"This is hard to cope with": the lived experience and coping strategies adopted amongst Australian women with pelvic girdle pain in pregnancy.

BACKGROUND: Women with pregnancy-related pelvic girdle pain (PPGP) report diminished ability to perform physical activities and experience higher rates of mood disorders, such as anxiety and depression, than pregnant women without PPGP. Despite these physical and psychological impacts, little is known about the lived experiences of PPGP amongst Australian women and the ways in which they cope. Situated within biographical disruption and social support theories, this study sought to gain a conceptual understanding of the experience and impact of PPGP on daily life, and how women cope with this condition during pregnancy. METHODS: A qualitative research design, situated within a phenomenological framework, using individual, semi-structured interviews consisting of open-ended questions was used with a flexible and responsive approach. Purposive sampling of pregnant women attending a single hospital included 20 participants between 14 and 38 weeks gestation, classified with PPGP as per recommended guidelines, with a mean (SD) age of 31.37 (4.16) years. Thematic analysis was performed where interview data was transcribed, coded, grouped into meaningful categories and then constructed into broad themes. RESULTS: Three themes were identified: 1. a transformed biography; 2. coping strategies; and 3. what women want. The pain experienced created a dramatic change in women's lives, making the pregnancy difficult to endure. Women utilised social support, such as family, to help them cope with pain, and a self-care approach to maintain a positive mindset and reduce stress. Although a few women received support from healthcare professionals, many reported a lack information on PPGP and limited societal recognition of the condition. Women wanted early education, personalised information and prompt referral to help them cope with PPGP. CONCLUSIONS: Findings from this study highlighted the complexity of living with PPGP as women attempted to deal with the unexpected impact on daily life by seeking support from partners and families, while also struggling with societal expectations. Although women with PPGP used a number of coping strategies, they sought greater support from healthcare professionals to effectively manage PPGP. These findings have important implications for the provision of health care to women living with PPGP. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12618001423202 .

Prevalence and Factors Associated with Pelvic Girdle Pain During Pregnancy in Australian Women: A Cross-Sectional Study.

STUDY DESIGN: Cross-sectional study conducted between December 2017 and October 2019. OBJECTIVE: To determine the prevalence and risk factors associated with pregnancy-related pelvic girdle pain (PPGP) in Australia. SUMMARY OF BACKGROUND DATA: PPGP is a common condition worldwide yet the prevalence and associated risk factors are not known in Australia. METHODS: A random sample of pregnant women (N = 780) of (mean [SD]) 31 (5) years of age between 14 and 38 weeks gestation attending ante-natal care in a tertiary referral hospital in Sydney, Australia was conducted. The main outcome measure was point-prevalence of PPGP as classified by recommended guidelines including a physical examination. A number of potential risk factors, including socio-demographic characteristics, country of birth, ethnicity, history of low back pain (LBP) and PPGP, family history of PPGP, occupational factors, and physical activity were investigated with logistic regression. RESULTS: The point-prevalence of PPGP in a random sample of 780 Australian women was 44% with the odds of having PPGP increasing with each additional week of gestation (odds ratio [OR]) (OR 1.02). Increasing parity (P = 0.03, OR 1.15), country of birth (P = 0.03), and greater duration of time spent standing (P = 0.009, OR 1.06) were associated with PPGP. The strongest predictors of PPGP were previous LBP and/or PPGP both pregnancy (P < 0.001, OR 4.35) and not pregnancy related (P < 0.001, OR 2.24), and a family history of PPGP (P < 0.001, OR 3.76). CONCLUSION: The prevalence of PPGP in Australian women was high with almost half the sample classified with PPGP, matching data reported worldwide. The identified risk factors associated with PPGP can be included in routine ante-natal care to screen women and identify those at risk of this common and disabling condition.Level of Evidence: 1.

Recognising ethnocultural diversity in chronic pain assessment: validation of the Pictorial Representation of Illness and Self Measure (PRISM) for use with culturally diverse communities.

BACKGROUND: A comprehensive and accurate assessment of pain is critical for successful pain management. However, there is a lack of reliable and valid assessment tools for exploring multidimensional aspects of the chronic pain experience in culturally and linguistically diverse communities. This study investigates the reliability and validity of the Pictorial Representation of Illness and Self Measure + (PRISM+) for evaluating pain-related suffering and the sociocultural context of chronic pain within culturally and linguistically diverse patient cohorts. METHOD: Three prospective validation studies are reported for three culturally and linguistically diverse communities. Two hundred and fifty-one patients with chronic pain who self-identified as Assyrian (n = 85), Arabic (n = 83) or Vietnamese (n = 83) completed a PRISM+ assessment, alongside a battery of standardised pain assessments. To evaluate construct validity, the position of the 'pain' disk placement was correlated with the Brief Pain Inventory (BPI), Depression Anxiety and Stress Scale (DASS), and the Short-Form 36 Health Survey (SF-36). For content validity, thematic analysis of patient narratives accompanying each disk placement was conducted. Test-retest reliability of repeated 'pain' and five additional disks (PRISM+) values was analysed using intra-class correlation coefficients. RESULTS: The PRISM pain assessment demonstrated moderate to good test-retest reliability for Arabic (ICC 0.76; 95% CI 0.65-0.84), Assyrian (ICC 0.65; 95% CI 0.50-0.76) and Vietnamese (ICC 0.82; 95% CI 0.73-0.88) patients. Moderate correlations between the PRISM 'pain' disk and sub-scores for the BPI, DASS and SF-36 were found (p < 0.001). Patient interpretations of the 'pain' disk aligned with accepted definitions of suffering, supporting content validity for PRISM. For the additional disks (PRISM+), moderate to good test-retest reliability (ICC 0.67-0.88) was observed and qualitative analysis highlighted each disk reflected social and cultural values. CONCLUSION: The PRISM demonstrates acceptable psychometric properties for measuring pain-related suffering for participants with chronic pain across three culturally and linguistically diverse communities. The use of additional disks (PRISM+) presents a reliable and valid option for exploring social and cultural dimensions of chronic pain in clinical encounters.

The Intersections of Chronic Noncancer Pain: Culturally Diverse Perspectives on Disease Burden.

OBJECTIVE: This study highlights the burden of chronic non-cancer-related pain from the perspectives of three culturally and linguistically diverse communities, using an intersectionality analysis. Specifically, we identify how multiple social identities intersect to account for the unequal distribution of the burden of chronic pain. DESIGN AND METHODS: Six focus groups of 41 culturally and linguistically diverse participants (Mandaean, Assyrian, and Vietnamese) living with chronic noncancer pain were conducted in South-West Sydney, Australia, between February and July 2015. Data were analyzed using inductive and intersectional methodology. RESULTS: The interaction between a patient with chronic pain from a culturally and linguistically diverse background and the health system is influenced by four identified social identities that interact to create relative positions of disadvantage for the patient within the health system and with health care providers. The social identities identified were ethnoculture, social class, migration status, and gender. CONCLUSIONS: Health care providers must consider how the intersectionality of social identities related to ethnoculture, social class, migration status, and gender can factor into the creation and maintenance of chronic pain disparities. A greater, more thoughtful incorporation of intersectionality in chronic pain research and clinical practice will ensure that pain management approaches are designed and applied in a way that reflects the social context of affected communities and individuals from those communities.

Integrating culturally informed approaches into physiotherapy assessment and treatment of chronic pain: a pilot randomised controlled trial.

OBJECTIVE: To evaluate patient engagement with, and the feasibility of, a novel, culturally adapted physiotherapy pain management approach. DESIGN: A participant-blinded and assessor-blinded pilot randomised controlled trial. SETTING: Outpatient physiotherapy departments at two public hospitals and one district pain clinic. PARTICIPANTS: Adults (n=48) with chronic musculoskeletal pain (daily pain >3 months), who self-identified as Mandaean, Assyrian or Vietnamese, were randomised to one of two physiotherapy treatment conditions. INTERVENTIONS: 24 participants underwent combined group and individualised treatment described as 'culturally adapted physiotherapy', while 24 underwent evidence-informed 'usual physiotherapy care'. Both treatment arms consisted of up to 10 sessions over a 3-month period. OUTCOME MEASURES: Patient engagement was measured via participant attendance, adherence and satisfaction data. Secondary outcomes included clinical measures of pain severity, interference and suffering, physical function and negative emotional state. RESULTS: 96% of participants undergoing culturally adapted physiotherapy completed treatment, compared with 58% of the usual physiotherapy group. For the culturally adapted group attendance (87%±18%) and adherence (68%±32%) were higher relative to usual care (68%±32% and 55%±43%). Satisfaction was similar for the culturally adapted (82.7%±13.4%) and usual care (79.3±17.3) groups. For secondary outcomes, a significant between-group effect for pain-related suffering in favour of the culturally adapted group was observed with a medium effect size (partial η2 0.086, mean 3.56, 95% CI 0.11 to 7), while results for pain severity, interference, physical function and negative emotional state were similar. CONCLUSIONS: Aligning treatment with the beliefs and values of culturally and linguistically diverse communities enhances patient engagement with physiotherapy. These results support the feasibility of a larger, multisite trial to determine if improved engagement with culturally adapted physiotherapy translates to improved clinical outcomes. TRIAL REGISTRATION NUMBER: ACTRN12616000857404; Pre-results.

How do Australian women cope with pelvic girdle pain during pregnancy? A qualitative study protocol.

INTRODUCTION: Pelvic girdle pain is commonly experienced during pregnancy and results in significant physical, psychosocial and work-related challenges. Few studies have investigated the lived experiences of pregnant women with pelvic girdle pain and their coping strategies. There is a need to develop a greater understanding of this prevalent condition among Australian women. Thus, this study seeks to gain information about the impact of pelvic girdle pain on daily life and how women cope with this condition during pregnancy. METHODS AND ANALYSIS: A qualitative research design, situated within a phenomenological framework, is adopted. The participants will be invited to describe their lived experiences of pregnancy-related pelvic girdle pain, the impact on their daily life and the strategies they use to cope with the condition. A stratified purposive sample will be undertaken to ensure the sample provides information-rich cases representative of women with pregnancy-related pelvic girdle pain. Face-to-face, individual, semistructured interviews will be conducted with participants at Westmead Hospital, Sydney, Australia. A solicited diary will be offered to any participants who may find attending the interview difficult. All participants will also be invited to attend a focus group session. The different methods of data collection used in this study will allow for triangulation, thereby increasing the trustworthiness of findings. ETHICS AND DISSEMINATION: Ethical approval has been granted by the Human Research Ethics Committees of Westmead Hospital, Sydney, and Western Sydney University, Sydney. Dissemination of results will be via journal articles and conference presentations.

Disruption of cortical synaptic homeostasis in individuals with chronic low back pain.

OBJECTIVE: Homeostatic plasticity mechanisms regulate synaptic plasticity in the human brain. Impaired homeostatic plasticity may contribute to maladaptive synaptic plasticity and symptom persistence in chronic musculoskeletal pain. METHODS: We examined homeostatic plasticity in fifty individuals with chronic low back pain (cLBP) and twenty-five pain-free controls. A single block (7-min) of anodal transcranial direct current stimulation ('single tDCS'), or two subsequent blocks (7-min and 5-min separated by 3-min rest; 'double tDCS'), were randomised across two experimental sessions to confirm an excitatory response to tDCS applied alone, and evaluate homeostatic plasticity, respectively. Corticomotor excitability was assessed in the corticomotor representation of the first dorsal interosseous muscle by transcranial magnetic stimulation-induced motor evoked potentials (MEPs) recorded before and 0, 10, 20, and 30-min following each tDCS protocol. RESULTS: Compared with baseline, MEP amplitudes increased at all time points in both groups following the single tDCS protocol (P < 0.003). Following the double tDCS protocol, MEP amplitudes decreased in pain-free controls at all time points compared with baseline (P < 0.01), and were unchanged in the cLBP group. CONCLUSION: These data indicate impaired homeostatic plasticity in the primary motor cortex of individuals with cLBP. SIGNIFICANCE: Impaired homeostatic plasticity could explain maladaptive synaptic plasticity and symptom persistence in cLBP.

Prevalence of pregnancy-related pelvic girdle pain and associated factors in Australia: a cross-sectional study protocol.

INTRODUCTION: Pregnancy-related pelvic girdle pain (PPGP) is a common musculoskeletal disorder. Women with PPGP report difficulty performing everyday functional activities, such as standing and walking. However, the magnitude of the problem remains unknown in Australia. It is important to determine how many women are affected by this condition and the factors associated with PPGP as this will direct healthcare services to being able to better manage women during pregnancy. Thus, this study aims to determine the prevalence of PPGP and associated factors in a Western Sydney population. METHODS AND ANALYSIS: This study is a cross-sectional study to be conducted at a single hospital in Australia. Participants will be over 18 years of age, between 14 and 38 weeks gestation and recruited randomly from all pregnant women attending antenatal care. Participants will have anthropomorphic measures recorded, such as height and body weight, and be asked to complete questionnaires about their current pregnancy, sociodemographic information, ethnoculture, occupational factors and participation in functional activities. The classification of PPGP will be made as per the published guidelines and will include a physical examination. ETHICS AND DISSEMINATION: Ethical approval has been granted by the Human Research Ethics Committees of Westmead Hospital, Sydney, and Western Sydney University, Sydney. Dissemination of results will be via journal articles and conference presentations. TRIAL REGISTRATION NUMBER: ACTRN12617000904370.

Integrating culturally informed approaches into the physiotherapy assessment and treatment of chronic pain: protocol for a pilot randomised controlled trial.

INTRODUCTION: There is strong evidence that biopsychosocial approaches are efficacious in the management of chronic pain. However, implementation of these approaches in clinical practice is known not to account for the beliefs and values of culturally and linguistically diverse (CALD) patients. This limitation in translation of research contributes to the disparities in outcomes for CALD patients with chronic pain adding to the socioeconomic burden of this prevalent condition. Cultural adaptation of chronic pain assessment and management is urgently required. Thus, the aim of this pilot randomised controlled trial (RCT) is to determine the feasibility, participant acceptance with and clinical effectiveness of a culturally adapted physiotherapy assessment and treatment approach when contrasted with 'usual evidence based physiotherapy care' for three CALD communities. METHODS AND ANALYSIS: Using a participant-blinded and assessor-blinded randomised controlled pilot design, patients with chronic pain who self-identify as Assyrian, Mandaean or Vietnamese will be randomised to either 'culturally adapted physiotherapy assessment and treatment' or 'evidence informed usual physiotherapy care'. We will recruit 16 participants from each ethnocultural community that will give a total of 24 participants in each treatment arm. Both groups will receive physiotherapy treatment for up to 10 sessions over 3 months. Outcomes including feasibility data, acceptance with the culturally adapted intervention, functional and pain-related measures will be collected at baseline and 3 months by a blinded assessor. Analysis will be descriptive for feasibility outcomes, while measures for clinical effectiveness will be explored using independent samples t-tests and repeated measures analysis of variance. This analysis will inform sample size estimates while also allowing for identification of revisions in the protocol or intervention prior to a larger scale RCT. ETHICS AND DISSEMINATION: This trial has full ethical approval (HREC/16/LPOOL/194). The results from this pilot RCT will be presented at scientific meetings and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ACTRN12616000857404.

An exploration of the experience of pain among culturally diverse migrant communities.

Objective. To explore the ethnocultural influences on the chronic pain experience in three culturally and linguistically diverse communities in Australia. Methods. Six focus groups were conducted with 34 women and 7 men (ages 36-74 years) who self-identified as Mandaean, Assyrian or Vietnamese. A purposive sample of community-dwelling adults living with chronic pain (daily pain >3 months) was recruited from community organizations. Participants were asked broadly about the meanings of chronic pain, acceptance, ethnocultural community expectations and approaches to pain management. A standardized interview collected sociodemographic and symptom data for descriptive purposes. Results. Inductive thematic analysis yielded a multidimensional web of themes interrelated with the pain experience. Themes of ethnocultural identity and migrant status were intertwined in the unique explanatory model of pain communicated for each community. The explanatory model for conceptualizing pain, namely biopsychosocial, biomedical or a traditional Eastern model, framed participants' approaches to health seeking and pain management. Conclusions. Chronic pain is theoretically conceptualized and experienced in diverse ways by migrant communities. Knowledge of cultural beliefs and values, alongside migration circumstances, may help providers deliver health care that is culturally responsive and thereby improve outcomes for migrant communities with chronic pain.

Reduced Short- and Long-Latency Afferent Inhibition Following Acute Muscle Pain: A Potential Role in the Recovery of Motor Output.

OBJECTIVE: Corticomotor output is reduced in response to acute muscle pain, yet the mechanisms that underpin this effect remain unclear. Here the authors investigate the effect of acute muscle pain on short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition to determine whether these mechanisms could plausibly contribute to reduced motor output in pain. DESIGN: Observational same subject pre-post test design. SETTING: Neurophysiology research laboratory. SUBJECTS: Healthy, right-handed human volunteers (n = 22, 9 male; mean age ± standard deviation, 22.6 ± 7.8 years). METHODS: Transcranial magnetic stimulation was used to assess corticomotor output, short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition before, during, immediately after, and 15 minutes after hypertonic saline infusion into right first dorsal interosseous muscle. Pain intensity and quality were recorded using an 11-point numerical rating scale and the McGill Pain Questionnaire. RESULTS: Compared with baseline, corticomotor output was reduced at all time points (p = 0.001). Short-latency afferent inhibition was reduced immediately after (p = 0.039), and long-latency afferent inhibition 15 minutes after (p = 0.035), the resolution of pain. Long-interval intra-cortical inhibition was unchanged at any time point (p = 0.36). CONCLUSIONS: These findings suggest short- and long-latency afferent inhibition, mechanisms thought to reflect the integration of sensory information with motor output at the cortex, are reduced following acute muscle pain. Although the functional relevance is unclear, the authors hypothesize a reduction in these mechanisms may contribute to the restoration of normal motor output after an episode of acute muscle pain.

Graft tensioning practices in anterior cruciate ligament reconstruction amongst orthopaedic surgeons in Australia: a national survey.

PURPOSE: The application of graft tension during anterior cruciate ligament reconstruction is considered an important feature of ACLR. However, wide variation exists in relation to graft tensioning practice limiting the ability to determine the best approach. Thus, the primary aim of this study was to describe current clinical practice amongst Australian orthopaedic surgeons with respect to graft tensioning and explore influencing factors. MATERIALS AND METHODS: A survey was developed to address the aims of the study and pilot testing was completed to confirm validity and reliability. The survey population was defined as Australian orthopaedic surgeons, associated with the Australian Orthopaedic Association sub-specialty of knee to target surgeons likely to perform ACLR. The final sampling frame consisted of 192 surgeons. RESULTS: Manual tensioning was the most common method (80.5 %), with a maximum one-handed pull the most frequent description and estimated tension ranged between 41 and 60 N with the knee positioned near full extension. Surgeons using a tensioning device tended to use a higher tension (mean 81.85 N), with the knee positioned at 30° flexion (40 %). Sixteen percent reported individualising tension on viscoelasticity of the graft, graft diameter, patient anthropometry and age. Patient outcomes and available evidence were the primary factors influencing tensioning protocol. CONCLUSION: Tensioning practices appear to consist of three main approaches, (1) manual tension using a sustained maximum one-handed pull, with tension estimated as 41-60 N, applied near full extension, (2) tensioning device, mean tension of 81.85 N, at 30° knee flexion, (3) individual approach based on size and viscoelastic properties of the graft, patient anthropometry, contralateral comparison to the other knee and age of the patient.

Novel adaptations in motor cortical maps: the relation to persistent elbow pain.

INTRODUCTION: Unilateral elbow pain results in sensorimotor dysfunction that is frequently bilateral, affects local and remote upper limb muscles, and persists beyond resolution of local tendon symptoms. These characteristics suggest supraspinal involvement. Here, we investigated 1) the excitability and organization of the M1 representation of the wrist extensor muscles and 2) the relation between M1 changes and clinical outcomes in lateral epicondylalgia (LE) (n = 11) and healthy control subjects (n = 11). METHODS: Transcranial magnetic stimulation was used to map the M1 representation of the extensor carpi radialis brevis (ECRB) and extensor digitorum (ED). RESULTS: The cortical representations of ECRB and ED were more excitable, and the centers of gravity for the two muscles were located closer together in LE than that in healthy controls. Increased ECRB excitability and closer location of the center of gravity were associated with higher pain severity at rest and/or in the preceding 6 months. A novel finding was a reduced number of discrete peaks in the representations of ECRB and ED in participants with LE compared with that in healthy controls. CONCLUSIONS: This finding may have broad implications for the control of the wrist extensor muscles in LE. These data provide evidence that cortical organization may be maladaptive in LE and suggest that reorganization may be associated with persistence/recurrence of pain.

The effect of electrical stimulation on corticospinal excitability is dependent on application duration: a same subject pre-post test design.

BACKGROUND: In humans, corticospinal excitability is known to increase following motor electrical stimulation (ES) designed to mimic a voluntary contraction. However, whether the effect is equivalent with different application durations and whether similar effects are apparent for short and long applications is unknown. The aim of this study was to investigate whether the duration of peripheral motor ES influenced its effect on corticospinal excitability. METHODS: The excitability of the corticomotor pathway to abductor pollicis brevis (APB) was measured in fourteen health subjects using transcranial magnetic stimulation before, immediately after and 10 minutes after three different durations (20-, 40-, 60-min) of motor ES (30Hz, ramped). This intervention was designed to mimic a voluntary contraction in APB. To control for effects of motor ES on the peripheral elements (muscle fibre, membrane, neuromuscular junction), maximum compound muscle actions potentials (M-waves) were also recorded at each time point. Results were analysed using a repeated measures analysis of variance. RESULTS: Peripheral excitability was reduced following all three motor ES interventions. Conversely, corticospinal excitability was increased immediately following 20- and 40-min applications of motor ES and this increase was maintained at least 20-min following the intervention. A 60-min application of motor ES did not alter corticospinal excitability. CONCLUSIONS: A 20-min application of motor ES that is designed to mimic voluntary muscle contraction is as effective as that applied for 40-min when the aim of the intervention is to increase corticospinal excitability. Longer motor ES durations of 60-min do not influence corticospinal excitability, possibly as a result of homeostatic plasticity mechanisms.

Initial graft tension and the effect on postoperative patient functional outcomes in anterior cruciate ligament reconstruction.

PURPOSE: The aim of this review was to investigate the effect of initial graft tension on patient-specific functional outcomes after anterior cruciate ligament reconstruction and determine whether a particular tension is associated with superior functional outcome. METHODS: We performed a systematic review of prospective randomized trials with a National Health and Medical Research Council Australia level of evidence of III or higher published between 1950 and July 2012. Studies using a semitendinosus-gracilis or bone-patellar tendon-bone autograft that reported graft tension and postoperative functional outcomes were included. Quantitative analysis was performed on available data by calculating effect size (ES) both at various time points and across tensions (in Newtons). RESULTS: Initial search strategies returned 457 original publications, of which 5 articles fulfilled all exclusion and inclusion criteria. The mean score for quality was 5.8 (SD, 1.3), with 12 being the highest possible score. When compared with the preoperative side-to-side difference in anterior tibial displacement, 80 N and 78.9 N of tension recorded the largest effect at 2 weeks or less (ES, -2.98 [range, -3.82 to -2.14]) and 12 months or more (ES, -2.45 [range, -3.40 to -1.51]) postoperatively, respectively. When we compared tensions, the largest effect was toward 80 N when compared with 20 N at 2 weeks or less after surgery (ES, 0.76 [range, 0.17 to 1.35]). CONCLUSIONS: The objective of this review was to systematically assess the literature to determine whether a particular initial graft tension results in superior outcomes after anterior cruciate ligament reconstruction. From the review, there is a trend toward an initial graft tension of 78.5 to 90 N resulting in a reduced side-to-side difference in anterior laxity. However, there is insufficient evidence to conclude whether patient-specific function is improved at any specific tension. LEVEL OF EVIDENCE: Level II, systematic review of Level II studies.

Interaction between simultaneously applied neuromodulatory interventions in humans.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a neuromodulatory technique with the potential to enhance the efficacy of traditional therapies such as neuromuscular electrical stimulation (NMES). Yet, concurrent application of tDCS/NMES may also activate homeostatic mechanisms that block or reverse effects on corticomotor excitability. It is unknown how tDCS and NMES interact in the human primary motor cortex (M1) and whether effects are summative (increase corticomotor excitability beyond that of tDCS or NMES applied alone) or competitive (block or reduce corticomotor excitability effects of tDCS or NMES applied alone). OBJECTIVE: To investigate corticomotor excitability in response to NMES after concurrent application of tDCS protocols that enhance (anodal tDCS) or suppress (cathodal tDCS) excitability of M1. METHODS: We used transcranial magnetic stimulation (TMS) to examine corticomotor excitability before and after the concurrent application of: i) NMES with anodal tDCS; and ii) NMES with cathodal tDCS. Effects were contrasted to four control conditions: i) NMES alone, ii) anodal tDCS alone, iii) cathodal tDCS alone, and iv) sham stimulation. RESULTS: Concurrent application of two protocols that enhance excitability when applied alone (NMES and anodal tDCS) failed to induce summative effects on corticomotor excitability, as predicted by homeostatic plasticity mechanisms. Combined cathodal tDCS and NMES suppressed the enhanced excitation induced by NMES, an effect that might be explained by calcium dependent anti-gating models. CONCLUSIONS: These novel findings highlight the complex mechanisms involved when two neuromodulatory techniques are combined and suggest that careful testing of combined interventions is necessary before application in clinical contexts.

Primary sensory and motor cortex excitability are co-modulated in response to peripheral electrical nerve stimulation.

Peripheral electrical stimulation (PES) is a common clinical technique known to induce changes in corticomotor excitability; PES applied to induce a tetanic motor contraction increases, and PES at sub-motor threshold (sensory) intensities decreases, corticomotor excitability. Understanding of the mechanisms underlying these opposite changes in corticomotor excitability remains elusive. Modulation of primary sensory cortex (S1) excitability could underlie altered corticomotor excitability with PES. Here we examined whether changes in primary sensory (S1) and motor (M1) cortex excitability follow the same time-course when PES is applied using identical stimulus parameters. Corticomotor excitability was measured using transcranial magnetic stimulation (TMS) and sensory cortex excitability using somatosensory evoked potentials (SEPs) before and after 30 min of PES to right abductor pollicis brevis (APB). Two PES paradigms were tested in separate sessions; PES sufficient to induce a tetanic motor contraction (30-50 Hz; strong motor intensity) and PES at sub motor-threshold intensity (100 Hz). PES applied to induce strong activation of APB increased the size of the N(20)-P(25) component, thought to reflect sensory processing at cortical level, and increased corticomotor excitability. PES at sensory intensity decreased the size of the P25-N33 component and reduced corticomotor excitability. A positive correlation was observed between the changes in amplitude of the cortical SEP components and corticomotor excitability following sensory and motor PES. Sensory PES also increased the sub-cortical P(14)-N(20) SEP component. These findings provide evidence that PES results in co-modulation of S1 and M1 excitability, possibly due to cortico-cortical projections between S1 and M1. This mechanism may underpin changes in corticomotor excitability in response to afferent input generated by PES.