Muscle mass and composition of the hip, thigh and abdominal muscles in women with and without hip osteoarthritis

The objective of this study was to compare muscle mass and composition between individuals with and without hip osteoarthritis. Twenty-four women with hip osteoarthritis (OA group) and 16 healthy women (healthy group) participated in this study. Muscle thickness (MT) and echo intensity (EI) were measured as indices of muscle mass and composition, respectively, using ultrasound imaging. Seven muscles were examined: gluteus maximus, gluteus medius, quadriceps femoris, rectus abdominis, external oblique, internal oblique and transversus abdominis. MT of only quadriceps femoris in the OA group was significantly thinner than that in the healthy group. EIs of gluteus medius, quadriceps femoris and rectus abdominis were significantly higher in the OA group than those in the healthy group. Thus, actual contractile tissue of gluteus medius and rectus abdominis substantially decreased, although muscle mass was similar, whereas both quantitative and qualitative changes occurred in quadriceps femoris in patients with hip OA.     

Does Rest Time before Ultrasonography Imaging Affect Quadriceps Femoris Muscle Thickness,Cross-Sectional Area and Echo Intensity Measurements?

In the work described here, our aim was to determine, in an elderly population, changes in muscle thickness (MT), cross-sectional area (CSA) and echo intensity (EI) of the quadriceps muscles at four time points (0, 5, 10 and 15 min; i.e., T0, T5, T10 and T15, respectively) after changing from a standing to supine position. Twenty-one elderly participants (14 men: 68.1 ± 4.6 y; 8 women: 66.8 ± 4.1 y) were evaluated at four time points. Rectus femoris CSA (RF_CSA), MT and EI of the quadriceps femoris (QF) muscles were assessed. EI significantly increased from T0 to T5, T10 and T15 (p < 0.001), whereas no differences were observed between T5 and T15 in the rectus femoris (RF_EI), vastus intermedius (VI_EI) and quadriceps femoris (QF_EI). No differences were observed between any time points in the RF_CSA and MT of QF muscles. In summary, these results suggest that periods >5 min are not necessary to obtain consistent MT and EI measurements of quadriceps femoris muscles in the elderly population.     

Quantity and Quality of the Lower Extremity Muscles in Women with Knee Osteoarthritis

The objective of the study described here was to compare lower extremity muscle quantity and quality between individuals with and those without knee osteoarthritis (OA). Twenty-one women with knee OA (mild, n = 8; severe, n = 13) and 23 healthy patients participated. Ultrasonography was used to measure muscle thickness (MT) and echo intensity (EI) of the rectus femoris, vastus intermedius, vastus lateralis, vastus medialis, biceps femoris, gluteus maximus, gluteus medius, gastrocnemius, soleus and tibialis anterior. MTs of the vastus medialis and vastus intermedius were smaller, and EIs of the vastus medialis, vastus intermedius, gluteus medius and tibialis anterior were larger, in the severe OA group compared than in the healthy group. Compared with the healthy group, the mild OA group had decreased MT and enhanced EI. Changes in quality and quantity occurring with knee OA progression differed among muscles. In the vastus medialis, change was observed from an earlier stage.     

Quantitative muscle ultrasonography in amyotrophic lateral sclerosis

In this study, we examined whether quantitative muscle ultrasonography can detect structural muscle changes in early-stage amyotrophic lateral sclerosis (ALS). Bilateral transverse scans were made of five muscles or muscle groups (sternocleidomastoid, biceps brachii/brachialis, forearm flexor group, quadriceps femoris and anterior tibialis muscles) in 48 patients with ALS. Twenty-five patients were also screened for fasciculations. Quantitative analysis revealed a significant increase in echo intensity in all muscles and a decrease in muscle thickness of the biceps brachii, forearm flexors and quadriceps femoris on both sides. Fasciculations were easy to detect in multiple muscles of all screened patients except one. We conclude that quantitative ultrasonography can be used to detect muscle changes caused by ALS in an early phase of the disease. (E-mail: m.zwarts@neuro.umcn.nl).     

The influence of fatigue on trunk muscle responses to sudden arm movements,a pilot study

OBJECTIVE: To examine fatigue induced changes in trunk muscle latencies following trunk muscle fatigue. DESIGN: A repeated measures within subject design.Background. Trunk muscle responses to sudden movements is of interest in clinical biomechanics and motor control. METHODS: Electromyographic profiles were recorded from transversus abdominis (finewire), internal oblique, rectus abdominis and external oblique and longissimus at the level of the 3rd lumbar vertebrae bilaterally. Four asymptomatic subjects performed arm-raising task using a visual cue before and after an isometric fatiguing trunk extension task. RESULTS: Feed-forward responses were not detected in all muscles for every trial. In general, following fatigue trunk muscle onset latencies occur earlier (left, P=0.0016; right, P=0.0475). CONCLUSIONS: Trunk muscle fatigue alters anticipatory postural adjustments in normal subjects. It remains unclear if there is a pattern for specific muscles changes between individuals and if these are reflected in individuals with low back pain. RELEVANCE: Trunk muscle fatigue and altered trunk muscles latencies to movement perturbations have been associated with low back pain. These findings suggest that there may be a link between centrally mediated response to isometric muscle fatigue and anticipatory motor control strategies.     

健康人群四肢近端肌肉剪切波弹性成像测量的初步研究

目的测量健康人群四肢近端肌肉剪切波速度,分析与其相关的因素。 方法选取2019年1月至2020年12月在四川大学华西医院招募的健康志愿者88例,记录受检者的性别、年龄、体质量指数（BMI）及运动习惯。测量不同肌肉（三角肌、肱二头肌、股直肌、股外侧肌）左右两侧及相同肌肉不同断面、不同位置及不同体位的剪切波速度,并对不同性别、年龄、BMI及运动状态的肌肉剪切波速度进行比较。随机抽取20例受试者,计算三角肌及股直肌剪切波速度测量的观察者间及观察者内一致性。 结果各肌肉纵断面剪切波速度左、右两侧比较,差异无统计学意义（P均＞0.05）。各肌肉剪切波速度纵断面均大于横断面（P均＜0.05）。肱二头肌伸直位纵断面,其剪切波速度肌腹外侧大于肌腹内侧（P均＜0.05）。肱二头肌剪切波速度伸直位均大于屈曲位（P均＜0.05）。三角肌、肱二头肌剪切波速度男性高于女性（P均＜0.05）。股外侧肌剪切波速度18~49岁组高于50~70岁组（P＜0.05）。肱二头肌剪切波速度BMI＜18.5 kg/m²组及18.5 kg/m²≤BMI＜24 kg/m²组均高于BMI≥24 kg/m²组,差异均有统计学意义（P均＜0.05）。三角肌剪切波速度规律运动者高于少运动者,差异有统计学意义（P＜0.05）。三角肌及股直肌的剪切波速度观察者内及观察者间一致性均为良好或优秀（ICC均＞0.88）。 结论剪切波弹性成像（SWE）能够用于定量测量健康人群肌肉的硬度值,肌肉的断面和部位及受检者的体位、性别、年龄、BMI和运动习惯为与其相关的因素,研究结果为特发性炎性肌病的进一步研究提供了依据。     

Intraclass correlation coefficient of trunk muscle thicknesses in different positions measured using ultrasonography

[Purpose] This study aimed to clarify the required number of measurements to calculate trunk muscle thickness at each position. [Participants and Methods] The participants were 30 elderly males aged >65 years. The right lumbar multifidus (L2), lumbar multifidus (L5), erector spinae, transversus abdominis, internal oblique, and external oblique muscle thicknesses were measured on longitudinal images obtained using ultrasonography in the lying, sitting, and standing positions. Two measurement values for each muscle thickness was used to calculate the intraclass correlation coefficient (1.1–1.5). [Results] The intraclass correlation coefficients of the abdominal muscle thickness measurements with “great reliabilities” were as follows: 1.3–1.5 for the external oblique muscle and 1.2–1.5 for the internal oblique and transversus abdominis muscles in the lying position; 1.3–1.5 for the external oblique and transversus abdominis muscles and 1.2–1.5 for the internal oblique muscle in the sitting position; the intraclass correlation coefficient in the standing position was 1.5 for the external oblique muscle 1.1–1.5 for the internal oblique muscle and 1.3–1.5 for the transversus abdominis muscle. In all the positions, the intraclass correlation coefficient of the measurements of the back-muscle thicknesses ranged from 1.1 to 1.5 for the right lumbar multifidus (L2), lumbar multifidus (L5), and erector spinae. [Conclusion] Depending on the posture, the abdominal muscles require multiple measurements, whereas the back muscles only require a single measurement.Key words: Intraclass correlation coefficient, Trunk muscle thicknesses, Ultrasonography     

Relationship between gait speed and trunk muscles in frail elderly individuals

[Purpose] The external and internal abdominal muscles may be related to gait speed; however, this has not yet been elucidated. In this study, we aimed to clarify the relationship between gait speed and trunk muscle thickness in elderly individuals. [Participants and Methods] The participants were 12 elderly individuals (4 males and 8 females, mean age 83.4 years old, SD ± 0.5) that attend a day service center. We measured the 5 m free gait speed, the 5 m fastest gait speed, and the thickness of five trunk muscles (the rectus abdominis [divided into three parts: upper, central, and lower], external oblique, internal oblique, transverse abdominis, and iliopsoas muscles). [Results] There were positive correlations between the free gait speed and the thickness of the lower rectus abdominis, internal oblique, and transverse abdominis muscles. There were also positive correlations between the fastest gait speed and the thickness of the lower rectus abdominis, internal oblique, and transverse abdominis muscles. [Conclusion] Incorporating muscle strength training of the lower rectus abdominis, internal oblique, and transverse abdominis muscles into existing lower limb muscle training protocols is important to effectively maintain the gait speed of elderly individuals.Key words: Gait speed, Trunk muscles, Frail elderly individuals     

实时剪切波超声弹性成像技术评估肌肉减少症患者骨骼肌弹性模量的研究

摘 要 目的 研究肌肉减少症患者股四头肌、腘绳肌和肱二头肌长轴剪切波速度（SWV）值特征,探讨实时剪切波超声弹性成像技术（SWE）评估肌肉减少症患者肌肉状态的应用价值。方法 选择22例肌肉减少症患者（病变组）和21例同期年龄、性别匹配的健康体检者（对照组）,应用剪切波超声弹性成像技术,获取病变组和对照组优势侧的股四头肌4块肌肉［股外侧肌（VL）,股直肌（RF）,股内侧肌（VM）和股中间肌（VI）］,腘绳肌3块肌肉［股二头肌（BF）,半腱肌（ST）和半膜肌（SM）］和肱二头肌（BB）松弛状态下长轴SWV值,并进行对比分析。结果 松弛状态下病变组与对照组的VL、RF、VM、VI、BF、ST、SM和BB肌肉的SWV数值差异有显著统计学意义(均P＜0.001)。松弛状态下病变组与对照组比较,VL、RF、VM、VI、BF、ST、SM和BB肌肉的SWV数值分别降低7.8%、7.0%、7.3%、7.3%、7.1%、7.3%、6.5%和6.7%。与对照组比较,病变组SM长轴的SWV值降低最小,VL长轴的SWV值降低最为显著。年龄和BMI指数均为老年人骨骼肌弹性模量的影响因素。结论 实时剪切波超声弹性成像技术可检测肌肉减少症患者较大骨骼肌弹性差异,为评估肌肉减少症患者肌肉状态提供了一种新的检测方法。     

An electromyographic analysis of quadriceps femoris muscle setting and straight leg raising

Physical therapists routinely advise patients to perform quadriceps femoris muscle setting or straight leg raising or both following knee surgery or trauma from knee injury. Little information exists, however, about the intensity of effort required from knee and hip musculature during the exercises. This study was designed to compare the level of electromyographic activity during maximally resisted straight leg raises with the level during quadriceps femoris muscle setting exercises for the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles. Forty healthy young adult men and women performed randomly ordered trials of each exercise in the supine position. Electromyographic activity was recorded from surface electrodes and normalized to values derived from maximal isometric trials. Statistical analysis demonstrated significantly greater (p less than .0001) vastus medialis, biceps femoris, and gluteus medius muscle activity during quadriceps femoris muscle setting. The rectus femoris muscle was significantly more active (p less than .0001) during the straight leg raise. The study demonstrated remarkably different muscle activation levels between the exercises studied and clearly indicates that selection of the exercises needs to be based on the therapeutic objectives.     

Reliability of muscle thickness and echo intensity measurements of the quadriceps: A novice examiner

IntroductionThis study aimed to investigate the reliability of muscle thickness (MT) and echo intensity (EI) of the quadriceps muscles using ultrasound imaging for a novice examiner.MethodsSixteen healthy adult women were included in the study, and images of the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis were obtained on the same day and after one week by an examiner who had not performed an experiment on the measurement of ultrasound imaging. The measurers who analyzed all images were completely blind to the subject's name and date and order of measurements. Intraclass correlation coefficients (ICCs) were used as relative within-day and between-day reliability of measurement. Absolute reliability was based on Bland–Altman analysis, standard error of measurement, and minimum detectable change.ResultsThe ICCs ranged from 0.76 to 0.95. As the results of the Bland–Altman analysis, all MTs and EIs included 0 in the 95% confidence interval of the mean difference.DiscussionOur results suggest that quadriceps ultrasound images have high reliability for MT and EI for all muscles. There were no systematic errors in both MT and EI.ConclusionIt might indicate that even novice examiners could obtain MT and EI measurements without systematic error after a few hours of practice.     

Muscle Ultrasound Changes Correlate With Functional Impairment in Spinal Muscular Atrophy

ObjectiveWe investigated ultrasound patterns of muscle involvement in different types of spinal muscular atrophy (SMA) and their correlation with functional status to determine the pattern of muscle compromise in patients with SMA and the potential role of ultrasound to evaluate disease progression.MethodsWe examined muscles (biceps brachii, rectus femoris, diaphragm, intercostals and thoracic multifidus) of 41 patients with SMA (types 1 to 4) and 46 healthy age- and sex-matched control individuals using B-mode ultrasound for gray-scale analysis (GSA), area (biceps brachii and rectus femoris) and diaphragm thickening ratio. Functional scales were applied to patients only. We analyzed ultrasound abnormalities in specific clinical subtypes and correlated findings with functional status.ResultsCompared with controls, patients had reduced muscle area and increased mean GSA for all muscles (p < 0.001), with an established correlation between the increase in GSA and the severity of SMA for biceps brachii, rectus femoris and intercostals (p = 0.03, 0.01 and 0.004 respectively) when using the Hammersmith Functional Motor Scale Expanded. Diaphragm thickening ratio was normal in the majority of patients, and intercostal muscles had higher GSA than diaphragm in relation to the controls.ConclusionUltrasound is useful for quantifying muscular changes in SMA and correlates with functional status. Diaphragm thickening ratio can be normal even with severe compromise of respiratory muscles in quantitative analysis, and intercostal muscles were more affected than diaphragm.     

Effect of corporal suspension and pendulum exercises on neuromuscular properties and functionality in patients with medullar thoracic injury

BackgroundTraumatic spinal cord injury (TSCI) is one of the most devastating injuries that has a physical impact on patients. The CHORDATA® method involves suspension and pendulous exercises and has been clinically used to treat patients with TSCI. Although empirically used to treat neurological patients, there is no scientific evidence of the efficacy of this method.PurposeTo evaluate the chronic effects of CHORDATA® method on torque, muscle activation, muscle thickness, and functionality in patients with traumatic spinal cord injury.MethodsTwenty-six male patients with medullar thoracic injury were randomly categorised into two groups: intervention group (n = 14) and control group (n = 12). Rehabilitation program comprised of 16 sessions of body suspension and pendulum exercises (twice/week). The maximal voluntary isometric trunk flexion and extension torques, muscle activation and thickness (external and internal oblique, rectus and transversus abdominis, longissimus, and multifidus muscles), and functionality (adapted reach test) were evaluated before and after of rehabilitation program.FindingsA significant increase was observed in maximal voluntary isometric torque (flexion, 58%; extension, 76%), muscle activation of the rectus abdominis muscle, and muscle thickness of all intervention group muscles, without changes in the control group. Compared to the pre-intervention period, the intervention group also showed improvement in functionality at post-intervention, but no such differences were noted in the control group.InterpretationThe corporal suspension and pendulum exercises training improved rectus abdominis muscle activation, trunk muscles structure and strength, and reaching capacity in medullar thoracic injury patients.     

Selective hypertrophy of the quadriceps musculature after 14 weeks of isokinetic and conventional resistance training

One of the fundamental adaptations observed with resistance training (RT) is muscle hypertrophy. Conventional and isokinetic machines provide different forms of mechanical stress, and it is possible that these two training modes could promote differing degrees of hypertrophic adaptations. There is a lack of data comparing the selective hypertrophy of the quadriceps musculature after training with a conventional knee extension machine versus an isokinetic machine. The purpose of this study was to evaluate the selective hypertrophy of the quadriceps musculature and knee extension maximal isometric torque after 14 weeks of conventional versus isokinetic RT. Thirty-five men were assigned to three groups: control group and training groups (conventional and isokinetic) performed three sets of unilateral knee extensions per session with a progressive loading scheme twice a week. Prior to and following the intervention, maximal isometric knee extensor torque was measured using an isokinetic dynamometer, and muscle thickness (MT) of quadriceps femoris muscles was assessed via ultrasound. The results indicated non-uniform changes in MT between the muscles that comprise the quadriceps femoris group. For the conventional group, significantly greater increases in rectus femoris thickness were evident versus all other quadriceps muscles (14%). For the isokinetic group, increases in RF thickness (11%) were significantly greater in comparison with the vastus intermedius only. Although the muscle thickness did not increase for all the quadriceps femoris muscles, the relative rectus femoris adaptation suggested a selective hypertrophy favouring this portion.     

Effects of Three Bridging Exercises on Local and Global Muscles of Middle Aged Women

[Purpose] This study investigated the muscle activity differences of three different lumbar stabilization exercises in a comparison of middle-aged and young women. [Subjects] Seventeen middle-aged women and fifteen young women were enrolled in this study. Patients with a history of any neurologic disorders, orthopedic disorders, or cardiopulmonary problems that would have affected their lumbar stabilization exercise performance were excluded. [Methods] All subjects performed 3 exercises while the surface electromographic activity was recorded of the rectus abdominis, internal oblique, multifidus, and iliocostalis lumbolum. The mean electromyographic amplitudes obtained during the exercise were normalized to the amplitude of maximal voluntary isometric contraction (%MVIC) to produce an inter-individually comparable muscle activity index. [Results] The highest muscle activity of middle-aged women was observed in the ring bridging exercise. The middle-aged women had higher levels of all muscle activaties than the young women, particularly in the multifidus muscle and iliocostalis lumborum. No significant difference in muscle activity ratio was observed between the local muscles and global muscles in the three different exercises, though the muscle activity ratio was the highest in the ring bridging exercise. The young women group showed a higher ratio of the internal oblique/rectus abdominus than the middle aged women in the bridging exercise. [Conclusion] The ring bridging exercise should be used for stabilizing the lumbar area because the young women showed a higher ratio than the middle aged women.Key words: Bridging exercise, Middle-aged women, Muscle activity     

Use of Shear Wave Elastography to Quantify Abdominal Wall Muscular Properties in Patients With Incisional Hernia

Shear wave elastography (SWE) is a potential modality that quantitatively measures the elasticity (shear wave speed [SWS]) of musculoskeletal structure. This SWS was bilaterally measured in the rectus abdominis (RA), external oblique (EO) muscle, internal oblique (IO) muscle and transversus abdominis (TrA) using SWE in 28 patients with incisional hernia and 14 healthy controls. The differences in muscle thickness for IO and TrA were significant between the two groups (p < 0.05). The SWS of RA, EO, IO and TrA was significantly higher in the incisional hernia patient group than in the healthy controls (p < 0.05). Significant differences were also observed between the upper and lower points in both groups (p < 0.05). The measurements of SWS help in evaluating the elastic properties of abdominal wall muscles, which could further aid in preparing treatment plans to improve muscle strength.     

Can activity within the external abdominal oblique be measured using real-time ultrasound imaging?

BACKGROUND: Differences in the function of the anterolateral abdominal muscles have been the subject of much investigation, but primarily using electromyography. Recently changes in thickness of transversus abdominis and internal oblique measured from real-time ultrasound images have been shown to represent activity within these muscles. However it is still unclear if such a change in thickness in external oblique similarly represents activity within that muscle. The purpose of this study was to investigate the relationship between change in thickness and muscle activity in the external oblique using real-time ultrasound and surface electromyography. METHODS: Simultaneous measurements of electromyography and real-time ultrasound images of external oblique were studied in up to 24 subjects during two tasks compared to the muscle at rest (1) isometric trunk rotation and (2) drawing in the lower abdomen. FINDINGS: Changes in muscle thickness correlated significantly with electromyography during isometric trunk rotation in the majority of subjects but with a significant difference between subjects. In contrast, the relationship between change in thickness and electrical activity in the muscle when drawing in the lower abdomen was significant in less than 50% of subjects and the muscle often got thinner. INTERPRETATION: Thickness changes of external oblique can be used as a valid indicator of electromyography activity during isometric trunk rotation, though the relationship is not as good as previously published data for transversus abdominis. Thickness changes of external oblique measured during lower abdominal drawing in cannot be used to detect activity within this muscle.     

An Investigation of the Association between Transversus Abdominis Myofascial Structure and Activation with Age in Healthy Adults using Ultrasound Imaging

BackgroundBecause of their importance in core stability, training the deep abdominal muscles, fascial structures and particularly the transversus abdominis, is a key component of many sport and physical therapy programs. However, there are gaps in knowledge about age-related changes in the structure and activation capacity of these muscles.Hypothesis/PurposeThis study investigated the association between deep abdominal muscles and fascial structures and transversus abdominis activation with age in healthy adults.Study designA cross-sectional study.MethodsEighty-six adults aged 18 to 77 participated in this study. An ultrasound image of their transversus abdominis, internal oblique, external oblique and associated fasciae was first captured at rest, then during a contraction of the transversus abdominis. Bivariate correlation analyses and hierarchical analyses were performed (significance level: p < 0.05).ResultsThe thickness of these three muscles decreases with age (ρ = -0.66 for external oblique, -0.51 for internal oblique and -0.58 for transversus abdominis), whereas the thickness of their fasciae increases (ρ = 0.39 for the fascia of external oblique, 0.54 for the fascia between internal oblique and external oblique, and 0.74 for the fascia between internal oblique and transversus abdominis). Transversus abdominis activation decreases with age (r =-0.44). Age accounts for 19.5% of the variance in transversus abdominis activation.ConclusionThese results demonstrate that normal aging is associated with changes in deep abdominal myofascial structures and transversus abdominis activation. Assessment of these metrics can provide valuable baseline information for physical therapists involved in rehabilitation and strengthening programs targeting older individuals.Level of evidenceLevel 2     

Tissue elasticity of in vivo skeletal muscles measured in the transverse and longitudinal planes using shear wave elastography

The aim of the present study was to measure in vivo skeletal muscle elasticity in the transverse and longitudinal planes using shear wave elastography and then to compare the image stability, measurement values and measurement repeatability between these imaging planes. Thirty‐one healthy males participated in this study. Tissue elasticity (shear wave velocity) of the medial gastrocnemius, rectus femoris, biceps brachii and rectus abdominis was measured in both the transverse and longitudinal planes using shear wave elastography. Image stability was evaluated by the standard deviation of the colour distribution in the shear wave elastography image. Measurement repeatability was assessed by the coefficient of variance obtained from three measurement values. Image stability of all tested muscles was significantly higher in the longitudinal plane (P<0·001), but measurement repeatability did not differ significantly between the imaging planes (P>0·05), except in the biceps brachii (P = 0·001). Measurement values of the medial gastrocnemius, rectus femoris and biceps brachii were significantly different between the imaging planes (P<0·001). Image stability and measurement values of shear wave elastography images varied with imaging plane, which indicates that imaging plane should be considered when measuring skeletal muscle tissue elasticity by shear wave elastography.     

Comparison of Muscle Activities Using a Pressure Biofeedback Unit during Abdominal Muscle Training Performed by Normal Adults in the Standing and Supine Positions

[Purpose] The purpose of this study was to assess the effects of draw-in exercise on abdominal muscle activity in the standing and supine positions. [Methods] Twenty healthy women participated in this study. The subjects were required to complete two draw-in exercises (standing and supine positions) using a biofeedback pressure unit. The root mean square (RMS) values of the EMG data were expressed as a percentage of the resting contraction. The data were analyzed using the independent t-test. [Results] According to the changes in the activities of the abdominal muscles, the draw-in exercise in the standing position produced the most significant increase in the activities of the rectus abdominis, the transverse abdominis, the internal oblique, and the external oblique muscles. [Conclusion] The activities of the trunk stability muscles (rectus abdominis, transverse abdominis, internal oblique, and external oblique) increased more in the standing than in the supine position, enabling the subjects to overcome gravity. Therefore, to strengthen the activation of the abdominal muscles, a standing position seems to be more effective than a supine position for draw-in exercises.Key words: Abdominal muscle activity, Positions, Pressure biofeedback unit