Low-cost electromyography: validity against a commercial system depends on exercise type and intensity

The aim of this study was to assess the validity of a custom-made low cost (LC) and a commercial surface EMG apparatus in controlled experimental conditions and different exercise types: maximal voluntary contractions (MVC) at 105, 90, 75, 60, 45 and 30° knee angle and explosive fix-end contractions of the knee extensors (75°) at an isometric dynamometer. sEMG of vastus lateralis was recorded from the same electrodes simultaneously, then analyzed in the same way; sEMG were finally expressed in percentage of those collected at 75°MVC. LC underestimated the sEMG signal at the more extended knee angles (30-60°), significant difference was observed only at 30°. In the explosive contractions no differences between devices were observed in average and peak sEMG, as well as in the time to peak and the activation time. Bland-Altman tests and correlation parameters indicate the LC device is not sensible enough to detect the time to peak and the peak values of the sEMG signal properly. Results suggest low-cost systems might be a valid alternative to commercial ones, but attention must be paid when analyzing rapid events.

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Development of Surface EMG Game Control Interface for Persons with Upper Limb Functional Impairments

Signals ◽

10.3390/signals2040048 ◽

2021 ◽

Vol 2 (4) ◽

pp. 834-851

Author(s):

Joseph K. Muguro ◽

Pringgo Widyo Laksono ◽

Wahyu Rahmaniar ◽

Waweru Njeri ◽

Yuta Sasatake ◽

...

Keyword(s):

Machine Learning ◽

Upper Limb ◽

People With Disabilities ◽

Surface Emg ◽

Functional Impairments ◽

Semg Signal ◽

Control Interface ◽

Directional Control ◽

Custom Made ◽

Significant Difference

In recent years, surface Electromyography (sEMG) signals have been effectively applied in various fields such as control interfaces, prosthetics, and rehabilitation. We propose a neck rotation estimation from EMG and apply the signal estimate as a game control interface that can be used by people with disabilities or patients with functional impairment of the upper limb. This paper utilizes an equation estimation and a machine learning model to translate the signals into corresponding neck rotations. For testing, we designed two custom-made game scenes, a dynamic 1D object interception and a 2D maze scenery, in Unity 3D to be controlled by sEMG signal in real-time. Twenty-two (22) test subjects (mean age 27.95, std 13.24) participated in the experiment to verify the usability of the interface. From object interception, subjects reported stable control inferred from intercepted objects more than 73% accurately. In a 2D maze, a comparison of male and female subjects reported a completion time of 98.84 s. ± 50.2 and 112.75 s. ± 44.2, respectively, without a significant difference in the mean of the one-way ANOVA (p = 0.519). The results confirmed the usefulness of neck sEMG of sternocleidomastoid (SCM) as a control interface with little or no calibration required. Control models using equations indicate intuitive direction and speed control, while machine learning schemes offer a more stable directional control. Control interfaces can be applied in several areas that involve neck activities, e.g., robot control and rehabilitation, as well as game interfaces, to enable entertainment for people with disabilities.

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Why USB-endoscope laryngoscopy is as effective as video laryngoscopy

Clinical & Investigative Medicine ◽

10.25011/cim.v43i2.33956 ◽

2020 ◽

Vol 43 (2) ◽

pp. E55-59

Author(s):

Meliha Findik ◽

Afsin E. Kayipmaz ◽

Cemil Kavalci ◽

Tugce Sencelikel Sencelikel ◽

Murat Muratoglu ◽

...

Keyword(s):

Direct Laryngoscopy ◽

Low Cost ◽

Video Laryngoscope ◽

Video Laryngoscopy ◽

Intubation Time ◽

Direct Laryngoscope ◽

Correct Placement ◽

Custom Made ◽

Significant Difference ◽

The Cost

Purpose: To compare the efficacy of a low-cost custom-made universal serial bus (USB) endoscope laryngoscope for intubation with a direct laryngoscope and a high-cost video laryngoscope in a mannequin study. Methods: We used one intubation simulator model (mannequin) in our study. A USB endoscope was mounted to the direct laryngoscope as a custom-made USB endoscope laryngoscope (USB-L). We used a video laryngoscope (Glidescope®, Verathon, USA) and a direct laryngoscope (Macintosh) for comparison. Intubation time and the correct placement of the tube were measured. Intubations were performed by two operators and results were compared. Results: We found a statistically significant difference between the video and direct laryngoscope groups (p < 0.001), as well as between the USB-L and direct laryngoscope groups (p = 0.001) for Operator 1. For Operator 2, there was a statistically significant difference between the video laryngoscope group and the direct laryngoscope group (p = 0.022); however, we did not find a significant difference between the USB-L group and the direct laryngoscope group (p = 0.154). Furthermore, there were no significant differences between the USB-L and video laryngoscope groups for either operator (p=0.347 for Operator 1 and p>0.999 for Operator 2). Conclusion: Our study showed that USB endoscope laryngoscope provided similar intubation time to video laryngoscopy at a fraction of the cost; and both had superior times in comparison with direct laryngoscopy.

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Comparison of lower limb muscle activity during the dynamic balance test between baseball pitchers and healthy young adults

Isokinetics and Exercise Science ◽

10.3233/ies-203163 ◽

2020 ◽

pp. 1-7

Author(s):

Jeongwoo Jeon ◽

Jiyeon Lee ◽

Jiheon Hong ◽

Jaeho Yu ◽

Jinseop Kim ◽

...

Keyword(s):

Young Adults ◽

Muscle Activity ◽

Vastus Lateralis ◽

Dynamic Balance ◽

Neuromuscular Control ◽

Surface Emg ◽

Knee Extensors ◽

Balance Test ◽

Lower Extremity Muscle ◽

Baseball Pitchers

BACKGROUND: Dynamic balance is an essential factor for efficient pitching by baseball pitchers. OBJECTIVE: To compare distances reached and lower-extremity muscle activity during the star excursion balance test (SEBT) in baseball pitchers and healthy young adults. METHODS: Nineteen baseball pitchers (BPG) and 20 healthy adults (HAG) were recruited. Surface EMG was used to measure the activity of vastus medialis (VM), vastus lateralis (VL), tibialis anterior, and lateral gastrocnemius. RESULTS: The BPG exhibited greater dynamic balance than in the HAG (p< 0.05) in the posteromedial (PM) and posterolateral (PL) directions. For the PM and PL directions, significantly greater muscle activity of VM and VL was found in the BPG than in the HAG (p< 0.05). CONCLUSION: SEBT performance is characterized by high-level VM and VL muscle activities. Neuromuscular control of knee extensors, such as the VM and VL of pitchers, might affect the dynamic balance measured by the SEBT.

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Muscle activation and blood flow do not explain the muscle length-dependent variation in quadriceps isometric endurance

Journal of Applied Physiology ◽

10.1152/japplphysiol.00712.2004 ◽

2005 ◽

Vol 98 (3) ◽

pp. 810-816 ◽

Cited By ~ 37

Author(s):

R. D. Kooistra ◽

C. J. de Ruiter ◽

A. de Haan

Keyword(s):

Blood Flow ◽

Blood Supply ◽

Vastus Lateralis ◽

Muscle Length ◽

Rectus Femoris ◽

Surface Emg ◽

Knee Extensors ◽

Emg Activity ◽

Central Activation ◽

Full Occlusion

We investigated the role of central activation in muscle length-dependent endurance. Central activation ratio (CAR) and rectified surface electromyogram (EMG) were studied during fatigue of isometric contractions of the knee extensors at 30 and 90° knee angles (full extension = 0°). Subjects ( n = 8) were tested on a custom-built ergometer. Maximal voluntary isometric knee extension with supramaximal superimposed burst stimulation (three 100-μs pulses; 300 Hz) was performed to assess CAR and maximal torque capacity (MTC). Surface EMG signals were obtained from vastus lateralis and rectus femoris muscles. At each angle, intermittent (15 s on 6 s off) isometric exercise at 50% MTC with superimposed stimulation was performed to exhaustion. During the fatigue task, a sphygmomanometer cuff around the upper thigh ensured full occlusion (400 mmHg) of the blood supply to the knee extensors. At least 2 days separated fatigue tests. MTC was not different between knee angles (30°: 229.6 ± 39.3 N·m vs. 90°: 215.7 ± 13.2 N·m). Endurance times, however, were significantly longer ( P < 0.05) at 30 vs. 90° (87.8 ± 18.7 vs. 54.9 ± 12.1 s, respectively) despite the CAR not differing between angles at torque failure (30°: 0.95 ± 0.05 vs. 90°: 0.96 ± 0.03) and full occlusion of blood supply to the knee extensors. Furthermore, rectified surface EMG values of the vastus lateralis (normalized to prefatigue maximum) were also similar at torque failure (30°: 56.5 ± 12.5% vs. 90°: 58.3 ± 15.2%), whereas rectus femoris EMG activity was lower at 30° (44.3 ± 12.4%) vs. 90° (69.5 ± 25.3%). We conclude that differences in endurance at different knee angles do not find their origin in differences in central activation and blood flow but may be a consequence of muscle length-related differences in metabolic cost.

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Wingate performance and surface EMG frequency variables are not affected by caffeine ingestion

Applied Physiology Nutrition and Metabolism ◽

10.1139/h06-030 ◽

2006 ◽

Vol 31 (5) ◽

pp. 597-603 ◽

Cited By ~ 43

Author(s):

Felicia Greer ◽

Jacobo Morales ◽

Michael Coles

Keyword(s):

Body Mass ◽

Power Output ◽

High Intensity ◽

Repeated Measures ◽

Surface Emg ◽

Knee Extensors ◽

Caffeine Ingestion ◽

Emg Signal ◽

Significant Difference ◽

Percent Decline

The ergogenic effect of caffeine and its mechanism of action on short-term, high-intensity exercise are controversial. One proposed mechanism is caffeine’s stimulatory effect on the central nervous system and thus, motor-unit excitation. The latter is non-invasively determined from surface electromyographic signal (EMG) frequency measures. The purpose of this study was to determine if power output and surface EMG frequency variables during high-intensity cycling were altered following caffeine ingestion. Eighteen recreationally active college males (mean ± SD age, 21.5 ± 1.8 y; height, 181.8 ± 0.5 cm; body mass, 84.7 ± 11.4 kg) performed the Wingate test (WG) after ingestion of gelatin capsules containing either placebo (PL; dextrose) or caffeine (CAFF; 5 mg/kg body mass). The trials were separated by 1 week and subjects were asked to withdraw from all caffeine-containing products for 48 h before each trial. From the resulting power–time records, peak power (PP; highest power output in 5 s), minimum power (MP; lowest power output in 5 s), and the percent decline in power (Pd) were calculated. Surface EMG records of the right vastus lateralis (VL) and the gastrocnemius (GA) muscles corresponding to the PP and MP periods were collected and used to determine the integrated electromyogram (IEMG), the mean (MNPF), and the median (MDPF) of the signal’s power spectrum. A 2-way repeated measures analysis of variance (ANOVA) (treatment × time) was conducted to determine the effect of caffeine on these variables across levels of time. Caffeine ingestion had no effect on PP (PL, 1049 ± 192 W; CAFF, 1098 ± 198 W), MP (PL, 762 ± 104 W; CAFF, 802 ± 124 W), or the Pd (PL, 47% ± 8.9%; CAFF, 48.2% ± 7.3%) compared with the placebo. For both muscles, MNPF and MDPF diminished significantly (p < 0.001) across time and to a similar degree in both the CAFF and PL trials. Regardless of muscle, CAFF had no effect on the percent change in IEMG from the first 5 s to the last 5 s. For both treatments, the GA displayed a significantly (p < 0.05) greater pre vs. post percent decline in the EMG signal amplitude compared with the VL. These results indicate that caffeine does not impact power output during a 30 s high-intensity cycling bout. Furthermore, these data suggest that caffeine does not impact the neuromuscular drive as indicated by the similar IEMG scores between treatments. Similarly, caffeine does not seem to impact the frequency content of the surface EMG signal and thus the nature of recruited motor units before and after the expression of fatigue. The lack of decline in the IEMG in the VL despite the decline in power output over the course of the WG suggests a peripheral as opposed to a neural mechanism of fatigue in this muscle. The significant difference in the pre vs. post percent decline in the GA IEMG score further supports this notion. The pre vs. post decline in the IEMG noted in the GA may suggest a fatigue-triggered change in pedaling mechanics that may promote dominance of knee extensors with less reliance on plantar flexors.

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Evaluation of a Low Cost Prosthetic Hand Controlled by Surface EMG Sensors and Vibrotactile Feedback

International Journal for Service Learning in Engineering Humanitarian Engineering and Social Entrepreneurship ◽

10.24908/ijsle.v13i2.12816 ◽

2018 ◽

Vol 13 (2) ◽

pp. 69-78

Author(s):

Victor Argueta-Diaz ◽

Cameron J Spitzfaden ◽

Durham Basso ◽

Hope L Ayers

Keyword(s):

Low Cost ◽

Surface Emg ◽

Average Score ◽

Prosthetic Hand ◽

Vibrotactile Feedback ◽

Semg Signal ◽

Subjective Data ◽

Feedback Type ◽

Control Schemes ◽

Flexor Digitorum

This study proposes a prosthetic hand with a simple control algorithm and off-the-shelf electronics. We designed this hand to be used and repaired in underdeveloped regions. A differential sEMG signal is obtained from the flexor digitorum superficialis and extensor digitorum muscles to control the position of the hand’s grasp. Three different hand control schemes (visual, vibrotactile and visual plus vibrotactile) were compared and tested in ten able-bodied individuals. We observed a better performance of the visual and vibrotactile control overall, but the vibrotactile feedback increased performance after several interactions. In subjective data evaluations vibrotactile and visual feedback had the highest scores in light and medium pressures, while visual-only feedback type had the highest average score for hard pressure.

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Synchronization of Lower Limb Motor Unit Activity During Walking in Human Subjects

Journal of Neurophysiology ◽

10.1152/jn.2001.86.3.1266 ◽

2001 ◽

Vol 86 (3) ◽

pp. 1266-1276 ◽

Cited By ~ 49

Author(s):

N. L. Hansen ◽

S. Hansen ◽

L.O.D. Christensen ◽

N. T. Petersen ◽

J. B. Nielsen

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Lower Limb ◽

Human Subjects ◽

Vastus Lateralis ◽

Surface Emg ◽

Medial Gastrocnemius ◽

Human Gait ◽

Knee Extensors ◽

Motor Unit Activity

Synchronization of motor unit activity was investigated during treadmill walking (speed: 3–4 km/h) in 25 healthy human subjects. Recordings were made by pairs of wire electrodes inserted into the tibialis anterior (TA) muscle and by pairs of surface electrodes placed over this muscle and a number of other lower limb muscles (soleus, gastrocnemius lateralis, gastrocnemius medialis, biceps femoris, vastus lateralis, and vastus medialis). Short-lasting synchronization (average duration: 9.6 ± 1.1 ms) was observed between spike trains generated from multiunit electromyographic (EMG) signals recorded by the wire electrodes in TA in eight of nine subjects. Synchronization with a slightly longer duration (12.8 ± 1.2 ms) was also found in 13 of 14 subjects for paired TA surface EMG recordings. The duration and size of this synchronization was within the same range as that observed during tonic dorsiflexion in sitting subjects. There was no relationship between the amount of synchronization and the speed of walking. Synchronization was also observed for pairs of surface EMG recordings from different ankle plantarflexors (soleus, medial gastrocnemius, and lateral gastrocnemius) and knee extensors (vastus lateralis and medialis of quadriceps), but not or rarely for paired recordings from ankle and knee muscles. The data demonstrate that human motor units within a muscle as well as synergistic muscles acting on the same joint receive a common synaptic drive during human gait. It is speculated that the common drive responsible for the motor unit synchronization during gait may be similar to that responsible for short-term synchronization during tonic voluntary contraction.

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Comparison of thigh muscle activations in single leg exercises: bench squat, step-up, airborne lunge

Pedagogy of Physical Culture and Sports ◽

10.15561/26649837.2021.0601 ◽

2021 ◽

Vol 25 (6) ◽

pp. 342-348

Author(s):

Fahri S. Çinarli ◽

Sena Çinarli ◽

Emin Kafkas

Keyword(s):

Muscle Activation ◽

Vastus Lateralis ◽

Biceps Femoris ◽

Thigh Muscle ◽

Knee Extensors ◽

Energy Costs ◽

Co Activation ◽

Significant Difference ◽

Muscle Activations ◽

Sports Sciences

Background and Study Aim. Single leg exercises have some advantages in terms of time, practice and energy costs. However, the activation values that occur in different single leg exercises can be used for training planning. The aim of this research was to examine the thigh muscle activation values during three different single leg exercises. Materials and Methods. Ten healthy male volunteers who were students of the faculty of sports sciences participated in the study. In the study, the EMG ampilitude values of the vastus medialis (VM), vastus lateralis (VL), semitendinosus (SEM) and biceps femoris (BF) muscles were examined during Step-up, Bench Squat and Airborne Lunge exercises. At the same time, Quadriceps (VM+VL): Hamstring (SEM+BF) ratios were determined. Results. Significant differences were detected in all thigh muscles in the ascent and descent phases (p<0.05). While the greatest activation for the quadriceps group was seen in the airborne lunge, the greatest activation for the hamstring group was detected in the bench squat. A statistically significant difference was found in terms of exercise practices in the quadriceps: hamstring (Q:H) ratio (F(2,18)=12.282, p=.003). It was seen that the most balanced exercise was bench squat (Q:H=2.55), and the most unbalanced exercise (agonist dominant) was airborne lunge (Q:H=5.51). Conclusions. The findings show that the exercises examined can be selected depending on the purpose of the training. While bench squats can be preferred for more balanced co-activation the airborne lunge can be preferred for dominant knee extensors.

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Evaluation of low-cost eddy covariance for CO2 fluxes over agroforestry and grassland

10.5194/egusphere-egu21-2181 ◽

2021 ◽

Author(s):

Justus van Ramshorst ◽

Christian Markwitz ◽

Timothy Hill ◽

Robert Clement ◽

Alexander Knohl ◽

...

Keyword(s):

Eddy Covariance ◽

Low Cost ◽

Arable Land ◽

Agroforestry Systems ◽

Post Processing ◽

Flux Dynamics ◽

Processing Scheme ◽

Cost System ◽

Custom Made ◽

Significant Difference

Agroforestry is an integration of trees in cropland or grassland and is discussed, within Germany and the EU, as a potential &#8220;Green Solution&#8221; for agriculture. Agroforestry alters the microclimate, productivity, biodiversity, and nutrient and water usage &#8211; as compared to standard agricultural practise. A potentially key benefit is the higher carbon sequestration of agroforestry, relative to monoculture systems, which could provide an interesting option for mitigating climate change, while still providing valuable arable land. Net ecosystem exchange studies of CO2 (NEE) of agroforestry systems are rare, in comparison to the extensive studies of NEE of agricultural systems (croplands and grasslands). Therefore, the current study, as part of the SIGNAL (sustainable intensification of agriculture through agroforestry) project, investigates the NEE of agroforestry compared to that of monoculture agriculture.At five locations across Germany, paired flux measurements above agroforestry and monoculture agronomy are performed using innovative low-cost CO2 eddy covariance sensors (slow response Vaisala GMP343 IRGA, with custom made housing). During the summer of 2020 simultaneous measurements of the low-cost setup and a LI-COR 7200 are performed, above grassland at 3.5 m and adjacent agroforestry grassland at 10 m measurements height.The low-cost eddy covariance system is able to capture the turbulent (diurnal) CO2 flux dynamics and the response to management activities. After spectral corrections and applying quality control, the low-cost system at the agroforestry site (slope = 0.92, R2 = 0.88) performs better than the low-cost system at the grassland site (slope = 0.67, R2 = 0.80), when compared to the LI-COR measurements. This is probably due to the difference in turbulence caused by different surface roughness and measurement height. The preliminary cumulative carbon flux during the four-month measurement campaign shows a significant difference between the grassland (source of (+) 16-38 gC/m2) and agroforestry grassland (sink of (-) 148-164 gC/m2), in favour of agroforestry. By applying post processing software, we aim to further optimize the frequency corrections for the low-cost system. In the future the obtained post processing scheme will be applied to the other low-cost eddy covariance systems within the project.

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“NO LOAD” Resistance Training Promotes High Levels of Knee Extensor Muscles Activation—A Pilot Study

Diagnostics ◽

10.3390/diagnostics10080526 ◽

2020 ◽

Vol 10 (8) ◽

pp. 526

Author(s):

Rafael Ribeiro Alves ◽

Carlos Alexandre Vieira ◽

Martim Bottaro ◽

Murilo Augusto Soares de Araújo ◽

Daniel Costa Souza ◽

...

Keyword(s):

Resistance Training ◽

Visual Feedback ◽

External Load ◽

Muscle Activation ◽

Vastus Lateralis ◽

Load Resistance ◽

Knee Extensors ◽

Emg Activity ◽

Functional Changes ◽

Significant Difference

The present article aims to compare electromyographic (EMG) activity of the knee extensors during traditional resistance training (TRT) and no load resistance training with or without visual feedback (NL-VF and NL-NF). Sixteen healthy men (age: 25.2 ± 3.6) volunteered to participate in the study. Participants visited the laboratory on three occasions involving: (1) a 10 repetition maximum test (10 RM test), (2) familiarization and (3) performance of knee extensions using TRT, NL-VF and NL-NF in a random order, with 10 min of rest between them. TRT involved the performance of a set to momentary muscle failure using the 10 RM load. NL-NF involved the performance of 10 repetitions with no external load, but with the intention to maximally contract the muscles during the whole set. NL-VF involved the same procedure as NL-NF, but a monitor was positioned in front of the participants to provide visual feedback on the EMG activity. Peak and mean EMG activity were evaluated on the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF). Results: there were no significant differences in VM and VL peak EMG activity among different situations. There was a significant difference for peak EMG activity for RF, where TRT resulted in higher values than NL-VF and NL-NF (p < 0.05). Higher values of mean EMG activity were found for VM, VL and RF during TRT in comparison with both NL-VF and NL-NF. Conclusions: resistance training with no external load produced high levels of peak muscle activation, independent of visual feedback, but mean activation was higher during TRT. These results suggest that training with no external load might be used as a strategy for stimulating the knee extensors when there is limited access to specialized equipment. Although the clinical applications of no load resistance training are promising, it is important to perform long-term studies to test if these acute results will reflect in muscle morphological and functional changes.

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