Browsing by Subject "Electromyography"

Now showing 1 - 7 of 7

Analysis of polymeric based electrodes coated with metallic thin films for biopotential applications
(2022-05-07) Hayes, Makenna June; Cullinan, Michael; Lopes, Claudia
This thesis analyzes the performance of dry surface electrodes through the monitoring of electromyographic bio signals and the application of sustained electrical stimulation. This new array of electrodes has been fabricated with common flexible polymeric substrates coated with metallic thin films and differ from conventional biopotential electrodes in that a layer of an electrolytic gel is not required. Experimental testing was conducted to analyze differences between peak-to-peak voltages during muscular contraction and noise amongst the varying electrode substrates and thin film coatings. From this, the optimal electrode substrate (polyurethane) and thin film coating (TiCu₀.₃₄) were determined and utilized for further testing. This thesis also investigates the relationship between acquired electromyographic signals and amount electrical stimulation and compares these results to commercially available electrodes. The results of the dry surface electrodes show comparable results to commercially available wet electrodes which indicates future inclusion of these electrodes into wearable rehabilitation devices.
Differential caregiving behaviors elicited by infant attractiveness : the role of adult affect
(2014-08) Schein, Stevie Scarlett; Langlois, Judith H.
Psychology
Enabling intuitive control of lower-limb assistive devices and their assessment through transverse sonomyographic sensing and machine learning
(2022-05-05) Rabe, Kaitlin Gail; Fey, Nicholas Phillip; Abraham, Lawrence D; Lenzi, Tomasso; Porter, Tyrone; Santacruz, Samantha
Assistive device technology has significantly improved within the last decade primarily due to the introduction and advancement of microprocessor-controlled and powered (i.e., robotic) prostheses and orthoses. However, there remains a gap between the mechanical capabilities of these devices and the biomechanical abilities of their wearers. There is a critical need for robust human-machine interfaces, which accurately sense various forms of locomotion and intuitively interact with the human wearer during a range of activities that comprise their daily lives. Such interfaces rely on a continuous estimation of user intent, which is derived from wearable or embedded sensing. Sonomyography, the evaluation of real-time dynamic ultrasound (US) imaging of skeletal muscle, has been recently proposed as a new sensing modality for assistive device control. Compared to a more conventional modality of muscle-based sensing known as surface electromyography (EMG) that detects changes in neural excitation of superficial muscle, sonomyography has the ability to track deformation of skeletal muscle ranging from superficial to deep tissue, and to sense these changes in multiple muscle groups with the same sensor. The overall objective of this research is to benchmark and demonstrate the feasibility of using transverse sonomyographic sensing as an input to various machine learning models for intuitive control systems and assessment methods of wearable lower-limb assistive devices. Following a discussion of the relevant prior work that led to this research in Chapter 1, in Chapter 2, we benchmark sonomyography against surface EMG for the continuous estimation of discrete ambulation tasks and analyze the contribution of superficial and deep US features. Next, in Chapters 3 and 4, sonomyographic sensing is compared to surface EMG sensing (as well as their fusion) for continuous estimation of joint kinematics and kinetics during various ambulation tasks. In Chapter 5, sonomyographic sensing is used as an input to forward models that predict future trajectories of limb motion and torque during ambulation. Subsequently, in Chapter 6, we compare sonomyography, mechanical-based sensing, and their fusion as tools to recognize how individuals with and without lower-limb amputation use their lower-extremity to complete widely-varying ambulation tasks. Finally, the overall conclusions of this work are discussed in Chapter 7. This research can impact the quality of life for individuals with mobility limitations by developing and testing new human-machine interfaces that are robust and ubiquitous to specific assistive devices and ambulation tasks. Therefore, our findings can help better translate robotic assistive technologies from lab-based settings into the lives of individuals.
Muscle force potentiation and motor unit firing patterns during fatigue : effects of muscular endurance training
(2010-05) Mettler, Joni Ann; Griffin, Lisa; Abraham, Larry; Farrar, Roger; Jones, Theresa; Spirduso, Waneen
Muscular fatigue limits athletic performance as well as activities of daily living that require repetitive or sustained contractile activity. The decrease in force output or inability to maintain a given force level during fatigue occurs as the result of neural and muscle physiological factors. In contrast to muscle fatigue, potentiation is an increase in muscle force following voluntary muscle activity. The simultaneously occurring processes of potentiation and fatigue influence force output. The aims of this research were to investigate parameters used to potentiate muscle via electrical stimulation and voluntary contraction, and to better understand how muscle force is sustained, we studied single motor unit firing patterns and force potentiation following muscular endurance training. In study 1, electrical stimulation trains matched for pulse number of various frequencies and of increasing pulse number at a given frequency were administered to determine the effects of these stimulation parameters and of the force-time integral (FTI) produced during the train on potentiation magnitude. No difference in potentiation magnitude was found across trains of matched pulse number for frequencies of 15, 25, 30 and 50 Hz. Potentiation increased as pulse number increased and there was a positive correlation between potentiation and the FTI. In study 2, we measured maximal potentiation following conditioning contractions (CC) of 25%, 50% and 100% maximal voluntary contraction (MVC) and during a 25% MVC fatigue task, pre-post 8 weeks of muscular endurance training. Results showed significant potentiation for all CC intensities. Potentiation increased as CC intensity increased and CC duration required to achieve maximal potentiation decreased as CC intensity increased. Muscular endurance training resulted in increased maximal potentiation, and potentiation was greater during the fatigue task after training. Potentiation was also correlated to endurance time. In study 3, the effects of muscular endurance training on motor unit firing rates were investigated. There was a small increase in mean motor unit firing rates during the course of the fatigue task after training. This research contributes to our understanding of muscular force production and muscular endurance. The findings suggest that motor unit firing frequency and force potentiation may contribute to enhanced muscular endurance.
Physiological and biomechanical factors of cycling performance
(2018-08-08) Leary, Brian Keith; Coyle, Edward F., 1952-
The two primary predictors of cycling performance are maximal oxygen consumption and lactate threshold. However, several physiological and biomechanical factors influence these variables. The purpose of study one was to investigate relative joint contribution, muscle activation, and muscle oxygenation differences between high (HLT) and low (LLT) lactate threshold cyclists with similar maximal oxygen consumption capabilities (VO [subscript 2max]). While there were no differences in muscle oxygenation, the HLT group had greater relative hip contribution at 90% of VO [subscript 2max] compared to the LLT group, as well as decreased vastus medialis EMG activation during exercise at 60 and 70% of VO [ subscript 2max] (p<0.05). These findings suggesting the HLT cyclists place a greater emphasis on the hip compared to the knee joint to generate power while cycling. The purpose of study two was to investigate the effects of short-term maximal power training on cycling peak oxygen consumption (VO [subscript 2peak-cycling]) in non-cyclists. Over the course of 5 days, the training group performed 10 maximal sprints a day each lasting ~4 seconds with two-minutes rest between each sprint. This protocol was designed to maximize recruitment of muscles involved in cycling while minimizing cardiovascular stress during training. Following training, absolute and relative VO [subscript 2peak-cycling] was 5.9 ± 1.6% and 5.6 ± 1.9% greater compared to pre-training (p<0.05), while in the control group VO [subscript 2peak-cycling] did not change (p>0.05). The improvement in VO [subscript 2peak-cycling] was accompanied by a 6.3 ± 2.5% increase (Pre: 228 ± 18 W vs. Post: 242 ± 19 W) in peak work rate achieved during post-testing in the training group (p<0.05). This suggests that VO [subscript 2peak-cycling] can be increased through maximal power training in non-cyclists likely as a result of increased ability to recruit additional muscle mass during intense cycling exercise. Taken together, these studies indicate that biomechanical muscle recruitment 'strategies' can influence both submaximal (i.e. LT [subscript VO2]) and peak oxygen consumption (i.e. VO [subscript 2peak-cycling]) during cycling.
Prediction of muscle force patterns in elbow flexion/extension and comparison with electromyography
(1990) Gonzalez, Roger Valles, 1963-; Barr, Ronald E., 1946-
The purpose of this study was to determine the contribution of the musculotendon actuators in human elbow flexion/extension. For this study, two experiments were conducted using video analysis and a third using electrogoniometer analysis. The video and electrogoniometer records of arm movements were analyzed and converted into kinematic data which were then used to calculate the net elbow joint torque. The methodology used in the experiments to study muscle contribution to flexion/extension at the elbow joint is discussed and the results of the experiments are presented. These torques were then partitioned among the muscles studied by assuming equal muscle stress across all muscles. Physiologic cross-Sectional Area (PSA) was used in calculating the stress in each muscle, therefore yielding individual muscle force patterns from the net joint torque. Predicted individual muscle force patterns were evaluated and compared to the integrated electromyogram (EMG) signals of each respective muscle by using a qualitative similarity analysis. In general, the results showed good qualitative profile correlation between the muscle force patterns predicted and the respective integrated EMG
The effects of exposure to attractive and unattractive infant faces on self-reported and psychophysiological affect
(2016-05) Schein, Stevie Scarlett; Langlois, Judith H.; Bigler, Rebecca; Woolley, Jacqueline; Echols, Catharine; Trujillo, Logan
The primary aim of this study was to determine the trajectory of self-reported liking ratings and psychophysiological affective responses to attractive and unattractive infant stimuli over multiple exposures to determine whether these trajectories would conform to the predictions of mere exposure theory or negativity bias. Participants viewed a block of attractive and unattractive infant photographs, repeated 25 times, while their liking ratings and corrugator supercilli, levator labii superioris, and zygomaticus major muscle responses were recorded. Overall, self-reported liking ratings decreased as a function of exposure to the unattractive infant faces, indicating that repeated exposure intensifies the initial negative evaluation of those faces, rather than increasing liking for all stimuli.