Effect of Spinal Sagittal Alignment in Sitting Posture on Swallowing Function in Healthy Adult Women: A Cross-Sectional Study.

Swallowing function is both directly and indirectly related to postures, such as head and cervical angle and body position. However, the effects of different sitting postures on oropharyngeal swallowing have not been investigated. This study aimed to investigate whether the change in thoracolumbar alignment affected the oropharyngeal swallowing. A total of 58 healthy adult women (mean age 22.2 ± 1.67 years) without dysphagia were enrolled in this cross-sectional study. Participants were positioned in three sitting postures: comfortable sitting (CS), thoracic upright sitting (TUS), and slump sitting (SS). In each sitting posture, the kyphosis index (using a flexicurve), head and cervical angles (using a digital camera), swallowing speed (100-ml water swallowing test), and oral and articulatory function [by maximum tongue pressure (MTP) and oral diadochokinesis (ODK)] were evaluated. SS showed the largest kyphosis index and was associated with a greater anterior translation of the head. Swallowing speed was significantly decreased in SS compared with CS (p = 0.002) and TUS (p = 0.020) and ODK was significantly decreased in SS compared with other postures, for both /ta/ (p = 0.004) and /ka/ (p < 0.001) syllables. Further, MTP tended to decrease in SS compared with TUS (p = 0.064). Our results suggest that changes in sitting posture with different thoracolumbar alignments affect swallowing speed and oral and articulatory function. Consequently, adjustments to reduce sitting postural kyphosis may improve swallowing speed and oral and articulatory function.

Trunk muscle activation patterns during active hip abduction test during remission from recurrent low back pain: an observational study.

BACKGROUND: The active hip abduction test (AHAbd) is widely used to evaluate lumbopelvic stability, but the onset of trunk muscle activation during the test in individuals with recurrent low back pain (rLBP) has not been investigated so far. It is important to investigate the pattern of trunk muscle activation during the AHAbd test to provide insight into the interpretation of observation-based assessment results; this may help to create exercise therapy interventions, from a movement control perspective, for people seeking treatment for rLBP. The purpose of this study was to compare the timing of trunk muscle activation between individuals with and without rLBP and to assess potential differences. METHODS: Seventeen subjects in remission from rLBP and 17 subjects without rLBP were recruited. We performed surface electromyography of the transversus abdominis/internal abdominal oblique, external oblique, erector spinae, and gluteus medius muscles during the AHAbd test on both sides. The onset of trunk muscle activation was calculated relative to the prime mover gluteus medius. The independent-samples t- and Mann-Whitney U tests were used to compare the onset of trunk muscle activation between the two groups. RESULTS: The onset of transversus abdominis/internal abdominal oblique activation on the ipsilateral (right AHAbd: -3.0 ± 16.2 vs. 36.3 ± 20.0 msec, left AHAbd: -7.2 ± 18.6 vs. 29.6 ± 44.3 ms) and contralateral sides (right AHAbd: -11.5 ± 13.9 vs. 24.4 ± 32.3 ms, left AHAbd: -10.1 ± 12.5 vs. 23.3 ± 17.2 ms) and erector spinae on the contralateral side (right AHAbd: 76.1 ± 84.9 vs. 183.9 ± 114.6 ms, left AHAbd: 60.7 ± 70.5 vs. 133.9 ± 98.6 ms) occurred significantly later in individuals with rLBP than in individuals without rLBP (p < 0.01). During the left AHAbd test, the ipsilateral erector spinae was also activated significantly later in individuals with rLBP than in individuals without rLBP (71.1 ± 80.1 vs. 163.8 ± 120.1 ms, p < 0.05). No significant difference was observed in the onset of the external oblique activation on the right and left AHAbd tests (p > 0.05). CONCLUSIONS: Our results suggest that individuals with rLBP possess a trunk muscle activation pattern that is different from that of individuals without rLBP. These findings provide an insight into the underlying muscle activation patterns during the AHAbd test for people with rLBP and may support aggressive early intervention for neuromuscular control.

Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site.

Tsubahara A, Kamiue M, Ito T, Kishimoto T, Kurozumi C. Measurement of maximal muscle contraction force induced by high-frequency magnetic stimulation: a preliminary study on the identification of the optimal stimulation site. Jpn J Compr Rehabil Sci 2021; 12: 27-31. Purpose: To identify the optimal stimulation site and technique for inducing strong muscle contraction using a high-frequency magnetic stimulator. Methods: High-frequency magnetic stimulation was administered to the right vastus lateralis (VL) of eight healthy adults at maximal intensity within the range of tolerable pain. The stimulation sites were as follows: section A, the area between the lateral edge of the base of the patella (LEBP) and the distal one-third of the thigh (point D); section B, the area between point D and the proximal one-third of the thigh (point P). Isometric maximal muscle contraction forces induced by magnetic stimulation (Stim-MCF) were compared between the two sections. Results: The Stim-MCF was significantly higher in section B than in section A. Additionally, the sites susceptible to stimulation were confined to a narrow area near point D in section A and the central part between points D and P in section B. The degree of pain was very low in both sections. Conclusion: The optimal site for magnetic stimulation of the VL was limited to the central part of the thigh. In addition to the superficial proximal sub-branch, the deep proximal sub-branch and/or deeply clustered motor nerve endings may have been stimulated. Our results suggested that moving the probe was a useful way to identify the site that elicited the strongest muscle contraction force.

Immediate changes in trunk muscle activation patterns during a lifting task following an abdominal drawing-in exercise in subjects with recurrent low back pain.

BACKGROUND: The abdominal drawing-in exercise could help improve delayed transversus abdominis (TrA) activation during limb movement in subjects with recurrent low back pain (rLBP). However, little is known about whether the same effect is observed during lifting tasks in subjects with rLBP. OBJECTIVE: This study aimed to clarify whether a single session of abdominal drawing-in exercise could correct the altered trunk muscle activation patterns during a lifting task in subjects with rLBP. METHODS: Fifteen subjects with rLBP performed lifting tasks before and immediately after three sets of 10 repetitions of isolated TrA voluntary contractions. The time of onset and activation amplitude during the lifting tasks were measured by surface electromyography (EMG) and compared between the trials before and immediately after exercise. RESULTS: During lifting, the onset of internal abdominal oblique/TrA (IO/TrA) and multifidus activation occurred earlier, the EMG amplitude of IO/TrA increased, and the EMG amplitude of erector spinae and multifidus decreased, compared with the pre-exercise data. CONCLUSIONS: These results suggest a possibility that the abdominal drawing-in exercise might be effective in improving the muscle recruitment pattern in people with rLBP.

Correlation between peak expiratory flow and abdominal muscle activity in elderly women while holding maximum expiration and performing the side bridge exercise.

INTRODUCTION: Expiratory flow is important to minimize the risk of infection by expelling foreign substances from the lungs. Abdominal muscle activities primarily produce expiratory flow. However, data on the association of abdominal muscle activity during expiratory effort and abdominal exercise posture with expiratory flow rate is limited. This study aimed to assess the correlation between expiratory flow and abdominal muscle activity while holding maximum expiration and performing the side bridge exercise in elderly women. METHODS: Rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscle activity was measured using electromyography in 14 elderly women (82.8 ±â€¯6.7 years), who could walk independently while performing 2 tasks: holding their breath after maximum expiration in the crook-lying position (maximum expiration), and performing the side bridge exercise on their knees without breathing instruction (side bridge). Peak expiratory flow (PEF) was obtained using a peak flow meter. Correlations between PEF and the abdominal muscle activity were determined using the Spearman rank correlation coefficient. RESULTS: The correlation coefficients between PEF and RA, EO, and IO activity while holding maximum expiration were 0.407 (p = 0.149), -0.345 (p = 0.227), and 0.732 (p = 0.003), respectively. The correlation coefficients between PEF and RA, EO, and IO activity while performing the side bridge exercise were -0.297 (p = 0.303), -0.552 (p = 0.041), and 0.147 (p = 0.615), respectively. CONCLUSIONS: Higher IO activity while holding maximum expiration or lower EO activity while performing the side bridge exercise was related to higher PEF. Thus, maximum expiration and abdominal exercise might be effective in the improvement or prevention of the decrease of expiratory flow.

Effect of pelvic belt on the perception of difficulty and muscle activity during active straight leg raising test in pain-free subjects.

A pelvic belt decreases patient-reported perception of difficulty during the active straight leg raising (ASLR) test in individuals with pelvic girdle pain. However, the influence of a pelvic belt on the perception of difficulty during ASLR was not investigated in pain-free subjects. Therefore, this influence excluding the impact of pain is not clear. This paper aimed to clarify the effect of a pelvic belt on the perception of difficulty and muscle activity during ASLR performance in the subjective heavier side leg in pain-free subjects. Twenty pain-free female subjects participated. ASLR using the subjective heavier side leg was performed under two conditions: without and with a pelvic belt. Muscle activation of the external oblique, internal oblique, rectus abdominis, rectus femoris, and biceps femoris was measured during ASLR using a surface electromyograph. Difference in perceived difficulty in performing ASLR with and without a belt was assessed. In total, 80% of subjects had decreased perception of difficulty using a pelvic belt during ASLR. For ASLR performed with a pelvic belt, muscle activity significantly decreased in the contralateral rectus abdominis, ipsilateral external oblique, and bilateral internal oblique (P<0.05), while it significantly increased in the contralateral biceps femoris (P<0.05). There were no significant differences in muscle activity of the ipsilateral rectus abdominis, contralateral external oblique, and ipsilateral rectus femoris between the two conditions (P>0.05). In conclusion, using a pelvic belt can decrease the perception of difficulty during ASLR, and the pelvic belt may improve impairment of load transfer between the trunk and pelvis.

Correlation between deep cervical flexor muscle thickness at rest and sternocleidomastoid activity during the craniocervical flexion test.

The purpose of this study was to clarify the relationship between the thickness of the deep cervical flexor muscles (longus capitis and longus colli) at rest and sternocleidomastoid activity during the craniocervical flexion test (CCFT). Thirteen healthy males participated in this study. The thickness of the deep cervical flexor muscles was measured by ultrasound imaging in a relaxed supine position. Activity of the sternocleidomastoid was measured by electromyography during the CCFT at five incremental levels (22, 24, 26, 28, and 30 mm Hg). Correlations between normalized muscle thickness relative to body mass index and sternocleidomastoid activity were determined. Significant negative correlations were observed between normalized muscle thickness and activity of the sternocleidomastoid at 26 (r = -0.622, P = 0.023) and 28 mmHg (r = -0.653, P = 0.015). Individuals with smaller deep cervical flexor muscles exhibited increased activity in the sternocleidomastoid during the CCFT.

Comparison between the effectiveness of expiration and abdominal bracing maneuvers in maintaining spinal stability following sudden trunk loading.

The purpose of this study was to clarify the effectiveness of expiration and abdominal bracing maneuvers in response to sudden trunk loading in healthy subjects. Fifteen healthy male subjects were anteriorly loaded under different experimental conditions. Tests were conducted at rest and while performing each of the stabilization maneuvers (expiration and abdominal bracing) at 15% of the maximal voluntary isometric contraction of the internal oblique muscle. Subjects had no knowledge of the perturbation timing. An electromyographic biofeedback system was used to control the intensity of internal oblique muscle activation. Muscular pre-activation of three trunk muscles (internal oblique, external oblique, and L3 erector spinae muscles) and lumbar acceleration in response to loading were measured. The expiration and abdominal bracing maneuvers promoted torso co-contraction, reduced the magnitude of lumbar acceleration, and increased spinal stability compared to the resting condition. There were no differences between the expiration and abdominal bracing maneuvers in the pre-activation of the three trunk muscles or in lumbar acceleration in response to loading. It appears that both expiration and abdominal bracing maneuvers are effective in increasing spinal stability in response to sudden anterior loading.

Correlation between neck slope angle and deep cervical flexor muscle thickness in healthy participants.

The purpose of this study was to clarify the correlation between neck slope angle and deep cervical flexor muscle thickness in healthy subjects. Forty-two healthy male (20.7 ± 2.6 years old) participated in this study. Neck slope angle was measured in a relaxed sitting posture. The deep cervical flexor muscle thickness was measured in a relaxed supine posture. The correlations between neck slope angle and normalized muscle thickness relative to body mass index were determined using Pearson's correlation coefficient. There was a moderate positive correlation between neck slope angle and normalized muscle thickness (r = 0.414, P = 0.006). The result demonstrated that participants with lower neck slope angles had smaller muscle thicknesses of the deep cervical flexor muscles. It appears that the deep cervical flexor muscle thickness might be associated with neck slope angle in a relaxed sitting posture.

Correlation Between Abdominal Muscle Thickness and Maximal Expiratory Pressure.

OBJECTIVES: The activity of abdominal muscles mainly produces high expiratory pressure. These include the rectus abdominis, external oblique, internal oblique, and transverse abdominis muscles. The purpose of this study was to determine whether maximal expiratory pressure is associated with each abdominal muscle thickness at rest. METHODS: Thirty-nine healthy male volunteers (mean age ± SD, 20.7 ± 2.7 years) participated in the study. The thickness of the right rectus abdominis, external oblique, internal oblique, and transverse abdominis muscles was measured by B-mode sonography in the supine position. The maximal expiratory pressure was obtained with a spirometer in the sitting position. The correlations between each abdominal muscle thickness and maximal expiratory pressure were determined by the Pearson correlation coefficient. RESULTS: The correlation coefficient between the rectus abdominis muscle and maximal expiratory pressure was 0.571 (P< .001). Correlation coefficients between the external oblique, internal oblique, and transverse abdominis muscles and maximal expiratory pressure were 0.297 (P = .066), 0.267 (P = .100), and 0.022 (P = .894), respectively. CONCLUSIONS: Our results indicate that the rectus abdominis muscle thickness might be more highly correlated with expiratory pressure production than the external oblique, internal oblique, and transverse abdominis muscle thickness.

Ultrasound imaging of the diagonal dimension of the deep cervical flexor muscles: A reliability study on healthy subjects.

The purpose of this study is to assess the reliability of a new ultrasound imaging (USI) parameter and procedure for the evaluation of the size of the deep cervical flexor (DCF) muscles. Thirty-one healthy male subjects (21.6 ± 2.5 years old) participated in this study. Two images of the diagonal dimension (DD) of the DCF of the subjects, at 1.5 fingerbreadths below the laryngeal prominence of the thyroid cartilage in a relaxed state, were taken on separate days with a 1-week interval. The intraclass correlation coefficient between the days was 0.82 (95% confidence interval, 0.65-0.91). The standard error of measurement and minimal detectable change were 0.8 mm and 2.1 mm, respectively. The results indicated that the DD may be used as a reliable USI parameter to measure the DCF thickness in healthy subjects.

Correlation between Peak Expiratory Flow and Abdominal Muscle Thickness.

[Purpose] The purpose of this study was to determine whether forced expiration is correlated with abdominal muscle thickness. [Subjects] Twenty-three healthy male volunteers participated in this study. [Methods] The peak expiratory flow (PEF) was obtained using a peak flow meter with subjects in the sitting position. The thicknesses of the right rectus abdominis, external oblique, internal oblique, and transverse abdominis muscles were measured using B-mode ultrasonography at the end of a relaxed expiration in the supine position. [Results] Among the abdominal muscles, only the thickness of the external oblique muscle displayed a significant correlation with PEF. [Conclusion] It appears that the thickness of the external oblique muscle might be associated with PEF during forced expiration.

Emetic stimulation inhibits the swallowing reflex in decerebrate rats.

The effects of emetic stimulation on the swallowing reflex were investigated in decerebrated rats. Hypoxia, gastric distension and LiCl administration were used as emetic stimulations. The swallowing reflex was elicited by electrical stimulation of the superior laryngeal nerve (SLN, 20 Hz, 3-5 V, 0.3 ms duration) for 20 s. To examine the effect of hypoxia, nitrogen gas was inhaled under artificial ventilation. There were significantly fewer swallows during a decrease in PO(2) than under air ventilation (p<0.05). The number of swallows during 3-ml stomach distension was significantly lower than that before distension (p<0.05). Intravenous administration of LiCl (100 mg/kg) also significantly reduced the number of swallows (p<0.05). The combination of SLN stimulation and emetic stimuli occasionally produced burst activity of abdominal muscles, which might be associated with the gag reflex. Both the gag and swallowing reflexes are well known to be mediated by the nucleus of the solitary tract. The physiological roles of the gag reflex and the swallowing reflex are considered to be reciprocal. Taken together, these results suggest that emetic stimulation inhibits the swallowing pattern generator via the nucleus of the solitary tract, which in turn facilitates the gag reflex.