Carolina Carneiro Peixinho

Ultrasound biomicroscopy for biomechanical characterization of healthy and injured triceps surae of rats

SUMMARY This work describes the use of ultrasound biomicroscopy (UBM) to follow up the degeneration–regeneration process after a laceration injury induced in the lateral gastrocnemius (LG) and soleus (SOL) muscles of rats. UBM (40 MHz) images were acquired and used for biomechanical characterization of muscular tissue, specifically using pennation angle (PA) and muscle thickness (MT). The animals were distributed in three groups: the variability group (VG; N=5), the gastrocnemius injured group (GG; N=6) and the soleus injured group (SG; N=5). VG rats were used to assess data variability and reliability (coefficients of variation of 9.37 and 3.97% for PA and MT, respectively). GG and SG rats were submitted to the injury protocol in the LG and SOL muscles of the right legs, respectively. UBM images of muscles of both legs were acquired at the following time points: before and after injury (immediately, 7, 14, 21 and 28 days). We observed an increase in PA for the non-injured leg 28 days after injury for both GG and SG rats (GG=10.68 to 16.53 deg and SG=9.65 to 14.06 deg; P<0.05). Additionally, MT presented a tendency to increase (GG=2.92 to 3.13 mm and SG=2.12 to 2.35 mm). Injured legs maintained pre-injury PA and MT values. It is suggested that a compensatory hypertrophic response due to the overload condition imposed to healthy leg. The results indicate that UBM allows qualitative and quantitative muscle differentiation among healthy and injured muscle at different stages after lesion.

Structural adaptations of rat lateral gastrocnemius muscle-tendon complex to a chronic stretching program and their quantification based on ultrasound biomicroscopy and optical microscopic images.

BACKGROUND A chronic regimen of flexibility training can increase range of motion, with the increase mechanisms believed to be a change in the muscle material properties or in the neural components associated with this type of training. METHODS This study followed chronic structural adaptations of lateral gastrocnemius muscle of rats submitted to stretching training (3 times a week during 8weeks), based on muscle architecture measurements including pennation angle, muscle thickness and tendon length obtained from ultrasound biomicroscopic images, in vivo. Fiber length and sarcomere number per 100μm were determined in 3 fibers of each muscle (ex vivo and in vitro, respectively), using conventional optical microscopy. FINDINGS Stretching training resulted in a significant pennation angle reduction of the stretched leg after 12 sessions (25%, P=0.002 to 0.024). Muscle thickness and tendon length presented no significant changes. Fiber length presented a significant increase for the stretched leg (8.5%, P=0.00006), with the simultaneous increase in sarcomere length (5%, P=0.041) since the stretched muscles presented less sarcomeres per 100μm. INTERPRETATION A stretching protocol with characteristics similar to those applied in humans was sufficient to modify muscle architecture of rats with absence of a sarcomerogenesis process. The results indicate that structural adaptations take place in skeletal muscle tissue submitted to moderate-intensity stretching training.

Deformação relativa e frouxidão do tendão calcanear durante mobilização articular passiva através de ultra-sonografia por imagem

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.

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.

In vivo passive mechanical properties estimation of Achilles tendon using ultrasound

A methodology is proposed for estimating Achilles tendon tangent modulus in vivo, to account for its large deformations and non-linear behavior. True stress is found dividing the axial force by the tendon true cross-sectional area (CSA), whose shrinking caused by axial tension is estimated with Poisson׳s coefficient. The true strain is calculated as the integral of incremental deformations along the tendon length change. Triceps surae tendon CSA and ankle moment arm, with the foot at relaxed equilibrium position, are estimated from subject-personalized data. Healthy males (N=19) volunteered for the study. The test consisted of passive ankle mobilization at the dynamometer with 5°/s velocity, from 30° of plantar flexion to the limit of dorsiflexion. Ultrasound was used to track myotendinous junction (MTJ) and tendon elongation, with the probe oriented over the medial gastrocnemius. Non-linear tendon stiffness pattern was observed during the joint range of motion, reaching 200N/mm peaks for the subjects with greater amplitudes of maximum dorsiflexion. The maximum values of modulus of elasticity, calculated from usual engineering stress and strain, (188.56±99.19MPa) were smaller than those reported in the literature for active maximum voluntary contractions tests. Maximum values for tangent modulus from true stress and strain were 312.38±171.95MPa. Such differences are likely to increase in large deformations.

Ultrasound biomicroscopy and claudication test for in vivo follow-up of muscle repair enhancement based on platelet-rich plasma therapy in a rat model of gastrocnemius laceration

PURPOSE To track the regeneration process of lateral gastrocnemius due to a muscle laceration in rats, and to treatment with plateletrich plasma (PRP). METHODS Ultrasound (40 MHz) images were used for measuring pennation angle (PA), muscle thickness (MT) and mean pixel intensity, along with claudication scores, of treated (PRPG) and non-treated (NTG) groups of rats. RESULTS NTG showed a PA increase for the non-injured leg (p<0.05) and a tendency of MT to increase, whereas for PRPG there were no differences. There was a progressive reduction of the claudication score for the PRPG group throughout the entire period, with an immediate difference after seven days (p<0.05), whereas the NTG had a significant reduction only at day 28 (p<0.05). CONCLUSION It was observed a compensatory hypertrophic response due to the overload condition imposed to healthy leg for NTG that did not occur in PRPG, suggesting an accelerated repair process of the injured leg due to treatment, anticipating its use.

Confiabilidade de medidas de arquitetura muscular do tríceps sural por ultrassonografia de imagem

Ha, atualmente, na literatura, poucas pesquisas de confiabilidade e validacao da quantificacao de parâmetros de arquitetura muscular por ultrassonografia (US), relatando informacoes importantes como o erro tipico da medida (ETM) e o coeficiente de correlacao intraclasse (ICC). O objetivo do estudo foi aplicar a tecnica de US para quantificar as medidas de comprimento da fibra (CF) e ângulo de penacao (AP) dos musculos gastrocnemios e determinar a confiabilidade e a reprodutibilidade dessas medidas. Duas imagens de cada gastrocnemio de 19 individuos jovens e saudaveis foram adquiridas com um equipamento de ultrassom modo-B (7,5MHz), em duas visitas. CF e AP foram medidos cinco vezes nas duas imagens de cada individuo, totalizando vinte medidas de cada parâmetro para cada participante. A confiabilidade do total das 760 medidas foi determinada atraves do coeficiente de variacao (CV), ICC e ETM. O CV do CF variou de 1,67 a 4,44% e do AP de 3,8 a 11,62%. Todos os ICC se encontram no intervalo de grande confiabilidade, com excecao do valor referente a medida interdias do AP do gastrocnemio medial (0,67). Os dois valores mais altos de ETM (3,1o e 3,7o) correspondem aos dois valores inferiores do ICC (0,67 e 0,83), referentes as medidas repetidas interdias dos gastrocnemios. As medidas de CF dos gastrocnemios medial e lateral apresentaram ETM de 2,17mm e 2,25mm, respectivamente. Os resultados obtidos demonstraram que a metodologia utilizada para medicao de CF e AP realizada em imagens de ultrassom apresentou alta confiabilidade.

Reliability of triceps surae muscle architecture measurements obtained with sonographic imaging

Ha, atualmente, na literatura, poucas pesquisas de confiabilidade e validacao da quantificacao de parâmetros de arquitetura muscular por ultrassonografia (US), relatando informacoes importantes como o erro tipico da medida (ETM) e o coeficiente de correlacao intraclasse (ICC). O objetivo do estudo foi aplicar a tecnica de US para quantificar as medidas de comprimento da fibra (CF) e ângulo de penacao (AP) dos musculos gastrocnemios e determinar a confiabilidade e a reprodutibilidade dessas medidas. Duas imagens de cada gastrocnemio de 19 individuos jovens e saudaveis foram adquiridas com um equipamento de ultrassom modo-B (7,5MHz), em duas visitas. CF e AP foram medidos cinco vezes nas duas imagens de cada individuo, totalizando vinte medidas de cada parâmetro para cada participante. A confiabilidade do total das 760 medidas foi determinada atraves do coeficiente de variacao (CV), ICC e ETM. O CV do CF variou de 1,67 a 4,44% e do AP de 3,8 a 11,62%. Todos os ICC se encontram no intervalo de grande confiabilidade, com excecao do valor referente a medida interdias do AP do gastrocnemio medial (0,67). Os dois valores mais altos de ETM (3,1o e 3,7o) correspondem aos dois valores inferiores do ICC (0,67 e 0,83), referentes as medidas repetidas interdias dos gastrocnemios. As medidas de CF dos gastrocnemios medial e lateral apresentaram ETM de 2,17mm e 2,25mm, respectivamente. Os resultados obtidos demonstraram que a metodologia utilizada para medicao de CF e AP realizada em imagens de ultrassom apresentou alta confiabilidade.

Effects of Functional Training and Calf Stretching on Risk of Falls in Older People: A Pilot Study

This study aimed to determine the effects of a functional training and ankle stretching program in triceps surae torque, passive stiffness index, and in the risk for fall indicators in older adults. Twenty women (73.4 ± 7.3 years) were allocated into an intervention or control group. The 12-week intervention consisted of functional training and calf stretching exercises performed twice a week. Measurements of peak passive and active torque, passive stiffness, maximum dorsiflexion angle, and indexes of risk for falls (Timed Up and Go, functional reach test, QuickScreen-test) were collected. There were no significant differences for all variables, except the maximum dorsiflexion angle, which increased in the intervention group from 33.78 ± 8.57° to 38.89 ± 7.52°. The exercise program was not sufficient to enhance performance on functional tests and decrease the risk for falls in older adults. The significant increase in the maximum dorsiflexion indicates a positive impact of stretching exercises.

Classification of individual flexibility: before and after a long-term stretching program

The evaluation of the stretching effects through mean values of the entire sample can hide different adaptations between groups with distinct characteristics of joint flexibility. This study aimed to employ artificial neural networks to classify subjects according to their flexibility level and to investigate the effects of a 10-week stretching training. The stretching group (SG, n = 9) performed stretching exercises for triceps surae muscles 4–5 times a week over 10 weeks. Maximum dorsiflexion angle (MDA) and peak passive torque (PPT) data at pre-intervention were used in a k-means (k = 3) algorithm to group participants as flexible, intermediate or stiff. A feed-forward artificial neural network (multilayer perceptron) was trained using the pre-intervention dataset with the k-means labeled groups and classified the post-intervention data generated after the stretching protocol. MDA of SG increased significantly (p = 0.015) from 24.72 ± 7.70 to 29.81 ± 6.95° whereas PPT showed no significant differences. Following intervention, two subjects from the SG shifted from the intermediate to the flexible group, whereas one stiff subject changed to the intermediate group. The control group presented a random pattern of group change. This approach can aid future analysis of different adaptations to stretching programs.