The lumbar multifidi muscles have been shown to atrophy after the first episode of low back pain and do not recover as a matter of course.1 The lumbar multifidi muscles are not considered prime movers of the spine; they are rich in muscle spindles and provide continuous feedback on segmental position, which contributes to spinal stability. This atrophy of the lumbar multifidi muscles may be a factor in length of recovery and high reoccurrence of low back pain among athletes. Exercise programs directed at strengthening the lumbar multifidi muscles have been shown to increase the cross-sectional area of the muscles, reduce pain, and improve function in athletes with low back pain.2 It has been proposed that the abdominal muscles, particularly the transversus abdominus, contribute to spine stability via their effects on intra-abdominal pressure and by affecting fascial tension.3 Documented motor control changes of the transversus abdominus muscle are associated with a higher long-term incidence of low back pain.3 Hides et al. found that patients who performed specific exercises to strengthen the transversus abdominus and lumbar multifidi muscles had a lower reoccurrence of back pain after 1 (30% vs 84%) and 2 (35% vs 75%) years.4
Ultrasound imaging is a noninvasive way to evaluate the size and dynamic behavior of trunk muscles and to provide real-time feedback to athletes with low back pain during motor control training.5 Ultrasound imaging has demonstrated measurement agreement of muscle thickness with magnetic resonance imaging6 and muscle contraction with electromyography.7 Inter-tester and intra-tester reliability has been established for ultrasound imaging of the trunk muscles for experienced and novice examiners.8,9
There are many ultrasound units on the market. A unit equipped with a low frequency (3 to 5 MHz) linear or curvilinear probe is typically used to image the trunk muscles.
The assessment of the transversus abdominus muscle is performed with the athlete supine in the hook-lying position with a pillow under the head. The transducer is placed transversely midway between the iliac crest and the inferior angle of the rib cage in the mid axillary line (Figure 1). The position of the transducer is manipulated until all three muscles (external oblique, internal oblique, and transversus abdominus) are visualized (Figure 1). To standardize the position of the transducer, the anterior fascial insertion of the transversus abdominus muscle is positioned within the field of view approximately 2 cm from the medial edge of the ultrasound image.3
Assessment of the transversus abdominus muscle (TA). EO = external oblique muscle; IO = internal oblique muscle
The transversus abdominus is an accessory respiratory muscle actively involved in voluntary expiration. The relaxed transversus abdominus image is acquired at the end of quiet inspiration.9 Once all three muscles are clearly in view, the image is captured and saved electronically. Muscle thickness is then measured, using digital calipers, as the distances between the hyperechoic superficial and deep muscle fascia of the transversus abdominus muscle at the thickest portion of the image (Figure 1).
To measure muscle activity, instructions on how to draw in the abdominal wall are given (take a relaxed breath in and out, hold the breath out, and then raise your belly button up into the arch of your rib cage toward your spine) and the contraction is held while the image is captured. Muscle thickness is measured as previously described. The difference in thickness between the two images is divided by the resting thickness and multiplied by 100 to get the percent of change.10 The percent of change is considered the degree of transversus abdominus muscle contraction. Initial measurements can be used to set training goals for the athlete. Normative reference ranges have been established for transversus abdominus resting and contraction thickness and are available for comparison.10
The assessment of the lumbar multifidi muscle is performed with the athlete lying prone with a pillow under the stomach for comfort (Figure 2). The transducer is positioned longitudinally at the midline of the lumbar spine, then moved slightly laterally and angled medially to obtain the image of the zygapophyseal joints, lumbar multifidi muscle, and thoracolumbar fascia.8 The perpendicular distance between the dorsal edge of the facet joint and the internal border of thoracolumbar fascia is considered the thickness of the lumbar multifidi muscle (Figure 2). The image is captured and then digital calipers are used to take the measurement.
Assessment of the lumbar multifidi muscles (LM).
The contraction image is acquired by lifting the contralateral arm off the plinth and holding it isometrically. This maneuver causes the lumbar multifidi muscle to contract in an effort to stabilize the spine. A 1- to 2-pound dumbbell can also be used to help facilitate the contraction. A second image is captured, measured, and compared to the resting thickness (Figure 2). The difference in thickness between the two images is divided by the resting thickness and multiplied by 100 to get the percent of change.10 The percent of change is considered the degree of lumbar multifidi muscle contraction.
Ultrasound images can provide valuable real-time feedback during motor control training. The athlete can quickly learn to engage the transversus abdominus and lumbar multifidi muscles, thereby stabilizing the spine, while performing specific core exercises. Once the athlete is able to effectively engage the core muscles, sports-specific movements are added to the rehabilitation program. Ultrasound imaging is gaining popularity with physicians, physical therapists, and athletic trainers alike. The cost for basic units has dropped considerably, making it an affordable, noninvasive option for evaluating trunk muscle function in athletes with low back pain.
- Hides J, Richardson C, Jull G. Multifidus muscle recovery is not automatic after resolution of acute first episode low back pain. Spine. 1996;21:2763–2769. doi:10.1097/00007632-199612010-00011 [CrossRef]
- Hides JA, Stanton W, McMahon S, Sims K, Richardson C. An effect of stabilization training on multifidus muscle cross-sectional area among young elite cricketers with low back pain. J Orthop Sports Phys Ther. 2008;38:101–108. doi:10.2519/jospt.2008.2658 [CrossRef]
- Hodges PW, Richardson CA. Insufficient muscular stabilization of the lumbar spine associated with low back pain: a motor control evaluation of transversus abdominus. Spine. 1996;21:2640–2650. doi:10.1097/00007632-199611150-00014 [CrossRef]
- Hides JA, Jull GA, Richardson CA. Long-term effects of specific stabilizing exercises for first-episode low back pain. Spine. 2001;26:E243–E248. doi:10.1097/00007632-200106010-00004 [CrossRef]
- Whittaker JL, Teyhen DS, Elliot JM, et al. Rehabilitative ultrasound imaging: understanding the technology and its application. J Orthop Sports Phys Ther. 2007;37:434–449. doi:10.2519/jospt.2007.2350 [CrossRef]
- Hides JA, Richardson CA, Jull GA. Magnetic resonance imaging and ultrasonography of the lumbar multifidus muscle: comparison of two different modalities. Spine. 1995;20:54–58. doi:10.1097/00007632-199501000-00010 [CrossRef]
- Vasseljen O, Dahl HH, Mork PJ, Torp HG. Muscle activity onset in the lumbar multifidus muscle recorded simultaneously by ultrasound imaging and intramuscular electromyography. Clin Biomech. 2006;21:905–913. doi:10.1016/j.clinbiomech.2006.05.003 [CrossRef]
- Wong AY, Parent EC, Kawchuk GN. Reliability of 2 ultrasonic imaging analysis methods in quantifying lumbar multifidus thickness. J Orthop Sports Phys Ther. 2013;43:251–262. doi:10.2519/jospt.2013.4478 [CrossRef]
- Djordjevic O, Djordjevic A, Konstantinovic L. Interrater and intrarater reliability of transvers abdominal and lumbar multifidus muscle thickness in subjects with and without low back pain. J Orthop Sports Phys Ther. 2014;44:979–988. doi:10.2519/jospt.2014.5141 [CrossRef]
- Teyhen DS, Childs JD, Stokes MJ, Wright AC, Dugan JL, George SZ. Abdominal and lumbar muscle size and symmetry at rest and during contracted states: normative reference ranges. J Ultrasound Med. 2012;311099–31110.