MRI Assessment of Swallow Muscle Activation with the Swallow Exercise Aid and with Conventional Exercises in Healthy Volunteers: An Explorative Biomechanical Study.

Swallowing muscle strength exercises are effective in restoring swallowing function. In order to perform the exercises with progressive load, the swallow exercise aid (SEA) was developed. Precise knowledge on which muscles are activated with swallowing exercises, especially with the SEA, is lacking. This knowledge would aid in optimizing the training program to target the relevant swallowing muscles, if necessary. Three healthy volunteers performed the three SEA exercises (chin tuck against resistance, jaw opening against resistance and effortful swallow) and three conventional exercises [conventional effortful swallow (cES), Shaker and Masako] in supine position inside an MRI scanner. Fast muscle functional MRI scans (generating quantitative T2-maps) were made immediately before and after the exercises. Median T2 values at rest and after exercise were compared to identify activated muscles. After the three SEA exercises, the suprahyoid, infrahyoid, sternocleidomastoid, and lateral pterygoid muscles showed significant T2 value increase. After the Shaker, the lateral pterygoid muscles did not show such an increase, but the three other muscle groups did. The cES and Masako caused no significant increase in any of these muscle groups. During conventional (Shaker) exercises, the suprahyoid, infrahyoid, and sternocleidomastoid muscles are activated. During the SEA exercises, the suprahyoid, infrahyoid, sternocleidomastoid, and lateral pterygoid muscles are activated. The findings of this explorative study further support the potential of the SEA to improve swallowing rehabilitation.

The influence of induced shoulder muscle pain on rotator cuff and scapulothoracic muscle activity during elevation of the arm.

BACKGROUND: Altered recruitment of rotator cuff and scapulothoracic muscles has been identified in patients with subacromial impingement syndrome. To date, however, the cause-consequence relationship between pain and altered muscle recruitment has not been fully unraveled. METHODS: The effect of experimental shoulder pain induced by injection of hypertonic saline in the supraspinatus on the activity of the supraspinatus, infraspinatus, subscapularis, trapezius, and serratus anterior activity was investigated during the performance of an elevation task by use of muscle functional magnetic resonance imaging in 25 healthy individuals. Measurements were taken at 4 levels (C6-C7, T2-T3, T3-T4, and T6-T7) at rest and after the elevation task performed without and with experimental shoulder pain. RESULTS: During arm elevation, experimentally induced pain caused a significant activity reduction, expressed as reduction in T2 shift of the IS (P = .029). No significant changes in T2 shift values were found for the other rotator cuff muscles or the scapulothoracic muscles. CONCLUSIONS: This study demonstrates that acute experimental shoulder pain has an inhibitory effect on the activity of the IS during arm elevation. Acute experimental shoulder pain did not seem to influence the scapulothoracic muscle activity significantly. The findings suggest that rotator cuff muscle function (infraspinatus) should be a consideration in the early management of patients with shoulder pain.

Intrinsic Foot Muscle Activation During Specific Exercises: A T2 Time Magnetic Resonance Imaging Study.

CONTEXT: The intrinsic foot muscles maintain the medial longitudinal arch and aid in force distribution and postural control during gait. Impaired intrinsic foot-muscle function has been linked to various foot conditions. Several rehabilitative exercises have been proposed to improve it; however, literature that identifies which individual muscles are activated during specific intrinsic foot-muscle exercises is lacking. OBJECTIVE: To describe changes in activation of the intrinsic plantar foot muscles after 4 exercises as measured with T2 magnetic resonance imaging (MRI). DESIGN: Descriptive laboratory study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Eight healthy National Collegiate Athletic Association Division I collegiate cross-country and track athletes (5 men and 3 women: age = 20 ± 0.93 years, height = 180.98 ± 10.84 cm, mass = 70.91 ± 7.82 kg). INTERVENTION(S): Participants underwent T2 MRI before and after each exercise. They completed 1 set of 40 repetitions of each exercise (short-foot exercise, toes spread out, first-toe extension, second- to fifth-toes extension). MAIN OUTCOME MEASURE(S): Percentage increases in muscle activation of the abductor hallucis, flexor digitorum brevis, abductor digiti minimi, quadratus plantae, flexor digiti minimi, adductor hallucis oblique, flexor hallucis brevis, and interossei and lumbricals (analyzed together) after each exercise were assessed using T2 MRI. RESULTS: All muscles showed increased activation after all exercises. The mean percentage increase in activation ranged from 16.7% to 34.9% for the short-foot exercise, 17.3% to 35.2% for toes spread out, 13.1% to 18.1% for first-toe extension, and 8.9% to 22.5% for second- to fifth-toes extension. All increases in activation had associated 95% confidence intervals that did not cross zero. CONCLUSIONS: Each of the 4 exercises was associated with increased activation in all of the plantar intrinsic foot muscles evaluated. These results may have clinical implications for the prescription of specific exercises to target individual intrinsic foot muscles.

The effect of experimental low back pain on lumbar muscle activity in people with a history of clinical low back pain: a muscle functional MRI study.

In people with a history of low back pain (LBP), structural and functional alterations have been observed at several peripheral and central levels of the sensorimotor pathway. These existing alterations might interact with the way the sensorimotor system responds to pain. We examined this assumption by evaluating the lumbar motor responses to experimental nociceptive input of 15 participants during remission of unilateral recurrent LBP. Quantitative T2 images (muscle functional MRI) were taken bilaterally of multifidus, erector spinae, and psoas at several segmental levels (L3 upper and L4 upper and lower endplate) and during several conditions: 1) at rest, 2) upon trunk-extension exercise without pain, and 3) upon trunk-extension exercise with experimental induced pain at the clinical pain-side (1.5-ml intramuscular hypertonic saline injections in erector spinae). Following experimental pain induction, muscle activity levels similarly reduced for all three muscles, on both painful and nonpainful sides, and at multiple segmental levels (P = 0.038). Pain intensity and localization from experimental LBP were similar as during recalled clinical LBP episodes. In conclusion, unilateral and unisegmental experimental LBP exerts a generalized and widespread decrease in lumbar muscle activity during remission of recurrent LBP. This muscle response is consistent with previous observed patterns in healthy people subjected to the same experimental pain paradigm. It is striking that similar inhibitory patterns in response to pain could be observed, despite the presence of preexisting alterations in the lumbar musculature during remission of recurrent LBP. These results suggest that motor output can modify along the course of recurrent LBP.

Effect of pre-fatigue method by leg extension exercise on recruitment state of synergists in thigh muscles during leg press exercise / 体力科学

The purpose of this study was to examine the recruitment state of synergistic muscles in the thigh muscles in leg press exercise with and without pre-fatigue method using transverse relaxation time (T2) on muscle functional magnetic resonance imaging (MRI). Nine healthy male subjects performed the following two types of exercise trials on separate days: 1) 5 sets of a leg press exercise with pre-fatigue method, which consisted of 3 sets of knee extension exercise (LP-pre), 2) 5 sets of a leg press exercise without pre-fatigue method (LP). Both exercises were performed at a load of 80% one-repetition maximum. Before and immediately after exercise, T2-weighted MR images of right-thigh were taken to calculate T2 values of twelve-thigh muscles. The T2 values for quadriceps femoris muscle and hamstrings in LP increased significantly after the exercise, except in the adductor magnus, adductor longus, gracilis, and sartorius. In contrast, the T2 values for all of the twelve-thigh muscles in LP-pre increased significantly after the exercise. Upon comparison between the two trials, the percentage changes in T2 value for the adductor magnus, adductor longus, and sartorius in LP-pre were found to be significantly greater than those in LP. These results suggest leg press exercise with pre-fatigue method may be effective to increase activity of synergistic muscles in thigh muscles during exercise.