Now showing items 1-20 of 6331

    • Associations between nutrition, energy expenditure and energy availability with bone mass acquisition in dance students: A 3-year longitudinal study

      Amorim, Tânia; Freitas, Laura; Metsios, George S.; Gomes, Thayse; Wyon, Matthew; Flouris, Andreas D.; Maia, José; Marques, Franklim; Nogueira, Luísa; Adubeiro, Nuno; et al. (Springer, 2021-12-31)
      Purpose To determine whether risk factors normally associated with low bone mass in athletic populations (i.e. nutrition intake, energy expenditure and energy availability) are significant predictors of bone mass changes in vocational dance students. Methods The total of 101 vocational dancers (63 females, 12.8±2.2yrs; 38 males, 12.7±2.2yrs) and 118 age-matched controls (50 females, 13.0±2.1yrs; 68 males, 13.0±1.8yrs) were monitored for three consecutive years. Bone mass parameters were measured annually at impact sites (femoral neck – FN; lumber spine – LS) and non-impact site (forearm) using DXA. Nutrition (3-day record), energy expenditure (accelerometer), energy availability and IGF-1 serum concentration (immunoradiometric assays) were also assessed. Results Female and male vocational dancers had consistently reduced bone mass at all anatomical sites (p<0.001) than controls. IGF-1 did not differ between male vocational dancers and controls, but female dancers showed it higher than controls. At baseline, calcium intake was significantly greater in female vocational dancers than controls (p<0.05). Male vocational dancers’ fat and carbohydrate intakes were significantly lower than matched controls (p<0.001 and p<0.05, respectively). Energy availability of both female and male vocational dancers was within the normal range. A significant group effect was found at the FN regarding energy intake (p<0.05) in female dancers. No significant predictors were found to explain bone mass differences in males. Conclusion Our 3-years study revealed that both female and male vocational dancers displayed lower bone mass compared to controls, at both impact and non-impact sites. The aetiology of these findings may be grounded on factors different than those usually considered in athletic populations.
    • Intentional forgetting of emotional memories in the item-method directed forgetting task

      Mercer, Tom; Hinton, Danny; Darby, Richard; Ahmed, Sumera (University of Wolverhampton, 2021-07)
      Forgetting is often viewed as a nuisance, but research has indicated that forgetting is an adaptive process that works to remove irrelevant information (Bjork,1989). Such 'intentional’ forgetting concerns the active removal of information from memory, with evidence coming from the Think/No-Think paradigm (Anderson & Green, 2004) and most importantly the Directed Forgetting paradigm (Bjork, 1970). The Directed Forgetting paradigm assesses intentional forgetting through the use of two cues (Remember and Forget) and a majority of studies suggest a successful inhibition of the 'Forget' items in comparison to the 'Remember' items. However, there is a long-term dispute within research in regard to valence and intentional forgetting. Specifically, it is unclear whether directed forgetting is reduced for emotional stimuli, in comparison to neutral stimuli. In the current thesis, Directed Forgetting was tested in six experiments and consistently reported when retrieval was assessed through free recall. The Directed Forgetting effect also applied to emotional material. However, valence differences for the 'Remember' cue (positive vs negative) were greater than the differences found for the 'Forget' cue. This suggests that both positive and negative words can be successfully forgotten. Additionally, factors such as time (Chapters 2, 3 and 5), individual differences (Chapters 4 [sex differences] and 5 [mood and emotional reactivity]) and stimuli characteristics (Chapters 5 [concreteness] and 7 [word type]) had a minimal impact on Directed Forgetting. The experiments within this thesis have been successful in highlighting DF within free recall. Yet when a cued recall procedure was used, the DF effect was abolished, and there actually seemed to be a form of inverted DF for negative words. Lastly, limitations, theoretical implications and future directions are considered in Chapter 8 (the general discussion).
    • An investigation of client loyalty in the construction professional services sector

      Hampton, Paul; Williams, Nicholas Michael (University of Wolverhampton, 2021-02)
      Construction professional services (CPS) suppliers perform several vital roles in the construction industry. Arguably, their success (and, in hard times, their survival) is determined by the loyalty of their clients. Loyal clients provide a reliable stream of revenue and help generate new business for CPS suppliers by providing recommendations and referrals. However, prior to this research, there were no known empirical studies which investigated CPS client loyalty. Using evidence obtained from a literature review, a conceptual model was developed that identified the key-candidate service-related antecedents of client loyalty. A phase of qualitative research was carried out using purposeful and snowball sampling. Semi-structured interviews were arranged with 20 respondents, with these being a mix of CPS clients and suppliers. The resulting data were subject to thematic analysis, and the conceptual model of CPS-client loyalty was refined based on the findings. A phase of quantitative research was carried out to test the degree to which the qualitative research findings could be generalised to the wider CPS-client population. This involved a survey, and analysis of the data using factor analysis and hypothesis testing using multiple regression. This was itself followed up using a phase of member checking with a group of experts to validate and help explain some discrepant findings. This research has made several contributions to knowledge. It provides empirical support for the existence of a multidimensional form of commitment in a CPS supplier-client context. It is the first known research to identify what CPS suppliers should focus on to be able to build and benefit from client loyalty. The results showed that service quality was the antecedent most strongly associated with loyalty. Affective commitment was found to be next in importance. A weak-but-significant relationship with locked-in commitment was also identified. It should be noted that sampling during both qualitative and quantitative phase of research was restricted to respondents from the UK Midlands. Therefore, there are limits to which the findings can be generalised beyond this geographical region. In summary, CPS suppliers are advised to focus first and foremost on fulfilling their clients’ rational desire for a high level of service quality. However, to achieve optimum levels of client loyalty, they should be mindful of the power of personal relationships between their employees and their clients. In this respect, they are advised to avoid rotating their account representatives where healthy relations and rapport are evident.
    • Nurses’ views on compassionate care: a study using Q methodology

      Gutteridge, Robin; Bond, Carol; Philp, Ann (University of Wolverhampton, 2021-06)
      Compassion and compassionate care are identified as essential elements in nursing. They enhance quality care, wellbeing, and the overall quality of patients’ lives. However, incidents of substandard care have highlighted inherent tensions between competing professional and organisational demands in a rapidly changing workplace. This research investigated nurses’ views of the promoters and inhibitors of provision and maintenance of compassionate care. Participants were third year student nurses and qualified nurses in a large inner-city Trust hospital. An integrative literature review revealed three overarching themes that impact on nurses’ ability to provide and maintain compassionate care. Sumner’s (2008a) Moral Construct of Caring in Nursing as Communicative Action Theory (MCCNCAT) was applied as the theoretical framework. Q methodology supported the investigation of subjectivity within an interpretive design. 54 statements were developed from the literature review and focus group participation, representing the breadth of debate on compassion and compassionate care. Participants (n=30) rank-ordered these statements onto a quasi-normal distribution grid (the Q sort). They provided post Q sort data via Report Sheets and semi-structured interviews; thematic analysis was used to explore interview data. Completed Q sorts were analysed using correlation and by-person factor analysis, resulting in two distinct factors. Some participants shared commonalities across factors and did not contribute to the construction of the factor estimates. Remaining participants (n=18) included student nurses (n=10) and qualified nurses (n=8). Compassionate care was found to be complex, interconnected, and multifaceted. There was consensus from student nurses and qualified nurses in the three overarching themes: • Personal/relational – Improved patient outcomes impact positively on patients and motivate nurses to provide compassionate care. Satisfaction gained from providing compassionate care creates a virtuous circle, enhancing wellbeing, personal motivation, professional commitment, and job performance. It supports collegial relationships and positive patient outcomes. • Organisational – Organisations must promote compassionate care, supporting nurses and providing necessary resources. Managers, leaders, mentors, and colleagues should demonstrate compassion towards patients and staff. Developing and supporting a culture of compassion can counter factors that inhibit compassionate care. Nurses should be encouraged to develop self-compassion, which promotes their own wellbeing. • Educational – Nurses’ clinical experiences should be connected to teaching and learning. This means replacing inappropriate didactic, classroom-based education with approaches that are experiential and creative, using strengthened links with practice, so that learning is relevant to the reality of clinical practice. These findings were incorporated in an explanatory diagram, underpinned by MCCNCAT (Sumner 2008a) which makes visible the dynamics involved and strategies that build and sustain compassionate care.
    • The maximal metabolic steady state: redefining the ‘gold standard’

      Jones, Andrew M; Burnley, Mark; Black, Matthew I; Poole, David C; Vanhatalo, Anni (Wiley, 2019-05-23)
      The maximal lactate steady state (MLSS) and the critical power (CP) are two widely used indices of the highest oxidative metabolic rate that can be sustained during continuous exercise and are often considered to be synonymous. However, while perhaps having similarities in principle, methodological differences in the assessment of these parameters typically result in MLSS occurring at a somewhat lower power output or running speed and exercise at CP being sustainable for no more than approximately 20–30 min. This has led to the view that CP overestimates the ‘actual’ maximal metabolic steady state and that MLSS should be considered the ‘gold standard’ metric for the evaluation of endurance exercise capacity. In this article we will present evidence consistent with the contrary conclusion: i.e., that (1) as presently defined, MLSS naturally underestimates the actual maximal metabolic steady state; and (2) CP alone represents the boundary between discrete exercise intensity domains within which the dynamic cardiorespiratory and muscle metabolic responses to exercise differ profoundly. While both MLSS and CP may have relevance for athletic training and performance, we urge that the distinction between the two concepts/metrics be better appreciated and that comparisons between MLSS and CP, undertaken in the mistaken belief that they are theoretically synonymous, is discontinued. CP represents the genuine boundary separating exercise in which physiological homeostasis can be maintained from exercise in which it cannot, and should be considered the gold standard when the goal is to determine the maximal metabolic steady state.
    • Physiological evidence that the critical torque is a phase transition, not a threshold

      Pethick, Jamie; Winter, Samantha L; Burnley, Mark (Lippincott, Williams & Wilkins, 2020-11-30)
      Introduction Distinct physiological responses to exercise occur in the heavy- and severe-intensity domains, which are separated by the critical power or critical torque (CT). However, how the transition between these intensity domains actually occurs is not known. We tested the hypothesis that CT is a sudden threshold, with no gradual transition from heavy- to severe-intensity behavior within the confidence limits associated with the CT. Methods Twelve healthy participants performed four exhaustive severe-intensity trials for the determination of CT, and four 30-min trials in close proximity to CT (one or two SE above or below each participant’s CT estimate; CT − 2, CT − 1, CT + 1, CT + 2). Muscle O2 uptake, rectified electromyogram, and torque variability and complexity were monitored throughout each trial, and maximal voluntary contractions (MVC) with femoral nerve stimulation were performed before and after each trial to determine central and peripheral fatigue responses. Results The rates of change in fatigue-related variables, muscle O2 uptake, electromyogram amplitude, and torque complexity were significantly faster in the severe trials compared with CT − 2. For example, the fall in MVC torque was −1.5 ± 0.8 N·m·min−1 in CT − 2 versus –7.9 ± 2.5 N·m·min−1 in the lowest severe-intensity trial (P < 0.05). Individual analyses showed a low frequency of severe responses even in the circa-CT trials ostensibly above the CT, but also the rare appearance of severe-intensity responses in all circa-CT trials. Conclusions These data demonstrate that the transition between heavy- and severe-intensity exercise occurs gradually rather than suddenly.
    • Prolonged depression of knee-extensor torque complexity following eccentric exercise

      Pethick, Jamie; Whiteaway, Katherine; Winter, Samantha L; Burnley, Mark; Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, UK. (Wiley, 2018-11-28)
      Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output. Exercise-induced muscle damage reduces muscle torque output for considerably longer than high-intensity fatiguing contractions. We hypothesized that muscle-damaging eccentric exercise would lead to a persistent decrease in torque complexity, whereas fatiguing exercise would not. Ten healthy participants performed five isometric contractions (6 s contraction, 4 s rest) at 50% maximal voluntary contraction (MVC) before, immediately after and 10, 30 and 60 min and 24 h after eccentric (muscle-damaging) and isometric (fatiguing) exercise. These contractions were also repeated 48 h and 1 week after eccentric exercise. Torque and surface EMG signals were sampled throughout each test. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis α exponent (DFA α). Global, central and peripheral perturbations were quantified using MVCs with femoral nerve stimulation. Complexity decreased after both eccentric [ApEn, mean (SD), from 0.39 (0.10) to 0.20 (0.12), P < 0.001] and isometric exercise [from 0.41 (0.13) to 0.09 (0.04); P < 0.001]. After eccentric exercise, ApEn and DFA α required 24 h to recover to baseline levels, but after isometric exercise they required only 10 min. The MVC torque remained reduced [from 233.6 (74.2) to 187.5 (64.7) N m] 48 h after eccentric exercise, with such changes evident only up to 60 min after isometric exercise [MVC torque, from 246.1 (77.2) to 217.9 (71.8) N m]. The prolonged depression in maximal muscle torque output is therefore accompanied by a prolonged reduction in torque complexity.
    • Identifying critical dimensions for project success in R&D public sector using Delphi study and validation techniques

      Hanif, Huma; Hanif, Aamer; Ahsan, Ali; Sadiq, Ali Safaa; Mirjalili, Seyedali; Alkazemi, Basem (IEEE, 2021-09-13)
      In the current century, organizations face ever increasing dynamic ecosystems and are constantly devising strategies to meet their challenges. These include the implementation of the right organizational structure and avoid project schedule delays to achieve projects’ success. Unfortunately, the classification of significant project success dimensions in the R&D public sector environment is still an elusive concept. This study adopts a multi-dimensional qualitative and quantitative approach to explore the critical dimensions of organizational structure and schedule management that enhance or hinder the project success in R&D of public sector organizations. In Phase 1, a Delphi Study is conducted, and results of reliability and other tests are the input of Phase 2. On the basis of these tests, variables have been selected for the next phase or final questionnaire. In Phase 2, through a survey of 285 responses in a public sector R&D environment, the proposed framework is validated by conducting face, content and construct validity. The results indicated that formalization, specialization, differentiation, coordination mechanism, decentralization and authority of managers have a significant effect on the schedule management and successful execution of R&D projects; whereas, centralization and departmentalization do not correlate strongly. The results also imply that decentralized organizational structures (organic) are more preferable than centralized structures (mechanistic) for the execution of R&D projects when proposed timelines are to be met timely. The proposed framework will act as a supporting mechanism for engineering managers to deal with organizational structure and schedule management factors in a highly uncertain R&D environment where projects deviate frequently from their anticipated timeline.
    • Conceptualising the surveillance of teachers

      Page, Damien (Taylor & Francis, 2016-09-06)
      Schools are risky places: the risk of a poor Ofsted report, the risk of sliding down league tables, the risk of teachers abusing children, the risk of teachers being falsely accused of abuse. As a result of risk anxiety and the ever-increasing sophistication of technology, the surveillance of teachers has proliferated, becoming a future-oriented pursuit to manage this risk. Drawing on the surveillance studies literature, this article attempts to theorise the surveillance of teachers. Firstly the article argues that there are three types of teacher surveillance: the vertical perpetuated by Ofsted and senior school leaders such as teaching observations and learning walks, but also students recording their teachers on mobile phones; horizontal surveillance enacted by peers in terms of concertive control, but also parental surveillance via online and offline networks; and, finally, intrapersonal surveillance embracing reflective practice, data reporting and self-policing proximity from children. The article then concludes by arguing that while surveillance in schools embraces the themes of modern surveillance in general, by doggedly retaining the proximal and the interpersonal, it should be considered a hybrid form between traditional and modern forms of surveillance.
    • Rapport

      Hamilton, Judith (Oxford University Press, 2021-08-07)
    • The surveillance of teachers and the simulation of teaching

      Page, Damien (Taylor & Francis, 2016-07-15)
      Just as surveillance in general has become more sophisticated, penetrative and ubiquitous, so has the surveillance of teachers. Enacted through an assemblage of strategies such as learning walks, parental networks, student voice and management information systems, the surveillance of teachers has proliferated as a means of managing the risks of school life, driven forward by neoliberal notions of quality and competition. However, where once the surveillance of teachers was panoptic, a means of detecting the truth of teaching behind fabrications, this article argues that surveillance within schools has become a simulation in Baudrillard’s terms, using models and codes such as the Teachers’ Standards and the Schools Inspection Handbook as predictors of future outcomes, simulating practice as a means of managing risk. And if surveillance in schools has become a simulation, then so perhaps has teaching itself, moving beyond a preoccupation with an essentialist truth of teaching to the hyperreality of normalised visibility and the simulation of teaching. This article argues that surveillance – including external agencies such as Ofsted – no longer exists to find the truth of teaching, the surveillance of teachers exists only to test the accuracy of the models and codes upon which the simulation is based.
    • Conspicuous practice: self-surveillance and commodification in English education

      Page, Damien (2017-10-23)
      Teachers in England have always been watched; only more recently have they been surveilled, with senior leaders, peers, students and stakeholders all collecting performance data. Yet surveillance in schools and colleges increasingly relies on watching the self, with teachers voluntarily participating in their own surveillance, making their practice visible for easy consumption by interested parties. This article builds on previous work on the surveillance of teachers to argue that this ‘conspicuous practice’ represents a convergence of surveillance and consumerism, with teachers being recreated as commodities and their own marketing agent, embodying the entrepreneurial self to maximise employability. Through social media such as Twitter and LinkedIn to exploiting open plan learning spaces, teachers engage in conspicuous practice for three main reasons: from fear, to avoid sanction; as a result of acculturation into commodified environments; as a means of routine resistance, employing the dramaturgical self for personal gain, to avoid work or re-appropriate professionalism.
    • Whiteliness and institutional racism: hiding behind (un)conscious bias

      Tate, Shirley Anne; Page, Damien (Routledge, 2018-02-01)
      ‘Unconscious bias happens by our brains making incredibly quick judgements and assessments without us realising. Biases are influenced by background, cultural environment and experiences and we may not be aware of these views and opinions, or of their full impact and implications. This article opposes this point of view by arguing that bias is not unconscious but is (un)conscious and linked to Charles Mills’ ‘Racial Contract’ and its ‘epistemologies of ignorance’. These epistemologies emerge from what the Equality Challenge Unit (ECU) calls ‘our background, cultural environment and personal experience’. Asserting that racism stems from ‘unconscious bias’ diminishes white supremacy and maintains white innocence as a ‘will to forget’ institutional racism. In equality and diversity training ‘unconscious bias’ has become a performative act to move beyond racism through training to participate in a constructed ‘post-racial’ reality. The article argues that through decolonizing ‘unconscious bias’, ‘white fragility’ and ‘self-forgiveness’ we can begin to see hidden institutional whiteliness at the base of (un)conscious bias.
    • The academic as consumed and consumer

      Page, Damien (Taylor & Francis, 2019-03-29)
      In an increasingly competitive environment that positions students as consumers, universities have become ever more marketised, responding to policy contexts that foreground value for money, consumer choice and competition. The intensity of marketisation is argued to have profoundly affected the nature of academic work and scholars themselves, recreating academics as commodities to be weighed and measured, becoming corporatised, alienated and inauthentic in their practice. Yet with the majority of accounts of the commodification of higher education focusing on students, the actual process of how academics become consumed is under-theorised. This article therefore begins with a discussion of the historical context, providing evidence of the familiar indices of marketisation such as rampant self-promotion, the scramble for external funding and intense competition. It argues that this commodified DNA of the university provides the context for the seduction of the modern academic within the consumer society, a movement from the gratification of needs to the perpetual frustration of desires through the ‘Diderot Effect’ of policy shifts. It concludes with an examination of how contemporary academic work can be viewed through the lens of consumerism and how academics themselves have become consumers.
    • Family engagement in alternative provision

      Page, Damien (Wiley, 2020-11-06)
      This article presents findings from research focusing on family engagement within alternative provision. With the existing literature on alternative provision scant, this article analyses the extensive assemblage of family engagement within settings as practitioners navigate complex family environments often characterised by poverty, crime and substance abuse. While settings create formalised structures of family engagement that prioritise a collaborative approach to children’s development—such as family learning days and daily positive phone calls—equally they work to attenuate the isolation and loneliness of families who feel as excluded as their child. Yet as important as structured engagement is, practitioners within alternative provision also engage in the improvised pragmatism of micro-work—the work that other agencies won’t or can’t do, such as escorting parents to medical appointments, sourcing furniture to fill empty houses or talking a child out from under their bed. The article argues that family engagement in alternative provision is cyclical, with families informing staff of behavioural incidents or learning opportunities, information that rapidly personalises communicative and pedagogical strategies within schools. In return, teachers update parents at the end of the day, offering ideas for home learning or approaches to managing challenging behaviours. The article concludes by identifying six domains of family engagement—behavioural, emotional, safeguarding, functional, pedagogic and capacity building—that can be used within alternative provision settings to ensure a holistic approach that provides deep support to families to maximise the successful re-engagement of children.
    • Fun, lifelong relationships and a safer community: understanding collective leadership practice in a grassroots association

      Jacklin-Jarvis, Carol; Rees, James (Bristol University Press, 2021-08-31)
      The relational processes and practices that create and sustain grassroots associations have received limited attention from researchers. This article addresses this gap, exploring collective leadership of grassroots associations through a ‘leadership-as-practice’ lens (Raelin, 2016a; 2016b). It adopts the concept of ‘bundles’ of leadership practice (Schatzki, 2005) to analyse data from a single ethnographic case study. Adopting this conceptual lens, we identify a set of ‘bundles’ of related practices – organising, engaging and accounting – that constitute the enduring reality of the grassroots association’s collective leadership.
    • Public Twitter data and transport network status

      Almohammad, A; Georgakis, P (IEEE, 2020-09-22)
      Twitter data can be collected and analysed to be used for predicting the status of a transport network at a given time and geographic location (e.g. forecasting disruptions, congestions, or road closures). However, this requires geolocating the tweets to define the parts of the transport network which may be related to these tweets. This paper investigates the relationship between the actual transport network status, with that being synthesised using public Twitter data in the Greater Manchester conurbation. Therefore, it answers the following question: are the sentiments of tweets around the incidents and accidents areas (or bounding boxes) different from the sentiments of tweets in the seamless traffic areas?. According to the used research methodology, analysis techniques, and sentiment detection APIs, it has been concluded that there is no significant difference between the sentiments in the tweets regardless the prevailing traffic conditions of the locations the tweets refer to.
    • Robust fragment-based framework for cross-lingual sentence retrieval

      Trijakwanich, Nattapol; Limkonchotiwat, Peerat; Sarwar, Raheem; Phatthiyaphaibun, Wannaphong; Chuangsuwanich, Ekapol; Nutanong, Sarana (Association for Computational Linguistics, 2021-12-31)
      Cross-lingual Sentence Retrieval (CLSR) aims at retrieving parallel sentence pairs that are translations of each other from a multilingual set of comparable documents. The retrieved parallel sentence pairs can be used in other downstream NLP tasks such as machine translation and cross-lingual word sense disambiguation. We propose a CLSR framework called Robust Fragment-level Representation (RFR) CLSR framework to address Out-of- Domain (OOD) CLSR problems. In particular, we improve the sentence retrieval robustness by representing each sentence as a collection of fragments. In this way, we change the retrieval granularity from the sentence to the fragment level. We performed CLSR experiments based on three OOD datasets, four language pairs, and three base well-known sentence encoders: m-USE, LASER, and LaBSE. Experimental results show that RFR significantly improves the base encoders’ performance for more than 85% of the cases.
    • Linguistic features evaluation for hadith authenticity through automatic machine learning

      Mohamed, Emad; Sarwar, Raheem (Oxford University Press, 2021-12-31)
      There has not been any research that provides an evaluation of the linguistic features extracted from the matn (text) of a Hadith. Moreover, none of the fairly large corpora are publicly available as a benchmark corpus for Hadith authenticity, and there is a need to build a “gold standard” corpus for good practices in Hadith authentication. We write a scraper in Python programming language and collect a corpus of 3651 authentic prophetic traditions and 3593 fake ones. We process the corpora with morphological segmentation and perform extensive experimental studies using a variety of machine learning algorithms, mainly through Automatic Machine Learning, to distinguish between these two categories. With a feature set including words, morphological segments, characters, top N words, top N segments, function words and several vocabulary richness features, we analyse the results in terms of both prediction and interpretability to explain which features are more characteristic of each class. Many experiments have produced good results and the highest accuracy (i.e., 78.28%) is achieved using word n-grams as features using the Multinomial Naive Bayes classifier. Our extensive experimental studies conclude that, at least for Digital Humanities, feature engineering may still be desirable due to the high interpretability of the features. The corpus and software (scripts) will be made publicly available to other researchers in an effort to promote progress and replicability.
    • Relationship between muscle metabolic rate and muscle torque complexity during fatiguing intermittent isometric contractions in humans

      Pethick, Jamie; Winter, Samantha L; Burnley, Mark; Endurance Research Group, School of Sport and Exercise Sciences, University of Kent, Canterbury, United Kingdom. (Wiley, 2019-09-25)
      To test the hypothesis that a system's metabolic rate and the complexity of fluctuations in the output of that system are related, thirteen healthy participants performed intermittent isometric knee extensor contractions at intensities where a rise in metabolic rate would (40% maximal voluntary contraction, MVC) and would not (20% MVC) be expected. The contractions had a 60% duty factor (6 sec contraction, 4 sec rest) and were performed until task failure or for 30 min, whichever occurred sooner. Torque and surface EMG signals were sampled continuously. Complexity and fractal scaling of torque were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Muscle metabolic rate was determined using near-infrared spectroscopy. At 40% MVC, task failure occurred after (mean ± SD) 11.5 ± 5.2 min, whereas all participants completed 30 min of contractions at 20% MVC. Muscle metabolic rate increased significantly after 2 min at 40% MVC (2.70 ± 1.48 to 4.04 ± 1.23 %·s-1 , P < 0.001), but not at 20% MVC. Similarly, complexity decreased significantly at 40% MVC (ApEn, 0.53 ± 0.19 to 0.15 ± 0.09; DFA α, 1.37 ± 0.08 to 1.60 ± 0.09; both P < 0.001), but not at 20% MVC. The rates of change of torque complexity and muscle metabolic rate at 40% MVC were significantly correlated (ApEn, ρ = -0.63, P = 0.022; DFA, ρ = 0.58, P = 0.037). This study demonstrated that an inverse relationship exists between muscle torque complexity and metabolic rate during high-intensity contractions.