Bernadette Murphy

The validity and reliability of surface EMG to assess the neuromuscular response of the abdominal muscles to rapid limb movement

The transversus abdominus muscle (TrA) has been demonstrated to be active prior to rapid movements of the upper and lower limbs. This activity is termed feed forward motivation. The lack of feed-forward activation for TrA has been demonstrated in subjects with low back pain. The measures used for investigation of TrA function have been fine-wire needle EMG. This limits the practical application of TrA study due to the cost and level of specialisation required for this technique. The objective of the current study was to investigate the validity and reliability of using a surface EMG site to replicate the findings for the feed-forward activation of TrA prior to rapid limb movement. A population of healthy, young males (n = 20) were studied and it was found that four of the subjects did not meet feed-forward criteria. These results were shown to be highly reliable after a 2-week period for the TrA/IO site only. The validity of the signal was further investigated using several functional tasks to specifically target muscles of the abdominal region. Using a cross-correlation analysis to evaluate crosstalk from adjacent muscles, it was concluded that the signal representing TrA/IO accurately demonstrates the functional activity of the muscle. This study has demonstrated a viable surface EMG method to evaluate the feed-forward activation of TrA/IO prior to rapid limb movement. This may lead to opportunities for the clinical application of this method. It was also a finding of this study that four asymptomatic subjects did not pre-activate, therefore providing a rationale for future prospective investigations on whether the lack of TrA/IO feed-forward activation is a cause or an effect of low back pain.

Pelvic floor function in elite nulliparous athletes

There is preliminary evidence linking long‐term participation in high‐impact exercise with poor performance in labor and increased incidence of stress urinary incontinence, which may be due to altered pelvic floor function. Recent work has shown that HIFIT (high‐impact, frequent intense training) athletes have an increased cross‐sectional area of the levator ani muscle group as visualized using magnetic resonance imaging (MRI). The aim of this study was to further characterize pelvic floor muscle function and pelvic organ descent in a nulliparous athletic population and compare it with non‐athletic controls matched for age and body mass index, using three‐dimensional/four‐dimensional (3D/4D) pelvic floor ultrasound imaging.

Increased deltoid and abdominal muscle activity during Swiss ball bench press.

The swiss is widely used in the recreational training environment as a supplement to conventional resistance training. One such application is to use the swiss ball as a bench support for bench press exercise. There is no evidence to indicate that the use of a swiss ball is beneficial for resistance training exercise. This study investigated muscle activity using surface electromyography of upper-body and abdominal muscles during the concentric and eccentric phases of the bench press on and off a swiss ball. Volunteers for this study were 14 resistance-trained subjects who performed isolated concentric and eccentric bench press repetitions using the 2 test surfaces with a 2-second cadence at a load equivalent to 60% maximum force output. The average root mean square of the muscle activity was calculated for each movement, and perceived exertion during the tasks was collected using a Borg Scale. The results of the study showed that deltoid and abdominal muscle activity was increased for repetitions performed using the swiss ball. Increased deltoid muscle activity supports previous findings for increased activity when greater instability is introduced to the bench press movement. Abdominal muscle activity increases were not hypothesized, but this finding provides scientific evidence for anecdotal reasoning behind swiss ball use as a potential core stability training device.

Altered Sensorimotor Integration With Cervical Spine Manipulation

OBJECTIVEnThis study investigates changes in the intrinsic inhibitory and facilitatory interactions within the sensorimotor cortex subsequent to a single session of cervical spine manipulation using single- and paired-pulse transcranial magnetic stimulation protocols.nnnMETHODnTwelve subjects with a history of reoccurring neck pain participated in this study. Short interval intracortical inhibition, short interval intracortical facilitation (SICF), motor evoked potentials, and cortical silent periods (CSPs) were recorded from the abductor pollicis brevis and the extensor indices proprios muscles of the dominant limb after single- and paired-pulse transcranial magnetic stimulation of the contralateral motor cortex. The experimental measures were recorded before and after spinal manipulation of dysfunctional cervical joints, and on a different day after passive head movement. To assess spinal excitability, F wave persistence and amplitudes were recorded after median nerve stimulation at the wrist.nnnRESULTSnAfter cervical manipulations, there was an increase in SICF, a decrease in short interval intracortical inhibition, and a shortening of the CSP in abductor pollicis brevis. The opposite effect was observed in extensor indices proprios, with a decrease in SICF and a lengthening of the CSP. No motor evoked potentials or F wave response alterations were observed, and no changes were observed after the control condition.nnnCONCLUSIONnSpinal manipulation of dysfunctional cervical joints may alter specific central corticomotor facilitatory and inhibitory neural processing and cortical motor control of 2 upper limb muscles in a muscle-specific manner. This suggests that spinal manipulation may alter sensorimotor integration. These findings may help elucidate mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation.

Muscle Activation Changes After Exercise Rehabilitation for Chronic Low Back Pain

OBJECTIVEnTo investigate the changes in 2 electromyographic measures, flexion relaxation (FR) response and feed-forward activation of the deep abdominals, associated with low back pain (LBP) after different rehabilitation interventions.nnnDESIGNnA 2x2 factorial design with subjects self-selecting treatment with randomization after 4 weeks to either the specific exercise group or exercise advice group for a further 12-week period.nnnSETTINGnGeneral community practitioners and university training center.nnnPARTICIPANTSnSubjects with chronic nonspecific LBP were recruited for this study. A total of 112 people were initially screened, and 60 were recruited for the study, with 50 being available for long-term follow-up.nnnINTERVENTIONnFour weeks of treatment (manipulative or nonmanipulation) and 12 weeks of subsequent exercise (supervised Swiss ball training or exercise advice).nnnMAIN OUTCOME MEASURESnThe Oswestry Disability Index, FR response measured at T12-L1 and L4-5, and feed-forward activation of the deep abdominal muscles.nnnRESULTSnMore rapid improvements in disability were identified for subjects who received the supervised exercise program. The FR response at L4-5 also increased more for those who received directly supervised exercise. Long-term follow-up showed that there was still a between-group difference in the FR response, despite no difference in self-rated disability. Long-term changes were observed for the feed-forward activation of the deep abdominals; however, no exercise or treatment effects were identified.nnnCONCLUSIONSnSupervised exercise rehabilitation leads to more rapid improvements in self-rated disability, which were associated with greater improvement in the low back FR response.

Memory related dysregulation of hippocampal function in major depressive disorder.

Hippocampal abnormalities have frequently been associated with major depressive disorder (MDD), however evidence of a functional hippocampal deficit has remained illusive. Here, functional magnetic resonance imaging (fMRI) is employed in conjunction with an associative memory paradigm to investigate functional irregularities of the hippocampus during the encoding process. The use of a focussed analytical approach and a behavioural task targeted to hippocampal function confirmed the hypothesis that the normal modulation of hippocampal activation by encoding strength is dysregulated in MDD. Further analysis demonstrated that this impairment of function was specific to the hippocampus. A double dissociation between groups in the hippocampus and intraparietal sulcus indicates that compensatory mechanisms may exist. These results show that MDD is associated with a dysregulation of hippocampal function that cannot be explained in terms of overall brain state or motivational stance and provides an important link between memory impairments and hippocampal changes in MDD.

How best to measure the levator hiatus: evidence for the non-Euclidean nature of the 'plane of minimal dimensions'.

To clarify whether the ‘plane of minimal dimensions’ of the levator hiatus on three‐dimensional (3D) ultrasound accurately represents the minimal anatomical transverse hiatal dimension during a Valsalva maneuver.

Delayed abdominal muscle onsets and self-report measures of pain and disability in chronic low back pain ☆

OBJECTIVEnThe objective of this study was the measure the onset time of the transverse abdominis (TA) muscle during rapid unilateral shoulder movements in individuals with chronic low back pain (LBP), and to evaluate the relationship between latency times and self-report measures of pain and disability.nnnDESIGNnDescriptive cross-sectional study.nnnSETTINGnUniversity laboratory.nnnPARTICIPANTSnEighty individuals with chronic LBP of a non-specific origin (males n=44, females n=36).nnnMAIN OUTCOME MEASURESnResponses of the right and left surface TA/internal obliques were measured using surface electromyography (EMG) during rapid unilateral shoulder flexion, abduction, and extension. Pain intensity was measured using a visual analog scale (VAS), and disability with the Oswestry disability index (ODI).nnnRESULTSnSeventy-five percent of individuals were identified as lacking feedforward activation. A significant sidexdirection main effect was identified, with the ipsilateral latency more delayed in flexion and abduction (F(2316)=58.2, p<0.001). Individuals without feedforward activation had lower ODI scores (23.2+/-6.9% vs 31.0+/-9.2%, mean difference 7.8%, 95% CI 3.9 to 11.6%, p<0.001). Regression analysis found that 17% of the variance in VAS scores for the entire sample (n=80) were explained by the latency times measured. This relationship was stronger when the sample was separated into individuals who did (n=20), and did not (n=60) have feedforward activation.nnnCONCLUSIONnDeep abdominal muscle onsets during rapid limb movement were significantly associated with self-rated pain scores. Seventy-five percent of individuals with chronic non-specific LBP exhibited delayed activation. No evidence has been provided in this study to support, or refute the use of specific localized deep abdominal contractions for exercise rehabilitation programs.

Changes in the flexion relaxation response following an exercise intervention.

Study Design. Pre and post 12-week training study using surface electromyography to measure the flexion relaxation response. Objective. To evaluate whether the active or passive phases of the flexion relaxation measurement changes following an exercise intervention in patients with low back pain. Summary of Background Data. Impaired neuromuscular activation is an area of specific interest in patients with chronic nonspecific low back pain (LBP). The flexion relaxation phenomenon is commonly measured in LBP patients; however, there is insufficient evidence about the changes in this measure following an intervention. Methods. Fifteen subjects with chronic LBP (7 females, 8 males) performed a 12-week training intervention. The main outcome measures were the Oswestry disability index, visual analog scale, and flexion relaxation response analyzed by the raw electromyograph (EMG) signal, the relative EMG signal, and the flexion relaxation ratio. Results. Disability and pain scores improved significantly after the 12-week intervention. There were no changes in the active components of the flexion relaxation measurement but an approximate 67% decrease in the amount of activity measured during the relaxation phase at full trunk flexion. Conclusion. The data suggest that afferent feedback changes may be explaining why there is improved electrical relaxation following an exercise intervention.

The Cervical Flexion-Relaxation Ratio: Reproducibility and Comparison Between Chronic Neck Pain Patients and Controls

Study Design. Reliability study. Objective. To determine the reproducibility of the cervical flexion-relaxation ratio (FRR) measured 4 weeks apart in a group of chronic neck pain patients and healthy control group and to compare the FRR between the 2 groups. Summary of Background Data. The cervical FRR measures the ability of the neck extensor muscles to relax during forward flexion, similar to the lumbar FRR. Its reliability and ability to discriminate neck pain patients from controls has not been investigated. Methods. Fourteen participants with chronic neck pain and a control group of 14 individuals with no neck pain were recruited via advertisement and word of mouth. The cervical FRR was determined at baseline and 4 weeks later using standardized electromyographic data collection and analysis procedures. Results. The mean FRR value for the combined left and right side data for the neck pain groups was 1.93 ± 0.8, and 1.73 ± 0.61 at 4-week follow-up. The intraclass correlation coefficient (ICC) was 0.83 (95% CI = 0.67–0.92). Three participants in the control group developed neck pain in the 4 weeks and their data were not included in the reliability calculation. For the control group, the combined (left and right side) mean FRR value was 4.09 ± 1.58 at baseline and 4.27 ± 1.71 on retest 4 weeks later. The ICC (intraclass r) was 0.89 (95% confidence interval = 0.76–0.95). The overall ICC for the combined groups was 0.92 (95% confidence interval = 0.86–0.95). An independent 2 group t test revealed a significant difference in the baseline FRR data between the control group and the neck pain group (P < 0.001). Conclusion. The cervical extensor muscles exhibit a consistent flexion-relaxation phenomenon in healthy control subjects and the measurement is highly reproducible when measured 4 weeks apart in both controls and chronic neck pain patients. The FRR in neck pain patients is significantly higher than in control subjects suggesting that this measure may be a useful marker of altered neuromuscular function.