. Electrical pulses were delivered at 100 Hz (1-ms pulse duration) and 20 Hz (5-ms pulse duration) for the high (HF) and low (LF) frequency protocols, respectively. The average peak forces in response to the first fatiguing trains were 21.2 ± 1.7, 21.5 ± 2.2 and 22.3 ± 2.2% MVIC for protocols 1, 2 and 3, respectively. A custom‐made switch was connected in series with the stimulator to control the pulse duration. 2005). Each testing session consisted of ‘fatiguing trains’ and pre‐ and postfatigue ‘testing trains’. The decline in force generated in response to the fatiguing trains for each protocol was used as a measure of the ‘muscle's performance’ or the muscle's ability to maintain force output in response to the fatiguing trains. Lu T, Song QH, Xu RM, Guo YH, Wang F, Hu JP, Wang Y, Zhang LY. 1999; Weber et al. The prefatigue testing trains were delivered with a rest time of 10 s. Fatiguing trains After the potentiation and prefatigue testing trains had been delivered, 176 fatiguing trains were delivered at a rate of one train every second (train duration, 300 ms; rest time, 700 ms). The remaining three sessions involved fatigue testing. In contrast, Godfrey et al. Set frequency and pulse duration to generate 20% MVIC target peak force Either the stimulation pulse duration or frequency of a 300 ms long train was varied to generate peak force equal to 20% of the subject's MVIC. 10.4028/www.scientific.net/AMM.568-570.359. 2). However, Protocols 3 and 1 showed comparable amounts of muscle fatigue and protocol 2 showed the least muscle fatigue when tested at the 600 μs pulse duration (Fig. Protocol 1 produced the smallest decline in peak force (21.5 ± 9.5%), protocol 2 produced an intermediate decline (27.4 ± 8.2%), and protocol 3 produced the largest decline (46.1 ± 6.7%) in peak force in response to the 60 Hz testing train at the same pulse duration as the fatiguing trains (F= 77.23; P < 0.01; Fig. Please note that the terms ‘medium pulse duration’ and ‘short pulse duration’ were operational definitions for the pulse durations used to generate the targeted force using 30 and 60 Hz trains for protocols 2 and 3, respectively. Pulse duration is measured when the current level is at 50% of its peak, usually expressed in microseconds. For example by increasing the pulse width while decreasing the amplitude. 1988; Sahlin et al. Pain relief can occur at various frequencies. That is, even if greater muscle fatigue was produced by the 100 Hz trains than the 20 Hz trains in their study (Matsunaga et al. One transducer emits sound with a 4 MHz frequency, and the other produces sound at a 6 MHz frequency. Hybrid impedance control of a knee joint orthosis. 2003; Johnston et al. (2002) delivered both supra‐ and submaximal stimulation intensities at the same frequency (40 Hz), different force levels were generated at the two intensities. 2006 Nov;91(6):967-76. doi: 10.1113/expphysiol.2006.033886. Thus, our results showed that although the difference in frequencies between protocols 2 and 3 was relatively large (30 versus 60 Hz), a relatively small difference in pulse duration between protocol 3 and protocol 2 enabled the targeted 20% MVIC force to be reached for both the protocols. Increasing the duration of a transmitted pulse increases its energy and improves target detection capability. 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