Abstract The honey bee Apis mellifera is a plant-pollinator that produces commercial products. It has female castes with workers performing tasks in the colonies and a queen, it has the longest lifespan, in charge of reproduction. This bee undergoes a population decline worldwide. Therefore, it is important to understand how aging affects the digestive tract of this insect. In the midgut, regenerative cells are organized in nests replacing the dead cells. This study verified the hypothesis that the number of regenerative cells decreases as A. mellifera queen ages. The midgut was evaluated in queens at the age of four days and eight, 11 and 25 months. The midgut of 11- and 25-month-old queens presented signs of epithelial disorganization in comparison with younger queens. The number of regenerative cell nests in the midgut decreases according to the age of the queen, but the number of cells per nest is similar. The decreased number of regenerative cell nests reveals a potential loss in the amount of these cells available for the renewal of the midgut epithelium. The absence of variations in the number of regenerative cells per nest according to the queen age indicates that these cells do not undergo proliferation before the differentiation.

Abstract The world is currently facing a severe economic crisis and the rational consumption and reuse of products, including waste are necessary. Agriculture wastes have importance containing beneficial and economic value matters, which unutilized may lead to environmental pollution. Date seed is one of these viable wastes with high nutritional value. Mass rearing of peach fruit flies is important to produce parasitoids for use in biological control programs or sterile insect techniques. In this study powder of date seeds were evaluated as an alternative diet for mass rearing of peach fruit fly Bactrocera zonata. The nutrient composition of the tested diet that contained date seed powder was rich in crude proteins (13.1%), crude carbohydrates (40.41), crude fats (4.6), crude fibers (8.4), and ashes (0.29). The results indicated that the date seed powder produced insects with quality parameters equivalent to FAO, IAEA/USDA standards, without differences with those reared on yeast. The histology of the reproductive system of B. zonata reveals that the female ovariole is of meristic-polytrophic type with successive stages of egg chambers. The male testis has a single long follicle with successive stages of spermatogenesis. Thus, date seed powder is a potential alternative diet for use in the mass rearing of the peach fruit fly.

Resumo A diversidade de fungos, incluindo espécies entomopatogênicas, é alta nos solos. Esses fungos são utilizados no manejo de pragas com facilidade de produção, multiplicação, aplicação e dispersão no campo. O objetivo foi avaliar a diversidade de fungos entomopatogênicos em solos de culturas de eucalipto e soja e áreas de mata nativa. Fungos entomopatogênicos foram isolados pelo “Bait Method” com larvas de Tenebrio molitor (Linnaeus, 1758) (Coleoptera: Tenebrionidae) de 10 amostras de solo por área, coletadas a 10 cm de profundidade em zig-zag. Os fungos isolados foram cultivados em três placas de Petri em meio BDA e seus micélios separados após sete dias de incubação em câmara tipo BOD. Fungos dos gêneros Aspergillus, Beauveria, Cordyceps, Fusarium, Metarhizium, Penicillium e Purpureocillium foram identificados. O “Bait Method” com larvas de T. molitor é eficiente para isolar fungos entomopatogênicos com maior diversidade em solos de área de mata nativa que naqueles com culturas de eucalipto e soja.

Abstract Soils present high fungal diversity, including entomopathogenic species. These fungi are used in pest control, providing easy production, multiplication, application, and dispersion in the field. The objective of the present study was to evaluate entomopathogenic fungal diversity in soils from eucalyptus and soybean crops and natural forest areas. These fungi were isolated using the “Bait Method” with Tenebrio molitor (Linnaeus, 1758) (Coleoptera: Tenebrionidae) larvae from 10 soil samples per area, collected at 10 cm deep in a zig-zag pattern. The isolated entomopathogenic fungi were cultivated in Petri dishes using PDA medium and their mycelia separated after seven days of incubation in a BOD-type chamber. Species of Aspergillus, Beauveria, Cordyceps, Fusarium, Metarhizium, Penicillium and Purpureocillium were identified. The “Bait Method” with T. molitor larvae is efficient to isolate entomopathogenic fungi with higher diversity from soils of the natural forest than the cultivated area.

ABSTRACT An important concern with the use of genetically modified (GM) plants expressing Bacillus thuringiensis (Bt) insecticidal toxins is the deleterious effect on non–target organisms. The predatory stink bug Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) is used in biological control programs and may be exposed to Bt toxins. This study evaluated the indirect effects of different Cry proteins on P. nigrispinus with the prey Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), fed on simple or pyramided Bt maize genotypes. The experiment was carried out in a completely randomized design with three treatments: i) Isohybrid (not Bt), ii) Herculex® (transgenic maize encoding Cry1F protein) and iii) PowerCore® (pyramidal transgenic maize encoding the Cry1F, Cry1A.105, and Cry2Ab2 proteins), which were used to feed S. frugiperda for 48 h. The caterpillars were used as prey by P. nigrispinus females. We evaluated the presence of Cry proteins, consumed prey biomass (predation), oviposition period, number of postures, number of eggs, number of eggs per posture, number of nymphs, egg viability, embryonic period, female longevity and development, and survival rates of immature. The results show that different Cry proteins move through the food chain of P. nigrispinus and provide evidence that the ingestion of three different proteins does not lead to unexpected synergistic effects. However, Cry toxins promoted histopathological changes in midgut cells of P. nigrispinus.

ABSTRACT The objective of this study was to evaluate cotton cultivars based on the compensatory increase of cotton squares in response to the simulation of the boll weevil damage. The first experiment aimed to evaluate cotton cultivars with greater compensatory increase in squares removed artificially from the plant. The experimental design was in randomized blocks, in a 4 × 2 factorial scheme with 100% removal of cotton squares at 50, 70 and 90 days after the emergence of the FM975WS, TMG81WS, IMA6501B2RF and BRS432B2RF cotton cultivars and passive production (without removal) and active (with removal) of cotton squares, with four replications. In the second experiment, boll weevil damage in the TMG80WS and BRS432B2RF, with greater and lesser compensatory increase of cotton squares, after their removal at 50 days of age, was evaluated. The experimental design was in randomized blocks, in a 2 × 2 factorial scheme, with the former cultivars sprayed with carbamate or not (control). The compensatory increase of cotton squares, mainly after their artificial removal at 50 and 70 days of age, of the TMG81WS, was greater. The cotton square compensatory increase after being artificially removed in the cotton cultivars was higher during the period of exponential production of these reproductive structures and can be used to select cultivars tolerant to boll weevil damage.

ABSTRACT The Hermanella complex is a well-established monophyletic group of Hagenulinae mayflies, but the phylogenetic relationships among its members are still being discussed. In order to fill some gaps in the taxonomy of this group we describe, for the first time, the eggs of eight species of this complex (Hermanella amere, Hermanella mazama, Hydromastodon sallesi, Hydrosmilodon gilliesae, Hydrosmilodon plagatus, Leentvaaria palpalis, Paramaka incognita, Paramaka sp.) using scanning electron microscopy, including some important members whose generic allocation have been questioned. The egg morphology in these eight species of Hermanella complex and their similarities with other species of the complex are discussed.

ABSTRACT Members of the Hydrophilidae, one of the largest families of aquatic insects, are potential models for the biomonitoring of freshwater habitats and global climate change. In this study, we describe the morphology of the male reproductive tract in the water scavenger beetle Tropisternus collaris. The reproductive tract in sexually mature males comprised a pair of testes, each with at least 30 follicles, vasa efferentia, vasa deferentia, seminal vesicles, two pairs of accessory glands (a bean-shaped pair and a tubular pair with a forked end), and an ejaculatory duct. Characters such as the number of testicular follicles and accessory glands, as well as their shape, origin, and type of secretion, differ between Coleoptera taxa and have potential to help elucidate reproductive strategies and the evolutionary history of the group.

RESUMO Basidiósporos do fungo ectomicorrízico Pisolithus microcarpus apresentam parede celular impermeável, característica possivelmente relacionada às baixas porcentagens de germinação desses propágulos, o que dificulta a obtenção de monocários e a utilização desses esporos em inoculantes. O objetivo deste estudo foi avaliar o efeito de diferentes concentrações de água sanitária comercial na permeabilização dos basidiósporos de P. microcarpus e analisar as alterações causadas na ultraestrutura da parede celular, na viabilidade e na capacidade germinativa desses propágulos. Basidiósporos fúngicos foram coletados em plantações de eucalipto e permeabilizados utilizando-se diferentes concentrações de água sanitária e tempos de exposição. Os basidiósporos foram então analisados por microscopia eletrônica de varredura e de transmissão. A porcentagem de basidiósporos permeabilizados variou com a marca comercial, concentração de água sanitária e o tempo de exposição. Basidiósporos de diferentes basidiocarpos diferiram na suscetibilidade ao tratamento de permeabilização com água sanitária. Alterações da ultraestrutura dos basidiósporos permeabilizados foram observadas nas concentrações de 15 e 50 % de água sanitária pelo tempo de exposição de 40 s, com mudanças de superfície e perda das espículas da camada mais externa da parede. Após a permeabilização com água sanitária a 5 % por 40 s, 80 % dos esporos permeabilizados encontravam-se viáveis, resultando na produção de colônias fúngicas após 15 dias de incubação desses propágulos na presença de Corymbia citriodora. No entanto, a porcentagem de germinação obtida: 0,001%, foi semelhante à de basidiósporos não-permeabilizados, indicando que outros fatores, além da permeabilidade da parede celular, são determinantes para o processo de germinação.

ABSTRACT Basidiospores of the ectomycorrhizal fungus Pisolithus microcarpus have an impermeable cell wall, a characteristic that is possibly related to the low germination percentages of these propagules, which makes it difficult to obtain monokaryons and use these spores in inoculants. The objective of this study was to evaluate the effect of different concentrations of commercial bleach on the permeabilization of P. microcarpus basidiospores and to analyze the alterations caused in the cell wall ultrastructure and the viability and germination capacity of these propagules. Fungal basidiospores were collected in eucalyptus plantations and permeabilized using different bleach concentrations and exposure times. The basidiospores were then analyzed by scanning and transmission electron microscopy. The percentage of permeabilized basidiospores varied with the commercial brand, bleach concentration, and exposure time. Basidiospores of different basidiocarps differed in susceptibility to permeabilization treatment with bleach. Changes in the ultrastructure of permeabilized basidiospores were observed at bleach concentrations of 15 and 50 % for an exposure time of 40 s, with surface changes and loss of the spicules of the outermost layer of the wall. After permeabilization with 5 % bleach for 40 s, 80 % of the permeabilized spores were viable, resulting in the production of fungal colonies after 15 days of incubation of these propagules in the presence of Corymbia citriodora. However, the germination percentage obtained, 0.001 %, was similar to that of non-permeabilized basidiospores, indicating that other factors, besides cell wall permeability, are determinant for the germination process.

Abstract Herbicides can impact non-target metabolic pathways in natural enemies and lead to the reduction of these populations in the field. Behavioral characteristics, morphology and histology of reproductive structures and reproduction of females of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) were evaluated under the effect of the herbicides atrazine, nicosulfuron and the mixture of both. The number of mature oocytes per ovary was lower in females exposed to the herbicides atrazine, nicosulfuron and the mixture of both. Herbicides did not affect the longevity and mortality of P. nigrispinus, therefore, they are selective for this predator. On the other hand, herbicides can cause sublethal effects by affecting the reproduction of predators.

ABSTRACT Due to their ecological and economic importance, honey bees have attracted much scientific attention, which has intensified due to the recent population decline of these insects in the several parts of the world. Among the factors related to these patterns, infection by pathogens are the most relevant, mainly because of the easy dissemination of these microorganisms. Although no zoonotic diseases are associated with these insects, the presence of infectious agents in bee products should still be considered because they play a role as disease dispersers, increasing the risk to animal health. Because of the possibility of dispersion of pathogens via bee products, this work aimed to identify the presence of spores of the pathogens Paenibacillus larvae, Ascosphaera apis and Nosema spp. in samples of honey, pollen and royal jelly that are registered with Brazil's Federal Inspection Service (S.I.F.) and commercially available in the state of São Paulo. Of the 41 samples of bee products analyzed, only one showed no contamination by any of these pathogens. N. ceranae and P. larvae had the highest prevalence considering all the samples analyzed (present in 87.80% and 85.37% of the total, respectively), with N. apis present in 26.83% and A. apis present in 73.17% of the samples. These results provide support for the formulation of government regulations for sanitary control of exotic diseases by preventing dispersion of pathogens, including through illegal importation, since local and international trade and the transfer of colonies between regions play important roles in the dispersion of these microorganisms.

RESUMO A geléia real pode conter grãos de pólen e sua presença pode ser usada para determinar a origem fitogeográfica do produto. Este estudo analisou a origem fitogeográfica de amostras comerciais de geléia real do Estado de São Paulo, com registro no Sistema de Inspeção Federal (SIF) brasileiro, que estavam contaminadas com os esporos da bactéria Paenibacillus larvae, causadora da doença Cria Pútrida Americana. Os grãos de pólen de Castanea apresentaram a maior porcentagem total, com menores percentuais de Cirsium/Carduus, Cistus, Parthenocissus, Prunus, Quercus, Robinia, Scrophulariaceae, Taraxacum, Tilia, dentre outros. Este espectro polínico é incompatível com amostras de geléia real produzidas no Brasil. O espectro polínico assemelhou- se ao de um produto importado, compatível com a origem do Hemisfério Norte. A legislação brasileira não exige que a origem fitogeográfica dos produtos apícolas importados seja analisada por procedimentos palinológicos, mas é obrigatório ter um certificado atestando a ausência de patógenos emitido pelo país de origem, monitorado com o objetivo de impedir que doenças exóticas penetrem no Brasil. A palinologia, portanto, provou ser fundamental na detecção de importações desses lotes contaminados.

ABSTRACT Royal jelly may contain pollen grains and their presence can be used to determine the phytogeographical origin of the product. This study analyzed the phytogeographical origin of commercial royal jelly samples from São Paulo State, tested as part of the Brazilian Federal Inspection System (SIF), found to be contaminated with spores of the bacterium Paenibacillus larvae, that causes the American Foulbrood Disease. The pollen grains of Castanea had the highest total percentage, with lower percentages of Cirsium/Carduus, Cistus, Parthenocissus, Prunus, Quercus, Robinia, Scrophulariaceae, Taraxacum, Tilia, among others. This pollen spectrum is incompatible with royal jelly samples produced in Brazil. The pollen spectrum resembled that of an imported product, compatible with the Northern Hemisphere origin. Brazilian legislation does not require the phytogeographic origin of imported bee products to be analyzed by palynological procedures, but it is mandatory to have a certificate issued by the country of origin attesting the absence of pathogens, monitored with the objective of preventing the exotic diseases from entering Brazil. Palynology, therefore, proved to be fundamental in detecting imports of this contaminated batches.

RESUMO As glândulas exócrinas desempenham importantes funções na organização social dos insetos, como a diferenciação de castas e inter-castas. Devido à sua plasticidade estrutural e funcional, estudos morfológicos destas glândulas contribuem para o melhor entendimento da biologia das abelhas sociais. Por isso, o objetivo deste estudo foi acompanhar o desenvolvimento pós-embrionário das glândulas intramandibulares de operárias da abelha sem ferrão Friesella schrottkyi (Friese, 1900) (Hymenoptera: Apidae) com análises histológicas e histoquímicas. As mandíbulas das pupas em diferentes estágios do desenvolvimento e operárias recém-emergidas foram analisadas. As glândulas intramandibulares de F. schrottkyi são divididas em dois tipos: glândulas da classe I na epiderme da mandíbula e da classe III, inseridas na cavidade da mandíbula que se abrem na superfície externa. As glândulas intramandibulares de F. schrottkyi se desenvolvem durante a transição de pré-pupa para pupa de olho branco como observado pelas alterações morfológicas nas células. As pupas de olhos pretos de F. schrottkyi apresentaram glândulas intramandibulares completamente desenvolvidas.

ABSTRACT Exocrine glands play important role in social organization of insects, such as caste and inter-caste differentiation. Due their functional and structural plasticity, morphological studies on such glands contribute to better understanding the biology of social bees. Therefore, the aim of the study was to characterize the sequence of the post-embryonic development of intramandibular glands of Friesella schrottkyi (Friese, 1900) (Hymenoptera: Apidae) workers using histological and histochemical analyses. The mandibles of pupae at different developmental stages and newly emerged adults were analyzed. The intramandibular glands of F. schrottkyi presented two types: class I glands, in the mandible epidermis and class III glands, inside the mandible cavity that open onto external surface. The intramandibular glands of F. schrottkyi developed during the transition from the prepupae to the white-eyed pupae, as shown by the morphological changes. Black-eyed pupae of F. schrottkyi presented fully developed intramandibular glands.

Resumo: O objetivo deste trabalho foi avaliar a distribuição espacial e temporal de Sarsina violascens (Lepidoptera: Noctuidae: Lymantriinae) em duas plantações de Eucalyptus cloeziana, uma com faixas de vegetação nativa (CFVN) e outra sem (SFVN). Adultos foram coletados com armadilhas luminosas, as quais foram instaladas: no interior de uma área com vegetação nativa (Cerrado), a 100 m da borda; na zona de contato entre a vegetação nativa e a plantação de E. cloeziana; no interior da plantação de E. cloeziana, a 250 m da borda; na parte central da faixa de vegetação nativa, cerca de 500 m da borda (CFVN) ou na zona de contato entre dois talhões de E. cloeziana (SFVN); e no interior da plantação de E. cloeziana, a 500 m da borda. O número de adultos de S. violascens coletados foi de 240 no sistema CFVN e de 1.378 no sistema SFVN. O menor número de indivíduos no sistema CFVN provavelmente foi devido ao favorecimento do controle biológico pelo aumento da riqueza de espécies com o uso de faixas de vegetação nativa. Essas faixas, intercaladas com plantações de E. cloeziana, possibilitam maior proporção de floresta nativa na paisagem e podem auxiliar na redução de infestações por S. violascens.

Abstract: The objective of this work was to evaluate spatial and temporal distributions of Sarsina violascens (Lepidoptera: Noctuidae: Lymantriinae) in two Eucalyptus cloeziana plantations, one with native vegetation strips (WNVS) and another without them (ONVS). Adults were collected with light traps, which were installed: inside an area of native vegetation (Cerrado), 100 m from the edge; at the contact zone between the native vegetation area and the E. cloeziana plantation; inside the E. cloeziana plantation, 250 m from the edge; at the central part of the native vegetation strip, around 500 m from the edge (WNVS) or in the contact zone between two E. cloeziana compartments (ONVS); and inside the E. cloeziana plantation, 500 m from the edge. The number of S. violascens adults collected was 240 in the system WNVS and 1,378 in the system ONVS. The lower number of individuals in the system WNVS was probably due to favored biological control provided by higher species richness with the use of native vegetation strips. These strips, intermingled with E. cloeziana plantations, allow a higher proportion of native forest in the landscape and can help to reduce S. violascens infestations.

Caryocar brasiliense (Caryocaraceae), un árbol símbolo de el Cerrado, tiene una amplia distribución y puede alcanzar los 10 m de altura y 6 m de ancho de copa. El objetivo fue estudiar la distribución de insectos chupadores (Hemiptera) y sus enemigos naturales en la copa de C. brasiliense en El Cerrado brasileño. La agrupación de las especies encontrada en la copa de los árboles de C. brasiliense mostró 1 y 3 especies raras, 9 y 7 especies comunes y 1 y 4 especies constantes para los insectos chupadores y sus enemigos naturales, respectivamente. La diversidad, el número de individuos y la riqueza de especies de Hemiptera y sus enemigos naturales fueron similares en todas las ramas del árbol huésped, según el muestreo en los puntos cardinales. Los depredadores Crematogaster sp. (Hymenoptera: Formicidae) y Zelus armillatus (Hemiptera: Reduviidae) fueron más abundante en la ramas orientadas hacia el este y el norte, respectivamente. Crematogaster sp. fue dominante en los árboles de C. brasiliense con predominio de Dikrella caryocar n. sp. (Hemiptera: Cicadellidae) y Pseudoccocus sp. (Hemiptera: Pseudococcidae). Los depredadores Trybonia sp. (Thysanoptera: Phlaeothripidae) y Chrysoperla spp. (Neuroptera: Chrysopidae) fueron mayores y disminuyeron el número de D. caryocar n. sp. y Aphis gossypii (Aphididae), respectivamente. El incremento de insectos chupadores aumentó la presencia de los enemigos naturales y la distribución diferencial de éstos influyó negativamente en los insectos chupadores. Se concluye que la velocidad y dirección de los vientos pueden afectar la distribución de insectos chupadores en la copa de los árboles de C. brasiliense, encontrándose las poblaciones más numerosas en la zona que no es afectada por el viento.

Caryocar brasiliense (Caryocaraceae), a tree characteristic of e Cerrado, is widely distributed and can reach a height of 10 meters with a six-meter-wide canopy. The objective of this study was to study the distribution of sucking insects (Hemiptera) and their natural enemies in the canopies of C. brasiliense trees in the Brazilian Cerrado. One rare, nine common, and one constant species of sucking insects and three rare, seven common, and four constant species of natural enemies were observed on C. brasiliense trees. The diversity, number of individuals, and species of Hemiptera and their natural enemies were similar in all four cardinal directions of branches of host trees. Abundance of the natural predators Crematogaster sp. (Hymenoptera: Formicidae) and Zelus armillatus (Hemiptera: Reduviidae) was highest on leaves of the east and north sides of the C. brasiliense trees, respectively. A large number of Crematogaster sp. was observed on C. brasiliense, with a predominance of Dikrella caryocar n. sp. (Hemiptera: Cicadellidae) and Pseudoccocus sp. (Hemiptera: Pseudococcidae) also being observed. The predators Trybonia sp. (Thysanoptera: Phlaeothripidae) and Chrysoperla sp. (Neuroptera: Chrysopidae) showed the highest numbers, while the number of D. caryocar n. sp. and Aphis gossypii (Aphididae) decreased, respectively, in comparison to the control. An increase in the number of sucking insects also increased the number of their natural enemies, and this differential distribution negatively influenced sucking insects. The speed and direction of wind may have affected the distribution of sucking insects on different sides of C. brasiliense trees, as higher populations were found on the sides without prevailing winds.

INTRODUÇÃO: a entorse em inversão do tornozelo, uma das lesões mais comuns do esporte, muitas vezes ocorre na fase final de um treino ou competição. Mesmo sabendo que a entorse é multifatorial, tal característica gera a hipótese que a fadiga muscular possa ser um fator predisponente para o desenvolvimento da lesão.OBJETIVO: a presente investigação propõe o estudo da resposta reflexa dos músculos fibular curto e longo em condições de fadiga.MÉTODOS: participaram do estudo 10 voluntárias do sexo feminino, sem histórico de entorse do tornozelo, fisicamente ativas. Utilizou-se uma plataforma simuladora da entorse em inversão do tornozelo, na qual ambos os pés das voluntárias foram fixados e somente abaixo do fixador do pé direito encontrava-se um transdutor de força. Para a indução da fadiga, inicialmente foi registrada a contração isométrica voluntária máxima (CIVM) em eversão. Durante a indução, as voluntárias foram orientadas a manter 70% da CIVM. No momento em que a força aplicada era menor que 60% da CIVM o protocolo era interrompido e as voluntárias imediatamente posicionadas sobre a plataforma simuladora. Antes e após a fadiga foram realizadas 10 simulações da entorse em ambos os tornozelos, de forma aleatória, e simultaneamente, o sinal eletromiográfico foi registrado. A análise, no domínio do tempo, contemplou o estudo da latência e da amplitude do sinal.RESULTADOS: após a fadiga não houve alteração da latência, no entanto, ocorreu uma redução da amplitude do sinal. A queda da amplitude do sinal pode ser considerada uma resposta ao processo de fadiga. Esse decréscimo é um indicativo da diminuição da capacidade de recrutamento das unidades motoras decorrentes das alterações do input neural que chega ao músculo.CONCLUSÃO: a fadiga muscular diminui a amplitude da resposta dos músculos eversores após a entorse do tornozelo.

INTRODUCTION: inversion ankle sprain is one of the most common sports injuries and it often occurs in the final phase of a training or competition. Although sprain is multifactorial, this characteristic leads to the hypothesis that muscle fatigue can be a predisposing factor to injury.OBJECTIVE: the present study was set to investigate the neuromuscular response of the fibularis brevis and longus in conditions of fatigue.METHODS: the study included 10 physically active female participants with no history of ankle sprain. To simulate the inversion ankle sprain, we used a simulation platform in which participant's feet were attached and, underneath the right foot strap only, there was a transducer. To induce fatigue, we first recorded the maximal voluntary isometric contraction (MVIC) in eversion. During the induction, the participants were instructed to maintain 70% of MVIC. When strength fell below 60% of MVIC, the protocol was interrupted and the participants were immediately placed on the simulation platform. Before and after fatigue, we conducted 10 sprain simulations in both ankles, randomly decided and simultaneously, the electromyographic signal registered. In the time domain, latency and signal amplitude were analyzed.RESULTS: after fatigue, the latency did not change, however there was a reduction of the signal amplitude. The drop in amplitude can be considered a response to the process of fatigue. This decrease indicates a reduction in the ability to recruit motor units due to changes in the neural input that reaches the muscle.CONCLUSION: muscle fatigue reduces the amplitude of the response of the eversion muscles after ankle sprain.

INTRODUCCIÓN: el esguince en inversión del tobillo, una de las lesiones más comunes del deporte, muchas veces ocurre en la fase final de un entrenamiento o competición. Aún sabiendo que el esguince es multifactorial, tal característica genera la hipótesis de que la fatiga muscular puede ser un factor de predisposición para el desarrollo de la lesión.OBJETIVO: la presente investigación propone el estudio de la respuesta refleja de los músculos fibular corto y largo en condiciones de fatiga.MÉTODOS: participaron en el estudio 10 voluntarias del sexo femenino sin historial de esguince de tobillo, físicamente activas. Se utilizó una plataforma simuladora del esguince en inversión del tobillo, en la que ambos pies de las voluntarias fueron fijados y solamente debajo del fijador del pie derecho se encontraba un transductor de fuerza. Para inducción de la fatiga inicialmente fue registrada la contracción isométrica voluntaria máxima (CIVM) en eversión. Durante la inducción las voluntarias fueron orientadas a mantener 70% de la CIVM. En el momento en que la fuerza aplicada era menor a 60% de la CIVM el protocolo era interrumpido y las voluntarias inmediatamente posicionadas sobre la plataforma simuladora. Antes y después de la fatiga fueron realizadas diez simulaciones de esguince bilateralmente de forma aleatoria y simultáneamente registrada la señal electromiográfica. El análisis, en el dominio del tiempo, contempló el estudio de la latencia y de la amplitud de la señal.RESULTADOS: después de la fatiga no hubo alteración de la latencia, sin embargo ocurrió reducción de la amplitud de la señal. La caída de la amplitud de la señal puede ser considerada una respuesta al proceso de fatiga. Esa disminución es un indicativo de la reducción de la capacidad de reclutamiento de las unidades motrices provenientes de las alteraciones del input neural que llega al músculo.CONCLUSIÓN: la fatiga muscular disminuye la amplitud de la respuesta de los músculos eversores después de esguince del tobillo.