Rehabilitative ultrasound imaging: understanding the technology and its applications

The opinion and experiences of Dutch orthopedic surgeons and radiologists about diagnostic musculoskeletal ultrasound imaging in primary care: a survey

INTRODUCTION AND AIM

The use of diagnostic musculoskeletal ultrasound (DMUS) in primary health care has increased in the recent years. Nevertheless, there are hardly any data concerning the reliability, accuracy and treatment consequences of DMUS used by physical therapists or general practitioners. Moreover, there are no papers published about how orthopedic surgeons or radiologists deal with the results of DMUS performed in primary care. Therefore, our aim is to evaluate the opinion, possible advantages or disadvantages and experiences of Dutch orthopedic surgeons and radiologists about DMUS in primary care.

METHODS

A cross-sectional survey in which respondents completed a self-developed questionnaire to determine their opinion, experiences, advantages, disadvantages of performing DMUS in primary care.

RESULTS

Questionnaires were sent to 838 Dutch orthopedic surgeons and radiologists of which 213 were returned (response rate 25.4%). Our respondents saw no additional value for health care for diagnostic DMUS in primary care. DMUSs were generally repeated in secondary care. They perceived more disadvantages than advantages of performing DMUS in primary care. Mentioned disadvantages were: 'false positive results' (71.4%), 'lack of experience' (70%), 'insufficient education' (69.5%), not able to relate the outcomes of DMUS with other forms of diagnostic imaging' (65.7%), and 'false negative results' (65.3%).

CONCLUSION

Radiologists and orthopedic surgeons sampled in the Netherlands show low trust in DMUS knowledge of physical therapists and general practitioners. The results should be interpreted with caution because of the small response rate and the lack of representativeness to other countries.

Do various baseline characteristics of transversus abdominis and lumbar multifidus predict clinical outcomes in nonspecific low back pain? A systematic review

Although individual reports suggest that baseline morphometry or activity of transversus abdominis or lumbar multifidus predict clinical outcome of low back pain (LBP), a related systematic review is unavailable. Therefore, this review summarized evidence regarding the predictive value of these muscular characteristics. Candidate publications were identified from 6 electronic medical databases. After review, 5 cohort studies were included. Although this review intended to encompass studies using different muscle assessment methods, all included studies coincidentally used ultrasound imaging. No research investigated the relation between static morphometry and clinical outcomes. Evidence synthesis showed limited evidence supporting poor baseline transversus abdominis contraction thickness ratio as a treatment effect modifier favoring motor control exercise. Limited evidence supported that high baseline transversus abdominis lateral slide was associated with higher pain intensity after various exercise interventions at 1-year follow-up. However, there was limited evidence for the absence of relation between the contraction thickness ratio of transversus abdominis or anticipatory onset of lateral abdominal muscles at baseline and the short- or long-term LBP intensity after exercise interventions. There was conflicting evidence for a relation between baseline percent thickness change of lumbar multifidus during contraction and the clinical outcomes of patients after various conservative treatments. Given study heterogeneity, the small number of included studies and the inability of conventional greyscale B-mode ultrasound imaging to measure muscle activity, our findings should be interpreted with caution. Further large-scale prospective studies that use appropriate technology (ie, electromyography to assess muscle activity) should be conducted to investigate the predictive value of morphometry or activity of these muscles with respect to LBP-related outcomes measures.

Reliability of 2 ultrasonic imaging analysis methods in quantifying lumbar multifidus thickness

STUDY DESIGN

Reliability study.

OBJECTIVES

To compare the within- and between-day intrarater reliability of rehabilitative ultrasound imaging (RUSI) using static images (static RUSI) and video clips (video RUSI) to quantify multifidus muscle thickness at rest and while contracted. Secondary objectives were to compare the measurement precision of averaging multiple measures and to estimate reliability in individuals with and without low back pain (LBP).

BACKGROUND

Although intrarater reliability of static RUSI in measuring multifidus thickness has been established, using video RUSI may improve reliability estimates, as it allows examiners to select the optimal image from a video clip. Further, multiple measurements and LBP status may affect RUSI reliability estimates.

METHODS

Static RUSI and video RUSI were used to quantify multifidus muscle thickness at rest and during contraction and percent thickness change in 27 volunteers (13 without LBP and 14 with LBP). Three static RUSI images and 3 video RUSI video clips were collected in each of 2 sessions 1 to 4 days apart. Reliability and precision were assessed using intraclass correlation coefficients, standard error of measurement, minimal detectable change, bias, and 95% limits of agreement.

RESULTS

Using an average of 2 measures yielded optimal measurement precision for static RUSI and video RUSI. Based on the average of 2 measures obtained under the same circumstance, there was no significant difference in the reliability estimates between static RUSI and video RUSI across all testing conditions. Reliability point estimates (intraclass correlation coefficient model 3,2) of multifidus thickness were 0.99 for within-day comparisons and ranged from 0.93 to 0.98 for between-day comparisons. The within- and between-day intraclass correlation coefficients (model 3,2) of percent thickness change ranged from 0.97 to 0.99 and from 0.80 to 0.90, respectively. The exploratory analysis showed no significant difference in the reliability estimates between asymptomatic and LBP participants across most testing conditions.

CONCLUSION

Both RUSI methods yielded high reliability estimates for multifidus muscle measurements. Using an average of 2 measures obtained optimal measurement precision. Overall, video RUSI is a reliable surrogate for static RUSI for multifidus muscle measurements and has the additional advantage of requiring shorter data collection time.

Ultrasound imaging evaluation of abdominal muscles after breast reconstruction with a unilateral pedicled transverse rectus abdominis myocutaneous flap

BACKGROUND

A muscle-sparing (MS) procedure using a full-width pedicled transverse rectus abdominis (RA) myocutaneous (TRAM) flap was developed to reduce abdominal morbidities after breast reconstruction. However, the effects of this procedure on the morphology of the remnant RA muscle and other abdominal muscles remain unclear.

OBJECTIVE

Ultrasound imaging was used to evaluate the morphology of the remnant RA muscle and other abdominal muscles in women with the MS pedicled TRAM flap procedure.

DESIGN

A case-control, cross-sectional design was used.

METHODS

Thirty-four women with an MS unilateral pedicled TRAM flap procedure after mastectomy (TRAM group) and 25 women who were healthy and matched for age (control group) participated. The curl-up test measured trunk flexor muscle strength. Ultrasound imaging measured the thickness of all abdominal muscles in all participants and the cross-sectional area of the RA muscle at rest and in an isometric position with the head raised in women in the TRAM group. Acoustic echogenicity and border visibility assessed the tissue composition of the remnant RA muscle.

RESULTS

Trunk flexor muscle strength was weaker in the TRAM group than in the control group. Compared with the remnant RA muscle in the contracted state, the remnant RA muscle in the relaxed state was thinner and had a smaller cross-sectional area. The remnant RA muscle in the relaxed state also was thinner, more echoic, and less visible than its contralateral counterpart. No differences in the thickness of the other abdominal muscles were found between the sides. The abdominal muscles in the TRAM group were smaller than those in the control group.

LIMITATION

Because a prospective, longitudinal design was not used, a definite cause-effect relationship could not be determined.

CONCLUSIONS

In women with an MS unilateral pedicled TRAM flap procedure, the remnant RA muscle retains its ability to change in size during contraction, albeit at reduced levels. Muscular atrophy occurs in other ipsilateral and contralateral abdominal muscles as well as the remnant RA muscle. Postoperative immobilization is the most likely cause of generalized weakness of the abdominal musculature.

Comparison of the sonographic features of the abdominal wall muscles and connective tissues in individuals with and without lumbopelvic pain

STUDY DESIGN

Cross-sectional, case-control study.

OBJECTIVES

To measure and compare the resting thickness of the 4 abdominal wall muscles, their associated perimuscular connective tissue (PMCT), and interrecti distance (IRD) in persons with and without lumbopelvic pain (LPP), using ultrasound imaging.

BACKGROUND

The muscles and PMCT of the abdominal wall assist in controlling the spine. Functional deficits of the abdominal wall muscles have been detected in populations with LPP. Investigations of the abdominal wall in those with LPP are primarily concerned with muscle, most commonly the transversus abdominis (TrA) and internal oblique (IO). Because the abdominal wall functions as a unit, all 4 abdominal muscles and their associated connective tissues should be considered concurrently.

METHODS

B-mode ultrasound imaging was used to measure the resting thickness of the rectus abdominis (RA), external oblique, IO, and TrA muscles; the PMCT planes; and IRD in 50 male and female subjects, 25 with and 25 without LPP (mean ± SD age, 36.3 ± 9.4 and 46.6 ± 8.0 years, respectively). Univariate correlation analysis was used to identify covariates. Analyses of covariance (ANCOVAs) and the Kruskal-Wallis test (IRD) were used to compare cohorts (α = .05).

RESULTS

The LPP cohort had less total abdominal muscle thickness (LPP mean ± SD, 18.9 ± 3.0 mm; control, 20.3 ± 3.0 mm; ANCOVA adjusted for body mass index, P = .03), thicker PMCT (LPP, 5.5 ± 0.2 mm; control, 4.3 ± 0.2 mm; ANCOVA adjusted for body mass index, P = .007), and wider IRD (LPP, 11.5 ± 2.0 mm; control, 8.4 ± 1.8 mm; Kruskal-Wallis, P = .005). Analysis of individual muscle thickness revealed no difference in the external oblique, IO, and TrA, but a thinner RA in the LPP cohort (LPP mean ± SD, 7.8 ± 1.5 mm; control, 9.1 ± 1.2 mm; ANCOVA adjusted for body mass index, P<.001).

CONCLUSION

To our knowledge, this is the first study to investigate the morphological characteristics of all 4 abdominal muscles and PMCT in individuals with LPP. The results suggest that there may be altered loading of the PMCT and linea alba secondary to an altered motor control strategy involving a reduced contribution of the RA. Further, the change in RA and connective tissue morphology may be more evident than changes in external oblique, IO, and TrA thickness in persons with LPP. The causes and functional implications of these changes warrant further investigation, as does the role of the RA muscle in the development and persistence of LPP.

Intramuscular temperature changes during and after 2 different cryotherapy interventions in healthy individuals

STUDY DESIGN

Crossover.

OBJECTIVES

To compare the time required to decrease intramuscular temperature 8°C below baseline temperature, and to compare intramuscular temperature 90 minutes posttreatment, between 2 cryotherapy modalities.

BACKGROUND

Cryotherapy is used to treat pain from muscle injuries. Cooler intramuscular temperatures may reduce cellular metabolism and secondary hypoxic injury to attenuate acute injury response, specifically the rate of chemical mediator activity. Modalities that decrease intramuscular temperature quickly may be beneficial in the treatment of muscle injuries.

METHODS

Eighteen healthy subjects received 2 cryotherapy conditions, crushed-ice bag (CIB) and cold-water immersion (CWI), in a randomly allocated order, separated by 72 hours. Each condition was applied until intramuscular temperature decreased 8°C below baseline. Intramuscular temperature was monitored in the gastrocnemius, 1 cm below subcutaneous adipose tissue. The primary outcome was time to decrease intramuscular temperature 8°C below baseline. A secondary outcome was intramuscular temperature at the end of a 90-minute rewarming period. Paired t tests were used to examine outcomes.

RESULTS

Time to reach an 8°C reduction in intramuscular temperature was not significantly different between CIB and CWI (mean difference, 2.6 minutes; 95% confidence interval: -3.10, 8.30). Intramuscular temperature remained significantly colder 90 minutes post-CWI compared to CIB (mean difference, 2.8°C; 95% confidence interval: 2.07°C, 3.52°C).

CONCLUSION

There was no difference in time required to reduce intramuscular temperature 8°C 1 cm below adipose tissue using CIB and CWI. However, intramuscular temperature remained significantly colder 90 minutes following CWI. These results provide clinicians with information that may guide treatment-modality decisions.

Abdominal and lumbar multifidus muscle size and symmetry at rest and during contracted States. Normative reference ranges

OBJECTIVES

The purpose of this study was to establish reference values for abdominal and lumbar multifidus muscles at rest and while contracted in a sample of active healthy adults.

METHODS

Three hundred forty participants (mean age ± SD, 21.8 ± 3.9 years; 96 females and 244 males) completed the study. Ultrasound imaging was used to assess the thickness of the transversus abdominis, internal and external oblique, rectus abdominis, and lumbar multifidus muscles. Additionally, the cross-sectional area of the rectus abdominis was assessed.

RESULTS

Although males had significantly thicker muscles than females (P < .05), the relative change in thickness during specified tasks was equivalent. Overall, relative muscle thickness and symmetry were similar to previous studies using smaller sample sizes.

CONCLUSIONS

These findings provide a robust data set of muscle thickness values measured by ultrasound imaging and can be used for comparison to those with pain, abnormal function, and pathologic conditions.

Recruitment of motor units in two fascicles of the semispinalis cervicis muscle

This study investigated the behavior of motor units in the semispinalis cervicis muscle. Intramuscular EMG recordings were obtained unilaterally at levels C2 and C5 in 15 healthy volunteers (8 men, 7 women) who performed isometric neck extensions at 5%, 10%, and 20% of the maximal force [maximum voluntary contraction (MVC)] for 2 min each and linearly increasing force contractions from 0 to 30% MVC over 3 s. Individual motor unit action potentials were identified. The discharge rate and interspike interval variability of the motor units in the two locations did not differ. However, the recruitment threshold of motor units detected at C2 (n = 16, mean ± SD: 10.3 ± 6.0% MVC) was greater than that of motor units detected at C5 (n = 92, 6.9 ± 4.3% MVC) (P < 0.01). A significant level of short-term synchronization was identified in 246 of 307 motor unit pairs when computed within one spinal level but only in 28 of 110 pairs of motor units between the two levels. The common input strength, which quantifies motor unit synchronization, was greater for pairs within one level (0.47 ± 0.32) compared with pairs between levels (0.09 ± 0.07) (P < 0.05). In a second experiment on eight healthy subjects, interference EMG was recorded from the same locations during a linearly increasing force contraction from 0 to 40% MVC and showed significantly greater EMG amplitude at C5 than at C2. In conclusion, synaptic input is distributed partly independently and nonuniformly to different fascicles of the semispinalis cervicis muscle.

Use of ultrasound imaging by physiotherapists: a pilot study to survey use, skills and training

OBJECTIVE

This study aimed to design and pilot a questionnaire to survey the use of ultrasound imaging (USI) by physiotherapists in the United Kingdom (UK), the type and content of ultrasound training physiotherapists using USI had undertaken and their perceived future training needs.

BACKGROUND

The use of USI by physiotherapists is becoming increasingly common but is highly operator dependent and there are safety and professional issues regarding use in physiotherapy practice. Currently there are no specific training guidelines relating to physiotherapists using USI.

METHODS

A questionnaire was developed, based on research literature and guidelines. Twelve experts in USI commented on the content and design. The electronic on-line questionnaire was piloted on groups that were likely to be users of USI.

RESULTS

Forty-six respondents completed the questionnaire. Results indicated that USI is used predominantly for biofeedback and there are many unmet training needs. Respondents reported a mismatch between techniques for which they had received training and those that they used in practice and indicated a more structured training framework is required.

CONCLUSIONS

The development and piloting of the questionnaire provides a starting point for a more extensive evaluation of how USI is being used, the training needs of physiotherapists and benefits as a biofeedback tool. Refinement is needed and replication in a larger sample. Results could assist the development of a structured formal training framework encompassing key skills.

Ultrasound measurement of the size of the anterior tibial muscle group: the effect of exercise and leg dominance

Background

Knowledge of normal muscle characteristics is crucial in planning rehabilitation programmes for injured athletes. There is a high incidence of ankle and anterior tibial symptoms in football players, however little is known about the effect of limb dominance on the anterior tibial muscle group (ATMG). The purpose of this study was to assess the effect of limb dominance and sports-specific activity on ATMG thickness in Gaelic footballers and non-football playing controls using ultrasound measurements, and to compare results from transverse and longitudinal scans.

Methods

Bilateral ultrasound scans were taken to assess the ATMG size in 10 Gaelic footballers and 10 sedentary controls (age range 18-25 yrs), using a previously published protocol. Both transverse and longitudinal images were taken. Muscle thickness measurements were carried out blind to group and side of dominance, using the Image-J programme.

Results

Muscle thickness on the dominant leg was significantly greater than the non-dominant leg in the footballers with a mean difference of 7.3%, while there was no significant dominance effect in the controls (p < 0.05). There was no significant difference between the measurements from transverse or longitudinal scans.

Conclusions

A significant dominance effect exists in ATMG size in this group of Gaelic footballers, likely attributable to the kicking action involved in the sport. This should be taken into account when rehabilitating footballers with anterior tibial pathology. Ultrasound is a reliable tool to measure ATMG thickness, and measurement may be taken in transverse or longitudinal section.

Ultrasound transducer shape has no effect on measurements of lumbar multifidus muscle size

OBJECTIVE

Evidence is currently lacking for guidance on ultrasound transducer configuration (shape) when imaging muscle to measure its size. This study compared measurements made of lumbar multifidus on images obtained using curvilinear and linear transducers.

METHOD

Fifteen asymptomatic males (aged 21-32 years) had their right lumbar multifidus imaged at L3. Two transverse images were taken with two transducers (5 MHz curvilinear and 6 MHz linear), and linear and cross-sectional area (CSA) measurements were made off-line. Reliability of image interpretation was shown using intra-class correlation coefficients (0.78-0.99). Muscle measurements were compared between transducers using Bland and Altman plots and paired t-tests. Relationships between CSA and linear measurements were examined using Pearson's Correlation Coefficients.

RESULTS

There were no significant differences (p > 0.05) in the measurements of the two transducers. Thickness and CSA measurements had small differences between transducers, with mean differences of 0.01 cm (SDdiff = 0.21 cm) and 0.03 cm(2) (SDdiff = 0.58 cm(2)) respectively. Width measures had a mean difference of 0.14 cm, with the linear transducer giving larger measures. Significant correlations (p < 0.001) were found between all linear measures and CSA, with both transducers (r = 0.78-0.89).

CONCLUSION

Measurements of multifidus at L3 were not influenced by the configuration of transducers of similar frequency. For the purposes of image interpretation, the curvilinear transducer produced better definition of the lateral muscle border, suggesting it as the preferable transducer for imaging lumbar multifidus.

Ultrasound imaging and muscle function

There is a growing trend in the physical therapy profession to use conventional grayscale brightness (B-mode) ultrasound imaging (USI) as a tool to assess the morphological (form and structure) and morphometric (measures of form) characteristics of muscle, and to use these findings to draw conclusions regarding muscle function. This trend is reflected in numerous published investigations. As many physical therapists may lack training in the principles and instrumentation underlying USI use, it is critical that therapists gain a clear understanding of the information that USI can, and cannot, provide about muscle function before employing the technique for either research or clinical applications. Failure to do so may result in the propagation of inaccurate terminology and beliefs. This paper aims to clarify the role that USI has in the assessment of muscle function, first, by briefly reviewing how conventional grayscale B-mode ultrasound images and clips are generated, and second, by summarizing the types of information that these images can provide. It also discusses the various factors that need to be considered when interpreting a dynamic USI assessment of muscle specifically as it relates to the assessment of muscle function.

The relationships between inter-recti distance measured by ultrasound imaging and abdominal muscle function in postpartum women: a 6-month follow-up study

STUDY DESIGN

A prospective longitudinal study.

BACKGROUND

Diastasis recti abdominis (DRA) is defined as an increase in the inter-recti distance (IRD), or width of the linea alba. It is a common occurrence in women postpartum. Little information exists on the short- and long-term recovery of IRD and the relationship between changes in IRD and the functional performance of the abdominal muscles.

OBJECTIVES

To investigate the natural recovery of IRD and abdominal muscle strength and endurance in women between 7 weeks and 6 months postpartum, and to examine the relationship between IRD and abdominal muscle function.

METHODS

Forty postpartum (25-37 years of age) and 20 age-matched, nulliparous females participated. IRD was measured at 4 locations (upper and lower margin of the umbilical ring, and 2.5 cm above and below the umbilical ring) with a 7.5-MHz linear ultrasound transducer. Trunk flexion and rotation strength and endurance were measured with manual muscle testing and curl-ups. Evaluation was conducted at 4 to 8 weeks and 6 to 8 months after childbirth in postpartum women, and only once for the nulliparous female controls.

RESULTS

During follow-up, the IRD at 2.5 cm above the umbilical ring and at the upper margin of the umbilical ring decreased (P = .013 and P = .002, respectively). The strength and static endurance of the abdominal muscles improved over time (P<.05). A negative correlation between IRD and abdominal muscle function at 7 weeks and 6 months postpartum was found (r = 0.34 to 0.51; P<.05, except for trunk flexion strength at 6 months postpartum [P = .064]). In addition, IRD changes between 7 weeks and 6 months postpartum were correlated with improvement in trunk flexion strength (Spearman rho = 0.38, P = .040). At 6 months after childbirth, postpartum women had greater mean ? SD IRDs at all 4 locations (from cranial to caudal: 1.80 ± 0.72, 2.13 ± 0.65, 1.81 ± 0.62, and 1.16 ± 0.58 cm) than those of nulliparous females (0.85 ± 0.26, 0.99 ± 0.31, 0.65 ± 0.23, and 0.43 ± 0.17 cm) (all P<.001). All abdominal strength and endurance measurements were less than those of nulliparous females (all P<.001).

CONCLUSIONS

The IRD and abdominal muscle function of postpartum women improved but had not returned to normal values at 6 months after childbirth. Future research is essential to explore the need for intervention and, if needed, the effectiveness of specific intervention to reduce the size of IRD in postpartum women.

Subcutaneous thigh fat assessment: a comparison of skinfold calipers and ultrasound imaging

CONTEXT

Skinfold calipers (SC) typically are used to determine subcutaneous fat thicknesses. Identifying the exact separation of muscle and fat can complicate measurements. Ultrasound imaging (USI) might provide a better technique for analyzing subcutaneous fat thicknesses.

OBJECTIVE

To compare measurements from SC and USI in assessing subcutaneous thigh fat thickness.

DESIGN

Descriptive laboratory study.

SETTING

Laboratory.

PATIENTS AND OTHER PARTICIPANTS

Twenty healthy adults (13 men, 7 women; age  =  26.9 ± 5.4 years, height  =  173.9 ± 7.3 cm, mass  =  77.4 ± 16.1 kg) participated.

INTERVENTION(S)

Participants were seated in 90° of knee flexion and 85° of trunk extension. A standardized template was used to identify measurement sites over the vastus medialis obliquus (VMO), distal rectus femoris (dRF), proximal rectus femoris (pRF), and vastus lateralis (VL). Three measurements at each of the 4 sites were made in random order and were averaged for each measurement tool by the same investigator.

MAIN OUTCOME MEASURE(S)

Fat thickness was measured in millimeters with SC and USI. Measurements at each site were compared using Pearson product moment correlations and Bland-Altman plots.

RESULTS

Strong correlations between measures were found at the VMO (r  =  .90, P < .001), dRF (r  =  .93, P < .001), pRF (r  =  .93, P < .001), and VL (r  =  .91, P < .001). Mean differences between measures ranged from 1.7 ± 2.4 mm (dRF) to 3.7 ± 2.6 mm (pRF), indicating that the SC resulted in larger thicknesses compared with USI. Limits of agreement, as illustrated by the Bland-Altman plots, were fairly wide at each site: from -3.38 mm to 7.74 mm at the VMO, from -3.04 mm to 6.52 mm at the dRF, from -1.53 mm to 8.87 mm at the pRF, and from -3.73 mm to 8.15 mm at the VL. All plots except for the VL demonstrated increasing overestimation via the SC as fat thicknesses increased.

CONCLUSIONS

We found strong correlations between the SC and USI; however, the large limits of agreement and increasing mean differences with larger fat thicknesses were a concern in terms of using this tool. When measuring subcutaneous fat thickness of the thigh, SC tended to overestimate thickness in individuals with higher fat values.

Validity and reliability of a simple ultrasound approach to measure medial gastrocnemius muscle length

Fixed shortening of a muscle, or contracture, often develops in individuals with an upper motor neuron disorder. A clinical measure of muscle length would therefore be useful for identifying the presence of muscle contracture, tracking changes over time and evaluating the effect of interventions. This study compared a novel ultrasound-tape length method with a previously validated freehand 3D ultrasound method for measuring muscle length. The ultrasound-tape method intra-session reliability was also assessed. Resting medial gastrocnemius muscle length was measured at three ankle joint angles in 15 typically developed (TD) adults and nine adults with cerebral palsy (CP) using the two methods. The ultrasound-tape method on average overestimated the muscle length in the TD group by <0.1% (95% CI, 6%) and underestimated in the muscle length in the CP group by 0.1% (95% CI, 6%) compared with the 3D ultrasound method. Intra-session reliability of the ultrasound-tape method was high, with intra-class correlation coefficients >0.99. The ultrasound-tape method has sufficient accuracy to detect clinically relevant differences and changes in medial gastrocnemius muscle length and may therefore be a useful clinical tool for assessing muscle length changes associated with contracture.

Discriminative and reliability analyses of ultrasound measurement of abdominal muscles recruitment

Rehabilitative ultrasound imaging has a great potential to be used as a tool in the assessment of trunk muscle function in patients with low back pain (LBP). However, a further investigation of the discriminative ability of this tool as well as the effect of operators' levels of training on reliability is warranted. Discriminative analysis of ultrasound and electromyography (EMG) measurements of transversus abdominus (TrA), obliquus internus (OI), and obliquus externus (OE) muscles function between people with and without LBP and the effect of operator's training on reliability of TrA muscle function of chronic LBP patients were conducted. For the discriminative study, measurements were collected from 10 subjects with LBP and 10 matched controls during isometric low load tasks with their limbs suspended. For the reliability study, in stage 1 the reliability of single ultrasonographic static images involved 4 operators (1 trained and 3 non-trained), whereas, in stage 2, two operators (1 trained and 1 non-trained) were used to determine the reliability of TrA thickness change. Methods used in the statistical analysis were pearson correlation and receiver operating characteristic curve for the discriminative study and intraclass correlation coefficient (ICC) for the reliability study. While ultrasound measures of OE muscle function showed poor association with EMG (r = 0.28, p = 0.22), TrA and OI function showed moderate to excellent association (TrA: r = 0.74, p < 0.000; OI: r = 0.85, p < 0.000). Ultrasound and EMG measures of TrA and OI function discriminated LBP patients from controls. Reliability of the assessment of TrA function with a trained operator (ICC = 0.92; 95% CI: 0.81-0.97) was substantially higher than a non-trained one (ICC = 0.44; 95% CI: -0.41-0.78). In conclusion, ultrasound measures of deep trunk function is a valid discriminative tool in LBP but highly dependent on operator's level of training.

Inter-rater reliability of ultrasound imaging of the trunk musculature among novice raters

OBJECTIVE

The purpose of this study was to determine the inter-rater reliability of ultrasound imaging for assessing trunk muscle morphologic characteristics at rest and while contracted among different pairs of novice raters. The secondary purpose was to compare 3 different measurement techniques for assessing lateral abdominal muscle thickness.

METHODS

A single-group repeated measures reliability study was conducted on 21 healthy participants (mean ± SD, 21.5 ± 4.4 years; 5 female and 16 male) without low back pain. Ultrasound images of the transversus abdominis, internal oblique, rectus abdominis, and lumbar multifidus muscles were obtained by different pairs of novice raters in a counterbalanced order. All raters received a standardized training program before obtaining measurements.

RESULTS

The intraclass correlation coefficient (1, 3) point estimates ranged from 0.86 to 0.94; the standard error of the measurement ranged from 0.04 to 0.16 cm for the thickness values and 0.67 cm(2) for the cross-sectional area of the rectus abdominis muscle. There was no meaningful difference between the different measurement techniques used to analyze the lateral abdominal muscles.

CONCLUSIONS

Good to excellent reliability was obtained for all measures by novice raters. Minimal differences in reliability were noted between the different measurement techniques to assess lateral abdominal muscle thickness.

A rationale for the provision of extrinsic feedback towards management of low back pain

Low back pain (LBP) is associated with dysfunction of global and local muscle systems, feedback and feedforward postural control mechanisms. Physiotherapists include the use of feedback as part of treatment protocols. Such feedback can focus on a variety of neuromuscular impairments, although the literature related to feedback on the management of LBP has focused mainly on local muscle system impairments. Furthermore, there are various characteristics of feedback that can lead to motor control enhancement or deterioration. The aim of this manuscript is to present a rationale for feedback provision as a rehabilitation tool on the management of LBP. Feedback provision should focus on the main neuromuscular impairment presented by the patient. The suggested rationale describes decision-making stages for the use and progress of feedback interventions. Local muscle system impairment might benefit more from parameter feedback provision, while global muscle system and feedback mechanism impairments may benefit better from program feedback. The described rationale has the potential to help clinicians select the appropriate feedback for the treatment of their patients. Additionally, the presented rationale could be used by researchers to assess how different forms of feedback provision impact on clinical outcomes.

A magnetic resonance imaging investigation into the function of the deep cervical flexors during the performance of craniocervical flexion

OBJECTIVE

Evidence suggests that the deep cervical flexors (DCFs) are important for the control of the cervical spine. The craniocervical flexion (CCF) test is a clinical test developed for patients with neck pain disorders based on the action of the DCFs. Because these muscles are deeply situated, it is difficult to reach the DCFs with surface electromyography. Magnetic resonance imaging (MRI) can be used to measure these muscles in cross section. The objective of this study was (1) to determine the reliability of MRI for measuring cross-sectional area (CSA) of the longus colli (Lco) and longus capitis (Lca) and (2) to evaluate the changes in CSA during contraction.

METHODS

Thirty healthy subjects aged 29 +/- 9.3 years were imaged using MRI. The CSA of the Lco and Lca was evaluated at 4 different levels (C0-C1, C2-C3, C4-C5, and C6-C7) at rest and during CCF.

RESULTS

The intraclass correlation coefficients for the CSA of the Lco and Lca showed good to excellent reliability (0.73-0.92), except at the C4-C5 level. There was a significant increase in CSA of both Lco (F = 6.79, P = .015) and Lca (F = 19.20, P <or= .001) due to CCF, and this was at different levels. The highest increases in CSA occurred at the C0-C1 level for the Lca (11.1%) and at the C2-C3 level for the Lco (17.4%).

CONCLUSIONS

This study demonstrated that the action of CCF resulted in a contraction of the Lco and Lca at different levels. The results indicate that MRI is a promising technique to evaluate changes in CSA during contraction.

Assessing contractile ability of the quadriceps muscle using ultrasound imaging

Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps force and rectus femoris (RF) dimensions were examined to assess USI for estimating contraction level. In 15 healthy males, mean age 24.8 years, isometric quadriceps force was measured in 90° knee flexion during submaximal and maximal voluntary contractions (MVCs) and at MVC in extension. Mid-thigh cross-sectional area (CSA), depth and width, and surface electromyography (EMG) of RF were recorded. Muscle width decreased curvilinearly as both force and EMG increased. At MVC, width was 3.2 ± 0.5 cm, 25% smaller than at rest (4.4 ± 0.7 cm), and similar to MVC in extension (-23%). CSA decreased linearly to -18% at MVC. RF thickness increased by only 10% (at 30% to MVC). Similar width changes at MVC in flexion and extension indicate the clinical potential of USI for assessing quadriceps contractility. Sensitivity is limited to assessing strength to within 25% of MVC in young males.

Validity of real-time ultrasound imaging to measure anterior hip muscle size: a comparison with magnetic resonance imaging

STUDY DESIGN

Clinical measurement, criterion standard.

OBJECTIVES

To investigate the validity of real-time ultrasound imaging (USI) to measure individual anterior hip muscle cross-sectional area.

BACKGROUND

The hip flexor muscles are important for hip joint function and could be affected by joint pathology or injury. Objectively documenting individual anterior hip muscle size can be useful in identifying muscle size asymmetry and monitoring treatment efficacy for patients with hip problems. USI offers a novel method of measuring individual muscle size in the clinic, but its validity in measuring the anterior hip muscles has not been investigated.

METHODS

Nine healthy participants (5 males, 4 females) underwent imaging of their iliopsoas, sartorius, and rectus femoris muscles with USI and magnetic resonance imaging. Bilateral muscle cross-sectional areas were measured on images from both modalities.

RESULTS

There was no significant difference (P>.05) in mean cross-sectional area measurements from USI and magnetic resonance imaging for each muscle. Agreement between measurements was high for the iliopsoas (left: intraclass correlation coefficient [ICC3,1] = 0.86; 95% confidence interval [CI]: 0.51, 0.97; right: ICC3,1 = 0.88; 95% CI: 0.57, 0.97), sartorius (left: ICC3,1 = 0.82; 95% CI: 0.41, 0.96; right: ICC3,1 = 0.81; 95% CI: 0.39, 0.95), and rectus femoris (left: ICC3,1 = 0.85; 95% CI: 0.49, 0.96; right: ICC3,1 = 0.89; 95% CI: 0.61, 0.97). Reliability of measuring each muscle with USI was high between 2 trials (ICCs3,1 = 0.84 to 0.94).

CONCLUSION

USI is a valid measure of iliopsoas, sartorius, and rectus femoris muscle size in healthy people, as long as a strict measurement protocol is followed.

Thickness of the middle trapezius muscle measured by rehabilitative ultrasound imaging: description of the technique and reliability study

A technique is described for measuring the thickness of the middle trapezius muscle using rehabilitative ultrasound imaging (RUSI). A test-retest study was employed to investigate the reliability of the technique in a convenience sample of 16 asymptomatic participants aged 20-41 (12 women). The middle trapezius muscle was imaged using RUSI with participants in a standardized sitting position. The principal investigator took measurements on two consecutive days to examine intra-rater reliability, and two additional investigators took measurements on the second day to investigate inter-rater reliability of the measurement technique. Reliability was examined using intra-class correlation coefficients (ICC), standard error of measurement (SEM), and Bland and Altman plots. The results demonstrated that inter-rater reliability was good between raters (ICC₂,₃ = 0.81, SEM = 0.94 mm) and was moderate for the same rater between days (ICC₃,₂ = 0.67, SEM = 1.0 mm). This study demonstrates that RUSI can be used reliably to measure muscle thickness of the middle trapezius muscle following the procedure described.

Ultrasound imaging transducer motion during clinical maneuvers: respiration, active straight leg raise test and abdominal drawing in

Clinical use of ultrasound imaging by physiotherapists is increasing; however, the clinical setting may be problematic due to variability inherent in the environment. As transducer motion interferes with accurate measurement, this study aimed to measure handheld transducer motion, relative to the pelvis, during a clinical simulation involving typical maneuvers employed in a physiotherapy assessment of the lumbopelvic region. Transducer motion about three axes and through one plane was measured (Vicon, Oxford, UK) on 12 participants during three clinical maneuvers at four abdominal imaging sites. Data were grouped and means used to determine discrepancies in transducer and pelvic motion for each imaging site/maneuver combination. None of the conditions produced large transducer motions relative to the pelvis and all findings were within previously established guidelines for acceptable amounts of transducer motion. These findings suggest that an ultrasound transducer can be held relatively stationary in a clinical setting, for the maneuvers tested.

Induced transducer orientation during ultrasound imaging: effects on abdominal muscle thickness and bladder position

The use of ultrasound imaging (USI) by physiotherapists to assess muscle behavior in clinical settings is increasing. However, there is relatively little evidence of whether the clinical environment is conducive to valid and reliable measurements. Accurate USI measurements depend on maintaining a relatively stationary transducer position, because motion may distort the image and lead to erroneous conclusions. This would seem particularly important during dynamic studies typical of a physiotherapy assessment. What is not known is how much transducer motion can occur before error is introduced. The aim of this study is to shed some light on this question. Eight healthy volunteers (19 to 52 y) participated. USI images were taken of the lateral abdominal wall (LAW) and bladder base (midline suprapubic) at various manually induced transducer orientations (approximately -10 to 10 degrees about 3 axes of rotation), which were quantified by a digital optical motion capture system. Measurements of transversus abdominis (TrA) thickness and bladder base position (cranial /caudal and anterior/posterior) were calculated. Repeated measures analysis of variance was performed to determine if the measurements obtained at the induced transducer orientations were statistically different (p<0.05) from an image corresponding to a reference or starting transducer orientation. Motion analysis data corresponding to measurements that did not differ from reference image measurements were summarized to provide a range of acceptable transducer motion (relative to the pelvis) for clockwise (CW)/counter-clockwise (CCW) rotation, cranial/caudal tilting, medial/lateral tilting and inward/outward displacement. There were no significant changes in TrA thickness measurements if CW/CCW transducer motion was <9 degrees and cranial/caudal or medial/lateral transducer tilting was <5 degrees . Further, there were no significant changes in measurements of bladder base position if CW/CCW transducer motion was <10 degrees , cranial/caudal or medial/lateral transducer tilting was <10 degrees and 8 degrees , respectively and inward/outward motion was <8 mm. These findings provide guidance on acceptable amounts of transducer motion relative to the pelvis when generating measurements of TrA thickness and bladder base position. Future sonographic studies and clinical assessment investigating these parameters could take these findings into account to improve imaging technique reliability.

Reproducibility of rehabilitative ultrasound imaging for the measurement of abdominal muscle activity: a systematic review

BACKGROUND

Rehabilitative ultrasound imaging (RUSI) measures of abdominal wall muscles are used to indirectly measure muscle activity. These measures are used to identify suitable patients and to monitor progress of motor control exercise treatment of people with low back pain.

PURPOSE

The purpose of this study was to systematically review reproducibility studies of RUSI for measuring thickness of abdominal wall muscles.

DATA SOURCES

Eligible studies were identified via searches of MEDLINE, EMBASE, and CINAHL. The authors also searched personal files and tracked references of the retrieved studies via the Web of Science Index.

STUDY SELECTION

Studies involving any type of reliability and or agreement of any type of ultrasound measurements (B or M mode) for any of the abdominal wall muscles were selected.

DATA EXTRACTION

Two independent reviewers extracted data and assessed methodological quality.

DATA SYNTHESIS

Due to heterogeneity of the studies' designs, pooling the data for a meta-analysis was not possible. Twenty-one studies were included, and these studies were typically of low quality and studied subjects who were healthy rather than people seeking care for low back pain. The studies reported good to excellent reliability for single measures of thickness and poor to good reliability for measures of thickness change (reflecting the muscle activity). Interestingly, no studies checked reliability of measures of the difference in thickness changes over time (representing improvement or deterioration in muscle activity).

CONCLUSIONS

The current evidence of the reproducibility of RUSI for measuring abdominal muscle activity is based mainly on studies with suboptimal designs and the study of people who were healthy. The critical question of whether RUSI provides reliable measures of improvement in abdominal muscle activity remains to be evaluated.

Performances of one-dimensional sonomyography and surface electromyography in tracking guided patterns of wrist extension

Electromyography (EMG) and ultrasonography have been widely used for skeletal muscle assessment. Recently, it has been demonstrated that the muscle thickness change collected by ultrasound during contraction, namely sonomyography (SMG), can also be used for assessment of muscles and has the potential for prosthetic control. In this study, the performances of one-dimensional sonomyography (1D SMG) and surface EMG (SEMG) signal in tracking the guided patterns of wrist extension were evaluated and compared, and the potential of 1D SMG for skeletal muscle assessment and prosthetic control was investigated. Sixteen adult normal subjects including eight males and eight females participated in the experiment. The subject was instructed to perform the wrist extension under the guidance of displayed sinusoidal, square and triangular waveforms at movement rates of 20, 30, 50 cycles per min. SMG and SEMG root mean squares (RMS) were collected from the extensor carpi radialis, respectively, and their RMS errors in relation to the guiding signals were calculated and compared. It was found that the mean RMS tracking errors of SMG under different movement rates were 18.9% +/- 2.6% (mean+/-SD), 18.3% +/- 4.5%, and 17.0% +/- 3.4% for sinusoidal, square and triangular guiding waveforms, while the corresponding values for SEMG were 30.3% +/- 0.4%, 29.0% +/- 2.7% and 24.7% +/- 0.7%, respectively. Paired t test showed that the RMS errors of SMG tracking were significantly smaller than those of SEMG. Significant differences in RMS tracking errors of SMG among the three movement rates (p<0.01) for all the guiding waveforms were also observed using one-way analysis of variance (ANOVA). The results suggest that SMG signal, based on further improvement, has great potential to be an alternative method to SEMG to evaluate muscle function and control prostheses.

Surplus value of hip adduction in leg-press exercise in patients with patellofemoral pain syndrome: a randomized controlled trial

BACKGROUND

A common treatment for patients with patellofemoral pain syndrome (PFPS) is strength (force-generating capacity) training of the vastus medialis oblique muscle (VMO). Hip adduction in conjunction with knee extension is commonly used in clinical practice; however, evidence supporting the efficacy of this exercise is lacking.

OBJECTIVE

The objective of this study was to determine the surplus effect of hip adduction on the VMO.

DESIGN

This study was a randomized controlled trial.

SETTING

The study was conducted in a kinesiology laboratory.

PARTICIPANTS

Eighty-nine patients with PFPS participated.

INTERVENTION

Participants were randomly assigned to 1 of 3 groups: hip adduction combined with leg-press exercise (LPHA group), leg-press exercise only (LP group), or no exercise (control group). Training consisted of 3 weekly sessions for 8 weeks.

MEASUREMENTS

Ratings of worst pain as measured with a 100-mm visual analog scale (VAS-W), Lysholm scale scores, and measurements of VMO morphology (including cross-sectional area [CSA] and volume) were obtained before and after the intervention.

RESULTS

Significant improvements in VAS-W ratings, Lysholm scale scores, and VMO CSA and volume were observed after the intervention in both exercise groups, but not in the control group. Significantly greater improvements for VAS-W ratings, Lysholm scale scores, and VMO volume were apparent in the LP group compared with the control group. There were no differences between the LP and LPHA groups for any measures.

LIMITATIONS

Only the VMO was examined by ultrasonography. The resistance level for hip adduction and the length of intervention period may have been inadequate to induce a training effect.

CONCLUSIONS

Similar changes in pain reduction, functional improvement, and VMO hypertrophy were observed in both exercise groups. Incorporating hip adduction with leg-press exercise had no impact on outcome in patients with PFPS.

Comparison of curvilinear and linear ultrasound imaging probes for measuring cross-sectional area and linear dimensions

The aim of the study was to determine whether different ultrasound probe/transducer configurations produce the same measurements. Two investigators undertook 10 scans of a general purpose semi-solid multi-tissue ultrasound phantom (phantom A) using two ultrasound scanners with a linear and curvilinear probe. From those 10 scans, two measurements of cross-sectional area (CSA), width and thickness were made. These measurements were then repeated with an open-top fluid-filled phantom, with 10% ethanol solution (phantom B). Intra- and inter-rater reliability were examined using Bland and Altman plots. Agreement between measurements made with the two probe types was also assessed using Bland and Altman plots. An independent samples t-test was used to compare statistical differences between probe type configuration. There was a significant difference (p < 0.05) and a tendency for increased measurements in CSA and width, and decreased measurements in thickness when using a curvilinear probe on phantom A, and these differences were not scanner specific. When imaging phantom B there were no significant differences in measurements between probe configurations; however there was a small bias for smaller CSA measurements with a curvilinear probe. In conclusion there are small differences in measurements obtained from different ultrasound probe configurations using a semi-solid phantom, but their clinical significance is unknown.

The validity of Rehabilitative Ultrasound Imaging for measurement of trapezius muscle thickness

The purpose of the study was to establish the validity of Rehabilitative Ultrasound Imaging (RUSI) against Magnetic Resonance Imaging (MRI) for measuring trapezius muscle thickness. Participants were asymptomatic subjects recruited from Trinity College Dublin and associated teaching hospitals. Four MRI axial slices were made through each of the C6, T1, T5 and T8 spinous processes, with the subject supine. RUSI was performed immediately after MRI at the same vertebral levels, with the subject prone. Linear measurements of trapezius muscle thickness were made off-line on both the MRI and Ultrasound scans, in three regions: lower, middle and upper trapezius. Bland and Altman limits of agreement and Pearson's correlation coefficient were used to analyse the relationship between thickness measures taken from MRI and RUSI. Eighteen subjects (9 women) participated, (age-range 21-42 years). Results demonstrated good agreement between MRI and RUSI measurements of the lower trapezius muscle at T8 (r=0.77) and moderate agreement at T5, (r=0.62). Results were poor for the middle (T1) and upper (C6) trapezius muscles, (r=-0.22 to 0.52) but may be explained by differences in both positioning and imaging planes between the 2 modalities. It was concluded that RUSI is a valid method of measuring lower trapezius muscle thickness.

Changes in deep abdominal muscle thickness during common trunk-strengthening exercises using ultrasound imaging

STUDY DESIGN

Cross-sectional study design.

OBJECTIVES

To characterize changes in muscle thickness in the transversus abdominis (TrA) and internal oblique (IO) muscles during common trunk-strengthening exercises, and to determine whether these changes differ based on age.

BACKGROUND

Although trunk-strengthening exercises have been found to be useful in treating those with low back pain (LBP), our understanding of the relative responses of the TrA and IO muscles during different exercises is limited.

METHODS AND MEASURES

Six commonly prescribed trunk-strengthening exercises were performed by 120 subjects (40 subjects per age group: 18-30, 31-40, and 41-50 years). Ultrasound imaging was used to measure the thickness of the TrA and IO during the resting and contracted state of each exercise. The average thickness of the muscles while in the contracted position was divided by the thickness values in the resting position for each exercise, based on 2 performances of each exercise. Two 3-by-6 repeated-measures analyses of variance were used to determine significant changes in muscle thickness of the TrA and IO, based on age group and exercise performed.

RESULTS

For both muscles, the trunk exercise-by-age interaction effect (TrA, P = .358; IO, P = .217) and the main effect for age (TrA, P = .615; IO, P = .219) were not significant. A significant main effect for trunk exercise for both muscles (P<.001) was found. The horizontal side-support (mean +/- SD contracted-rest thickness ratio: TrA, 1.95 +/- 0.69; IO, 1.88 +/- 0.52) and the abdominal crunch (mean +/- SD contracted-rest thickness ratio: TrA, 1.74 +/- 0.48; IO, 1.63 +/- 0.41) exercises resulted in the greatest change in muscle thickness for both muscles. The abdominal drawing-in maneuver (mean +/- SD contracted-rest thickness ratio: TrA, 1.73 +/- 0.36; IO, 1.14 +/- 0.33) and quadruped opposite upper and lower extremity lift (mean +/- SD contracted-rest thickness ratio: TrA, 1.59 +/- 0.49; IO, 1.25 +/- 0.36) exercises resulted in changes in TrA muscle thickness with minimal changes in IO muscle thickness.

CONCLUSION

Changes in TrA and IO muscle thickness differed across 6 commonly prescribed trunk-strengthening exercises among healthy subjects without LBP. These differences did not vary by age. This information may be useful for informing exercise prescription.

A low-cost B-mode USB ultrasound probe

The Universal Serial Bus (USB) is now the ubiquitous interface bus of choice for connecting peripherals to personal computers and laptops. USB 2.0 is a half-duplex bus running at 480 Mb/s and each peripheral can draw as much as 500 mA of current at a nominal 5 V from the USB connector. We have developed a family of USB-based, B-mode probes that connect directly to a personal computer or laptop and that draw as little as 250 mA (1.25 W) when forming ten 5 MHz images/second. The pulser/receiver, high voltage supply, analog-to-digital converter, servo and USB interface are implemented on a small circuit board inside the probe body. After raw data are transferred to the computer, gain compensation, interpolation, filtering and other data processing are performed by the host processor. This gives flexibility to developers and allows enhancements to the system to be incorporated via software updates. In addition, the raw data are available for storage and later postprocessing. There are several advantages to this architectural approach to B-mode imaging, including low cost, portability and optimal signal-to-noise performance. This paper describes the advantages of the architecture of the probe family, discusses the hardware/software division of the required processing steps and presents example images from a 12.5 MHz ophthalmic probe.

Rehabilitative ultrasound imaging of the posterior paraspinal muscles

Interest in rehabilitative ultrasound imaging (RUSI) of the posterior paraspinal muscles is growing, along with the body of literature to support integration of this technique into routine physical therapy practice. This clinical commentary reviews how RUSI can be used as an evaluative and treatment tool and proposes guidelines for its use for the posterior muscles of the lumbar and cervical regions. Both quantitative and qualitative applications are described, as well as measurement reliability and validity. Measurement of morphological characteristics of the muscles (morphometry) in healthy populations and people with spinal pathology are described. Preliminary normal reference data exist for measurements of cross-sectional area (CSA), linear dimensions (muscle depth/thickness and width), and shape ratios. Compared to individuals without low back pain, changes in muscles' size at rest and during the contracted state have been observed using RUSI in people with spinal pathology. Visual observation of the image during contraction indicates that RUSI may be a valuable biofeedback tool. Further investigation of many of these observations is required using controlled studies to provide conclusive evidence that RUSI enhances clinical practice.

Rehabilitative ultrasound imaging of the abdominal muscles

Rehabilitative ultrasound imaging (RUSI) of the abdominal muscles is increasingly being used in the management of conditions involving musculoskeletal dysfunctions associated with the abdominal muscles, including certain types of low back and pelvic pain. This commentary provides an overview of current concepts and evidence related to RUSI of the abdominal musculature, including issues addressing the potential role of ultrasound imaging in the assessment and training of these muscles. Both quantitative and qualitative aspects associated with clinical and research applications are considered, as are the possible limitations related to the interpretation of measurements made with RUSI. Research to date has utilized a range of methodological approaches, including different transducer placements and imaging techniques. The pros and cons of the various methods are discussed, and guidelines for future investigations are presented. Potential implications and opportunities for clinical use of RUSI to enhance evidence-based practice are outlined, as are suggestions for future research to further clarify the possible role of RUSI in the evaluation and treatment of abdominal muscular morphology and function.