Supraspinal Fatigue Impedes Recovery From a Low-Intensity Sustained Contraction in Old Adults

This study determined the contribution of supraspinal fatigue and contractile properties to the age difference in neuromuscular fatigue during and recovery from a low-intensity sustained contraction. Cortical stimulation was used to evoke measures of voluntary activation and muscle relaxation during and after a contraction sustained at 20% of maximal voluntary contraction (MVC) until task failure with elbow flexor muscles in 14 young adults (20.9 ± 3.6 yr, 7 men) and 14 old adults (71.6 ± 5.4 yr, 7 men). Old adults exhibited a longer time to task failure than the young adults (23.8 ± 9.0 vs. 11.5 ± 3.9 min, respectively, P \u3c 0.001). The time to failure was associated with initial peak rates of relaxation of muscle fibers and pressor response (P \u3c 0.05). Increments in torque (superimposed twitch; SIT) generated by transcranial magnetic stimulation (TMS) during brief MVCs, increased during the fatiguing contraction (P \u3c 0.001) and then decreased during recovery (P = 0.02). The increase in the SIT was greater for the old adults than the young adults during the fatiguing contraction and recovery (P \u3c 0.05). Recovery of MVC torque was less for old than young adults at 10 min post-fatiguing contraction (75.1 ± 8.7 vs. 83.6 ± 7.8% of control MVC, respectively, P = 0.01) and was associated with the recovery of the SIT (r = −0.59, r2 = 0.35, P \u3c 0.001). Motor evoked potential (MEP) amplitude and the silent period elicited during the fatiguing contraction increased less for old adults than young adults (P \u3c 0.05). The greater fatigue resistance with age during a low-intensity sustained contraction was attributable to mechanisms located within the muscle. Recovery of maximal strength after the low-intensity fatiguing contraction however, was impeded more for old adults than young because of greater supraspinal fatigue. Recovery of strength could be an important variable to consider in exercise prescription of old populations

Supraspinal Fatigue Is Similar in Men and Women for a Low-Force Fatiguing Contraction

Purpose: This study determined the contribution of supraspinal fatigue to the sex difference in neuromuscular fatigue for a low-intensity fatiguing contraction. Because women have greater motor responses to arousal than men, we also examined whether cortical and motor nerve stimulation, techniques used to quantify central fatigue, would alter the sex difference in muscle fatigue. Methods: In study 1, cortical stimulation was elicited during maximal voluntary contractions (MVC) before and after a submaximal isometric contraction at 20% MVC with the elbow flexor muscles in 29 young adults (20 ± 2.6 yr, 14 men). In study 2, 10 men and 10 women (19.1 ± 2.9 yr) performed a fatiguing contraction in the presence and absence of cortical and motor nerve stimulation. Results: Study 1: Men had a briefer time to task failure than women (P = 0.009). Voluntary activation was reduced after the fatiguing contraction (P \u3c 0.001) similarly for men and women. Motor-evoked potential area and the EMG silent period increased similarly with fatigue for both sexes. Peak relaxation rates, however, were greater for men than women and were associated with time to task failure (P \u3c 0.05). Force fluctuations, RPE, HR, and mean arterial pressure increased at a greater rate for men than for women during the fatiguing contraction (P \u3c 0.05). Study 2: Time to task failure, force fluctuations, and all other physiological variables assessed were similar for the control session and stimulation session (P\u3e 0.05) for both men and women. Conclusions: Supraspinal fatigue was similar for men and women after the low-force fatiguing contraction, and the sex difference in muscle fatigue was associated with peripheral mechanisms. Furthermore, supraspinal fatigue can be quantified in both men and women without influencing motor performance

First description of natural Echinococcus multilocularis infections in chinchilla ( Chinchilla laniger ) and Prevost's squirrel ( Callosciurus prevostii borneoensis )

This report describes for the first time the occurrence of alveolar echinococcosis in two exotic rodent species in Europe. A pet chinchilla (Chinchilla laniger) was euthanized due to a painful enlargement of the abdominal cavity, and a Prevost's squirrel (Callosciurus prevostii borneoensis) was found dead in the enclosure of a zoo. At necropsy, extended liver lesions consisting of small vesicles and cysts were observed in the livers of both animals. Histological examination revealed that these cysts were composed of an outer, homogenous, eosinophilic layer and an inner, cellular germinal layer. The cysts from both animals contained numerous protoscolices. The morphological diagnosis of Echinococcus multilocularis metacestode infections was confirmed by molecular mean

Defining And Displaying Gallo: Language And Ideology In Upper Brittany, France

This dissertation examines discourse practices in and about Gallo, a marginalized Romance language of Upper Brittany, France. Specifically, it explores how various Gallo social actors (advocates, performers, teachers and students) defined, labeled and displayed Gallo, as they constructed it as a language capable of participating in modernity, producing local authority, and forging links with loved people and places. Gallo was popularly imagined as part of a rural past and dismissed as a “deformation” of French, unlike the Breton language, which stood as a salient emblem of Brittany’s cultural distinctiveness. This dissertation elucidates the ideological and everyday consequences of using this ostensibly “traditional” language in “modern” times. Using interactional and ethnographic data collected during twelve months of fieldwork, I investigate how Gallo was represented in multiple contexts: celebratory festivals, association meetings, artistic performances, language classrooms, everyday conversations, and ethnographic interviews. I argue that strategies of Gallo representation involved not just explicit statements about the language but also bids by speakers to assign themselves, as well as interlocutors and/or publics, to participant roles and stances. By occupying these positions, participants jointly articulated language and speakerhood. First, I examine how Gallo was defined as a “language” rather than as deformed French, in promotional materials and performances, and I illustrate how these genres positioned a participant role of Gallo recognizer as desirable and achievable. Second, I explore the implications of patois and gallo as language labels. While Gallo advocates often preferred gallo, I elucidate how even patois allowed speakers to draw useful social distinctions and to meaningfully connect disparate people and places. Thirdly, I discuss how dictionaries, a prominent part of Gallo advocate culture, served as icons of Gallo’s existence and “weight,” indexes of modernity, and triggers for the performance of local expertise. Finally, I show how performers on stage constructed audience members as competent evaluators of Gallo. In sum, this dissertation illustrates that language is both social object and social action. When individuals and institutions propose a representation of a language, they also propose associated participant roles, stances, and figures of speakerhood, which are open to creative recontextualization through interaction and artistic performance

Stressor-Induced Increase in Muscle Fatigability of Young Men and Women is Predicted by Strength but Not Voluntary Activation

This study investigated mechanisms for the stressor-induced changes in muscle fatigability in men and women. Participants performed an isometric-fatiguing contraction at 20% maximal voluntary contraction (MVC) until failure with the elbow flexor muscles. Study one (n = 55; 29 women) involved two experimental sessions: 1) a high-stressor session that required a difficult mental-math task before and during a fatiguing contraction and 2) a control session with no mental math. For some participants (n = 28; 14 women), cortical stimulation was used to examine mechanisms that contributed to muscle fatigability during the high-stressor and control sessions. Study two (n = 23; nine women) determined the influence of a low stressor, i.e., a simple mental-math task, on muscle fatigability. In study one, the time-to-task failure was less for the high-stressor session than control (P \u3c 0.05) for women (19.4%) and men (9.5%): the sex difference response disappeared when covaried for initial strength (MVC). MVC force, voluntary activation, and peak-twitch amplitude decreased similarly for the control and high-stressor sessions (P \u3c 0.05). In study two, the time-to-task failure of men or women was not influenced by the low stressor (P \u3e 0.05). The greater fatigability, when exposed to a high stressor during a low-force task, was not exclusive to women but involved a strength-related mechanism in both weaker men and women that accelerated declines in voluntary activation and slowing of contractile properties

Stressor-Induced Increase in Muscle Fatigability of Young Men and Women is Predicted by Strength but Not Voluntary Activation

This study investigated mechanisms for the stressor-induced changes in muscle fatigability in men and women. Participants performed an isometric-fatiguing contraction at 20% maximal voluntary contraction (MVC) until failure with the elbow flexor muscles. Study one (n = 55; 29 women) involved two experimental sessions: 1) a high-stressor session that required a difficult mental-math task before and during a fatiguing contraction and 2) a control session with no mental math. For some participants (n = 28; 14 women), cortical stimulation was used to examine mechanisms that contributed to muscle fatigability during the high-stressor and control sessions. Study two (n = 23; nine women) determined the influence of a low stressor, i.e., a simple mental-math task, on muscle fatigability. In study one, the time-to-task failure was less for the high-stressor session than control (P \u3c 0.05) for women (19.4%) and men (9.5%): the sex difference response disappeared when covaried for initial strength (MVC). MVC force, voluntary activation, and peak-twitch amplitude decreased similarly for the control and high-stressor sessions (P \u3c 0.05). In study two, the time-to-task failure of men or women was not influenced by the low stressor (P \u3e 0.05). The greater fatigability, when exposed to a high stressor during a low-force task, was not exclusive to women but involved a strength-related mechanism in both weaker men and women that accelerated declines in voluntary activation and slowing of contractile properties

Metagenome-assembled genome sequences of three uncultured planktomarina sp. strains from the Northeast Atlantic Ocean

We report three metagenome-assembled genomes (MAGs) of Planktomarina strains from coastal seawater (Portugal) to help illuminate the functions of understudied Rhodobacteraceae bacteria in marine environments. The MAGs encode proteins involved in aerobic anoxygenic photosynthesis and a versatile carbohydrate metabolism, strengthening the role of Planktomarina species in oceanic carbon cycling.Portuguese Foundation for Science and Technology: EXPL/MAR-EST/1664/2013 PTDC/MAR-BIO/1547/2014, UIDB/04565/2020, PD/BD/143029/2018, CEECIND/00788/2017,PTDC/BIA-MIC/31996/2017;Institute of Bioengineering and Biosciences (iBB) by the Programa Operacional Regional de Lisboa 007317; Helmholtz Association VH-NG-1248.info:eu-repo/semantics/publishedVersio