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Diagnostic overshadowing refers to a phenomenon whereby people with mental health conditions encounter inadequate or delayed medical attention and misdiagnosis. This occurs when physical symptoms are mistakenly attributed to their mental health condition. This paper presents a scoping review focusing on direct causes and background factors of diagnostic overshadowing in the context of hepatitis C infection in people who inject drugs and have concurrent mental health conditions. Despite significant strides in hepatitis C treatment with direct-acting antiviral drugs, the complex interplay of mental health conditions and physical symptoms necessitates a nuanced approach for accurate diagnosis and effective screening. This review was conducted using Joanna Briggs Institute's methodology for scoping reviews. The databases searched included Medline, Embase, PsycInfo, Global Health, CINAHL and Scopus. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). The search strategies identified 1995 records. Overall, 166 studies were excluded. Forty-two (42) studies met the inclusion criteria. Three (n = 3) studies represented direct causes, and 39 (n = 39) with background factors related to diagnostic overshadowing. Studies highlighted six key themes encompassing diagnostic overshadowing, with communication barriers, stigma and knowledge deficiencies being the most prominent. Recognising and addressing diagnostic overshadowing in chronic hepatitis C will lead to increased screening, diagnosis and timely administration of life-saving antiviral therapy, resulting in profound enhancements in well-being and health outcomes. Moreover, this proactive approach will play a pivotal role in advancing the global effort towards eliminating hepatitis C by 2030., (© 2024 The Author(s). International Journal of Mental Health Nursing published by John Wiley & Sons Australia, Ltd.)

Introduction: Contingency management (CM) is the most effective treatment for reducing methamphetamine use. We sought to understand why CM has not been taken up to manage methamphetamine use disorder in Australia., Methods: Six focus groups (4-8 participants per group) were conducted with health workers from agencies in Australia that provided drug-related health care to people who use methamphetamine. These agencies had no previous experience delivering CM for substance use. The potential acceptability and feasibility of implementing CM in their services were discussed., Results: Participants felt that it would be beneficial to have an evidence-based treatment for methamphetamine use disorder. This sentiment was offset by concerns that CM conflicted with a client-centred harm-reduction approach and that it dictated the goal of treatment as abstinence. It was also perceived as potentially coercive and seen to reify the power imbalance in the therapeutic relationship and therefore potentially reinforce stigma. There was also concern about the public's perception and the political acceptability of CM, who would fund CM, and the inequity of providing incentives only to clients with a methamphetamine use disorder. Some concerns could be ameliorated if the goals and structure of CM could be tailored to a client's needs., Discussion and Conclusions: Many healthcare workers were keen to offer CM as an effective treatment option for people with methamphetamine use disorder, but CM would need to be sufficiently flexible to allow it to be tailored to client needs and implemented in a way that did not adversely impact the therapeutic relationship., (© 2024 The Authors. Drug and Alcohol Review published by John Wiley & Sons Australia, Ltd on behalf of Australasian Professional Society on Alcohol and other Drugs.)

Background: There are no approved pharmacotherapies for methamphetamine use disorder. Two preliminary phase 2 randomised controlled trials have found mirtazapine, a tetracyclic antidepressant, to be effective in reducing methamphetamine use. The proposed Tina Trial is the first phase 3 placebo-controlled randomised trial to examine the effectiveness and safety of mirtazapine as an outpatient pharmacotherapy for methamphetamine use disorder., Methods: This is a multi-site phase 3 randomised, double-blind, placebo-controlled parallel trial. Participants are randomly allocated (1:1) to receive either mirtazapine (30 mg/day for 12 weeks) or matched placebo, delivered as a take-home medication. The target population is 340 people aged 18-65 years who have moderate to severe methamphetamine use disorder. The trial is being conducted through outpatient alcohol and other drug treatment clinics in Australia. The primary outcome is measured as self-reported days of methamphetamine use in the past 4 weeks at week 12. Secondary outcomes are methamphetamine-negative oral fluid samples, depressive symptoms, sleep quality, HIV risk behaviour and quality of life. Other outcomes include safety (adverse events), tolerability, and health service use. Medication adherence is being monitored using MEMS® Smart Caps fitted to medication bottles., Discussion: This trial will provide information on the safety and effectiveness of mirtazapine as a pharmacotherapy for methamphetamine use disorder when delivered as an outpatient medication in routine clinical practice. If found to be safe and effective, this trial will support an application for methamphetamine use disorder to be included as a therapeutic indication for the prescription of mirtazapine., Trial Registration: Australian and New Zealand Clinical Trials Registry ACTRN12622000235707. Registered on February 9, 2022., (© 2024. The Author(s).)

Introduction: Stigma has negative consequences for the health of people who inject drugs and people living with hepatitis C virus (HCV). This study evaluated factors associated with stigma related to injecting drug use (IDU) or HCV and those associated with being treated negatively by health workers., Methods: ETHOS Engage is an observational cohort study of people who inject drugs attending drug treatment clinics and needle and syringe programs in Australia. Participants completed a questionnaire including IDU- and HCV-related stigma, and negative treatment by health workers. Logistic regression was used to identify factors associated with experiencing stigma and negative treatment in a cross-sectional sample., Results: Of 1,211 participants, 31% were women, 64% had injected drugs in the previous month, and 65% had been diagnosed with HCV. IDU-related stigma was reported by 57% of participants and was associated with being a woman, higher than Year 10 education, homelessness, opioid agonist treatment, recent injecting, overdose history, hospitalisation for drug use, and unknown HCV status. HCV-related stigma was reported by 34% of participants diagnosed with HCV and was associated with being a woman, homelessness, receptive needle/syringe sharing, arrest for drug use/possession, and recent HCV testing. Negative treatment from health workers was reported by 45% of participants and was associated with being a woman, receptive needle/syringe sharing, hospitalisation for drug use, and arrest for drug use/possession., Discussion and Conclusions: Results highlight important intersections and disparities in stigmatising experiences among people who inject drugs. Considering these intersections can assist health services provide more inclusive care., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: TB has received speaker fees from Gilead Sciences. JG reports personal fees from Abbott, Abbvie, Cepheid, Gilead Sciences, and Roche and grants from Abbvie, bioLytical, Cepheid, Gilead Sciences, and Hologic, outside the submitted work. GD reports grants from AbbVie and Gilead Sciences. LD has received investigator-initiated untied educational grants for studies of opioid medications in Australia from Indivior, Mundipharma and Seqirus. HV has received honorarium from Gilead Sciences. All remaining authors have no potential conflicts to declare., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Introduction: There is little knowledge of the perspectives of people who use methamphetamine and have participated in clinical trials, and none for interventions not intended to address abstinence. A better understanding of these experiences could lead to more patient centred clinical trial design. This study seeks to understand the experiences of people who completed a clinical trial of lisdexamfetamine for the treatment of acute methamphetamine withdrawal., Methods: Thematic analysis of open-ended, semi-structured interviews with eight people who participated in an inpatient clinical trial of lisdexamfetamine for acute methamphetamine withdrawal. Interviews were conducted between days 3 and 6 of admission to an inner-city Sydney hospital., Results: Participants described how research procedures, the research setting, and the investigational product affected their experiences while enrolled in a clinical trial. Of particular importance to participants were transparent and low burden trial procedures, a welcoming trial environment, trusting relationships and effective communication, which were linked with the participants' subsequent decision to remain enrolled in the trial., Discussion: The experiences of participants in this clinical trial can be distilled into four meta-themes: agency, caring-trust, safety, and communication. Participants spontaneously linked these experiences with a capacity to remain enrolled in the study. By considering the experiences of trial participants in clinical trial design, researchers can improve the experiences of future trial participants and facilitate their choice to remain enrolled in clinical trials., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: LSA is supported by an NDARC PhD Scholarship. MF has received unrestricted funding for research purposes from Indivior and Sequiiris. SS has received clinical research supplies from Alkermes. NE and KJS are employed by NCCRED. No other investigators have any conflicts of interest to declare., (Copyright © 2024. Published by Elsevier B.V.)

Introduction: Contingency management (CM) is currently the most efficacious treatment for methamphetamine use, yet it is rarely available in routine care. We examined the viewpoints of people who use methamphetamine on CM as a potential treatment for methamphetamine use disorder., Methods: Semi-structured qualitative interviews with 30 Australians aged 18 years or older who had used methamphetamine at least weekly in the past 6 months., Results: Participants reported overall positive attitudes towards CM as a potential treatment option for methamphetamine use disorder. However, there was need for greater flexibility in meeting participant treatment goals (e.g., reduced use or complete abstinence), with particular concern about the viability of initiating abstinence, both in terms of the sufficiency of the initial financial incentive and managing withdrawal symptoms. There was strong interest in the use of digital technologies to provide remote CM, particularly around the convenience and flexibility this offered. Despite this, participants remained keen to access adjunctive treatment and support services but stressed that engagement with these additional services should not be mandatory. Marketing of CM will need to address preconceptions about drug-testing used in abstinence-based CM being punitive (especially urine testing) and its connotations with criminal justice interventions., Discussion and Conclusion: Positive attitudes towards CM bode well for potential uptake should CM be made available in routine clinical practice. However, there is a need to adapt CM to ensure it is feasible and attractive to people who are seeking treatment for methamphetamine use disorder., (© 2023 The Authors. Drug and Alcohol Review published by John Wiley & Sons Australia, Ltd on behalf of Australasian Professional Society on Alcohol and other Drugs.)

Introduction: Long-acting injectable depot buprenorphine is a recent addition to the suite of opioid agonist therapies (OAT) used to treat opioid use disorder (OUD). However, there has been little research that focuses on the lived experience of people receiving depot buprenorphine treatment and reasons for why people decide to discontinue. The aim of this study was to explore what it is like to receive depot buprenorphine and to understand the motivations behind why people discontinue., Methods: Open-ended, semi-structured interviews were conducted between November 2021 and January 2022 with individuals who were either currently receiving depot buprenorphine or had discontinued or were in the process of discontinuing depot buprenorphine. Liberati, et al.'s (2022) adaptation of Dixon-Woods's (2006) candidacy framework was used to analyse the participant experiences., Results: 40 participants (26 male, 13 female, 1 undisclosed; mean age 42 years) were interviewed about their experience with depot buprenorphine. At the time of the interview, 21 were currently receiving depot buprenorphine and 19 had discontinued this treatment or were in the process of discontinuing. Participants cited 4 key reasons why they decided to discontinue depot buprenorphine:1) feeling forced into the program, 2) experiencing negative side-effects, 3) finding the treatment ineffective, and 4) wanting to stop depot buprenorphine/OAT to use opioids again or feeling 'cured' and no longer in need of OAT. Participants were ultimately discussing issues related to clinician-patient power relations, agency and bodily autonomy, and the pursuit of well-being., Conclusion: Depot buprenorphine remains a promising treatment for OUD and offers potential to improve treatment adherence. Instances of restricted OAT choice and consumer concerns regarding a lack of agency must be addressed in order to enhance therapeutic relationships. Clinicians and other healthcare workers in this field also need greater access to information about depot buprenorphine to better address issues patients face during treatment. More research is required to understand patient and treatment choice given the options of these new treatment formulations., Competing Interests: Declarations of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Background: Awareness of hepatitis C virus (HCV) infection status among people who inject drugs (PWID) can empower people with diagnosis, enable treatment uptake, and facilitate elimination. We aimed to evaluate awareness of HCV infection status among a large national cohort of PWID in an era of unrestricted HCV treatment., Methods: ETHOS Engage is an observational cohort study of PWID attending drug treatment clinics and needle and syringe programs in Australia. Participants completed a questionnaire containing self-reported HCV data (including infection status: never tested, tested/unknown, no current HCV infection [HCV RNA not detectable], current HCV infection [HCV RNA detectable]) and underwent point-of-care HCV RNA testing (Xpert® HCV Viral Load Fingerstick). Awareness was defined as concordant self-reported HCV status and test result. Awareness was assessed among all participants, those with current HCV infection, and participants who reported a lifetime history of HCV treatment. Logistic regression was used to assess factors associated with awareness in these three populations., Results: Among 2,305 PWID, 65% (n=1,506) were aware of their HCV infection status (self-reported HCV status matched HCV point-of-care result). Awareness of infection status was higher among those who were not currently infected (70%, n=1,281/1,818) compared to those with current HCV infection (46%, n=225/487). After adjusting, those with current HCV infection were less likely to be aware of infection status (aOR: 0.40, 95%CI: 0.30, 0.45). Among those who reported a lifetime history of HCV treatment, 71% (n=592/829) were aware of their HCV infection status., Conclusion: Among a large cohort of PWID in Australia, awareness of HCV infection status is sub-optimal, with particularly concerning levels among those with active infection. Increased and simplified testing, post-test counselling, and post-treatment monitoring is warranted., Competing Interests: Declarations of Interest JG is a consultant/advisor and has received research grants from AbbVie, Camurus, Cepheid, Gilead, Hologic, Indivior, and Merck outside the submitted work. GJD is a consultant/advisor and has received research grants from Merck, Gilead, and AbbVie outside the submitted work. LD has received investigator-initiated untied educational grants for studies of opioid medications in Australia from Indivior, Mundipharma and Seqirus. CT has received speaker fees from AbbVie and Gilead and has received an unrestricted education grant from Terumo. PR has received speaker fees from Gilead and MSD, and research funding from Gilead., (Copyright © 2022. Published by Elsevier B.V.)

Background: There is no effective treatment for methamphetamine withdrawal. This study aimed to determine the feasibility and safety of a tapering dose of lisdexamfetamine for the treatment of acute methamphetamine (MA) withdrawal., Methods: Open-label, single-arm pilot study, in an inpatient drug and alcohol withdrawal unit assessing a tapering dose of oral lisdexamfetamine dimesylate commencing at 250 mg once daily, reducing by 50 mg per day to 50 mg on Day 5. Measures were assessed daily (days 0-7) with 21-day telephone follow-up. Feasibility was measured by the time taken to enrol the sample. Safety was the number of adverse events (AEs) by system organ class. Retention was the proportion to complete treatment. Other measures included the Treatment Satisfaction Questionnaire for Medication (TSQM), the Amphetamine Withdrawal Questionnaire and craving (Visual Analogue Scale)., Results: Ten adults seeking inpatient treatment for MA withdrawal (9 male, median age 37.1 years [IQR 31.7-41.9]), diagnosed with MA use disorder were recruited. The trial was open for 126 days; enroling one participant every 12.6 days. Eight of ten participants completed treatment (Day 5). Two participants left treatment early. There were no treatment-related serious adverse events (SAEs). Forty-seven AEs were recorded, 17 (36%) of which were potentially causally related, all graded as mild severity. Acceptability of the study drug by TSQM was rated at 100% at treatment completion. Withdrawal severity and craving reduced through the admission., Conclusion: A tapering dose regimen of lisdexamfetamine was safe and feasible for the treatment of acute methamphetamine withdrawal in an inpatient setting., Competing Interests: Conflict of interest LSA is supported by an NDARC PhD Scholarship. MF has received unrestricted funding for research purposes from Indivior and Sequiiris. SS has received clinical research supplies from Alkermes. NE and KJS are employed by NCCRED. No other investigators have any conflicts of interest to declare., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Introduction: Methamphetamine (MA) use disorder is an important public health concern. MA withdrawal is often the first step in ceasing or reducing use. There are no evidence-based withdrawal treatments, and no medication is approved for the treatment of MA withdrawal. Lisdexamfetamine (LDX) dimesilate, used in the treatment of attention deficit hyperactivity disorder and binge eating disorder has the potential as an agonist therapy to ameliorate withdrawal symptoms, and improve outcomes for patients., Methods: A single arm, open-label pilot study to test the safety and feasibility of LDX for the treatment of MA withdrawal. Participants will be inpatients in a drug and alcohol withdrawal unit, and will receive a tapering dose of LDX over five days: 250mg LDX on Day 1, reducing by 50mg per day to 50mg on Day 5. Optional inpatient Days 6 and 7 will allow for participants to transition to ongoing treatment. Participants will be followed-up on Days 14, 21 and 28. All participants will also receive standard inpatient withdrawal care. The primary outcomes are safety (measured by adverse events, changes in vital signs, changes in suicidality and psychosis) and feasibility (the time taken to enrol the sample, proportion of screen / pre-screen failures). Secondary outcomes are acceptability (treatment satisfaction questionnaire, medication adherence, concomitant medications, qualitative interviews), retention to protocol (proportion retained to primary and secondary endpoints), changes in withdrawal symptoms (Amphetamine Withdrawal Questionnaire) and craving for MA (visual analogue scale), and sleep outcomes (continuous actigraphy and daily sleep diary)., Discussion: This is the first study to assess lisdexamfetamine for the treatment of acute MA withdrawal. If safe and feasible results will go to informing the development of multi-centre randomised controlled trials to determine the efficacy of the intervention., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: Michael Farrell as Director of NDARC has received unrestricted funding for research purposes from Indivior and Sequiiris. Steve Shoptaw has received clinical research supplies from Alkermes. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

This study evaluated HCV treatment initiation among people who inject drugs (PWID) following an intervention of campaign days involving peer connection, point-of-care HCV RNA testing, and linkage to nursing support. ETHOS Engage is an observational cohort study of PWID attending 25 drug treatment clinics and needle and syringe programs in Australia (May 2018-September 2019). Point-of-care results were provided to the nurse, facilitating confirmatory testing and treatment. The study aimed to evaluate treatment uptake and factors associated with treatment at 24 months post-enrolment. There were 317 people with current HCV infection and eligible for treatment (median age 43, 65% male, 15% homeless, 69% receiving opioid agonist treatment, 70% injected in last month). Overall, 15% (47/317), 27% (85/317), 38% (120/317), and 49% (155/317) of people with current HCV infection had initiated treatment at 3-, 6-, 12-, and 24-months following testing, respectively. Homelessness (adjusted hazard ratio (aHR): 0.40; 95% confidence interval: 0.23, 0.71) and incarceration in the past 12 months (vs. never, aHR:0.46; 0.28, 0.76) were associated with decreased treatment initiation in the 24 months post-enrolment. This testing campaign intervention facilitated HCV treatment uptake among PWID. Further interventions are needed to achieve HCV elimination among people experiencing homelessness or incarceration.

Background: Evaluating trends in HCV treatment and prevalence is crucial for monitoring elimination. We evaluated the change in current infection and treatment among people who inject drugs (PWID) between 2018-2019 and 2019-2021., Methods: ETHOS Engage is an observational cohort study of PWID attending drug treatment clinics and needle and syringe programs in Australia. Participant enrolment occurred over two periods, Wave 1 (May 2018-September 2019, 25 sites) and Wave 2 (November 2019-June 2021, 21 sites), with baseline questionnaire completion and point-of-care HCV RNA testing (Xpert® HCV Viral Load Fingerstick). Logistic regression was used to identify factors associated with current HCV infection and historic HCV treatment., Results: 2,395 individuals were enrolled across the two recruitment waves (66% male, median age 43, 72% current opioid agonist therapy, and 65% injecting in the previous month). HCV prevalence decreased from 24% to 17% between 2018-2019 and 2019-2021, respectively (p=0.003). HCV treatment increased from 66% to 74% between 2018-2019 and 2019-2021, respectively (p<0.001). After adjusting, there was a reduction in current HCV infection in 2019-2021 (adjusted odds ratio [aOR] 0.62; 95% CI, 0.50, 0.77) compared to 2018-2019. Other factors associated with current infection included homelessness (aOR, 1.70; 1.26, 2.30), incarceration (vs. never; historic: aOR 1.69; 95%CI 1.31, 2.19; recent: aOR 1.85; 95%CI, 1.35, 2.54), and recently injecting drugs (vs. >12 months ago; previous month

Background: Evidence regarding the acceptability of contingency management is limited. We investigated the willingness of people who inject drugs to participate in a randomised controlled trial (RCT) involving financial incentives to initiate HCV treatment., Methods: ETHOS Engage is an observational cohort study of people with a history of injecting drug use who either injected in the past six months or receive opioid agonist therapy (OAT) in Australia. We assessed willingness to participate in a RCT with financial incentives and factors associated with preference for entire incentive ($60) at first clinic visit versus delayed incentive with logistic regression., Results: 93% (593/635) of eligible participants agreed to participate in an RCT with financial incentives of which 24% were Aboriginal or Torres Strait Islander, 84% had completed secondary school, and 59% injected drugs in the prior month. Willingness to participate in an RCT increased by amount offered: unspecified (72%), $20 (75%), $60 (80%), and $100 (85%). The preferred incentive distribution method over three clinical visits was entire incentive at first clinical visit (32%). Among those with a preferred distribution method (n = 369), factors associated with entire incentive at first clinic visit were being Aboriginal or Torres Strait Islander (aOR 1.75; 95% CI 1.05-2.94), completion of secondary school (aOR 0.46; 95% CI 0.26-0.83) and mainly injected heroin in month prior (aOR 1.82; 95% CI 1.03-3.20)., Conclusion: Most participants were willing to participate in an RCT involving financial incentives to initiate treatment but differed regarding distribution. Study findings inform implementation of incentives in clinical practice., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Introduction: This study aimed to gather a range of opinions, including those of affected people (consumers, concerned others) to identify clinical research priorities for methamphetamine and emerging drugs of concern in Australia, to guide the work of the National Centre for Clinical Research on Emerging Drugs (NCCRED)., Methods: A priority setting study was conducted (February-March 2019) in four phases: online stakeholder survey, thematic analysis of responses, rapid literature review, expert panel ranking of priorities against predetermined criteria., Results: Forty-seven respondents completed the survey, including people identifying as one or more of: researcher (53%, n = 25), clinician (45%; n = 21), family/friend/caregiver of someone who uses methamphetamine/emerging drugs (15%, n = 7) and consumer of methamphetamine/emerging drugs (13%, n = 6). Expert panel, evidence-informed top-ranked clinical research priorities for methamphetamine were: strategies to overcome barriers to intervention uptake, pilot medication trials for adults seeking treatment, and communication strategies regarding evidence-based treatments. For emerging drugs of concern, top-ranked priorities were: piloting community-located drug checking, feasibility of social media/other opportunities to alert consumers of emerging risks, GHB overdose and withdrawal management, and impacts of an early warning information system on reducing harms., Discussion and Conclusions: We demonstrate feasibility of a structured, collaborative clinical research priority setting process. Results have informed the establishment of NCCRED; using the identified priorities to guide seed funding, fellowships/scholarships and research programs. Broader uptake of this methodology by policymakers/research funders would assist to embed areas of concern identified by affected communities and other stakeholders in research prioritisation., (© 2021 The Authors. Drug and Alcohol Review published by John Wiley & Sons Australia, Ltd on behalf of Australasian Professional Society on Alcohol and other Drugs.)

Background: In 2016, following a flurry of government inquiries and taskforces including calls for mandatory treatment regimes, the Australian community nominated methamphetamine as the drug most likely to be associated as a problem substance. Mandatory treatment for alcohol and other drug problems in Australia consists of broadly two mechanisms compelling a person into treatment: involuntary treatment or civil commitment regimes; and coercive treatment regimes, usually associated with the criminal justice system. This paper aims to provide a review of the evidence for mandatory treatment regimes for people who use methamphetamines., Methods: Using a narrative review methodology, a comprehensive literature and citation search was conducted. Five hundred two search results were obtained resulting in 41 papers that had cited works of interest., Results: Small, but robust results were found with coercive treatment programs in the criminal justice system. The evidence of these programs specifically with methamphetamine use disorders is even less promising. Systematic reviews of mandatory drug treatment regimes have consistently demonstrated limited, if any, benefit for civil commitment programs. Despite the growing popular enthusiasm for mandatory drug treatment programs, significant clinical and ethical challenges arise including determining decision making capacity in people with substance use disorders, the impact of self determination and motivation in drug treatment, current treatment effectiveness, cost effectiveness and unintended treatment harms associated with mandatory programs., Conclusion: The challenge for legislators, service providers and clinicians when considering mandatory treatment for methamphetamines is to proportionately balance the issue of human rights with effectiveness, safety, range and accessibility of both existing and novel mandatory treatment approaches.

In this study we compared substrate oxidation and muscle oxygen availability during sustained intermittent intense and continuous submaximal exercise with similar overall (i.e. work and recovery) oxygen consumption (VO2). Physically active subjects (n = 7) completed 90 min of an intermittent intense (12 s work:18 s recovery) and a continuous submaximal treadmill running protocol on separate days. In another experiment (n = 5) we compared oxygen availability in the vastus lateralis muscle between these two exercise protocols using near-infrared spectroscopy. Initially, overall VO(2) (i.e. work and recovery) was matched, and from 37.5 min to 67.5 min of exercise was similar, although slightly higher during continuous exercise (8%; P < 0.05). Energy expenditure was constant (22.5-90 min of exercise) and was not different in intermittent intense [0.81 (0.01) kJ x min(-1). kg(-1)] and continuous submaximal [0.85 (0.01) kJ x min(-1) x kg(-1)] exercise. Overall exercise intensity, represented as a proportion of peak aerobic power (VO2(peak)), was 68.1 (2.5)% VO2(peak) and 71.8 (1.8)% VO2(peak) for intermittent and continuous exercise protocols, respectively. Fat oxidation was almost 3 times lower (P < 0.05) and carbohydrate oxidation was approximately 1.2 times higher (P < 0.05) during intermittent compared to continuous exercise, despite the same overall energy expenditure. Capillary plasma lactate was constant from 15 to 90 min of exercise, and pyruvate was constant from 15 to 75 min, although both were higher (P < 0.0001, lactate; P < 0.001, pyruvate) during intermittent [5.05 (0.28) mM, 200 (7) microM, respectively] compared to continuous exercise [2.41 (0.10) mM, 114 (4) microM, respectively]. There was no difference between protocols for either plasma glycerol or non-esterified fatty acids. The decrease in muscle oxygenation during work periods of intermittent exercise resulted in a lower nadir oxygenation [54.62 (0.41)%] compared to continuous exercise [58.82 (0.21)%, P < 0.001]. The decline in oxygenation was correlated with treadmill speed (r = 0.72; P < 0.05). These results show a difference in substrate utilisation and muscle oxygen availability during sustained intermittent intense and continuous submaximal exercise, despite a similar overall VO(2) and identical energy expenditure.

The purpose of this study was to compare rates of substrate oxidation in two protocols of intermittent exercise, with identical treadmill speed and total work duration, to reduce the effect of differences in factors such as muscle fibre type activation, hormonal responses, muscle glucose uptake and non-esterified fatty acid (NEFA) availability on the comparison of substrate utilisation. Subjects (n = 7) completed 40 min of intermittent intense running requiring a work:recovery ratio of either 6 s:9 s (short-interval exercise, SE) or 24 s:36 s (long-interval exercise, LE), on separate days. Another experiment compared O(2) availability in the vastus lateralis muscle across SE (10 min) and LE (10 min) exercise using near-infrared spectroscopy (RunMan, NIM. Philadelphia, USA). Overall (i.e. work and recovery) O(2) consumption (VO(2)) and energy expenditure were lower during LE (P < 0.01, P < 0.05, respectively). Overall exercise intensity, represented as a proportion of peak aerobic power (VO2(peak)), was [mean (SEM)] 64.9 (2.7)% VO2(peak) (LE) and 71.4 (2.4)% VO2(peak) (SE). Fat oxidation was three times lower (P < 0.01) and carbohydrate oxidation 1.3 times higher (P < 0. 01) during LE, despite the lower overall exercise intensity. Plasma lactate was constant and was higher throughout exercise in LE [mean (SEM) 5.33 (0.53) mM, LE; 3.28 (0.31) mM, SE; P < 0.001)]. Plasma pyruvate was higher and glycerol was lower in LE [215 (17) microM, 151 (13) microM, P < 0.05, pyruvate; 197 (19) microM, 246 (19) microM, P < 0.05, glycerol]. There was no difference between protocols for plasma NEFA concentration (n = 4) or plasma noradrenaline and adrenaline. Muscle oxygenation declined in both protocols (P < 0.001), but the nadir during LE was lower [52.04 (0. 60)%] compared to SE [61.85 (0.51)%; P < 0.001]. The decline in muscle oxygenation during work was correlated with mean lactate concentration (r = 0.68; P < 0.05; n = 12). Lower levels of fat oxidation occurred concurrent with accelerated carbohydrate metabolism, increases in lactate and pyruvate and reduced muscle O(2) availability. These changes were associated with proportionately longer work and recovery periods, despite identical treadmill speed and total work duration. The proposal that a metabolic regulatory factor within the muscle fibre retards fat oxidation under these conditions is supported by the current findings.

The aim of this study was to determine exercise intensity and metabolic response during singles tennis play. Techniques for assessment of exercise intensity were studied on-court and in the laboratory. The on-court study required eight State-level tennis players to complete a competitive singles tennis match. During the laboratory study, a separate group of seven male subjects performed an intermittent and a continuous treadmill run. During tennis play, heart rate (HR) and relative exercise intensity (72 +/- 1.9% VO2max; estimated from measurement of heart rate) remained constant (83.4 +/- 0.9% HRmax; mean +/- s(x)) after the second change of end. The peak value for estimated play intensity (1.25 +/- 0.11 steps x s(-1); from video analysis) occurred after the fourth change of end (P< 0.005). Plasma lactate concentration, measured at rest and at the change of ends, increased 175% from 2.13 +/- 0.32 mmol x l(-1) at rest to a peak 5.86 +/- 1.33 mmol x l(-1) after the sixth change of end (P < 0.001). A linear regression model, which included significant terms for %HRmax (P< 0.001), estimated play intensity (P < 0.001) and subject (P < 0.00), as well as a %HRmax subject interaction (P < 0.05), accounted for 82% of the variation in plasma lactate concentration. During intermittent laboratory treadmill running, % VO2peak estimated from heart rate was 17% higher than the value derived from the measured VO2 (79.7 +/- 2.2% and 69.0 +/- 2.5% VO2peak respectively; P< 0.001). The %VO2peak was estimated with reasonable accuracy during continuous treadmill running (5% error). We conclude that changes in exercise intensity based on measurements of heart rate and a time-motion analysis of court movement patterns explain the variation in lactate concentration observed during singles tennis, and that measuring heart rate during play, in association with preliminary fitness tests to estimate VO2, will overestimate the aerobic response.

An enzymatic assay for the determination of nonesterified fatty acid concentrations in milk and plasma is described. The procedure is semiautomated for use with a plate luminometer or plate spectrophotometer and enables routine batch processing of large numbers of small samples (< or =5 microL). Following the activation of nonesterified fatty acids (NEFA) by acylCoA synthetase, the current assay utilizes UDP-glucose pyrophosphorylase to link inorganic pyrophosphate to the production of NADH through the reactions catalyzed by phosphoglucomutase and glucose-6-phosphate 1-dehydrogenase. With this assay sequence the formation of NADH from NEFA is complete within 50 min at 37 degrees C. Enzymatic spectrophotometric techniques were unsuitable for NEFA determination in human milk due to the opacity of the sample. The use of the NADH-luciferase system has overcome this problem, allowing the enzymatic determination of NEFA in human milk. Sample collection and treatment procedures for milk and plasma have been developed to prevent enzymatic lipolysis and to limit interference from enzymes present in milk. The recovery of palmitic acid added to milk and plasma samples was 94.9+/-2.9 and 100+/-4.5%, respectively. There was no difference (P = 0.13) in plasma NEFA concentrations determined by the current method and a commercially available enzymatic spectrophotometric technique (Wako NEFA-C kit). Plasma NEFA concentrations determined by gas chromatography were 28% higher compared to both the Wako NEFA-C kit and the current method.

Three-dimensional, high-speed cinematography was used to compare backspin backhand techniques of high performance players hitting low (5.4 cm below hip height) and high (41.6 cm above hip height) bouncing balls using their preferred method of holding the racket (eastern backhand or continental grip: hand generally on top of the handle) and non-preferred ('behind the handle') grip. The Direct Linear Transformation method was used for three-dimensional space reconstruction from two-dimensional images recorded from laterally placed phase-locked cameras operating at 200 Hz. The only significant differences (P < 0.05) caused by the change in grip were that the ball was impacted further in front of the body when using the non-preferred grip, and a lower peak racket-shoulder speed was recorded for a high bouncing ball when using the non-preferred grip. Irrespective of the type of grip, the players significantly modified (P < 0.01) their technique to hit a high bouncing ball by adopting a more upright trunk, more rotated shoulder alignment (racket shoulder pointing more towards opponent), a larger front knee angle and a more abducted upper arm. Hitting a high ball was also characterized by a less inclined approach trajectory of the racket, a more vertical racket-face and a different speed profile for the segments of the upper limb and racket.