A speckle tracking application of ultrasound to evaluate activity of multilayered cervical muscles

The Relationship of Ultrasound Measurements of Muscle Deformation With Torque and Electromyography During Isometric Contractions of the Cervical Extensor Muscles

OBJECTIVES

Speckle tracking analysis (STA) of ultrasound (US) images quantifies the longitudinal deformation of a region of muscle tissue to provide a mechanical measure of muscle activity. As the validity and reliability of this method has not yet been adequately assessed, the aim of this study was to determine the validity and reliability of STA in the dorsal neck muscles during isometric neck extension contractions.

METHODS

Twenty volunteers performed 3 repetitions of isometric neck extension in a dynamometer at 10%, 20%, 40%, 60%, and 80% of maximal voluntary torque while US and surface electromyography (EMG) data were recorded. Speckle tracking analysis was then used to calculate measurements of muscle deformation. The relationship among torque, muscle deformation (separate for each muscle and summed), and EMG was evaluated using linear regressions and Spearman's correlation coefficients. The reliability of EMG and muscle deformation was determined using intraclass correlation coefficients (ICCs).

RESULTS

Muscle deformation in 4 of the 5 muscles when examined separately and collectively was significantly related to torque (P < .05); however, the relationship was weak (r² = 0.03-0.18). In contrast, a strong linear relationship was observed between torque and EMG (P < .001, r² = 0.83). Poor to moderate reliability of muscle deformation measures (ICC: 0.02-0.69) was found compared with EMG, which was highly reliable (ICC: 0.67-0.90).

CONCLUSION

These results suggest that the validity of US STA measurements for isometric contractions of the dorsal neck muscles is questionable. Further investigation into this method is required before it can be used as a tool to measure muscle activity.

Ultrasound Investigation of Dorsal Neck Muscle Deformation During a Neck Rotation Exercise

OBJECTIVES

Neck-specific exercise can reduce neck pain and increase function, but information on how different neck muscle layers are activated during neck exercises is scarce. The aim of this study was to investigate deformation and deformation rate in 5 dorsal neck muscles and the correlation among these muscles during a loaded dynamic exercise used in clinical practice.

METHODS

Deformation and deformation rate were investigated in 5 dorsal right-sided neck muscles in 20 individuals without neck pain using ultrasonography and speckle-tracking analyses. Repeated-measures analysis of variance was used to measure differences between the muscles, and correlations between neck muscles were analyzed with Kendall's tau.

RESULTS

Deformation in left (contralateral) rotation showed significant differences among the muscles (P = .01), with higher deformation of the semispinalis capitis muscle compared with the trapezius muscle (P = .02). There were no significant differences among the 5 neck muscles in right (unilateral) rotation (P = .46). There were significant differences in deformation rate among muscles in both right and left rotation (P < .01). The trapezius muscles have the lowest deformation rate in right rotation (P < .01). In left rotation, the trapezius and multifidus muscles showed lower deformation rates compared with most of the other muscles (P < .03). Almost all muscles were correlated in both deformation and deformation rate.

CONCLUSION

The quadruped standing loaded dynamic neck exercise seemed to activate all the investigated neck muscles, with a tendency for more activation of the semispinalis capitis.

Automatic Detection of Contracting Muscle Regions via the Deformation Field of Transverse Ultrasound Images: A Feasibility Study

Accurate identification of contracting muscles can help us to understand the muscle function in both physiological and pathological conditions. Conventional electromyography (EMG) have limited access to deep muscles, crosstalk, or instability in the recordings. Accordingly, a novel framework was developed to detect contracting muscle regions based on the deformation field of transverse ultrasound images. We first estimated the muscle movements in a stepwise calculation, to derive the deformation field. We then calculated the divergence of the deformation field to locate the expanding or shrinking regions during muscle contractions. Two preliminary experiments were performed to evaluate the feasibility of the developed algorithm. Using concurrent intramuscular EMG recordings, Experiment I verified that the divergence map can capture the activity of superficial and deep muscles, when muscles were activated voluntarily or through electrical stimulation. Experiment II verified that the divergence map can only capture contracting muscles but not muscle shortening during passive movements. The results demonstrated that the divergence can individually capture the activity of muscles at different depths, and was not sensitive to muscle shortening during passive movements. The proposed framework can automatically detect the regions of contracting muscle, and could potentially serve as a tool to assess the functions of a group of muscles concurrently.

Effect of Core Stability Training Monitored by Rehabilitative Ultrasound Image and Surface Electromyogram in Local Core Muscles of Healthy People

Background

The purpose of this study is to investigate the influence of transverses abdominis and lumbar multifidus thickness activation and electromyogram signal characteristics after core stability training monitored by rehabilitative ultrasound imaging and surface electromyogram.

Methods

60 healthy volunteers were allocated randomly into two groups, one of which received monitoring training and the other participated identical training without monitoring. Ultrasound image and surface electromyogram signal were collected at 0, 4, and 8 weeks during training. The muscle thickness activation ratio value and integrated electromyogram value were then extracted. During the training, the monitoring group was monitored by real-time rehabilitative ultrasound imaging and surface electromyogram while the control group was not.

Results

There are no differences in performance of local core muscles between both groups before training (p > 0.05). Compared with the control group, the thickness contraction ratio value and integrated electromyogram value of core muscles in the monitoring group were higher after 8 weeks' training (p < 0.05).

Conclusion

Together, the core stability training monitored by rehabilitative ultrasound imaging and surface electromyogram can markedly activate and enhance local core muscles in healthy people, providing a potential strategy to treat low back pain more effectively.