No abstract

In joints with 3 degrees of freedom, such as the shoulder joint, the association of different movements results in changes in the behavior of the moment arm of the muscles. The capacity of torque production for the same movement can be changed when movements take place in a different plane. The objective of this study is to quantify differences between torque production and resultant force estimated during the shoulder external rotation in two movement planes: the transverse and sagittal planes (with 90° of shoulder abduction). Eight individuals were evaluated using an isokinetic dynamometer and an eletrogoniometer for movements in the transverse plane and six individuals for movements in the sagittal plane. The results showed that the execution of the external rotation in the sagittal plane allowed greater torque magnitudes and resultant force compared with those in the transverse plane, probably owing to a prestretching of infraspinatus and teres minor.

No abstract

Objectives Previous studies in a high-income country have demonstrated that people with and without low back pain (LBP) have an implicit bias that bending and lifting with a flexed lumbar spine is dangerous. These studies present two key limitations: use of a single group per study; people who recovered from back pain were not studied. Our aims were to evaluate: implicit biases between back posture and safety related to bending and lifting in people who are pain-free, have a history of LBP or have current LBP in a middle-income country, and to explore correlations between implicit and explicit measures within groups. Methods Exploratory cross-sectional study including 174 participants (63 pain-free, 57 with history of LBP and 54 with current LBP). Implicit biases between back posture and safety related to bending and lifting were assessed with the Implicit Association Test (IAT). Participants completed paper-based (Bending Safety Belief [BSB]) and online questionnaires (Tampa Scale of Kinesiophobia; Back Pain Attitudes Questionnaire). Results Participants displayed significant implicit bias between images of round-back bending and lifting and words representing “danger” (IATD-SCORE: Pain-free group: 0.56 (IQR=0.31–0.91; 95% CI [0.47, 0.68]); history of LBP group: 0.57 (IQR=0.34–0.84; 95% CI [0.47, 0.67]); current LBP group: 0.56 (IQR=0.24–0.80; 95% CI [0.39, 0.64])). Explicit measures revealed participants hold unhelpful beliefs about the back, perceiving round-back bending and lifting as dangerous (BSBthermometer: Pain-free group: 8 (IQR=7–10; 95% CI [7.5, 8.5]); history of LBP group: 8 (IQR=7–10; 95% CI [7.5, 9.0]); current LBP group: 8.5 (IQR=6.75–10; [7.5, 9.0])). There was no correlation between implicit and explicit measures within the groups. Conclusions In a middle-income country, people with and without LBP, and those who recovered from LBP have an implicit bias that round-back bending and lifting is dangerous.

Shoulder injuries are often related to rotator cuff muscles. Although there are various models for muscle force estimation, it is difficult to ensure that the results obtained with such models are reliable. The aim of the current study was to compare two models of muscle force estimation. Eight subjects, seven male and one female (mean age of 24 yr; mean height of 1.83 m), performed five isokinetic maximum concentric contractions of internal and external shoulder rotation. Two models with different algorithms were used. In both, the input data consisted of the measured internal rotation moment. Comparisons were made between the difference and the average results obtained with each model of muscle force estimation. There was reasonable agreement among the results for force between the two models for subscapularis, pectoralis major, and anterior deltoideus muscles results. Conversely, poor correlation was found for the latissimus dorsi, teres major, and middle deltoid. These results suggest that the algorithm structure might have a strong effect on muscle force estimation results.

The aim of this study was to compare shoulder muscle force and moment production during external rotation performed in the transverse and sagittal planes. An optimization model was used for estimating shoulder muscle force production of infraspinatus, teres minor, supraspinatus, anterior deltoid, middle deltoid and posterior deltoid muscles. The model uses as input data the external rotation moment, muscle moment arm magnitude, muscle physiologic cross-sectional area and muscle specific tension. The external rotation moment data were gathered from eight subjects in transverse and six subjects in sagittal plane using an isokinetic dynamometer. In the sagittal plane, all studied muscles presented larger estimated force in comparison with the transverse plane. The infraspinatus, teres minor, supraspinatus and posterior deltoid muscles presented larger moment in sagittal when compared with transverse plane. When prescribing shoulder rehabilitation exercises, therapists should bear in mind the described changes in muscle force production.

RESUMOEstimar a força dos músculos do ombro e compreender o quanto cada músculo contribui para produção do torque em determinado movimento articular torna-se indispensável para a compreensão do movimento humano, bem como para o planejamento da reabilitação de pacientes com disfunções no ombro. Neste sentido, o presente estudo tem como principal objetivo estimar a força muscular e analisar a contribuição dos múscu-los Infra-espinhoso, Redondo Menor, Supra-espinhoso, Deltóide Posterior e Deltóide Médio no torque de rotação externa dinâmico do ombro no plano transverso. Para isso, um modelo de otimização gerado no software MATLAB‚ 7.0 (MathWork Inc, Massachusetts -USA), capaz de estimar a produção de força e torque de cada um dos músculos rotadores externos do ombro foi utilizado.Os músculos Infra-espinhoso e Redondo Menor apresentaram um pico de torque de 22Nm em 20º e 6Nm em 28º, respectivamente, quando o ombro encontrava-se em rotação interna. A magnitude máxima de força alcançada por estes músculos foi de 996N para o Infraespinhoso e 306N para o Redondo Menor. Os músculos Supra-espinhoso, Deltóide Posterior e Deltóide Médio praticamente não produziram torque e obtiveram magnitudes pequenas de força. Estes resultados apontam que os músculos Infraespinhoso e Redondo Menor são preferencialmente recrutados para o gesto de rotação externa do ombro.Palavras-chave: ombro, torque muscular, força muscular e modelo de otimização. ABSTRACT Model for force and moment prediction of shoulder external rotation muscles in the transverse plane Estimating shoulder muscle forces and understanding the contribution of each muscle to the torque generated during joint movement is indis-