ORCID Profile
0000-0002-7205-0117
Current Organisations
University of Victoria
,
University of Technology Sydney
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Publisher: Elsevier BV
Date: 11-2020
Publisher: Wiley
Date: 17-06-2013
Publisher: Wiley
Date: 31-10-2016
DOI: 10.1113/EP085753
Publisher: Springer Science and Business Media LLC
Date: 29-10-2014
DOI: 10.1007/S00421-014-3027-2
Abstract: This study examined whether changes in pH throughout the physiologic range would have a differential effect on central and peripheral factors associated with fatigue and force production during submaximal lower limb isometric exercise to task failure. Eight males completed three experimental trials [0.2 g kg(-1) ammonia chloride (ACD) 0.3 g kg(-1) calcium carbonate (PLA) or 0.3 g kg(-1) sodium bicarbonate (ALK)], each consisting of submaximal calf contractions at 55% of maximal voluntary contraction (MVC) to task failure. Every minute of the task subjects performed an MVC, coupled with stimulation of the tibial nerve during and immediately post MVC. Time to task failure was not different between trials (ACD 531 ± 166 s, PLA 592 ± 163 s, ALK 596 ± 150 s p = 0.31). MVC force in all trials declined 29 % from the start of exercise to the fifth minute (mean decline of 371 ± 26 N p < 0.001), however was not different between trials (p = 0.21). Fatigue was mediated in all trials by central and peripheral factors, as declines in voluntary activation, V/M-wave in the soleus and the potentiated resting twitch litudes were evident throughout the task (p < 0.05). Central fatigue appeared to be muscle specific, as reductions in central drive (V/M-wave and rate of sEMG rise) persisted in the soleus but not the medial gastrocnemius. These data suggest that calf fatigue associated with intermittent, isometric contractions to task failure is unaffected by alterations in pH however, central drive reductions may be muscle specific.
Publisher: SAGE Publications
Date: 2020
Abstract: Unilateral neglect is a debilitating condition that can occur after stroke and can affect a variety of domains and modalities, including proprioception. Proprioception is a sensorimotor process essential to motor function and is thus important to consider in unilateral neglect. To date, there has not been a comprehensive review of studies examining the various aspects of proprioceptive impairment in unilateral neglect after stroke. This review aimed to determine if people with unilateral neglect have more severe proprioceptive impairments than those without unilateral neglect after stroke. The MEDLINE, Embase, Scopus, CINAHL and Web of Science databases were searched from inception to September 2019 using an a priori search strategy. Two independent reviewers screened abstracts and full texts, and extracted data from the included full texts. A third reviewer resolved disagreements at each step. Risk of bias was assessed using the AXIS Quality Assessment tool. A total of 191 abstracts were identified, with 56 eligible for full-text screening. A total of 18 studies were included in the review and provided evidence that people with unilateral neglect have more severe proprioceptive impairment than people without unilateral neglect. This impairment is present in multiple subtypes of unilateral neglect and aspects of proprioception. Most studies had a moderate risk of bias. People with unilateral neglect after stroke are more likely to have impaired processing of multiple types of proprioceptive information than those without unilateral neglect. However, the available evidence is limited by the large heterogeneity of assessment tools used to identify unilateral neglect and proprioception. Unilateral neglect and proprioception were rarely assessed comprehensively. PROSPERO Registration: CRD42018086070.
Publisher: Wiley
Date: 08-07-2021
DOI: 10.1111/CTR.14409
Abstract: Diaphragmatic dysfunction is common after cardiothoracic surgery, but few studies report its incidence and consequences after lung transplantation. We aimed to estimate the incidence of diaphragmatic dysfunction using ultrasound in lung transplant patients up to 3 months postoperatively and evaluated the impact on clinical outcomes. This was a single‐center prospective observational cohort study of 27 lung transplant recipients using diaphragmatic ultrasound preoperatively, at 1 day, 1 week, 1 month, and 3 months postoperatively. Diaphragmatic dysfunction was defined as excursion 10 mm in men and 9 mm in women during quiet breathing. Clinical outcomes measured included duration of mechanical ventilation, length of stay (LOS) in Intensive Care (ICU), and hospital LOS. Sixty‐two percentage of recipients experienced new, postoperative diaphragmatic dysfunction, but the prevalence fell to 22% at 3 months. No differences in clinical outcomes were found between those with diaphragmatic dysfunction compared to those without. Patients who experienced diaphragmatic dysfunction at 1 day postoperatively were younger and had a lower BMI than those who did not. Diaphragmatic dysfunction is common after lung transplant, improves significantly within 3 months, and did not impact negatively on duration of mechanical ventilation, LOS in ICU or hospital, or discharge destination.
Publisher: BMJ
Date: 2022
DOI: 10.1136/BMJOPEN-2021-054875
Abstract: Meta-research. To compare the prevalence of reporting p values, effect estimates and clinical relevance in physiotherapy randomised controlled trials (RCTs) published in the years 2000 and 2018. We performed a meta-research study of physiotherapy RCTs obtained from six major physiotherapy peer-reviewed journals that were published in the years 2000 and 2018. We searched the databases Embase, Medline and PubMed in May 2019, and extracted data on the study characteristics and whether articles reported on statistical significance, effect estimates and confidence intervals for baseline, between-group, and within-group differences, and clinical relevance. Data were presented using descriptive statistics and inferences were made based on proportions. A 20% difference between 2000 and 2018 was regarded as a meaningful difference. We found 140 RCTs: 39 were published in 2000 and 101 in 2018. Overall, there was a high prevalence ( %) of reporting p values for the main (between-group) analysis, with no difference between years. Statistical significance testing was frequently used for evaluating baseline differences, increasing from 28% in 2000 to 61.4% in 2018. The prevalence of reporting effect estimates, CIs and the mention of clinical relevance increased from 2000 to 2018 by 26.6%, 34% and 32.8% respectively. Despite an increase in use in 2018, over 40% of RCTs failed to report effect estimates, CIs and clinical relevance of results. The prevalence of using p values remains high in physiotherapy research. Although the proportion of reporting effect estimates, CIs and clinical relevance is higher in 2018 compared to 2000, many publications still fail to report and interpret study findings in this way.
Publisher: American Physiological Society
Date: 15-02-2014
DOI: 10.1152/JAPPLPHYSIOL.01166.2013
Abstract: With fatiguing exercise, firing of group III/IV muscle afferents reduces voluntary activation and force of the exercised muscles. These afferents can also act across agonist/antagonist pairs, reducing voluntary activation and force in nonfatigued muscles. We hypothesized that maintained firing of group III/IV muscle afferents after a fatiguing adductor pollicis (AP) contraction would decrease voluntary activation and force of AP and ipsilateral elbow flexors. In two experiments ( n = 10) we examined voluntary activation of AP and elbow flexors by measuring changes in superimposed twitches evoked by ulnar nerve stimulation and transcranial magnetic stimulation of the motor cortex, respectively. Inflation of a sphygmomanometer cuff after a 2-min AP maximal voluntary contraction (MVC) blocked circulation of the hand for 2 min and maintained firing of group III/IV muscle afferents. After a 2-min AP MVC, maximal AP voluntary activation was lower with than without ischemia (56.2 ± 17.7% vs. 76.3 ± 14.6% mean ± SD P 0.05) as was force (40.3 ± 12.8% vs. 57.1 ± 13.8% peak MVC P 0.05). Likewise, after a 2-min AP MVC, elbow flexion voluntary activation was lower with than without ischemia (88.3 ± 7.5% vs. 93.6 ± 3.9% P 0.05) as was torque (80.2 ± 4.6% vs. 86.6 ± 1.0% peak MVC P 0.05). Pain during ischemia was reported as Moderate to Very Strong. Postfatigue firing of group III/IV muscle afferents from the hand decreased voluntary drive and force of AP. Moreover, this effect decreased voluntary drive and torque of proximal unfatigued muscles, the elbow flexors. Fatigue-sensitive group III/IV muscle nociceptors act to limit voluntary drive not only to fatigued muscles but also to unfatigued muscles within the same limb.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2020
DOI: 10.1249/MSS.0000000000002362
Abstract: Fatigue-related group III/IV muscle afferent firing from agonist, antagonist or distal muscles impairs the ability to drive the elbow flexors maximally, that is, reduces voluntary activation. In the lower limb, the effect of feedback from distal muscles on the proximal knee extensors is unknown. Here, we test whether maintained group III/IV afferent feedback from the plantarflexor muscles reduces voluntary activation of the knee extensors. On 2 d, voluntary activation of the knee extensors during maximal voluntary contractions (MVCs) was assessed in 12 participants before and after a 3-min fatiguing task of the plantarflexors. On 1 d, an inflatable cuff around the calf occluded blood flow for 2 min immediately postexercise (cuff day). The other day had no occlusion (no-cuff day). Supramaximal stimulation of the femoral nerve elicited superimposed twitches during MVC of the knee extensors and resting twitches 2 to 3 s after relaxation. Pain (0–10 point scale) was reported throughout. In the 2 min after the 3-min fatiguing plantarflexor task, voluntary activation was 5.3% (SD, 7%) lower on the cuff day than on the no-cuff day ( P = 0.045), and MVC force was reduced by 13% (SD, 16%) ( P = 0.021). The resting twitch was similar on both days ( P = 0.98). Pain rated 4.9 points higher with the cuff inflated ( P = 0.001). Maintained group III/IV afferent feedback from the fatigued plantarflexor muscles reduced maximal force and voluntary activation of the unfatigued knee extensors, suggesting that afferents from the calf act centrally to inhibit the ability to drive the motoneurones of the knee extensors.
Publisher: SAGE Publications
Date: 12-04-2022
DOI: 10.1177/02692155221091509
Abstract: To establish the effectiveness of relaxation and related therapies in treating Multiple Sclerosis related symptoms and sequelae. PsycINFO, PubMed, Embase, CINAHL, ProQuest Dissertations and Theses Global databases were searched. We included studies from database inception until 31 December 2021 involving adult participants diagnosed with multiple sclerosis or disseminated sclerosis, which featured quantitative data regarding the impact of relaxation interventions on multiple sclerosis-related symptoms and sequelae. Studies which examined multi-modal therapies - relaxation delivered in combination with non-relaxation interventions - were excluded. Risk of bias was assessed using the Revised Risk of Bias tool for randomised trials - ROB2, Risk of Bias in Non-Randomised Studies of Interventions ROBINS-I), and within and between-group effects were calculated (Hedges' Twenty-eight studies met inclusion criteria. Twenty-three of these were randomised controlled trials, with 1246 total participants. This review reports on this data, with non-randomised study data reported in supplemental material. Post -intervention relaxation was associated with medium to large effect-size improvement for depression, anxiety, stress and fatigue. The effects of relaxation were superior to wait-list or no treatment control conditions however, comparisons with established psychological or physical therapies were mixed. In idual studies reported sustained effects (≤ 6 months) with relaxation for stress, pain and quality of life. Most studies were rated as having a high/serious risk of bias. There is emerging evidence that relaxation therapies can improve outcomes for persons with multiple sclerosis. Given the high risk of bias found for included studies, stronger conclusions cannot be drawn.
Publisher: Informa UK Limited
Date: 09-07-2020
Publisher: Elsevier BV
Date: 12-2011
Publisher: American Physiological Society
Date: 15-02-2015
DOI: 10.1152/JAPPLPHYSIOL.00375.2014
Abstract: During fatiguing upper limb exercise, maintained firing of group III/IV muscle afferents can limit voluntary drive to muscles within the same limb. It is not known if this effect occurs in the lower limb. We investigated the effects of group III/IV muscle afferent firing from fatigued ipsilateral and contralateral extensor muscles and ipsilateral flexor muscles of the knee on voluntary activation of the knee extensors. In three experiments, we examined voluntary activation of the knee extensors by measuring changes in superimposed twitches evoked by femoral nerve stimulation. Subjects attended on 2 days for each experiment. On one day a sphygmomanometer cuff occluded blood flow of the fatigued muscles to maintain firing of group III/IV muscle afferents. After a 2-min extensor contraction ( experiment 1 n = 9), mean voluntary activation was lower with than without maintained ischemia (47 ± 19% vs. 87 ± 8%, respectively P 0.001). After a 2-min knee flexor maximal voluntary contraction (MVC) ( experiment 2 n = 8), mean voluntary activation was also lower with than without ischemia (59 ± 21% vs. 79 ± 9% P 0.01). After the contralateral (left) MVC ( experiment 3 n = 8), mean voluntary activation of the right leg was similar with or without ischemia (92 ± 6% vs. 93 ± 4% P = 0.65). After fatiguing exercise, activity in group III/IV muscle afferents reduces voluntary activation of the fatigued muscle and nonfatigued antagonist muscles in the same leg. However, group III/IV muscle afferents from the fatigued left leg had no effect on the unfatigued right leg. This suggests that any “crossover” of central fatigue in the lower limbs is not mediated by group III/IV muscle afferents.
Publisher: Elsevier BV
Date: 12-2011
Publisher: Elsevier BV
Date: 04-2022
Publisher: American Physiological Society
Date: 04-2018
DOI: 10.1152/JAPPLPHYSIOL.00739.2017
Abstract: During fatiguing voluntary contractions, the excitability of motoneurons innervating arm muscles decreases. However, the behavior of motoneurons innervating quadriceps muscles is unclear. Findings may be inconsistent because descending cortical input influences motoneuron excitability and confounds measures during exercise. To overcome this limitation, we examined effects of fatigue on quadriceps motoneuron excitability tested during brief pauses in descending cortical drive after transcranial magnetic stimulation (TMS). Participants ( n = 14) performed brief (~5-s) isometric knee extension contractions before and after a 10-min sustained contraction at ~25% maximal electromyogram (EMG) of vastus medialis (VM) on one ( n = 5) or two ( n = 9) days. Electrical stimulation over thoracic spine elicited thoracic motor evoked potentials (TMEP) in quadriceps muscles during ongoing voluntary drive and 100 ms into the silent period following TMS (TMS-TMEP). Femoral nerve stimulation elicited maximal M-waves (M max ). On the 2 days, either large (~50% M max ) or small (~15% M max ) TMS-TMEPs were elicited. During the 10-min contraction, VM EMG was maintained ( P = 0.39), whereas force decreased by 52% (SD 13%) ( P 0.001). TMEP area remained unchanged ( P = 0.9), whereas large TMS-TMEPs decreased by 49% (SD 28%) ( P = 0.001) and small TMS-TMEPs by 71% (SD 22%) ( P 0.001). This decline was greater for small TMS-TMEPs ( P = 0.019 n = 9). Therefore, without the influence of descending drive, quadriceps TMS-TMEPs decreased during fatigue. The greater reduction for smaller responses, which tested motoneurons that were most active during the contraction, suggests a mechanism related to repetitive activity contributes to reduced quadriceps motoneuron excitability during fatigue. By contrast, the unchanged TMEP suggests that ongoing drive compensates for altered motoneuron excitability. NEW & NOTEWORTHY We provide evidence that the excitability of quadriceps motoneurons decreases with fatigue. Our results suggest that altered intrinsic properties brought about by repetitive activation of the motoneurons underlie their decreased excitability. Furthermore, we note that testing during voluntary contraction may not reflect the underlying depression of motoneuron excitability because of compensatory changes in ongoing voluntary drive. Thus, this study provides evidence that processes intrinsic to the motoneuron contribute to muscle fatigue of the knee extensors.
Publisher: Elsevier BV
Date: 05-2020
Publisher: American Physiological Society
Date: 03-2021
DOI: 10.1152/JAPPLPHYSIOL.00717.2020
Abstract: We discovered that the contemporary procedure for assessing voluntary activation of the knee extensor muscles with transcranial magnetic stimulation (TMS) is invalid. TMS activates too few agonist quadriceps motoneurons and too many antagonist hamstrings motoneurons to estimate the resting twitch accurately. A modified procedure, in which TMS-evoked superimposed twitches are considered together with the resting twitch from femoral nerve stimulation, is valid but only in select in iduals who meet rigorous eligibility criteria.
Publisher: Cold Spring Harbor Laboratory
Date: 22-07-2019
DOI: 10.1101/710921
Abstract: Proprioceptive impairment is a potential contributing factor to the clinical presentation of Unilateral Neglect (UN), a common and debilitating condition that can occur after stroke. To date there has not been a comprehensive review of studies examining the various aspects of proprioception in UN after stroke. To determine if the presence of UN is associated with more severe proprioceptive deficit in stroke affected populations. The MEDLINE, Embase, Scopus, CINAHL and Web of Science databases were searched from inception to January 2019 using an a priori search strategy. Two independent reviewers screened abstracts and full texts. Two reviewers then independently extracted data from each full text. A third reviewer resolved disagreements at each step. Risk of bias was assessed using the AXIS Quality Assessment tool. For full protocol see PROSPERO, registration number CRD42018086070. One-hundred and sixty-seven abstracts were identified, of which fifty-four were eligible for full text screening. A total of 18 papers were included in the review. More severe proprioceptive deficit is associated with the presence of UN after stroke. However, the available evidence is limited by the large heterogeneity of assessment of both UN and proprioception, and level of study quality. UN and proprioception are seldom completely assessed in research, and it is likely this is true in everyday clinical practice.
Start Date: 2015
End Date: 2018
Funder: Multiple Sclerosis Research Australia
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