Objectives:
Blood Flow Restriction (BFR) training provides partial occlusion at the proximal upper and lower extremities and has been shown to improve muscular strength and hypertrophy following an ...injury or surgery. By eliciting hypoxic intramuscular conditions, we can stimulate adaptive processes in skeletal muscle in a similar manner to high intensity resistance training but at substantially lower and safer exercise workloads (20-30%1RM). While much of the literature has focused on tissues distal to the site of occlusion, recent findings (Lambert et al 2021, Bowman et al 2020) have observed proximal benefits (increased muscle mass, work capacity, and performance) to upper extremity BFR in the shoulder region during rotator cuff training in both general population adults and pitching athletes. These findings were partially attributed to increased muscle activation (via electromyography, EMG) observed while extremities were under occlusion. However, only one standardized occlusion pressure (50%LOP) was utilized during these investigations as typical in current literature. The purpose of the present study was to compare muscle activation (EMG amplitude, EMGa) of the shoulder region during BFR training at variable occlusion pressures in order to optimize application and muscle-specific targeting of BFR for rehabilitation and preventative shoulder training.
Methods:
Institutional review board approval was first obtained. Fifteen healthy subjects (7 males and 8 females; age 29.4 ± 4.26 y.o.) from a sports medicine physical therapy clinic were recruited and consented to participate in this study. Individuals were excluded if they had any pre-existing shoulder pathology in the dominant limb, active participation in a structured upper body weight regimen, or any history of vascular compromise that may render use of BFR inappropriate. Each participant underwent 4 different experimental sessions, which included performing 3 common exercises for the shoulder to failure on the dominant limb; dumbbell scaption, cable external rotation (ER) @ 0°, and cable internal rotation (IR) @ 0°. Exercises were completed with BFR using an automated tourniquet system (Delfi Medical Innovations®) at a different pre-assigned occlusion pressure (0, 25, 50, 75% LOP) each session. Load was determined using 20% of a one-repetition maximum (1RM) for each exercise utilizing a maximal voluntary isometric contraction (MVIC) test. EMGa data utilizing surface electrodes (Delsys, Natick, MA, US) were recorded from target shoulder muscles proximal to the occlusive cuff during testing - anterior deltoid, middle deltoid, posterior deltoid, infraspinatus, teres minor, and upper trapezius muscles. Repetitions to failure (RTF) and assessments of discomfort (VAS, 0-10) with each exercise at the various occlusive pressures were also collected for analysis. Raw EMGa measures were averaged across the first 30 contractions for IR and scaption as well as the first 20 contractions for ER following normalization to 5 calibration contractions at 0% LOP. A mixed model ANOVA repeated on occlusion pressure was performed followed by a Bonferroni post hoc test for pairwise comparisons. Type I error set at ∝=0.05.
Results:
EMG findings are presented in Figure 1 demonstrating a significant effect of occlusion level on shoulder muscle activation for all exercises (p<0.05). Of note, continued significant increases in EMGa were not observed above 50%LOP with the exception of the teres minor during IR (Figure 1A) or the posterior deltoid during scaption (Figure 1C). As shown in Figure 2, significant decreases in repetitions to failure relative to 0%LOP were observed at 75%LOP for all exercises as well as at 50%LOP for scaption (p<0.05). Also shown in Table 1, a linear increase in discomfort was observed for all exercises with increasing LOP (p<0.01).
Conclusions:
There appears to be several distinct differences in muscle activation about the shoulder complex based on the exercise as well as occlusive pressure; including a common trend of heightened EMG activity being concurrent with an increase in LOP. These findings may indicate that added occlusion leads to greater muscle utilization, enhancing exercise selection and prescription dependent on the targeted muscle group. However, based on these data, there may be an element of diminishing returns past 50% LOP for the exercises and musculature studied, ultimately limiting efficacy past this occlusion stimulus when considering discomfort or total achievable exercise volume. While limited to the population study, these findings paired with those found in general and athletic populations may be used to establish BFR guidelines which may be suitable for shoulder rehabilitation or injury prevention.
Background: muscle activation measured by electromyography (EMG) provides additional insight into functional differences between movements and muscle involvement. Objective: to evaluate the EMG of ...triceps surae during heel-raise exercise in healthy subjects performed at leg press machine with different feet positions. Methods: ten trained healthy male adults aged between 20 and 30 years voluntarily took part in the study. After biometric analyses the EMG signals were obtained using a 8-channel telemeterized surface EMG system (EMG System do Brazil, Brazil Ltda) (amplifier gain: 1000x, common rejection mode ratio >100 dB, band pass filter: 20 to 500 Hz). All data was acquired and processed using a 16-bit analog to digital converter, with a sampling frequency of 2kHz on the soleus (Sol), medial (GM) and lateral (GL) gastrocnemius muscles in both legs, in accordance with the recommendations of SENIAN. The root mean square (RMS) of the EMG amplitude was calculated to evaluate muscle activity of the three muscles. After being properly prepared for eletromyography procedures, all subjects were instructed to perform 3 sets of 5 repetitions during heel-raise exercise using the maximal load that enabled 10 repetitions on leg press 45° machine, each set being performed with one of the following feet positions: neutral (0º), internal and external rotation (both with 45° from neutral position). The tests were sequential and applied a 5-minute rest interval between sets. The order of the tests was randomized. Results: thought had been found interaction (F=0.27, P= 0.75) on RMS parameters and feet position, the values of Sol muscle were significantly (F=17.86, P= 0.003) lower compared with GL and GM muscles independently of feet position. Conclusion: The change in the feet position during the heel-rise exercise performed in the leg press does not influence the activation of the triceps surae, and the soleus is less activated than the gastrocnemius in that exercise.
The relatively large pick-up volume of surface electrodes has for long motivated the concern that muscles other than that of interest may contribute to surface electromyograms (EMGs). Recent findings ...suggest however the pick-up volume of surface electrodes may be smaller than previously appreciated, possibly leading to the detection of surface EMGs insensitive to muscle activity. Here we combined surface and intramuscular recordings to investigate how comparably action potentials from gastrocnemius and soleus are represented in surface EMGs detected with different inter-electrode distances. We computed the firing instants of motor units identified from intramuscular EMGs detected from gastrocnemius and soleus while five participants stood upright. We used these instants to trigger and average surface EMGs detected from multiple skin regions along gastrocnemius. Results from 66 motor units (whereof 31 from gastrocnemius) revealed the surface-recorded amplitude of soleus action potentials was 6% of that of gastrocnemius and did not decrease for inter-electrode distances smaller than 4 cm. Gastrocnemius action potentials were more likely detected for greater inter-electrode distances and their amplitude increased steeply up to 5 cm inter-electrode distance. These results suggest that reducing inter-electrode distance excessively may result in the detection of surface EMGs insensitive to gastrocnemius activity without substantial attenuation of soleus crosstalk.
Memories Faulkner, Zane Edward; Leaver, Echo Elizabeth
Imagination, cognition and personality,
12/2016, Letnik:
36, Številka:
2
Journal Article
Recenzirano
The fallibility of memory has important implications for various disciplinary fields, as well as societal interests. Research on false memory abounds in terms of the ability of researchers to implant ...memories for plausible and highly implausible negative events. The extant literature does not currently answer the question of whether memories for positive events can be implanted. Moreover, previous research has attempted, with mixed success, to discriminate between true and false memories employing different objective and subjective measures. Currently, there is still no conclusive way to distinguish between true and false memories. The present study expanded upon the current deficits in the research literature by inducing both positive and negative false memory events in participants. Physiological measures (i.e., skin conductance, heart rate, electromyography, and pulse plethysmography) were employed in an effort to discriminate between participants’ true and false memories. Results indicated that positive and negative events can be implanted at an impressively high rate and with a very simple manipulation. False memories were found to exhibit a greater arousal pattern than true memories and, specifically with electromyography, positive false memories elicited greater arousal patterns than positive true memories.
Objectives/Hypothesis
Laryngeal muscle activation is a complex and dynamic process. Current evaluation methods include needle and surface electromyography (sEMG). Limitations of needle ...electromyography include patient discomfort, interpretive complexity, and limited duration of recording. sEMG demonstrates interpretive challenges given loss of spatial selectivity. Application of high‐density sEMG (HD sEMG) arrays were evaluated for potential to compensate for spatial selectivity loss while retaining benefits of noninvasive monitoring.
Study Design
Basic science.
Methods
Ten adults performed phonatory tasks while a 20‐channel array recorded spatiotemporal data of the anterior neck. Data were processed to provide average spectral power of each electrode. Comparison was made between rest, low‐, and high‐pitch phonation. Two‐dimensional (2D) spectral energy maps were created to evaluate use in gross identification of muscle location.
Results
Three phonatory tasks yielded spectral power measures across the HD sEMG array. Each electrode within the array demonstrated unique power values across all subjects (P < .001). Comparison of each electrode to itself across phonatory tasks yielded differences in all subjects during rest versus low versus high, rest versus low, and rest versus high and in 9/10 subjects (P < .001) for low versus high phonation. Symmetry of HD sEMG signal was noted. Review of 2D coronal energy maps allowed for gross identification of cricothyroid muscle amidst anterior strap musculature.
Conclusions
HD sEMG can be used to identify differences in anterior neck muscle activity between rest, low‐, and high‐pitch phonation. HD sEMG of the anterior neck holds potential to enhance diagnostic and therapeutic monitoring for pathologies of laryngeal function.
Level of Evidence
NA
Laryngoscope, 129:2347–2353, 2019
A proposal for new diagnostic criteria for ALS Shefner, Jeremy M.; Al-Chalabi, Ammar; Baker, Mark R. ...
Clinical neurophysiology,
August 2020, 2020-08-00, 20200801, Letnik:
131, Številka:
8
Journal Article
This tutorial is aimed primarily to non-engineers, using or planning to use surface electromyography (sEMG) as an assessment tool for muscle evaluation in the prevention, monitoring, assessment and ...rehabilitation fields. The main purpose is to explain basic concepts related to: (a) signal detection (electrodes, electrode–skin interface, noise, ECG and power line interference), (b) basic signal properties, such as amplitude and bandwidth, (c) parameters of the front-end amplifier (input impedance, noise, CMRR, bandwidth, etc.), (d) techniques for interference and artifact reduction, (e) signal filtering, (f) sampling and (g) A/D conversion, These concepts are addressed and discussed, with examples.
The second purpose is to outline best practices and provide general guidelines for proper signal detection, conditioning and A/D conversion, aimed to clinical operators and biomedical engineers. Issues related to the sEMG origin and to electrode size, interelectrode distance and location, have been discussed in a previous tutorial. Issues related to signal processing for information extraction will be discussed in a subsequent tutorial.
Advanced forearm prosthetic devices employ classifiers to recognize different electromyography (EMG) signal patterns, in order to identify the user's intended motion gesture. The classification ...accuracy is one of the main determinants of real-time controllability of a prosthetic limb and hence the necessity to achieve as high an accuracy as possible. In this paper, we study the effects of the temporal and spatial information provided to the classifier on its off-line performance and analyze their inter-dependencies. EMG data associated with seven practical hand gestures were recorded from partial-hand and trans-radial amputee volunteers as well as able-bodied volunteers. An extensive investigation was conducted to study the effect of analysis window length, window overlap, and the number of electrode channels on the classification accuracy as well as their interactions. Our main discoveries are that the effect of analysis window length on classification accuracy is practically independent of the number of electrodes for all participant groups; window overlap has no direct influence on classifier performance, irrespective of the window length, number of channels, or limb condition; the type of limb deficiency and the existing channel count influence the reduction in classification error achieved by adding more number of channels; partial-hand amputees outperform trans-radial amputees, with classification accuracies of only 11.3% below values achieved by able-bodied volunteers.
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