Self-organising maps in the analysis of strains of human abdominal wall to identify areas of similar mechanical behaviour.

The study refers to the application of a type of artificial neural network called the Self-Organising Map (SOM) for the identification of areas of the human abdominal wall that behave in a similar mechanical way. The research is based on data acquired during in vivo tests using the digital image correlation technique (DIC). The mechanical behaviour of the human abdominal wall is analysed during changing intra-abdominal pressure. SOM allow to study simultaneously three variables in four time/load steps. The variables refer to the principal strains and their directions. SOM classifies all the abdominal surface data points into clusters that behave similarly in accordance with the 12 variables. The analysis of the clusters provides a better insight into abdominal wall deformation and its evolution under pressure than when observing a single mechanical variable. The presented results may provide a better understanding of the mechanics of the living human abdominal wall. It might be particularly useful when selecting proper implants as well as for the design of surgical meshes for the treatment of abdominal hernias, which would be mechanically compatible with identified regions of the human anterior abdominal wall, and possibly open the way for patient-specific solutions.

Numerical investigation of a finite element abdominal wall model during breathing and muscular contraction.

BACKGROUND AND OBJECTIVE: Ventral hernia repair is faced with high recurrence rates. The personalization of the diagnosis, the surgical approach and the choice of the prosthetic implant seem relevant axes to improve the current results. Numerical models have the potential to allow this patient-specific approach, yet currently existing models lack validation. This work extensively investigated a realistic finite element abdominal wall model including the implementation of muscle activation. METHODS: A parametric 3D finite element model composed of bone, muscle and aponeurotic structures was introduced. Hyperelastic anisotropic materials were implemented. Two loading scenarios were simulated: passive inflation of the abdominal cavity to represent, e.g., breathing, and passive inflation followed by muscular activation to simulate other daily activities such as cough. The impact of the inter-individual variability (e.g., BMI, tissue thickness, material properties, intra-abdominal pressure (IAP) and muscle contractility) on the model outputs was studied through a sensitivity analysis. RESULTS: The overall model predictions were in good agreement with the experimental data in terms of shape variation, muscles displacements, strains and midline forces. A total of 34 and 41 runs were computed for the passive and active sensitivity analysis respectively. The regression model fits rendered high R-squared in both passive (84.0 ± 6.7 %) and active conditions (82.0 ± 8.3 %). IAP and muscle thickness were the most influential factors for the selected outputs during passive (breathing) activities. Maximum isometric stress, muscle thickness and pre-activation IAP were found to drive the response of the simulations involving muscular contraction. The material properties of the connective tissue were essential contributors to the behaviour of the medial part of the abdominal wall. CONCLUSIONS: This work extensively investigated a realistic abdominal wall model and evaluated its robustness using experimental data from literature. Such a model could improve patient-specific simulation for ventral hernia surgical planning, prevention, and repair or implant evaluation. Further investigations will be conducted to evaluate the impact of the surgical technique and the mechanical characteristic of prosthetic meshes on the model outputs.

Dynamic-MRI quantification of abdominal wall motion and deformation during breathing and muscular contraction.

BACKGROUND AND OBJECTIVE: Biomechanical assessment of the abdominal wall represents a major prerequisite for a better understanding of physiological and pathological situations such as hernia, post-delivery recovery, muscle dystrophy or sarcopenia. Such an assessment is challenging and requires muscular deformations quantification which have been very scarcely reported in vivo. In the present study, we intended to characterize abdominal wall deformations in passive and active conditions using dynamic MRI combined to a semiautomatic segmentation procedure. METHODS: Dynamic deformations resulting from three complementary exercises i.e. forced breathing, coughing and Valsalva maneuver were mapped in a transversal abdominal plane and so for twenty healthy volunteers. Real-time dynamic MRI series were acquired at a rate of 182 ms per image, then segmented semi-automatically to follow muscles deformation through each exercise. Circumferential and radial strains of each abdominal muscle were computed from the geometrical characteristics' quantification, namely the medial axis length and the thickness. Muscular radial displacement maps were computed using image registration. RESULTS: Large variations in circumferential and radial strains were observed for the lateral muscles (LM) but remained low for the rectus abdominis muscles (RA). Contraction phases of each exercise led to LM muscle shortening down to -9.6 ± 5.9% during Valsalva maneuver with a 16.2 ± 9.6% thickness increase. Contraction also led to inward radial displacement of the LM up to 9.9 ± 4.1 mm during coughing. During maximal inhalation, a significant 10.0 ± 6.6% lengthening was quantified for LM while a significant thickness decrease was computed for the whole set of muscles (-14.7 ± 6.6% for LM and -7.3 ± 6.5% for RA). The largest displacement was observed for the medial part of RA (17.9 ± 8.0 mm) whereas the posterior part of LM underwent limited motion (2.8 ± 2.3 mm). Displacement rate and correlation between muscle thickness and medial axis length during each exercise provided insights regarding subject-specific muscle function. CONCLUSIONS: Dynamic MRI is a promising tool for the assessment of the abdominal wall motion and deformations. The corresponding metrics which have been continuously recorded during the exercises provided global and regional quantitative information. These metrics offer perspectives for a genuine clinical evaluation tool dedicated to the assessment of abdominal muscles function in both healthy subjects and patients.

Feasibility study of oxidized hyaluronic acid cross-linking acellular bovine pericardium with potential application for abdominal wall repair.

Bovine pericardium(BP)is one of the biological membranes with extensive application in tissue engineering. To fully investigate the potential clinical applications of this natural biological material, a suitable cross-linking reagent is hopefully adopted for modification. Glutaraldehyde (GA) is a clinically most common synthetic cross-linking reagent. In the study, oxidized hyaluronic acid (AHA) was developed to substitute GA to fix acellular bovine pericardium (ABP) for lower cytotoxicity, aiming to evaluate the feasibility of AHA as a cross-linking reagent and develop AHA-fixed ABP as a biological patch for abdominal wall repair. The AHA with the feeding ratio (1.8:1.0) has an appropriate molecular weight and oxidation degree, almost no cytotoxicity and good cross-linking effect. The critical cross-linking characteristics and cytocompatibility of AHA-fixed ABP were also investigated. The results demonstrated that 2.0% AHA-fixed ABP had the most suitable mechanical properties, thermal stability, resistance to enzymatic degradation and hydrophilicity. Moreover, 2.0% AHA-fixed samples exhibited an excellent cytocompatibility with human peritoneal mesothelial cells (HPMC) and low antigenicity. It also showed a prominent anti-calcification ability required for abdominal wall repair. Our data provided experimental basis for future research on AHA as a new cross-linking reagent and AHA-fixed ABP for abdominal wall repair.

A breathing movement sensor for chest radiography during inspiration in children aged less than 3 years: a prospective randomized controlled study.

Chest radiographs should be obtained at the peak of inspiration so that radiological findings can be precisely interpreted. However, this is not easily achieved, particularly in young children who do not follow the instruction to hold their breath. We developed a sensor that detects the breathing movements and conducted a randomized controlled study to determine whether the sensor would increase the proportion of chest radiographs obtained in the inspiration phase. We recruited 124 infants and children aged less than 3 years, who visited the pediatric department of a general hospital in Tokyo, Japan, and allocated them into one of two groups: with-sensor and without-sensor groups. Overall, 81% of all images were obtained during inspiration. The proportion of chest radiographs taken during inspiration was not statistically different between the two groups (81% vs. 82%). In the with-sensor group, radiologic technologists were able to obtain chest radiographs of the same quality while not observing the chest movement, but the sensor. The use of the sensor did not increase the proportion of chest radiographs taken in the inspiration phase in this study. However, this null result may indicate the possibility of utilizing the sensor for automatizing chest radiography in the future.

Ultrasound Imaging of the Superficial Fascial System Can Predict the Subcutaneous Strength of Abdominal Tissue Using Mean Gray Value Quantification.

BACKGROUND: This study is the first to correlate sonographic findings of subcutaneous tissue to structural and biomechanical properties. METHODS: Precisely sized tissue specimens (59 samples) were collected from five abdominoplasty procedures. A Philips Lumify L12-4 linear array probe, connected to an Android tablet, was used to obtain ultrasound images of the superficial fascial system. A no. 1 Vicryl suture on a CTX needle placed though a needle guide within a three-dimensionally printed template ensured equal bites of subcutaneous tissue across specimens. Suture pull-out strength was measured until failure at a displacement rate of 2.12 mm/second using an Admet MTEST Quattro. Mean gray value for the superficial fascial system in associated ultrasonographic images was quantified by CellProfiler. RESULTS: Superficial fascial system visualization can be accomplished using high-resolution portable ultrasound. Comparing multiple specimens' imaging, interpatient and intrapatient variability of superficial fascial system quantity and structural characteristics are apparent. The superficial fascial system is highly abundant in some patients, but has limited presence in others. Individual-specimen mean gray value and whole-patient mean gray value positively correlated with tissue tensile strength (p = 0.006) and patient-average tissue tensile strength (p = 0.036), respectively. Whole-patient mean gray value accounted for 98.5 percent of the variance seen in patient-average tensile strength, making it a strong predictor for tensile strength. CONCLUSIONS: Portable ultrasound and image-processing technology can visualize, quantify, and predict subcutaneous tissue strength of the superficial fascial system. The superficial fascial system quantity correlates with suture tensile strength. Clinically, preoperative superficial fascial system quantification may aid in outcome predictions, manage patient expectations, and potentially lower complication rates. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, V.

Cough, sniff and maximal static pressure patterns in spinal muscular atrophy.

In spinal muscular atrophy (SMA), respiratory muscles are heterogeneously involved with a weakness of the intercostal muscles, possibly of the abdominal wall muscles, and a relatively spared diaphragm, resulting in cough impairment. An abnormal inspiratory cough phase pattern has been reported in SMA II and III. This short communication analyzed the esogastric pressures during voluntary cough in 49 SMA II and III patients. Four different patterns of coughing, reflecting an increasing degree of respiratory muscle weakness, were identified. The "mild weakness" profile was observed mainly in SMA III, while the "severe weakness" profile, which seems to correspond to the absence of abdominal muscle activity, was observed only in a few patients with SMA II. The cough profiles of 6 patients are presented together with their sniff and maximal static pressures measurements. Different esogastric pressure patterns were observed during these forceful maneuvers, suggesting variable involvement of the intercostal and abdominal muscles, and diaphragm during the evolution of SMA II and III.

Abdominal wall elasticity of children during pneumoperitoneum.

OBJECTIVE: Laparoscopic surgery in children is often hampered by limited working space. This is partially compensated by stretching the child's abdominal wall. The volume of space that can be gained and changes to abdominal wall elasticity with respect to age are unknown. In the current research, we studied the extent of abdominal wall elasticity while establishing pneumoperitoneum in children. METHODS: One hundred and sixty three children less than 18 years of age, undergoing elective laparoscopic surgery were recruited for the study. After induction of general anesthesia with a standardized muscle relaxant dose, a length of 5 cm was marked above, below and lateral to the umbilicus. The length of the marking was measured under increasing intraabdominal pressure (IAP of 0, 4, 6, 8, 10, 12 mmHg). The measurements were repeated to assess the effect of prestretching. The patients were divided into two groups: infants (less than one year of age) and older children (more than one year of age). RESULTS: Depending on the age and axes of the measurements, a child's abdomen stretches up to 17% on average, with induction of pneumoperitoneum. The percentage of stretch tapers off as the IAP approaches peak pressure. As children become older, the longitudinal abdominal wall elasticity decreases, but the transverse abdominal wall elasticity increases. Regardless of age, prestretching results in a statistically significant increase in the elasticity over the transverse and lower sagittal abdominal wall. CONCLUSION: A child's abdominal wall has considerable expandability. The characteristics of elasticity change depending on the axis and age. Prestretching can improve intraabdominal working space. This knowledge is helpful in port position design for minimally invasive surgery in children. LEVEL OF EVIDENCE: Level II.

Synchronized abdominal compression as a novel treatment of life-threatening preschool asthma.

Introduction: In severe asthma, management of life-threatening air trapping that persists despite initiation of standard asthma treatment is difficult in the absence of extracorporeal membranous oxygenation.Case study: Three children with life-threatening asthma could not be adequately ventilated despite maximum conventional treatment because of severe air trapping. A novel method of active expiration by abdominal compression with a standard ventilator was adopted with immediate effect with significant improvement in ventilation.Conclusion: Synchronized abdominal compression is a novel and simple method that allows an effective treatment of severe air trapping in an intubated paralyzed asthma child.

Correlating Abdominal Wall Thickness and Body Mass Index to Predict Usefulness of Right Lower Quadrant Ultrasound for Evaluation of Pediatric Appendicitis.

OBJECTIVES: To inform selective and efficient use of appendix ultrasound (US) beyond adult parameters of body mass index (BMI) of less than 25 kg/m, we correlate abdominal wall thickness (AWT) with age and BMI to generate parameters for male and female children. Information presented in chart format can aid in the decision to utilize US for the evaluation of appendicitis. METHODS: In this observational study, 1600 pediatric computed tomography scans of the abdomen and pelvis were analyzed to obtain measurements of AWT in the right lower quadrant. Measurements were correlated by patient age, BMI, and sex. Results and consensus-based recommendations were presented in chart format with color-coded groupings to allow for convenient referencing in the clinical setting. RESULTS: One thousand four hundred eighty-eight computed tomography scans and AWT measurements were included. All age groups with BMI of less than 25 kg/m and all male and female groups younger than 6 years regardless of BMI had median AWT of less than 4 cm resulting in strong recommendation for US. Males older than 6 years and all female age groups with BMI of greater than 30 kg/m and female older than 15 years and BMI of greater than 25 kg/m had AWT of more than 5 cm resulting in low recommendation for US. CONCLUSIONS: While the BMI cutoff standard of less than 25 kg/m for usefulness of appendix US holds in the adult population, our data expand the acceptable range in children younger than 9 years regardless of BMI and male children with BMI up to 30 kg/m. Female children younger than 15 years with a BMI up to 30 kg/m may also be amenable to right lower quadrant US based on AWT. These parameters inform selective and efficient use of US for appendix evaluation.

Relationship between the degree of abdominal wall movement and the image quality of contrast-enhanced MRI: semi-quantitative study especially focused on the occurrence of transient severe motion artifact.

PURPOSE: To reveal the relationship between abdominal movement and artifact, and to reveal if the transient artifact in arterial phase is caused by transient abdominal movement (TAM) in contrast-enhanced (CE) MRI. MATERIALS AND METHODS: 325 CE-MRI series (206 with EOB and 119 with EGCM) were included. The abdominal movement was classified into three groups by respiratory bellows waveform (= bellows grade, BG 1-3), and MR image quality (= artifact score, AS) was graded 1-5 for the precontrast, arterial and portal venous phase, respectively. The relationship between the BG and AS was evaluated. The occurrence of transient artifact in arterial phase was compared to the degree of TAM. RESULTS: In the acquisitions with BG3, all images showed AS of > 2, while no images had AS of > 4 in the acquisitions with BG1. Numbers of transient artifact in the arterial phase with no-abdominal movement (NAM), mild-TAM, severe-TAM were 0 of 120, 4 of 27, 7 of 8 in EOB and 0 of 91, 1 of 4, 0 of 0 in EGCM, respectively. CONCLUSION: Image quality is highly correlated with abdominal movement. Moreover, artifact in arterial phase was not observed in NAM, which indicated abdominal movement is the direct cause of artifact.

Outcomes specific to patient sex after open ventral hernia repair.

BACKGROUND: Male and female hernia patients often have different surgical history, fat distribution, and medical comorbidities. Female surgical patients seemingly experience worse outcomes after open ventral hernia repair. This study evaluates the impact of sex and the distribution of abdominal adiposity on outcomes after open ventral hernia repair. METHODS: A prospective hernia database was queried for patients from 2007 to 2018 with a computed tomography within 1 year of open ventral hernia repair. Three-dimensional volumetric analysis was performed. Demographics, abdominal fat distribution, operative characteristics, and outcomes were evaluated by sex using univariate and multivariate analysis. RESULTS: A total of 1,178 patients were identified, 57.8% were female. Compared with males, females had higher mean body mass index (34.8 ± 8.5 vs 31.7 ± 6.4 kg/m2, P < .0001), previous abdominal operations (3.3 ± 1.5 vs 2.6 ± 1.3, P < .0001), and preoperative chronic pain (33.5 vs 26.4%, P = .009). There was no difference in history of recurrence, age, steroid use, smoking, diabetes, or hernia volume between sexes (P ≥ .17 all values). Males had larger defects (168.1 ± 148.2 vs 138.8 ± 126.8 cm2, P = .001) and intra-abdominal volume (intra-abdominal fat volume; 6,279 ± 2,614 vs 4,454 ± 2,196 cm3, P < .0001). Females had larger subcutaneous fat volume (subcutaneous fat volume; 7,453 ± 6,600 vs 5,708 ± 3,275 cm3, P < .0001), and ratio of hernia to intra-abdominal volume (hernia volume to intra-abdominal fat volume; 0.33 ± 0.52 vs 0.22 ± 0.42, P < .0001). On univariate analysis, females had higher rates of readmission, wound complication, and intervention for pain after open ventral hernia repair (P ≤ .02 all values). On multivariate analysis, females had shorter duration of stay (-1.36 day, standard error 0.49, P = .006) with higher readmission rate (odd ratio, 1.64; 95% confidence interval, 1.15-2.34). CONCLUSION: Female hernia patients in our population are more comorbid, with higher body mass index, thicker subcutaneous fat volume and a higher ratio of hernia volume to intra-abdominal fat volume. These differences are associated with more extensive surgical intervention, such as panniculectomy and higher rates of adverse outcomes after open ventral hernia repair. However, these differences are not fully explained by identified comorbidities and warrant further investigation.

Physiologic Tension: Technique for Measuring and Baseline Values.

Tension is one of the most discussed terms related to hernia surgery and repair. Despite the universally accepted opinion that tension and reduction of tension are important concepts in hernia repair, there is very little known about the physiologic tension of the abdominal wall related to ventral hernia repair. The purpose of this project was to attempt to measure physiologic tension in patients without hernia repair and help determine a normal baseline tension. Patients were enrolled in a prospective institutional review board-approved protocol to measure abdominal wall tension from February 2014 to present. Patients undergoing abdominal surgery without hernia repair were included. Demographic information and operative details were documented. Abdominal wall tensions were measured using scales attached to Kocher clamps that are clamped to the fascia and then brought together in the midline. Total tension, surgeon's estimation of tension, and grading of the fascia were recorded. Descriptive statistics were calculated. Eleven patients met the inclusion criteria and had tension measurements performed during surgery. The average age was 58 years, with 55 per cent of them being white and 82 per cent being male, with an average BMI of 27. Operations included exploratory laparotomy for small bowel pathology in six patients, colorectal surgery in three patients, and splenectomy in a trauma patient. Average tension measurements for these patients were 1.9 lbs. Surgeon grading of tension was an average of 2.2 (range, 1-5). Obtaining tension measurements is feasible during abdominal surgery. Physiologic tension seems to be approximately 2 pounds. Further study is needed with a larger sample of patients.

Implementation of a new constitutive model for abdominal muscles.

BACKGROUND AND OBJECTIVE: Abdominal hernia repair is one of the most often performed surgical procedures worldwide. Numerical simulations of the abdominal wall mechanics can be a valuable tool to devise actions aimed at preventing hernia formation. A first step towards this goal is the development of consistent constitutive models for the tissues that form the human abdominal wall. In this study we propose, for each of the tissues involved, a new formulation of the so-called transversely isotropic hyperelastic model (TIHM). METHODS: We propose a new TIHM for the human abdominal wall tissues and we present a systemic view of the methodology that we have implemented in the present study. First we consider the mathematical background of the TIHM. The novelty of our formulation is that both the isotropic and the fiber contributions to the strain energy function are characterized exclusively by polynomial convex functions of certain invariant quantities. Then, we provide a detailed description on how the constitutive model is implemented into an open source finite element (FE) software. In our approach we use the specific interface provided by the MFront software to incorporate our TIHM formulation into the Code Aster FE solver. For each of the tissues considered, the values of the TIHM constants are adjusted by means of a numerical simulation of previous experimental data from tensile tests. RESULTS: We studied the following abdominal wall tissues: linea alba, rectus sheath, external oblique muscle, internal oblique muscle, transversus abdominis muscle and rectus abdominis muscle. Our formulation closely reproduces tensile test data for each tissue in the corresponding FE numerical simulation. CONCLUSIONS: The new TIHM formulation is suitable for a future numerical investigation of the abdominal wall, which will in turn help us to assess the best zone to practice a colostomy. The methodology implemented in the present study can be easily extended in the future to develop and implement a TIHM for active muscles and/or a different type of constitutive model which might be suitable to characterize other tissues of biomedical interest.

Ultrasound Probe Pressure on the Maternal Abdominal Wall and the Effect on Fetal Middle Cerebral Artery Doppler Indices.

Background and objectives: Doppler ultrasound of umbilical and fetal vessels is useful for monitoring fetal well-being, fetal anemia, intrauterine growth retardation, and other perinatal outcomes. The adverse perinatal outcome and circulatory changes can be reflected in fetal Doppler studies. The aim of this study was to evaluate the effect of increased pressure exerted on the maternal abdominal wall during routine ultrasound on the middle cerebral artery (MCA), resistance index (RI), pulsatility index (PI), and peak systolic velocity (PSV). Materials and Methods: A prospective study was conducted, in which we included 40 pregnant women between 24 + 0 and 41 + 3 gestational weeks (GW), with singleton pregnancies, without any associated pathologies, undergoing routine US examination. We recorded the flow velocity waveforms in the MCA, and we measured the RI, PI, PSV, and the applied pressure on to the maternal abdominal wall-needed for a proper evaluation of MCA. We then repeated the same measurements at two different higher pressure levels, at the same time having a proper image of the targeted vessel. Results: We found significant differences for the PI and RI levels with an increase in abdominal pressure (median PI 1.46, 1.58, and 1.92, respectively; median RI 0.74, 0.78, and 0.85, respectively; p < 0.05), for both PI and RI. At the same time, we found no significant differences for PSV in the studied group in relationship with increase in abdominal pressure (median PSV 39.56, 40.10, and 39.70, respectively; p > 0.05). Conclusions: The applied abdominal pressure by the examiner's hand, during routine US scan in pregnancy, can modify the MCA parameters of blood flow resistance (PI and RI) when measured by Doppler US, thus influencing the diagnostic accuracy in a series of pregnancy associated pathologies, such as chronic fetal distress (CFD) or intrauterine growth restriction (IUGR).

Abdominal skin tensile strength in aesthetic and massive weight loss patients and its role in ventral hernia repair.

BACKGROUND: Clarifying the biomechanics of abdominal skin could lead to different uses for this tissue such as the ventral repair of hernias in patients with excess skin and incisional hernias. The objective of this study was to compare the maximum tensile strength of abdominal skin to commercial meshes and to verify whether or not it varies between aesthetic patients and massive weight-loss patients. METHODS: Experimental cross-sectional study. Skin samples sized 32 × 20 mm were taken from 15 abdominoplasties and 10 panniculectomies. The skin specimens were analyzed in vertical and horizontal tensile strength tests. Results were compared between the two groups including their traction directions. Commercial meshes were also tested. The results were analyzed using the Generalized Estimating Equation. RESULTS: The maximum tensile strength supported vertically by abdominal dermis was 403.5 ± 27.4 N in the abdominoplasty group and 425.9 ± 33.9 N in the panniculectomy group. Horizontally, the values were 596.5 ± 32.2 N and 612.5 ± 43.9 N respectively. The strengths between traction directions were significantly different (p < 0.001). There were no differences between the groups with regard to the maximum tensile strength (p = 0.472). Tested commercial meshes had the following values: polypropylene 104.6 N, low-weight polypropylene 54.4 N, polytetrafluorethylene (PTFE) 82.2 N, and hydrated porcine small-intestinal submucosa 60.0 N. CONCLUSION: In our study, the tensile strength of the tested human abdominal dermis samples, both aesthetic and post-bariatric, was superior to the commercial meshes. Therefore, in selected cases, abdominal dermis could be an alternative tool in abdominal reconstruction during panniculectomies with concomitant hernia repair.

Bilateral differences in the trunk muscle volume of skilled golfers.

Repetitive mechanical load applied to a body part may lead to hypertrophy of its muscles. If a movement requires asymmetric activation of bilateral muscles, this may result in differences in muscle size between the sides. This study aimed to investigate the degree of bilateral differences in the trunk muscle volume of golfers by comparing with non-golfers. Seventeen male right-handed golfers and eleven (nine right- and two left-handed) non-golfers participated. Trunk muscle volume was determined using magnetic resonance imaging, and the degree of asymmetry was calculated as the ratio of trunk muscle volume on the left to trunk muscle volume on the right side in right-handers and vice-versa in left-handers. Golfers had significantly larger lateral abdominal wall (LA) muscle volume than non-golfers: 12.36 ± 1.12 vs. 9.96 ± 0.94 cm3/kg; erector spinae: 9.12 ± 1.16 vs. 7.88 ± 0.84 cm3/kg; psoas major (PM): 6.27 ± 0.88 vs. 5.51 ± 0.98 cm3/kg; rectus abdominis (RA): 4.15 ± 0.54 vs. 3.50 ± 0.64 cm3/kg; and multifidus: 3.61 ± 0.41 vs. 3.05 ± 0.40 cm3/kg (p < 0.05). The degree of bilateral asymmetry of the LA, PM, and RA volume was significantly greater in golfers than in non-golfers (LA: -8.63 ± 7.40% vs. 1.94 ± 2.76%; PM: -9.10 ± 5.25% vs. -0.48 ± 5.96%; RA: 6.36 ± 6.50% vs. -2.12 ± 9.64%, respectively, p < 0.05). Right-handed golfers had greater left LA and PM volume compared to the right (LA: 5.89 ± 0.55 vs. 6.48 ± 0.65 cm3/kg; PM: 3.00 ± 0.42 vs. 3.27 ± 0.47 cm3/kg; p < 0.05) and had greater right RA volume compared to the left (2.15 ± 0.32 vs. 2.00 ± 0.24 cm3/kg, p < 0.05). These findings suggest that skilled, long-term golfers develop large volume and bilateral asymmetry of their trunk muscles.

Effects of 1-year weight loss intervention on abdominal skeletal muscle mass in Japanese overweight men and women.

BACKGROUND AND OBJECTIVES: Limited information is available on how weight loss intervention programs affect skeletal muscle mass especially in trunk. METHODS AND STUDY DESIGN: A total of 235 overweight Japanese men and women aged 40-64 years with a body mass index of 28.0 to 44.8 kg/m2 participated in this randomized controlled intervention study. They were randomly divided into a lifestyle intervention group and control group. Before and after the one-year lifestyle intervention for weight loss an abdominal transverse image was acquired by computed tomography. The cross-sectional areas (CSAs) of visceral fat, subcutaneous fat, and skeletal muscle of rectus abdominis, abdominal oblique, iliopsoas, and erector spinae muscle were calculated. RESULTS: The body weight changed by approximately -5% in the intervention groups. The corresponding values for subcutaneous fat and visceral fat CSAs were -10.8 to -17.5% in both sexes. The reductions observed in skeletal muscle CSAs were significantly less (-6.0% and -7.2% in the men and women intervention groups respectively) than those in fat tissue CSAs. The CSA of each of the four skeletal muscle groups also significantly decreased; however, after adjustments for body weight at each time point, only reductions in the iliopsoas muscle in both sex and abdominal oblique muscles in men remained significant. CONCLUSIONS: The lifestyle weight loss intervention might reduce the relative amount of the abdominal skeletal muscles especially in iliopsoas muscle.

The effects of the muscular contraction on the abdominal biomechanics: a numerical investigation.

Abdominal wall biomechanics is strongly affected by muscular contraction and intra-abdominal pressure (IAP) which characterize different physiological functions and daily tasks. However, the active muscular behavior is generally not considered in current computational models of the abdominal wall. The aim of this study is to develop a numerical model mimicking muscular activation and IAP. A three dimensional Finite Element model of a healthy abdominal wall is developed detailing the principal abdomen components reconstructed upon anatomical data and medical images. Fascial tissues, aponeuroses and linea alba are modelled as hyperelastic fiber-reinforced materials, while a three-element Hill's model is assumed for muscles. Numerical analyses are performed increasing the IAP up to 100 mmHg and simultaneously activating the muscular structures. The obtained abdominal behavior is compared to a similar model with same IAPs, but passive muscles conditions. Abdomen stiffness and strength are computed in regions in which hernias can potentially occur. A global stiffening of the abdominal wall is found corresponding to a low abdomen deformation and the membrane force on fascial structures is reduced by muscular contraction. Representing active muscular contraction leads to advanced findings, otherwise membrane force results overestimated considering a purely passive behavior for the abdominal wall.