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Biomedical subjects

C A Byrne

Publications and source records attributed to C A Byrne.

9 recordsLinked to original sources
PubMed2006

Effect of walking speed changes on tibialis anterior EMG during healthy gait for FES envelope design in drop foot correction.

Functional electrical stimulation may be used to correct hemiplegic drop foot. An optimised stimulation envelope to reproduce the EMG pattern observed in the tibialis anterior (TA) during healthy gait has been proposed by O'Keeffe et al. [O'Keeffe, D.T., Donnelly, A.E., Lyons, G.M., 2003. The development of a potential optimised stimulation intensity envelope for drop foot applications. IEEE Transactions on Neural Systems and Rehabilitation Engineering]. However this envelope did not attempt to account for changes in TA activity with walking speed. The objective of this paper was to provide data to enable the specification of an algorithm to control the adaptation of an envelope with walking speed. Ten young healthy subjects walked on a treadmill at 11 different walking speeds while TA EMG was recorded. The results showed that TA EMG recorded around initial contact and at toe off changed with walking speed. At the slowest velocities, equivalent to hemiplegic walking, the toe-off burst (TOB) of EMG activity had larger peak amplitude than that of the heel-strike burst (HSB). The peak amplitude ratio of TOB:HSB was 1:0.69 at the slowest speed compared to, 1:1.18 and 1:1.5 for the self-selected and fastest speed, respectively. These results suggest that an FES envelope, which produces larger EMG amplitude for the TOB than the HSB, would be more appropriate at walking speeds typical of hemiplegic patients.

Adaptation, Physiological↗
PubMed2005

Rectus femoris surface myoelectric signal cross-talk during static contractions.

The clinical application of EMG requires that the recorded signal is representative of the muscle of interest and is not contaminated with signals from adjacent muscles. Some authors report that surface EMG is not suitable for obtaining information on a single muscle but rather reflects muscle group function [J. Perry, C.S. Easterday, D.J. Antonelli, Surface versus intramuscular electrodes for electromyography of superficial and deep muscles. Physical Therapy 61 (1981) 7-15]. Other authors report however, that surface EMG is adequate to determine individual muscle function, once guidelines pertaining to data acquisition are followed [D.A. Winter, A.J. Fuglevand, S.E. Archer. Cross-talk in surface electromyography: theoretical and practical estimates. Journal of Electromyography and Kinesiology 4 (1994) 15-26]. The aim of this study was to determine whether surface EMG was suitable for monitoring rectus femoris (RF) activity during static contractions. Five healthy subjects, having given written informed consent, participated in this trial. Surface and fine wire EMG from the rectus femoris and the vastus lateralis (VL) muscles were recorded simultaneously during a protocol of static contractions consisting of knee extensions and hip flexions. Ratios were used to quantify the relationship between the surface EMG amplitude value and the fine wire EMG amplitude value for the same contraction. The results showed that hip flexion contractions elicited RF activation only and that knee extension contractions elicited fine wire activity in VL only. When the relationship between RF surface and RF fine wire electrodes was compared for hip flexion and knee extension contractions, it was observed that for all subjects, there was a tendency for increased RF surface activity in the absence of RF fine wire activity during knee extensions. It was concluded that the activity recorded by the RF surface electrode arrangement during knee extension consisted of EMG from the vastii, i.e., cross-talk and that vastus intermedius was the most likely origin of the erroneous signal. Therefore it is concluded that for accurate EMG information from RF, fine wire electrodes are necessary during a range of static contractions.

Adult↗
PubMed2001

Stimulus artifact removal using a software-based two-stage peak detection algorithm.

The analysis of stimulus evoked neuromuscular potentials or m-waves is a useful technique for improved feedback control in functional electrical stimulation systems. Usually, however, these signals are contaminated by stimulus artifact. A novel software technique, which uses a two-stage peak detection algorithm, has been developed to remove the unwanted artifact from the recorded signal. The advantage of the technique is that it can be used on all stimulation artifact-contaminated electroneurophysiologic data provided that the artifact and the biopotential are non-overlapping. The technique does not require any estimation of the stimulus artifact shape or duration. With the developed technique, it is not necessary to record a pure artifact signal for template estimation, a process that can increase the complexity of experimentation. The technique also does not require the recording of any external hardware synchronisation pulses. The method avoids the use of analogue or digital filtering techniques, which endeavour to remove certain high frequency components of the artifact signal, but invariably have difficulty, resulting in the removal of frequencies in the same spectrum as the m-wave. With the new technique the signal is sampled at a high frequency to ensure optimum fidelity. Instrumentation saturation effects due to the artifact can be avoided with careful electrode placement. The technique was fully tested with a wide variety of electrical stimulation parameters (frequency and pulse width) applied to the common peroneal nerve to elicit contraction in the tibialis anterior. The program was also developed to allow batch processing of multiple files, using closed loop feedback correction. The two-stage peak detection artifact removal algorithm is demonstrated as an efficient post-processing technique for acquiring artifact free m-waves.

Action Potentials↗
PubMed1999

The socioeconomic impact of interpersonal violence on women.

Prospective data from a nationally representative sample of women were used to examine 4 objective indexes of social adjustment following direct, interpersonal crime. Household income, marital status, employment, and education level were evaluated as risk factors for and outcomes of victimization. Data were collected in 3 waves at 1-year intervals, and 2,863 women completed all 3 waves. Results indicate that women experience increased risk for victimization when income is below poverty level and when newly divorced. Further, victimization appears to increase women's risk for unemployment, reduced income, and divorce. The cyclical nature of victimization is discussed.

Adult↗
PubMed1999

Intimate violence and post-traumatic stress disorder among individuals with cocaine dependence.

Intimate physical assault and post-traumatic stress disorder (PTSD) were assessed in a sample of 91 adults seeking treatment for cocaine dependence. Physical assault included self-report of aggravated assault with a weapon, aggravated assault without a weapon, and simple assault. PTSD was assessed with a structured interview. Overall, 85.7% of the participants reported having been physically assaulted at least once during their lifetime. Slightly less than half of these individuals (46.2%) reported physical assault by an intimate partner. Close to half also met criteria for PTSD at some point in their lives. Women were more likely than men to be physically assaulted by an intimate partner and to report PTSD. Men who experienced physical assault by an intimate were more likely to report PTSD than men assaulted by others. Male victims of intimate violence had higher scores on certain subscales measuring addiction severity than male victims assaulted by others. Findings suggest careful assessment of intimate violence is essential given its high prevalence among cocaine-dependent women and men and its association with PTSD.

Adult↗
PubMed1998

The quality of the intimate relationships of male Vietnam veterans: problems associated with posttraumatic stress disorder.

This study examined the quality of the intimate relationships of male Vietnam veterans. Heterosexual couples in which the veteran had posttraumatic stress disorder (PTSD; n = 26) were compared to couples in which the veteran did not have PTSD (n = 24). Over 70% of the PTSD veterans and their partners reported clinically significant levels of relationship distress compared to only about 30% of the non-PTSD couples. Relationship difficulties appeared to encompass a wide range of areas, with PTSD veterans and their partners reporting that they had more problems in their relationships, more difficulties with intimacy, and had taken more steps toward separation and divorce than the non-PTSD veterans and their partners. The degree of relationship distress was correlated with the severity of veterans' PTSD symptoms, particularly symptoms of emotional numbing. Research and clinical implications of the results are discussed.

Analysis of Variance↗
PubMed1998

Female partners' estimations of male veterans' combat-related PTSD severity.

This study investigated concordance between male Vietnam veterans' and their female partners' reports of veterans' posttraumatic stress disorder (PTSD) symptoms. Fifty male Vietnam combat veterans and their partners rated the severity of their own PTSD symptoms. Also, partners rated the severity of veterans' symptoms. Results indicated modest levels of agreement in reports of symptom presence/absence. Partner ratings of veterans' PTSD severity were positively correlated with veteran reports and partners' own self-reported PTSD symptoms. After controlling for veterans' self-reported symptoms, partners' symptoms significantly predicted their estimates of veterans' avoidance symptoms, but not veterans' reexperiencing or hyperarousal symptoms. Theoretical and practical implications of these findings are discussed.

Adult↗
PubMed1996

The cycle of trauma; relationship aggression in male Vietnam veterans with symptoms of posttraumatic stress disorder.

This study examined the association between symptoms of Posttraumatic Stress Disorder (PTSD) in male Vietnam veterans and their use of aggressive behavior in relationships with intimate female partners. Fifty couples participated in the study. Veterans reported on their PTSD symptoms, and veterans and partners completed measures assessing the veterans' use of physical, verbal, and psychological aggression during the preceding year as well as measures of their own perceptions of problems in the relationship. Results indicated that PTSD symptomatology places veterans at increased risk for perpetrating relationship aggression against their partners. The association between veterans' PTSD symptoms and their use of aggression in relationships was mediated by relationship problems. Clinical implications of these findings and suggestions for future research are discussed.

Aggression↗