ABSTRACT The objective of this study was to evaluate the performance, carcass yield and growth curves of different commercial strains of broiler chicken. 2400 day-old chicks, males and females of the Cobb500, RossAp95, Hubbard Flex and a new Francesa line were used. The birds were distributed in a completely randomized design in a factorial arrangement 4x2 (line x sex), forming eight treatments with 10 replicates each. The birds were fed with the same diet. Feed intake, weight gain and feed conversion were determined. At 42 days, it was determined at the request of carcass and cuts of each lineage. The Gompertz model was applied to a growth curve for each line. The RossAP95 line shows the best performance results. Growth curves showed lower sexual dimorphism in the Hubbard Flex line. The Hubbard Flex strain presented higher thigh yield and a Cobb500 genetics the higher breast yield. Based on the results found it was observed that the RossAP95 performed better. Hubbard Flex line exhibits the least sexual dimorphism. The Cobb500 have better yield for breast and as Hubbard Flex birds greater thigh yield.

CONTEXTUALIZAÇÃO: O alongamento muscular é amplamente empregado no tratamento e na prevenção de doenças musculoesqueléticas. Estudos utilizam informações subjetivas do paciente como "desconforto" e "tensão sem dor" para limitar intensidade de alongamento, sem estabelecer uma tensão adequada de estiramento. OBJETIVO: Estudar a relação entre tensão aplicada e informações subjetivas, durante alongamento estático passivo para analise da reprodutibilidade e variações nas informações sensoriais. MÉTODOS: Participaram 20 jovens com idade média de 20 anos (±2,25), sem experiência prévia com programa de alongamento, divididos em dois grupos: G1 - participou de programa de alongamento dos músculos isquiotibiais, G2 sem programa de alongamento. Os grupos foram submetidos a três avaliações para mensurar o torque e a atividade eletromiográfica (EMG), nas posições de sensação de desconforto (SD) sem dor e sensação de desconforto com dor (SDD), por meio de um sistema de aquisição de sinais, constituído de condicionador de sinais, eletrodo bipolar ativo de superfície, célula de carga, eletrogoniômetro, sensor de pressão e modelo biomecânico. RESULTADO: As análises do torque nas posições SD e SDD revelaram comportamento semelhante nos dois grupos, sem diferenças significantes entre as três avaliações (P > 0.05), demonstrando reprodutibilidade das informações subjetivas dos grupos nas duas posições. A EMG nas posições de SD e SDD não mostrou diferença significante com a EMG obtida em repouso. CONCLUSÃO: Este trabalho revelou que a informação da sensação subjetiva de alongamento é confiável, segura e possível de ser reproduzida clinicamente.

BACKGROUND: Muscle stretching is widely used in the prevention and treatment of musculoskeletal diseases. Previous studies have used subjective information like "discomfort" and "tension without pain" for limiting the intensity of stretching, but without establishing appropriate tensions for stretching. OBJECTIVE: To study the relationship between applied tension and subjective information during static passive stretching, in order to analyze the reproducibility and variability of sensorial information. METHOD: Twenty subjects (mean age: 20 ± 2.25 years) without previous experience of stretching programs were recruited and divided into two groups. G1 participated in a hamstring muscle stretching program, while G2 did not follow a stretching program. Both groups underwent three evaluations to quantify torque and electromyographic activity, in positions that produced a sensation of discomfort without pain (SD) and a sensation of discomfort with pain (SDP), using a signal acquisition system consisting of a signal conditioner, active bipolar surface electrode, load cell, electrogoniometer, pressure sensor and biomechanical model. RESULTS: The torque analyses in the SD and SDP positions showed similar behavior in the two groups, without significant differences between the three evaluations (p > 0.05), thereby demonstrating the reproducibility of the subjective information from the groups in the two positions. Electromyography in the SD and SDP positions did not show significant differences in relation to the findings at rest. CONCLUSION: This study demonstrated that the subjective information on stretching sensations is reliable and secure, and can be reproduced clinically.