771 research outputs found
Progressive hyperthermia elicits distinct responses in maximum and rapid torque production
No full textObjectivesTo 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
No full textThis 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 textLongitudinal study of jumping mechanics in master athletes
No full textThis 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 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
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
From Pedrolino to a Pierrot: The Origin, Ancestry and Ambivalence of the British Pierrot Troupe
No full textIn this article, the author considers the British development of the seaside Pierrot troupe, arguing that its construction is consistent with the notion of invented tradition, and the associated concerns with identity and nationality. Tracing the history of the character from its origins as Pedrolino in the commedia dell’arte, the article considers the traditional and novel elements of the British form. This also allows a brief account of the origin and aesthetics of the British tradition. Reflecting on the synthesis of the archaic and contemporary dimensions of the form, the author proposes that the new structure constructed an ambivalent class of character. The composition of both troupes and audiences was drawn from across the range of social strata. Through its collectivity and its treatment of contemporary social themes, it is argued the British Pierrot troupe approached and negotiated questions of a cultural and national identity in the late-Victorian period.
Dave Calvert is a Senior Lecturer at the University of Huddersfield, UK. His research
interests include street theatre, Applied Theatre and learning disabled
performance. He is also a member of The Pierrotters, the last remaining seaside
Pierrot troupe
Examining Hardiness, Coping and Stress-Related Growth Following Sport Injury
No full textThis study aimed to explain how injured athletes high in hardiness experienced stress-related growth and why athletes low in hardiness are less likely to derive such benefits. Twenty participants were theoretically sampled into high (n = 10) and low (n = 10) hardiness groups. Semistructured interviews were used for data collection. Findings revealed that athletes high in hardiness experienced stress-related growth from having an emotional outlet, which enabled them to reframe their injury and experience positive affect. In contrast, athletes low in hardiness had no emotional outlet, which led to suboptimal outcomes. These findings have important implications for practitioners working with injured athletes
Examining the relationship between hardiness and perceived stress-related growth in a sport injury context
No full textThis study examined the relationship between hardiness, coping and perceived stress-related growth (SRG) in a sport injury context. Due to the exploratory nature of the study, a cross-sectional design was employed, whereby 206 previously injured athletes (148 male, 58 female, Mage = 22.23 years) who had recently returned to sport completed three questionnaires: Dispositional Resilience Scale, Stress-Related Growth Scale, and Brief COPE. Pearson product–moment correlations and Preacher's and Hayes's (2008) bootstrapping procedure were used to analyze the data. Findings revealed a significant positive relationship between hardiness and perceived SRG. Two coping strategies were found to mediate this relationship: emotional support and positive reframing. This would suggest that those higher in hardiness may have fostered SRG by mobilising their social support for emotional reasons (e.g., moral support, sympathy or understanding) and having the ability to construe their injury in positive terms; however, more rigorous methodologies are needed to confirm or refute these observations. These findings support some of the central tenets of Joseph and Linley's (2005) organismic valuing theory and provide implications for professional practice. Future researchers should embrace qualitative inquiry to enhance the interpretability and meaningfulness of these findings (e.g., interpretative phenomenological analysis, narrative analysis), and use prospective, longitudinal pre-to-post sport injury designs to further substantiate them
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