354 research outputs found
Progressive hyperthermia elicits distinct responses in maximum and rapid torque production
Full text linkObjectivesTo investigate the effect of progressive whole-body hyperthermia on maximal, and rapid voluntary torque production, and their neuromuscular determinants.DesignRepeated measures, randomised.MethodsNine participants performed sets of neuromuscular assessments in HOT conditions (~50°C, ~35% relative humidity) at rectal temperatures (Tre) of 37, 38.5 and 39.5°C and in CON conditions (~22°C, ~5% relative humidity) at a Tre of ~37°C and pre-determined comparative time-points. Electrically evoked twitch (single impulse) and octet (8 impulses at 300 Hz) responses were measured at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were measured during 3-5 s isometric maximal voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary isometric contractions from rest.ResultsAll neuromuscular variables were unaffected by time in CON. In HOT, MVT, normalised EMG at MVT and VA were lower at 39.5°C compared to 37°C (p<0.05). Early- (0-50 ms) and middle- (50-100 ms) phase voluntary RTD were unaffected by increased Tre (p>0.05), despite lower normalised EMG at Tre 39.5°C (p<0.05) in rapid contractions. In contrast, late-phase (100-150 ms) voluntary RTD was lower at 38.5°C and 39.5°C compared to 37°C (p<0.05) in HOT. Evoked twitch and octet RTD increased with increased Tre (p<0.05). ConclusionsHyperthermia reduced late-phase voluntary RTD, likely due to reduced neural drive and the reduction in MVT. In contrast, early- and middle-phase voluntary RTD were unaffected by hyperthermia, likely due to the conflicting effects of reduced neural drive but faster intrinsic contractile properties.© 2021, Sports Medicine Australia. Published by Elsevier Ltd. The attached document (embargoed until 19/03/2023) is an author produced version of a paper published in JOURNAL OF SCIENCE AND MEDICINE IN SPORT uploaded in accordance with the publisher’s self-archiving policy. The final published version (version of record) is available online at the link. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.</p
Voluntary torque production is unaffected by changes in local thermal sensation during normothermia and hyperthermia
Full text linkThis study investigated altered local head and neck thermal sensation on maximal and rapid torque production during voluntary contractions. Nine participants completed four visits in two environmental conditions: at rectal temperatures ∼39.5°C in hot (HOT; ∼50°C, ∼39% relative humidity) and ∼37°C in thermoneutral (NEU; ∼22°C, ∼46% relative humidity) conditions. Local thermal sensation was manipulated by heating in thermoneutral conditions and cooling in hot conditions. Evoked twitches and octets were delivered at rest. Maximum voluntary torque (MVT), normalised surface electromyography (EMG) and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions of the knee extensors. Rate of torque development (RTD) and EMG were measured during rapid voluntary contractions. MVT (P = 0.463) and RTD (P = 0.061) were similar between environmental conditions despite reduced VA (−6%; P = 0.047) and EMG at MVT (−31%; P = 0.019). EMG in the rapid voluntary contractions was also lower in HOT versus NEU during the initial 100 ms (−24%; P = 0.035) and 150 ms (−26%; P = 0.035). Evoked twitch (+70%; P < 0.001) and octet (+27%; P < 0.001) RTD during the initial 50 ms were greater in the HOT compared to NEU conditions, in addition to a faster relaxation rate of the muscle (−33%; P < 0.001). In conclusion, hyperthermia reduced neural drive without affecting voluntary torque, likely due to the compensatory effects of improved intrinsic contractile function and faster contraction and relaxation rates of the knee extensors. Changes in local thermal perception of the head and neck whilst hyperthermic or normothermic did not affect voluntary torque
Maximal voluntary torque and rate of torque development are not effected by whole-body hyperthermia or ten consecutive days of isothermic heat acclimation.
No full textPenser l’hégémonie dans le monde contemporain
No full textIs There a Possible Dialogue Between Hegemony and Cosmopolitanism? Interview with Frédéric Ramel -- What do the two concepts of hegemony and cosmopolitanism imply? Are they opposed or is there a possible dialogue between them? In a recently published chapter (“Competition for Hegemony ” in the edited volume Cosmopolitanism in Hard Times), Professor of political science at Sciences Po CERI Frédéric Ramel questions these concepts and explores their scope. The following is an interview with the author. Interview by Miriam Perier, CERI
Longitudinal study of jumping mechanics in master athletes
Full text linkThis investigation forms part of a larger project studying running gait in master athletes. Improved dynamic performance has been shown to be associated with low leg stiffness values (Laffaye et al., 2005). Previously a cross-sectional analysis of jumping suggested that leg compression reduced and leg stiffness increased with age, whilst joint
contributions to these changes were found to be subject dependent (Diss et al, 2006). The aim of this longitudinal study is to examine the effect of ageing on vertical jump performance indicators such as leg compression and stiffness in master athletes. (Work in progress)
The State from its Margins: A perspective from street level Turkey
No full textMuhtars, the lowest-level elected political position in Turkey, hold an ambiguously defined place within the administrative hierarchy. Research Professor at CERI Elise Massicard is the author of Street-Level Governing (Stanford University Press ), the first book to investigate how muhtars carry out their role—not only what they are supposed to do, but how they actually operate—providing an ethnographic study of the state as viewed from its margins. She answers our questions on the muhtar as a hybrid object and her research
The reliability of kinetic and kinematic variables used to analyse normal running gait
No full textThe purpose of this study was to assess the reliability of 24 kinetic and kinematic variables from three synchronized systems used to represent normal running gait. Five male runners (mean 23.4 years, mass 80.2 kg) ran down a runway at a constant velocit
Internship as degree modality at inter-institucional relations centre -CERI-, 2019-3
No full textEste documento da cuenta el trabajo de pasantía realizado por el autor durante el período 2019-3 como modalidad de grado en el Centro Interinstitucional de la Universidad Distrital Francisco José de Caldas. El objetivo propuesto es "contribuir desde los conocimientos particulares de la Licenciatura en Educación Básica con Énfasis en Inglés, a los procesos misionales del Centro Interinstitucional -CERI- ". Para lograrlo, las actividades se llevaron a cabo en diferentes oficinas del CERI, incluida la oficina del director. Entre otras, las tareas realizadas fueron: Traducción de documentos, organización de archivos físicos, participación en el programa "Relacciones" en LAUD 90.4 FM Stereo, etc. Al final, los beneficios fueron mutuos. El estudiante adquirió experiencia en el campo de la administración educativa y el CERI recibió apoyo en diferentes campos desde la perspectiva del estudiante.This paper documents the internship work carried out by the author during the period 2019-3 as a degree modality at the Interinstitutional Center -CERI- of the Universidad Distrital Francisco José de Caldas. The proposed objective is "to contribute from the particular knowledge of the Bachelor of Basic Education with an Emphasis in English, to the missioanl processes of the Inter-institutional Center -CERI- ". To achieve this, the activities were carried out in different CERI offices, including the director's office. Among others, the tasks performed were: Document translation, organization of physical files, participation in the "Relacciones" program at LAUD 90.4 FM Stereo, etc. In the end, the benefits were mutual. The student gained experience in the field of educational administration, and CERI obtained support in different fields from the student´s perspective
Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate but does not affect voluntary torque production
No full textPurpose: this study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. Methods: ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. Results: acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P < 0.05), increased evoked torques (P < 0.05), and shortened contraction and relaxation rates (P < 0.05). HA lowered resting rectal temperature and heart rate after 10 days (P < 0.05), and increased sweating rate after 5 and 10 days (P < 0.05), no differences were observed between 5 and 10 days. The hyperthermia-induced reduction in twitch half-relaxation was attenuated after 5 and 10 days of HA, but there were no other effects on neuromuscular function either in normothermic or hyperthermic conditions. Conclusion: HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.</p
Writing, creativity and environments : [book review] Ceri Sullivan and Graeme Harper (eds) Authors at Work: The Creative Environment
No full textThe author reviews the book : Ceri Sullivan and Graeme Harper (eds) Authors at Work: The Creative Environment, Essays and Studies Collection, vol 62, 2009 (ISSN 0071-1357) The English Association, UK/DS Brewer, Cambridge, ISBN 978-1-84384-195-
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