Strain and slackness of achilles tendon during passive joint mobilization via imaging ultrasonography

Background: In vivo study of the mechanical behavior of tendons may bring advances in evaluating the impact of intervention programs for flexibility and strength, in clinical practice and sports. Objective: The aim of this study was to quantify the relative strain and slackness of achilles tendons during passive mobilization, for four ankle joint angles and two knee angles. Methods: The displacement of the muscle-tendon junction was quantified by means of ultrasound images acquired during passive ankle mobilization, with the aid of an electrogoniometer and an electromyograph to ensure the achievement of the required angles and muscle inactivity, respectively. Results: The strain values ranged from 4.28%±2.37 to -0.94%±1.58 for the fully extended knee, and from 2.38%±1.63 to -2.32%±2.16% for the flexed knee. Conclusions: The values found in this study confirm those in the literature and demonstrate how the Achilles tendon participates in length changes in the muscle-tendon unit during passive movement. These results suggest that the mechanical properties of tendinous tissues affect the relationship between the length of muscle fibers and the joint angle, even during this type of movement

Efeitos de um programa de alongamento crônico na tensão do tendão calcanear através de ultrassonografia

Introdução e objetivo: As propriedades mecânicas do tendão calcâneo podem sofrer mudanças quando submetido a intervenções crônicas. No entanto, os efeitos sobre a tensão do tendão calcâneo a um programa de alongamento crônico ainda não estão claros na literatura. O objetivo deste trabalho foi avaliar os efeitos de um programa de alongamento na tensão do tendão calcâneo. Materiais e métodos: 14 indivíduos foram divididos em grupos de alongamento (n=8) e controle (n=6). O protocolo de alongamento consistiu de duas séries de 30 segundos de dois exercícios estáticos durante 10 semanas. A tensão passiva máxima (força passiva máxima/área de secção transversa (AST)) foi estimada através da quantificação da AST do tendão calcâneo em imagens ultrassonográficas adquiridas durante mobilização passiva do tornozelo em dinamômetro isocinético. Resultados: A amplitude máxima de dorsiflexão aumentou de 26,12 ± 6,13° para 28,87 ± 7,32° (p=0,03) no grupo experimental, enquanto as outras variáveis (torque passivo máximo, força passiva máxima, AST e tensão passiva máxima) não apresentaram mudanças significativas. Discussão: O aumento da amplitude máxima de dorsiflexão é indicativo de adaptações estruturais, visto que o mesmo não foi acompanhado de aumentos no torque passivo, força passiva e tensão máxima, o que sugere que outras adaptações estruturais do tendão tenham ocorrido, ou que a variação da AST tenha sido relativamente pequena para o ganho de amplitude articular encontrado. Conclusão: sugere-se que adaptações estruturais relacionadas com o aumento da amplitude articular não estão ligadas à AST do tendão ou que a medição complexa desta variável oculte variações pequenas da mesma. ABSTRACTEffects of chronic stretching program in the calcaneal tendon strain by ultrasoundIntroduction and Purpose: The mechanical properties of Achilles tendon can change when submitted to chronic interventions. However, the effects on this tendon stress due to a chronic stretching training are still not clear. The aim of the present study was to evaluate the effects of a 10-week stretching program on the Achilles tendon stress Methods: 14 subjects were assigned to a stretching (n=8) and a control group (n=6). The stretching protocol was applied during 10 weeks (total of 45 sessions), using two sets of 30 seconds of two different exercises. The maximum stress (maximum force/cross-sectional area (CSA)) was estimated using measurements of tendon CSA in ultrasound images obtained during passive dorsiflexion in an isokinetic dynamometer. Results: The maximum dorsiflexion angle increased from 26.12 ± 6.13° to 28.87 ± 7.32° (p=0.03) in the stretching group. All other variables (maximum passive torque, maximum passive fore, CSA and maximum tension) presented no significant changes. Discussion: The increase in the maximum dorsiflexion angle indicates structural adaptations because no torque, force and stress increase was observed, which would other structural adaptations or that, the CSA increase associated with the amplitude gain was relatively small. Conclusion: It is suggested that structural adaptations related to the amplitude increase are not associated to the tendon CSA. Otherwise, the complex methodology used to measure CSA may hide small adaptations

Reliability of triceps surae muscle architecture measurements obtained with sonographic imaging

There are few studies in the literature concerning the reliability and validity of the quantification of muscle architecture parameters using ultrasound that also report important information such as typical error of measurement (TEM) and intraclass correlation coefficient (ICC). The aim of this study was to use ultrasound imaging to quantify fiber length (FL) and pennation angle (PA) of the gastrocnemius muscle and to determine the reliability and reproducibility of these measurements. Two images of each gastrocnemius of 19 young healthy subjects were acquired using ultrasound equipment (7.5 MHz), in two visits. FL and PA were measured five times on each image, for a total of twenty measurements of each parameter. The overall reliability of the 760 measurements was determined through coefficients of variation (CV), ICC and TEM. The CV of FL ranged from 1.67 to 4.44% and from 3.8 to 11.62% for the PA. All ICC were within the high reliability range, with the exception of the between-visits PA value of the medial gastrocnemius (0.67). The two highest TEM values (3.1° and 3.7°) correspond to the two lowest ICC values (0.67 and 0.83), referring to repeated between-visit measurements of the medial and lateral gastrocnemius. FL measurements of the medial and lateral gastrocnemius had a TEM of 2.17 and 2.25 respectively. The results showed that ultrasound-based measurement of FL and PA exhibits high reliability

Reliability of measurements of rat lateral gastrocnemius architectural parameters obtained from ultrasound biomicroscopic images.

This study used ultrasound biomicroscopy (UBM) to quantify the pennation angle (PA) and muscle thickness (MT) of rat skeletal muscle and evaluated the reliability and reproducibility of the method by statistical analysis, determining the coefficient of variation (CV), intraclass correlation coefficient (ICC) and typical error of measurement. A UBM system with a center frequency of 40 MHz was used to acquire images of the right lateral gastrocnemius of ten male Wistar rats on two different days and with two ankle positions (90° or 150°). Two independent measurements of the PA and MT were randomly performed in each of three picture frames. The analysis resulted in CVs of 10.47% and 4.81% for the PA and the MT, respectively, for the ankle at 90° and 9.24% and 5.98% for the ankle at 150°. Additionally, the ICC values ranged from 0.75 to 0.92 for the PA and 0.57 to 0.99 for the MT. Statistically significant differences between the ankle positions were observed for the PA (p = 0.00013). The reliability of the PA and MT measurements for the rat right lateral gastrocnemius, determined from the ultrasound biomicroscopy images, was high (>0.90) for the methodology proposed. This finding indicates the potential of ultrasound biomicroscopy for quantitative muscle characterization and the longitudinal examination of tissue adaptation to different conditions of use, disease and rehabilitation

Mean, standard deviation (SD), coefficient of variation (CV), typical error of measurement (TEM) and intraclass correlation coefficient (ICC) of the muscle thickness acquired on two separate days (day 1 and day 2) for the ankle positions of 90° and 150° and considering the measurements performed on both days.

<p>Mean, standard deviation (SD), coefficient of variation (CV), typical error of measurement (TEM) and intraclass correlation coefficient (ICC) of the muscle thickness acquired on two separate days (day 1 and day 2) for the ankle positions of 90° and 150° and considering the measurements performed on both days.</p

Quantification of muscle thickness and pennation angle on the UBM image.

<p>UBM image showing muscle details and the traces used to quantify the muscle thickness (MT) and pennation angle (PA) of the lateral gastrocnemius muscle.</p

Rat hindlimb immobilization for image acquisition.

<p>Picture of a rat hindlimb immobilized for image acquisition with the aid of an external fixation at (A) 150° and (B) 90°.</p

Typical error of measurement (TEM) and intraclass correlation coefficient (ICC) values for the ankle at 90° and 150°, considering both the two measurements of the PA determined from each of the three frames and the measurements’mean of each of the three frames compared pair-to-pair.

<p>Typical error of measurement (TEM) and intraclass correlation coefficient (ICC) values for the ankle at 90° and 150°, considering both the two measurements of the PA determined from each of the three frames and the measurements’mean of each of the three frames compared pair-to-pair.</p