In vivo measurement of the effect of intra-abdominal pressure on the human spine

Thickness of the abdominal wall and pelvic floor dysfunctions in men who practice crossfit vs no crossfit: An observational study

INTRODUCTION

The objective of this study is to compare the thickness of the transverse abdominis, internal oblique, external oblique, rectus abdominis, and rectus abdominis distance, the quality of life (SF-36), the presence of chronic pelvic pain (CPPQ-Mohedo), and sexual dysfunction (IIEF) in men who practice CrossFit® versus men who do not.

DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOME MEASURES

Sixty-four healthy men with an average age of 37.19 were recruited at a private sports club and divided into two groups for this cross-sectional observational study. Additionally, participants completed the CPPQ-M, IIEF, and SF-36 questionnaires.

RESULTS

Significant differences were found in the thickness of the internal oblique at rest (p = 0.018, d = 0.61), which was greater in the CrossFit® group. In the SF-36 quality of life questionnaire (p = 0.05, d = 0.50), the CrossFit® group also obtained a higher score.

CONCLUSION

CrossFit® improves the quality of life and self-esteem of the participants, in addition to increasing the thickness of the internal oblique. Neither more chronic pelvic pain nor more erectile dysfunction was observed in the CrossFit® group.

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

Effect of strengthening and weakening of abdominal and dorsal muscles on lumbar spine loads in parents of disabled children

Pain in the lower part of the back is one of the most common chronic illnesses globally. This work aimed to determine the impact of the reinforcement of particular groups of abdominal and dorsal muscles on the loads exerted on the lumbar section of the spine in 30 mothers of children with motor disabilities. An optical Ariel Performance Analysis System recorded and processed the kinematics data of everyday activities. Tests investigating the effects of the strengthening or weakening of abdominal and dorsal muscles on loading in the lumbar section of the spine utilized the AnyBody Modelling System. Input data for the simulations included mean values of body positions, while the effects of strengthening or weakening of muscles were simulated in the muscle forces model by introducing different values for muscle physiological cross-sectional area (PCSA). Simulations used decreasing or increasing PCSA values of abdominal muscles and the erector spinae. The analysis involved component and resultant force values on the lumbosacral joint (L5-S1) of the spine and intra-abdominal pressure values. The highest reduction of the resultant reaction value in L5-S1 was observed in the simulations that increased the PCSA of the transverse abdominal (TrA). Indeed, a double increase in the TrA cross-section caused a reduction of the resultant reaction in L5-S1 by 30% and the anterior-posterior and proximal-distal forces by approximately 20-30%. Increased PCSA of the erector spinae exerted higher loads on the spine. These results indicate that strengthening weakened abdominal muscles, particularly TrA, in parents of children with motor disabilities reduces lower spinal loads during daily activities.

Effects of breathing exercises on low back pain in clinical: A systematic review and meta-analysis

OBJECTIVE

This study aims to systematically evaluate the effect of breathing exercises on the low back pain (LBP).

METHODS

The studies of relevant randomized controlled trials (RCTs) testing the effect of breathing exercises on LBP were selected after strict screening from the establishment of PubMed, EMBASE, Cochrane Library, Web of Science, CBM, and CNKI databases until September 2022. The studies included were then independently assessed for risk bias by two investigators. The PRISMA 2020 statement was followed in this study.

RESULTS

11 RCTs involving 383 patients were included in this analysis. Results showed that the effective rate of LBP patients after breathing exercises was significantly higher than those in the control group, and the VAS (Visual Analogue Score) and ODI (Oswestry Disability Index) scores of LBP patients were significantly lower than those in the control group [VAS: MD = -0.50, 95% CI (-0.88, -0.11), I2 = 76%, p = 0.0009; ODI: MD = -2.46, 95% CI (-3.41, -1.52), I2 = 20%, p = 0.28]. The results of subgroup showed that the duration of treatment had little effect on the effect of breathing exercises, and breathing exercises alone could also have a positive effect on LBP. However, there were methodological limitations in the included studies, future studies should ensure blinded outcome assessors and full reporting to reduce bias risks. Because this review is a study of breathing exercises as an intervention without any adverse events, all studies did not involve safety assessments.

CONCLUSIONS

The results indicated that breathing exercises have a positive effect on alleviating LBP, but due to the lack of methodological rigor and some limitations of the included studies, more critical RCTs are still needed in the future to verify the precision of this conclusion. The protocol was registered in PROSPERO (No. CRD42022345561).

Muscle-driven forward dynamic active hybrid model of the lumbosacral spine: combined FEM and multibody simulation

Most spine models belong to either the musculoskeletal multibody (MB) or finite element (FE) method. Recently, coupling of MB and FE models has increasingly been used to combine advantages of both methods. Active hybrid FE-MB models, still rarely used in spine research, avoid the interface and convergence problems associated with model coupling. They provide the inherent ability to account for the full interplay of passive and active mechanisms for spinal stability. In this paper, we developed and validated a novel muscle-driven forward dynamic active hybrid FE-MB model of the lumbosacral spine (LSS) in ArtiSynth to simultaneously calculate muscle activation patterns, vertebral movements, and internal mechanical loads. The model consisted of the rigid vertebrae L1-S1 interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, facet joints, and force actuators representing the muscles. Morphological muscle data were implemented via a semi-automated registration procedure. Four auxiliary bodies were utilized to describe non-linear muscle paths by wrapping and attaching the anterior abdominal muscles. This included an abdominal plate whose kinematics was optimized using motion capture data from upper body movements. Intra-abdominal pressure was calculated from the forces of the abdominal muscles compressing the abdominal cavity. For the muscle-driven approach, forward dynamics assisted data tracking was used to predict muscle activation patterns that generate spinal postures and balance the spine without prescribing accurate spinal kinematics. During calibration, the maximum specific muscle tension and spinal rhythms resulting from the model dynamics were evaluated. To validate the model, load cases were simulated from -10° extension to +30° flexion with weights up to 20 kg in both hands. The biomechanical model responses were compared with in vivo literature data of intradiscal pressures, intra-abdominal pressures, and muscle activities. The results demonstrated high agreement with this data and highlight the advantages of active hybrid modeling for the LSS. Overall, this new self-contained tool provides a robust and efficient estimation of LSS biomechanical responses under in vivo similar loads, for example, to improve pain treatment by spinal stabilization therapies.

Hip Pain and Movement Dysfunction Associated With Nonarthritic Hip Joint Pain: A Revision

The Academy of Orthopaedic Physical Therapy (AOPT), formerly the Orthopaedic Section of the American Physical Therapy Association (APTA), has an ongoing effort to create evidence-based practice guidelines for orthopaedic physical therapy management of patients with musculoskeletal impairments described in the World Health Organization's International Classification of Functioning, Disability, and Health (ICF). This is an update to the 2014 Clinical Practice Guideline (CPG) for Hip Pain and Movement Dysfunction Associated with Nonarthritic Hip Joint Pain. The goals of the revision were to provide a concise summary of the contemporary evidence since publication of the original guideline and to develop new recommendations or revise previously published recommendations to support evidence-based practice. This current CPG covers pathoanatomical features, clinical course, prognosis, diagnosis, examination, and physical therapy interventions in the management of nonarthritic hip joint pain. J Orthop Sports Phys Ther 2023;53(7):CPG1-CPG70. doi:10.2519/jospt.2023.0302.

Proof of Concept Testing of Safe Patient Handling Intervention Using Wearable Sensor Technology

BACKGROUND

Healthcare workers make up one of the occupations in the United States that experience the most musculoskeletal injuries. These injuries are often related to the movement and repositioning of patients. Despite previous injury prevention attempts, injury rates remain at an unsustainable level. The purpose of this proof-of-concept study is to provide preliminary testing of the impact of a lifting intervention on common biomechanical risk factors for injury during high-risk patient movements.; Methods: A before-and-after (quasi-experimental) design was utilized to compare biomechanical risk factors before and after a lifting intervention. Kinematic data were collected using the Xsens motion capture system, while muscle activations were collected with the Delsys Trigno EMG system.

RESULTS

Improvements were noted in the lever arm distance, trunk velocity, and muscle activations during the movements following the intervention; Conclusions: The contextual lifting intervention shows a positive impact on the biomechanical risk factors for musculoskeletal injury among healthcare workers without increasing the biomechanical risk. A larger, prospective study is needed to determine the intervention's ability to reduce injuries among healthcare workers.

Multibody Models of the Thoracolumbar Spine: A Review on Applications, Limitations, and Challenges

Numerical models of the musculoskeletal system as investigative tools are an integral part of biomechanical and clinical research. While finite element modeling is primarily suitable for the examination of deformation states and internal stresses in flexible bodies, multibody modeling is based on the assumption of rigid bodies, that are connected via joints and flexible elements. This simplification allows the consideration of biomechanical systems from a holistic perspective and thus takes into account multiple influencing factors of mechanical loads. Being the source of major health issues worldwide, the human spine is subject to a variety of studies using these models to investigate and understand healthy and pathological biomechanics of the upper body. In this review, we summarize the current state-of-the-art literature on multibody models of the thoracolumbar spine and identify limitations and challenges related to current modeling approaches.

Efficacy of telehealth core exercises during COVID-19 after bariatric surgery: a randomized controlled trial

BACKGROUND

Bariatric surgery (BS) is presently the most durable and effective intervention to address severe obesity. BS results in significant weight loss and body composition changes, with reductions in both fat mass and lean mass. Conequently, muscle tissue wasting and a reduction in muscle strength and endurance seem to take place. Some studies have evaluated the impact of resistance training on changes in lean body mass and muscle strength either alone or along with protein supplementation in the first year after BS. However, the effects of core stabilization training on core endurance, postural control, and aerobic capacity in patients after BS have not been evaluated.

AIM

This study assessed the effect of a home telehealth core stabilization exercise program on core stability, postural control, and aerobic capacity in patients after BS.

DESIGN

A single-blinded randomized controlled trial.

SETTING

Home-based exercise program.

POPULATION

Patients after BS.

METHODS

Fifty-four patients who underwent BS randomly assigned into study and control groups. The study group followed a telehealth supervised home core stabilization program for 8 weeks, while the control group did not receive any form of exercises. Core endurance tests, postural stability, and aerobic capacity were assessed at baseline and after 8 weeks in both groups.

RESULTS

No significant difference was noted between groups at baseline (P>0.05). The outcome of the group comparisons showed significant improvement in core endurance tests, postural stability, and aerobic capacity in the study group. Between groups comparision showed that the study group scores significantly higher than the control group (P<0.05). However, the control group showed non-significant changes in any measured variables after eight weeks (P>0.05).

CONCLUSIONS

Eight weeks of a home-based telehealth core exercise program improves core endurance, postural stability, and aerobic capacity in patients after BS.

CLINICAL REHABILITATION IMPACT

The core stabilization exercise is an important rehabilitation program that should be implemented after BS. Telehealth is an alternative rehabilitation tool during the COVID -19 pandemic.

Postural-respiratory function of the diaphragm assessed by M-mode ultrasonography

OBJECTIVES

The diaphragm changes position and respiratory excursions during postural loading. However, it is unclear how it reacts to lifting a load while breath-holding or breathing with simultaneous voluntary contraction of the abdominal muscles (VCAM). This study analyzed diaphragm motion in healthy individuals during various postural-respiratory situations.

METHODS

31 healthy participants underwent examination of the diaphragm using M-mode ultrasonography, spirometry, and abdominal wall tension (AWT) measurements. All recordings were performed simultaneously during three consecutive scenarios, i.e., 1. Lifting a load without breathing; 2. Lifting a load and breathing naturally; 3. Lifting a load and breathing with simultaneous VCAM.

RESULTS

Using paired-samples t-tests, lifting a load without breathing displaced the diaphragm's expiratory position more caudally (P < .001), with no change noted in the inspiratory position (P = .373). During lifting a load breathing naturally, caudal displacement of the diaphragm's inspiratory position was presented (P < .001), with no change noted in the expiratory position (P = 0.20) compared to tidal breathing. Total diaphragm excursion was greater when loaded (P = .002). Lifting a load and breathing with VCAM demonstrated no significant changes in diaphragm position for inspiration, expiration, or total excursion compared to natural loaded breathing. For all scenarios, AWT measures were greater when lifting a load (P < .001).

CONCLUSION

In healthy individuals, caudal displacement and greater excursions of the diaphragm occurred when lifting a load. The postural function of the diaphragm is independent of its respiratory activity and is not reduced by the increase in AWT.

Development and evaluation of a numerical spine model comprising intra-abdominal pressure for use in assessing physiological changes on abdominal compliance and spinal stability

BACKGROUND

Abdominal compliance is the "measure of ease of abdominal expansion" and determines whether a patient can withstand high intra-abdominal pressures. Thus, high compliance indicates that the abdomen can expand relatively freely, while low compliance restricts abdominal expansion. The global objective of the present work is to evaluate the effect of physiological changes on abdominal compliance using a comprehensive spine finite element model inclusive of intra-abdominal pressure.

METHODS

The effect of changing Young's modulus, abdominal wall thickness, and abdominal radii on abdominal compliance were evaluated. Intra-abdominal pressure and thoracolumbar fascia forces were also evaluated to assess abdominal physiological changes effects on overall static spinal stability.

FINDINGS

Results showed that as wall thickness increased, compliance decreased. Similar findings were made with an increase in abdominal radius and Young's modulus. Furthermore, the active reduction in compliance, caused by increased elasticity and abdominal radius, resulted in an increase in spinal supportive forces originating from the thoracolumbar fascia and intra-abdominal pressurization, along with an increase in spine displacement from its original stable position. There was no clear stability trend for the case of changing abdominal wall thickness as fluctuations were present.

INTERPRETATION

Investigated mechanics and data trends suggested that dangerously low compliance levels might result from poor abdominal elasticity and thickening fat layers. This led to a direct discussion and recommendations for obesity conditions and laparoscopy applications. Lastly, static spinal stability showed to improve through increasing active abdominal compliance by means of actively engaging abdominal pressure, hence augmenting abdominal active elasticity.

Breathing Exercises for Improving Cognitive Function in Patients with Stroke

Patients with stroke may experience a certain degree of cognitive decline during the period of recovery, and a considerable number of such patients have been reported to show permanent cognitive damage. Therefore, the period of recovery and rehabilitation following stroke is critical for rapid cognitive functional improvements. As dysfunctional breathing has been reported as one of the factors affecting the quality of life post stroke, a number of studies have focused on the need for improving the breathing function in these patients. Numerous breathing exercises have been reported to enhance the respiratory, pulmonary, cognitive, and psychological functions. However, scientific evidence on the underlying mechanisms by which these exercises improve cognitive function is scattered at best. Therefore, it has been difficult to establish a protocol of breathing exercises for patients with stroke. In this review, we summarize the psychological, vascular, sleep-related, and biochemical factors influencing cognition in patients and highlight the need for breathing exercises based on existing studies. Breathing exercises are expected to contribute to improvements in cognitive function in stroke based on a diverse array of supporting evidence. With relevant follow-up studies, a protocol of breathing exercises can be developed for improving the cognitive function in patients with stroke.

Effect of interferential current on deep abdominal muscle thickness

[Purpose] We aimed to investigate the effects of various modulated interferential currents on deep abdominal muscle thicknesses of healthy participants using ultrasound imaging. [Participants and Methods] We recruited twenty-two healthy male participants for this study. We compared the rate of change in muscle thickness of the abdominal muscles under different stimulation interferential current conditions. [Results] The change in interclass correlation coefficient of muscle thickness for each electrical stimulation by attached electrode altering was 0.738–0.998, indicating normal to good reliability. The rate of change for all muscle thicknesses under interferential current at 2.5 kHz and 20 Hz was significantly greater than that under the other conditions. [Conclusion] An interferential current at 2.5 kHz and 20 Hz is a feasible and reproducible way to train the abdominal muscles.

Electromyographic Comparison of an Abdominal Rise on a Ball with a Traditional Crunch

We propose a new exercise, the abdominal rise on the ball, to replace the traditional crunch in exercise programs. The aim of this study is to compare the activity of the abdominal muscles when performing an ARB with the same activity when performing a traditional crunch. Twenty healthy adults participated in the study. Surface electromyography (EMG) was recorded from the upper and lower rectus abdominis (URA, LRA), internal oblique (IO), external oblique (EO), transversus abdominis (TrA), and erector spinae (ES). EMG values were normalized to maximal voluntary isometric contraction. A paired t-test, nonparametric Wilcoxon test and correlation coefficient were used for statistical analysis. The normalized EMG values of EO, TrA and ES, were statistically significantly higher during the abdominal rise on the ball compared to the traditional crunch, while URA, LRA and IO were significantly lower during the abdominal rise on the ball compared to the traditional crunch. TrA, EO and IO are sufficiently activated during an abdominal rise on a ball, so the exercise could be deemed effective for strengthening these muscles.

Embodiment of intra-abdominal pressure in a flexible multibody model of the trunk and the spinal unloading effects during static lifting tasks

The role of intra-abdominal pressure (IAP) in spinal load reduction has remained controversial, partly because previous musculoskeletal models did not introduce the pressure generating mechanism. In this study, an integrated computational methodology is proposed to combine the IAP change with core muscle activations. An ideal gas relationship was introduced to calculate pressure distribution within the abdominal cavity. Additionally, based on flexible multibody dynamics, a muscle membrane element was developed by incorporating the muscular fiber deformation, inter-fiber stiffness, and volume constancy. This element was then utilized in discretizing the diaphragm and transversus abdominis, forming an IAP-muscle coupling system of the abdominal cavity. Based on this methodology, a forward dynamic simulation of spinal flexion was presented to examine the unloading effect of abdominal breathing. The results confirm that core muscle contraction during the abdominal breathing cycle can substantially reduce the forces of spinal compression together with trunk extensor muscles, and this effect is more pronounced when the IAP increase is produced by contraction of the transversus abdominis. This unloading effect still holds even with the co-activation of other abdominal muscles, providing a potential choice when designing trunk movements during weight-lifting tasks.

Mechanisms of postural control in older adults based on surface electromyography data

OBJECTIVES

The present study aimed to clarify the mechanisms of postural control during standing in older adults and document the mechanisms of age-related motor control based on changes in muscle activities.

METHODS

A total of 26 healthy male adults (older adult group, ≥65-78 years: n = 16; younger adult group, 20-23 years: n = 10) participated in this study. Ground reaction force and kinematic data of the lower limbs (hip, knee, and ankle), and electromyographic data from 6 postural muscles on the right side were recorded and quantified for each motor phase during rapid voluntary center of pressure (COP) shift.

RESULTS

Although hip strategy was more frequently observed in older adults than in young adults (56.3% vs. 20.0%), no muscle activity of hip agonists was observed in some (31.3%) older adults. Furthermore, older adults had a statistically significant delay in the inhibition of postural muscles during anticipatory postural adjustments (p < 0.05). After the onset of COP motion, the co-contraction time between agonists and antagonists was significantly prolonged in the older adults than in the younger adults (p < 0.05), and the reciprocal muscle pattern was unclear in the older adults. Prior to the termination of movement, agonist activity continued longer in the older adult group than in the younger adult group; that is, inhibition was insufficient in the older adult group.

CONCLUSION

A series of postural strategies during the voluntary movement task were altered in older adults, and this was significantly related not only with the activation but also the inhibition of postural muscles.

Postural and respiratory function of the abdominal muscles: A pilot study to measure abdominal wall activity using belt sensors

BACKGROUND: The abdominal muscles play an important respiratory and stabilization role, and in coordination with other muscles regulate intra-abdominal pressure (IAP) to stabilize the spine. OBJECTIVE: To examine a new, non-invasive method to measure activation of the abdominal wall and compare changes in muscle activation during respiration while breathing under a load, and during instructed breathing. METHODS: Thirty-five healthy individuals completed this observational crossover study. Two capacitive force sensors registered the abdominal wall force during resting breathing stereotype, instructed breathing stereotype and under a load. RESULTS: Mean abdominal wall force increased significantly on both sensors when holding the load compared to resting breathing (Upper Sensor: P< 0.0005, d=-0.46, Lower Sensor: P< 0.0005, d=-0.56). The pressure on both sensors also significantly increased during instructed breathing compared to resting breathing (US: P< 0.0005, d=-0.76, LS: P< 0.0005, d=-0.78). CONCLUSIONS: The use of capacitive force-sensors represent a new, non-invasive method to measure abdominal wall activity. Clinically, belts with capacitive force sensors can be used as a feedback tool to train abdominal wall activation.

Abdominal Muscle Activation During Common Modifications of the Trunk Curl-up Exercise

ABSTRACT

Crommert, ME, Bjerkefors, A, Tarassova, O, and Ekblom, MM. Abdominal muscle activation during common modifications of the trunk curl-up exercise. J Strength Cond Res 35(2): 428-435, 2021-The purpose of this study was to investigate effects of common modifications of trunk curl-up exercise on the involvement of the abdominal muscles, particularly the deepest muscle layer, transversus abdominis (TrA). Ten healthy females performed 5 different variations of the trunk curl-up at a standardized speed, varying the exercise by assuming 3 different arm positions and applying left and right twist. Indwelling fine-wire electromyography (EMG) electrodes were used to record from TrA, obliquus internus (OI), obliquus externus (OE), and rectus abdominis (RA) unilaterally on the right side. Increasing the load by changing the arm position during a straight trunk curl-up increased the EMG of all abdominal muscles. Obliquus internus and TrA showed higher activation during right twist compared with left twist, whereas OE displayed the opposite pattern. Rectus abdominis did not show any change in activation level between twisting directions. The apparent load dependency on the activation level of all muscles, and the twisting direction dependency of all muscles except RA, are in keeping with the fiber orientation of the muscles. Notably, also TrA, with a less obvious mechanical role with regards to fiber orientation, increased activation with load during the straight trunk curl-up. However, the highest activation level of TrA during the trunk curl-up was only 40% of a maximum contraction; thus, it might not be the most suitable strength training exercise for this muscle.

A concise overview of non-invasive intra-abdominal pressure measurement techniques: from bench to bedside

This review presents an overview of previously reported non-invasive intra-abdominal pressure (IAP) measurement techniques. Each section covers the basic physical principles and methodology of the various measurement techniques, the experimental results, and the advantages and disadvantages of each method. The most promising non-invasive methods for IAP measurement are microwave reflectometry and ultrasound assessment, in combination with an applied external force.

Does Intra-abdominal Pressure Have a Causal Effect on Muscle Strength of Hip and Knee Joints?

ABSTRACT

Tayashiki, K, Kanehisa, H, and Miyamoto, N. Does intra-abdominal pressure have a causal effect on muscle strength of hip and knee joints? J Strength Cond Res 35(1): 41-46, 2021-It remains unclear whether intra-abdominal pressure (IAP) has a causal effect on lower-limb muscle strength. This study aimed to clarify whether or not changes in IAP, induced by changing breathing state, influence muscle strength of hip and knee extensor and flexor. Eighteen healthy males (age: 22.0 ± 2.2 years, height: 1.71 ± 0.03 m, and body mass: 68.1 ± 6.1 kg) performed maximal voluntary isometric contractions (MVICs) of hip and knee extensor and flexor during breath-hold at full inspiration (inspiratory condition) or expiration (expiratory condition), or during normal breath-hold (normal condition). Intra-abdominal pressure was obtained by a pressure transducer placed in the rectum and determined at the time at which the developed torque reached to the maximum. The IAP during each MVIC was significantly greater in inspiratory condition than in expiratory condition (p < 0.05). The maximal torque of hip extensor was significantly greater in inspiratory condition than in expiratory condition (p < 0.05). By contrast, the maximal torque of each of hip flexor, knee extensor, and knee flexor was not different among the 3 breath-hold conditions. The IAP was significantly correlated with the maximal torque of hip extensor in each breath-hold condition. The current results suggest that a sufficient increase in IAP has a causal effect to specifically improve muscle strength of hip extensor.

Cardiorespiratory demands of competitive rock climbing

Rock climbing has become a mainstream sport, contested on the Olympic stage. The work/rest pattern of bouldering is unique among disciplines, and little is known about its physiological demands. This study characterised the cardiorespiratory responses to simulated competition. Eleven elite boulderers (7 male) volunteered to participate (age = 23.3 ± 4.5 years; mass = 68.2 ± 9.7 kg; stature = 1.73 ± 0.06 m; body fat = 10.4% ± 5%). Subjects completed incremental treadmill running to determine maximal capacities. On a separate day, they undertook a simulated Olympic-style climbing competition comprising 5 boulder problems, each separated by 5 min of rest. Pulmonary ventilation, gas exchange, and heart rate were assessed throughout. Total climbing time was 18.9 ± 2.7 min. Bouldering elicited a peak oxygen uptake of 35.8 ± 7.3 mL·kg^-1·min^-1 (∼75% of treadmill maximum) and a peak heart rate of 162 ± 14 beats·min^-1 (∼88% of maximum). Subjects spent 22.9% ± 8.6% of climbing time above the gas exchange threshold. At exercise cessation, there was an abrupt and significant increase in tidal volume (1.4 ± 0.4 vs. 1.8 ± 0.4 L; p = 0.006, d = 0.83) despite unchanged minute ventilation. Cardiorespiratory parameters returned to baseline within 4 min of the rest period. In conclusion, competitive bouldering elicits substantial cardiorespiratory demand and evidence of tidal volume constraint. Further studies are warranted to explore the effect of cardiorespiratory training on climbing performance. Novelty: Competitive bouldering evokes a high fraction of maximal oxygen uptake and prolonged periods above the gas exchange threshold. Climbing appears to impose a constraint on tidal volume expansion. Cardiorespiratory indices in elite climbers return to baseline within 2-4 min.

Comparative Effect of Liuzijue Qigong and Conventional Respiratory Training on Trunk Control Ability and Respiratory Muscle Function in Patients at an Early Recovery Stage From Stroke: A Randomized Controlled Trial

OBJECTIVES

To compare the effects of Liuzijue Qigong and conventional respiratory training on trunk control ability and respiratory muscle functions in patients at an early recovery stage from stroke.

DESIGN

A single-blind, randomized controlled trial.

SETTING

A hospital.

PARTICIPANTS

Patients (N=60) within 2 months poststroke.

INTERVENTIONS

The experimental group (n=30) received conventional rehabilitation training combined with Liuzijue exercise, and the control group (n=30) received conventional rehabilitation training combined with conventional respiration training. The training in the 2 groups was conducted 5 times per week for 3 weeks.

MAIN OUTCOME MEASURES

Trunk Impairment Scale (TIS), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF), maximum expiratory mid-flow (MMEF), diaphragmatic movement, the change of intra-abdominal pressure (IAP), Berg Balance Scale (BBS), and Modified Barthel Index (MBI). All outcome measures were assessed twice (at baseline and 3 weeks).

RESULTS

Both groups significantly improved in TIS, MIP, FVC, PEF, and the change of IAP, BBS, and MBI when pre- and postassessments (P<.05) were compared. Compared with the control group, there was a significant difference in the experimental group in the static sitting balance subscale (P=.014), dynamic balance subscale (P=.001), coordination subscale (P<.001), TIS total scores (P<.001; effect size [ES]=0.9), MIP (P=.012; 95% confidence interval [CI], 2.23-17.69; ES=0.67), MEP (P=.015; 95% CI, 1.85-16.57; ES=0.65), change of IAP (P=.001), and MBI (P=.016; 95% CI, 1.51-14.16; ES=0.64). No significant differences were found between the 2 groups in FEV1 (P=.24), FVC (P=.43), PEF (P=.202), MMEF (P=.277), the diaphragmatic movement of quiet breathing (P=.146), deep breathing (P=.102), and BBS (P=.124).

CONCLUSIONS

Liuzijue exercise showed more changes than conventional respiratory training in improving trunk control ability, respiratory muscle functions, and activities of daily living ability in patients at an early recovery stage from stroke.

Reconsideration of pelvic floor muscle training to prevent and treat incontinence after radical prostatectomy

Urinary incontinence is common after radical prostatectomy. Pelvic floor muscle training provides a plausible solution. Although early trials provided promising results, systematic reviews have questioned the efficacy of this intervention. A major consideration is that most clinical trials in men have applied principles developed for pelvic floor muscle training for stress urinary incontinence in women, despite differences in anatomy between sexes and differences in the mechanisms for continence/incontinence. Literature regarding continence control in men has been conflicting and often based on erroneous anatomy. New understanding of continence mechanisms in men, including the complex contribution of multiple layers of striated pelvic floor muscles, and detailed consideration of the impact of radical prostatectomy on continence anatomy and physiology, have provided foundations for a new approach to pelvic floor muscle training to prevent and treat incontinence after prostatectomy. An approach to training can be designed to target the pathophysiology of incontinence. This approach relies on principles of motor learning and exercise physiology, in a manner that is tailored to the individual patient. The aims of this review are to consider new understanding of continence control in men, the mechanisms for incontinence after radical prostatectomy, and to review the characteristics of a pelvic floor muscle training program designed to specifically target recovery of continence after prostatectomy.

Numerical Investigation of Intra-abdominal Pressure Effects on Spinal Loads and Load-Sharing in Forward Flexion

The intra-abdominal pressure (IAP), which generates extensor torque and unloads the spine, is often neglected in most of the numerical studies that use musculoskeletal (MSK) or finite element (FE) spine models. Hence, the spinal loads predicted by these models may not be realistic. In this work, we quantified the effects of IAP variation in forward flexion on spinal loads and load-sharing using a novel computational tool that combines a MSK model of the trunk with a FE model of the ligamentous lumbosacral spine. The MSK model predicted the trunk muscle and reaction forces at the T12-L1 junction, with or without the IAP, which served as input in the FE model to investigate the effects of IAP on spinal loads and load-sharing. The findings confirm the unloading role of the IAP, especially at large flexion angles. Inclusion of the IAP reduced global muscle forces and disc loads, as well as the intradiscal pressure (IDP). The reduction in disc loads was compensated for by an increase in ligament forces. The IDP, as well as the strain of the annular fibers were more sensitive to the IAP at the upper levels of the spine. Including the IAP also increased the ligaments' load-sharing which reduced the role of the disc in resisting internal forces. These results are valuable for more accurate spinal computational studies, particularly toward clinical applications as well as the design of disc implants.

Anticipatory postural control differs between low back pain and pelvic girdle pain patients in the absence of visual feedback

PURPOSE

The aim of this study was to examine the effect of vision on anticipatory postural control (APA) responses in two groups of clinically diagnosed chronic low back pain patients, those with Posterior Pelvic Girdle pain and those with Non-Specific Low Back Pain compared to a matched group of healthy controls during the modified Trendelenburg task.

METHODS

Seventy-eight volunteer participants (60 females and 18 males) gave informed consent to take part in this study. 39 with confirmed LBP or PGP lasting longer than 12 weeks and 39 healthy matched controls performed 40 single leg lift tasks (hip flexion to 90° as quickly as possible) with their non-dominant lower limb. A force plate was used to determine the medial-lateral displacement of the center of pressure, and the initiation of weight shift; kinematics was used to determine initiation of leg lift; and electromyography was used to determine onset times from the external oblique (EO), internal oblique (IO) and lumbar multifidus (MF), gluteus maximus (GM) and biceps femoris (BF).

RESULTS

The PGP group showed significantly longer muscle onset latencies in the BF, EO MF with visual occlusion (F_2,746 = 4.51, p < .0001).

CONCLUSION

The muscle onset delays identified between the two LBP sub-groups suggests that pain may not be the primary factor in alteration of APA response. The PGP group show a greater reliance on vision which may signal impairment in multiple feedback channels.

Progressive Respiratory Muscle Training for Improving Trunk Stability in Chronic Stroke Survivors: A Pilot Randomized Controlled Trial

BACKGROUND

Stroke weakens the respiratory muscles, which in turn may influence the trunk stability; it is unclear whether the progressive respiratory muscle training (RMT) is effective in improving the trunk stability. The aim of this study was to investigate the effects of progressive RMT with trunk stabilization exercise (TSE) on respiratory muscles thickness, respiratory muscle functions, and trunk stability in chronic stroke survivors.

METHODS

This is a pilot randomized controlled trial. Chronic stroke survivors (n = 33) who were able to sit independently participated in the tstudy. The participants were allocated into the RMP with TSE group or the TSE group. The respiratory muscle thickness during resting and contraction were measured. Maximal expiratory pressure (MEP), peak expiratory flow (PEF), and forceful expiratory volume at 1 sec (FEV1) for forced expiratory muscle function and maximal inspiratory pressure (MIP), peak inspiratory flow (PIF), and vital capacity (VC) for inspiratory muscle function were examined. Trunk stability was estimated by maximal velocity and path length of the center of pressure (COP) by using a balance board with sitting posture.

RESULTS

The respiratory muscle thickness was significantly increased on the affected side in the RMT group than in the TSE group. The MEP, PEF, MIP, and PIF were significantly increased in the RMT group than in the TSE group; however, FEV1 and VC showed no significant differences between the 2 groups. Trunk stability for the maximal velocity of COP of extension and affected side bending was significantly increased in the RMT group than in the TSE group. In addition, the maximal path length of COP of flexion, extension, affected/less affected side bending was significantly increased in the RMT group than in the TSE group.

CONCLUSIONS

RMT combined with TSE can be suggested as an effective method to improve the respiratory muscle thickness, respiratory muscle functions, and trunk stability in chronic stroke survivors as opposed to TSE only.

Effects of Vojta approach on diaphragm movement in children with spastic cerebral palsy

The purpose of this study was to examine the effects of Vojta approach on the gross motor function and diaphragm movement in children with spastic cerebral palsy (CP). Ten children with spastic CP were randomly assigned to a general physiotherapy group (trunk strengthening exercise and gait training) (n=5) and a Vojta approach group (n=5). Interventions were implemented for 30 min per time, 3 times a week for a total of 6 weeks. Ultrasonography was used to measure the areas of the diaphragm (during inspiration, expiration) before and after the interventions, the gross motor function measure (GMFM)-88 was used for evaluation of the gross motor function. In the results of this study, there was a significant difference between before and after GMFM-sitting in the experimental group (P<0.05), a significant difference in changes of inspiration between the two groups (P<0.05). Given these results, Vojta approach may be presented as an effective treatment method for improving sitting position and diaphragm movement during inspiration in children with spastic CP.

Pulmonary and respiratory muscle function in response to 10 marathons in 10 days

PURPOSE

Marathon and ultramarathon provoke respiratory muscle fatigue and pulmonary dysfunction; nevertheless, it is unknown how the respiratory system responds to multiple, consecutive days of endurance exercise.

METHODS

Nine trained individuals (six male) contested 10 marathons in 10 consecutive days. Respiratory muscle strength (maximum static inspiratory and expiratory mouth-pressures), pulmonary function (spirometry), perceptual ratings of respiratory muscle soreness (Visual Analogue Scale), breathlessness (dyspnea, modified Borg CR10 scale), and symptoms of Upper Respiratory Tract Infection (URTI), were assessed before and after marathons on days 1, 4, 7, and 10.

RESULTS

Group mean time for 10 marathons was 276 ± 35 min. Relative to pre-challenge baseline (159 ± 32 cmH₂O), MEP was reduced after day 1 (136 ± 31 cmH₂O, p = 0.017), day 7 (138 ± 42 cmH₂O, p = 0.035), and day 10 (130 ± 41 cmH₂O, p = 0.008). There was no change in pre-marathon MEP across days 1, 4, 7, or 10 (p > 0.05). Pre-marathon forced vital capacity was significantly diminished at day 4 (4.74 ± 1.09 versus 4.56 ± 1.09 L, p = 0.035), remaining below baseline at day 7 (p = 0.045) and day 10 (p = 0.015). There were no changes in FEV₁, FEV₁/FVC, PEF, MIP, or respiratory perceptions during the course of the challenge (p > 0.05). In the 15-day post-challenge period, 5/9 (56%) runners reported symptoms of URTI, relative to 1/9 (11%) pre-challenge.

CONCLUSIONS

Single-stage marathon provokes acute expiratory muscle fatigue which may have implications for health and/or performance, but 10 consecutive days of marathon running does not elicit cumulative (chronic) changes in respiratory function or perceptions of dyspnea. These data allude to the robustness of the healthy respiratory system.

Decreased Respiratory Muscle Function Is Associated with Impaired Trunk Balance among Chronic Stroke Patients: A Cross-sectional Study

The abdominal muscles play a role in trunk balance. Abdominal muscle thickness is asymmetrical in stroke survivors, who also have decreased respiratory muscle function. We compared the thickness of the abdominal muscles between the affected and less affected sides in stroke survivors. In addition, the relationship between respiratory muscle function and trunk balance was evaluated. Chronic stroke patients (18 men, 15 women; mean age, 58.94 ± 12.30 years; Mini-Mental Status Examination score ≥ 24) who could sit without assist were enrolled. Abdominal muscle thickness during rest and contraction was measured with ultrasonography, and the thickening ratio was calculated. Respiratory muscle function assessment included maximum respiratory pressure, peak flow, and air volume. Trunk function was evaluated using the Trunk Impairment Scale, and trunk balance was estimated based on the center of pressure velocity and path length within the limit of stability in sitting posture. Abdominal muscles were significantly thinner on the affected side, and the thickening ratio was lower in the affected side (P < 0.05). In addition, the higher thickening ratio of the affected side showed significant relationship with higher trunk function. Moreover, higher respiratory muscle function was significantly correlated with higher level of trunk function and balance in stroke patients (P < 0.05). Thus, chronic stroke survivors have decreased abdominal muscle thickness on the affected side, and respiratory muscle function has positive correlation with trunk function and balance. We propose that respiratory muscle training should be included as part of trunk balance training in chronic stroke patients.

Effects of core strength training on core stability

[Purpose] To investigate the effects of core strength training on core stability with and without the Valsalva maneuver. [Participants and Methods] Twenty-four students were randomly assigned to the training and control groups. Students in the training group undertook a 4-week training program that included exercises for the transverse abdominis, multifidus, diaphragm, and pelvic floor muscles, whereas students in the control group performed their usual activities. Participants were required to perform four types of task with and without the Valsalva maneuver. Seated stabilometry was assessed according to the center of pressure (COP). [Results] In the training group, the rectus area in the quiet sitting position with the Valsalva maneuver was enlarged and the length of trajectory during a sudden perturbation task was decreased. No significant changes to the COP were seen in the control group. [Conclusion] Some parameters of core stability improved after participants completed a 4-week core strength training program.

Abdominoplasty Improves Low Back Pain and Urinary Incontinence

BACKGROUND

The authors studied the incidence of low back pain and urinary incontinence in the postpartum population presenting for abdominoplasty, and the extent of improvement following the operation.

METHODS

This multicenter prospective study used validated questionnaires: the Oswestry Disability Index for back pain and the International Consultation on Incontinence Questionnaire-Urinary Incontinence-Short Form for urinary incontinence. Questionnaires were administered preoperatively and at 6 weeks and 6 months postoperatively.

RESULTS

Results cover 214 patients from nine centers. The mean age was 42.1 years, the mean parity was 2.5, and the mean body mass index was 26.3 kg/m. The mean surgical statistics were as follows: weight removed, 1222 g; liposuction volume, 795 ml; and diastasis, 4.5 cm. Eighty-seven percent of the abdominoplasties were either radical, high lateral tension, or high oblique tension. The mean Oswestry Disability Index score preoperatively was 21.6 percent, and 8.8 percent had no back pain. The mean score was 8 percent at 6 weeks and 3.2 percent at 6 months. These results are statistically significant. The mean International Consultation on Incontinence Questionnaire score preoperatively was 6.5; of the patients assessed, 27.5 percent had no incontinence. This score fell to 1.6 at 6 weeks, and the same, 1.6, at 6 months. These results are also statistically significant. Preoperative predictors of back pain were body mass index greater than 25 kg/m and umbilical hernia; predictors of incontinence were age older than 40 years and vaginal deliveries. There were no significant predictors of postoperative back pain or urinary incontinence improvement at 6 months. All methods of abdominoplasty produced similar improvement.

CONCLUSION

Abdominoplasty with rectus repair creates a significant improvement in the functional symptoms of low back pain and urinary incontinence.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Early initiation of a strength training based rehabilitation after lumbar spine fusion improves core muscle strength: a randomized controlled trial

Background

To analyze the safety and effects of early initiation of rehabilitation including objective measurement outcomes after lumbar spine fusion based on principles of strength training.

Methods

The study recruited 27 patients, aged 45 to 70 years, who had undergone lumbar spine fusion. The method of concealed random allocation without blocking was used to form two groups. The strength training group started rehabilitation 3 weeks after surgery. Patients exercised twice weekly over 9 weeks focusing on muscle activation of lumbopelvic stabilization muscles. The control group followed a standard postoperative protocol, where no exercises were performed at that stage of rehabilitation. Functional outcomes and plain radiographs were evaluated at 3 weeks and subsequently at 3 and 18 months after the surgery.

Results

No hardware loosening of failure was observed in the training group. Both groups improved their walking speed after 3 months (p < 0.01), although improvement in the training group was significantly greater than in the control group (p < 0.01). Moreover, the training group significantly improved after the training period in all isometric trunk muscles measurements (p < 0.03), standing reach height (p < 0.02), and pre-activation pattern (p < 0.05). After 18 months, no training effects were observed.

Conclusions

The study showed that early initiation of a postoperative rehabilitation program based on principles of strength training is safe, 3 weeks after lumbar spine fusion, and enable earlier functional recovery than standard rehabilitation protocol.

Trial registration

The study is registered at the US National Institutes of Health (ClinicalTrials.gov) NCT03349580. The date of registration: November 21, 2017 - Retrospectively registered.

The rib cage stiffens the thoracic spine in a cadaveric model with body weight load under dynamic moments

The thoracic spine presents a challenge for biomechanical testing. With more segments than the lumbar and cervical regions and the integration with the rib cage, experimental approaches to evaluate the mechanical behavior of cadaveric thoracic spines have varied widely. Some researchers are now including the rib cage intact during testing, and some are incorporating follower load techniques in the thoracic spine. Both of these approaches aim to more closely model physiological conditions. To date, no studies have examined the impact of the rib cage on thoracic spine motion and stiffness in conjunction with follower loads. The purpose of this research was to quantify the mechanical effect of the rib cage on cadaveric thoracic spine motion and stiffness with a follower load under dynamic moments. It was hypothesized that the rib cage would increase stiffness and decrease motion of the thoracic spine with a follower load. Eight fresh-frozen human cadaveric thoracic spines with rib cages (T1-T12) were loaded with a 400 N compressive follower load. Dynamic moments of ± 5 N m were applied in lateral bending, flexion/extension, and axial rotation, and the motion and stiffness of the specimens with the rib cage intact have been previously reported. This study evaluated the motion and stiffness of the specimens after rib cage removal, and compared the data to the rib cage intact condition. Range-of-motion and stiffness were calculated for the upper, middle, and lower segments of the thoracic spine. Range-of-motion significantly increased with the removal of the rib cage in lateral bending, flexion/extension, and axial rotation by 63.5%, 63.0%, and 58.8%, respectively (p < 0.05). Neutral and elastic zones increased in flexion/extension and axial rotation, and neutral zone stiffness decreased in axial rotation with rib cage removal. Overall, the removal of the rib cage increases the range-of-motion and decreases the stiffness of cadaveric thoracic spines under compressive follower loads in vitro. This study suggests that the rib cage should be included when testing a cadaveric thoracic spine with a follower load to optimize clinical relevance.

Clinical potential of implantable wireless sensors for orthopedic treatments

INTRODUCTION

Implantable wireless sensors have been used for real-time monitoring of chemicals and physical conditions of bones, tendons and muscles to diagnose and study orthopedic diseases and injuries. Due to the importance of these sensors in orthopedic care, a critical review, which not only analyzes the underlying technologies but also their clinical implementations and challenges, will provide a landscape view on their current state and their future clinical role.

AREAS COVERED

By conducting an extensive literature search and following the leaders of orthopedic implantable wireless sensors, this review covers the battery-powered and battery-free wireless implantable sensor technologies, and describes their implementation for hips, knees, spine, and shoulder stress/strain monitoring. Their advantages, limitations, and clinical challenges are also described.

EXPERT COMMENTARY

Currently, implantable wireless sensors are mostly limited for scientific investigations and demonstrative experiments. Although rapid advancement in sensors and wireless technologies will push the reliability and practicality of these sensors for clinical realization, regulatory constraints and financial viability in medical device industry may curtail their continuous adoption for clinical orthopedic applications. In the next five years, these sensors are expected to gain increased interest from researchers, but wide clinical adoption is still unlikely.

Exercise-induced diaphragm fatigue in a Paralympic champion rower with spinal cord injury

The aim of this case report was to determine whether maximal upper body exercise was sufficient to induce diaphragm fatigue in a Paralympic champion adaptive rower with low-lesion spinal cord injury (SCI). An elite arms-only oarsman (age: 28 yr; stature: 1.89 m; and mass: 90.4 kg) with motor-complete SCI (T₁₂) performed a 1,000-m time trial on an adapted rowing ergometer. Exercise measurements comprised pulmonary ventilation and gas exchange, diaphragm EMG-derived indexes of neural respiratory drive, and intrathoracic pressure-derived indexes of respiratory mechanics. Diaphragm fatigue was assessed by measuring pre- to postexercise changes in the twitch transdiaphragmatic pressure (P_di,tw) response to anterolateral magnetic stimulation of the phrenic nerves. The time trial (248 ± 25 W, 3.9 min) elicited a peak O₂ uptake of 3.46 l/min and a peak pulmonary ventilation of 150 l/min (57% MVV). Breath-to-stroke ratio was 1:1 during the initial 400 m and 2:1 thereafter. The ratio of inspiratory transdiaphragmatic pressure to diaphragm EMG (neuromuscular efficiency) fell from rest to 600 m (16.0 vs. 3.0). Potentiated P_di,tw was substantially reduced (-33%) at 15-20 min postexercise, with only partial recovery (-12%) at 30-35 min. This is the first report of exercise-induced diaphragm fatigue in SCI. The decrease in diaphragm neuromuscular efficiency during exercise suggests that the fatigue was partly due to factors independent of ventilation (e.g., posture and locomotion). NEW & NOTEWORTHY This case report provides the first objective evidence of exercise-induced diaphragm fatigue in spinal cord injury (SCI) and, for that matter, in any population undertaking upper body exercise. Our data support the notion that high levels of exercise hyperpnea and factors other than ventilation (e.g., posture and locomotion) are responsible for the fatigue noted after upper body exercise. The findings extend our understanding of the limits of physiological function in SCI.

Influence of Upper-Body Exercise on the Fatigability of Human Respiratory Muscles

Purpose

Diaphragm and abdominal muscles are susceptible to contractile fatigue in response to high-intensity, whole-body exercise. This study assessed whether the ventilatory and mechanical loads imposed by high-intensity, upper-body exercise would be sufficient to elicit respiratory muscle fatigue.

Methods

Seven healthy men (mean ± SD; age = 24 ± 4 yr, peak O₂ uptake [V˙O_2peak] = 31.9 ± 5.3 mL·kg⁻¹·min⁻¹) performed asynchronous arm-crank exercise to exhaustion at work rates equivalent to 30% (heavy) and 60% (severe) of the difference between gas exchange threshold and V˙O_2peak. Contractile fatigue of the diaphragm and abdominal muscles was assessed by measuring pre- to postexercise changes in potentiated transdiaphragmatic and gastric twitch pressures (P_di,tw and P_ga,tw) evoked by supramaximal magnetic stimulation of the cervical and thoracic nerves, respectively.

Results

Exercise time was 24.5 ± 5.8 min for heavy exercise and 9.8 ± 1.8 min for severe exercise. Ventilation over the final minute of heavy exercise was 73 ± 20 L·min⁻¹ (39% ± 11% maximum voluntary ventilation) and 99 ± 19 L·min⁻¹ (53% ± 11% maximum voluntary ventilation) for severe exercise. Mean P_di,tw did not differ pre- to postexercise at either intensity (P > 0.05). Immediately (5–15 min) after severe exercise, mean P_ga,tw was significantly lower than pre-exercise values (41 ± 13 vs 53 ± 15 cm H₂O, P < 0.05), with the difference no longer significant after 25–35 min. Abdominal muscle fatigue (defined as ≥15% reduction in P_ga,tw) occurred in 1/7 subjects after heavy exercise and 5/7 subjects after severe exercise.

Conclusions

High-intensity, upper-body exercise elicits significant abdominal, but not diaphragm, muscle fatigue in healthy men. The increased magnitude and prevalence of fatigue during severe-intensity exercise is likely due to additional (nonrespiratory) loading of the thorax.

Causal effect of intra-abdominal pressure on maximal voluntary isometric hip extension torque

PURPOSE

Intra-abdominal pressure (IAP) has been recently shown to be associated specifically with maximal voluntary isometric contraction (MVC) torque of hip extension, although the causal relationship remains unclear. The present study aimed to elucidate whether IAP has a causal effect on hip extension MVC torque.

METHODS

IAP during hip extension MVC was changed by controlling the lung volume (i.e., depth of inspiration). Twelve healthy males conducted MVCs of hip extension during breath-hold at full inspiration (inspiratory condition) or expiration (expiratory condition), or during normal breath-hold (normal condition). IAP during MVCs was measured a pressure transducer placed in the rectum.

RESULTS

The IAP during hip extension MVC was significantly higher in inspiratory condition (132.0 ± 46.1 mmHg) than in the other two conditions and also higher in normal condition (104.6 ± 35.9 mmHg) than in expiratory condition (77.0 ± 39.1 mmHg). The hip extension MVC torque was significantly higher in inspiratory condition (297.7 ± 82.7 N m) than in expiratory condition (266.4 ± 84.5 N m). In each condition, the hip extension MVC torque correlated with IAP during the MVC task.

CONCLUSION

The current results suggest that IAP has a positive causal effect on hip extension MVC torque and that a sufficient increase in IAP directly leads to an enhancement of hip extension MVC torque.

Optimising conservative management of chronic low back pain: study protocol for a randomised controlled trial

Background

Lower back pain is a global health issue affecting approximately 80% of people at some stage in their life. The current literature suggests that any exercise is beneficial for reducing back pain. However, as pain is a subjective evaluation and physical deficits are evident in low back pain, using it as the sole outcome measure to evaluate superiority of an exercise protocol for low back pain treatment is insufficient. The overarching goal of the current clinical trial is to implement two common, conservative intervention approaches and examine their impact on deficits in chronic low back pain.

Methods/design

Forty participants, 25–45 years old with chronic (>3 months), non-specific low back pain will be recruited. Participants will be randomised to receive either motor control and manual therapy (n = 20) or general strength and conditioning (n = 20) exercise treatments for 6 months. The motor control/manual therapy group will receive twelve 30-min sessions, ten in the first 3 months (one or two per week) and two in the last 3 months. The general exercise group will attend two 1-hour sessions weekly for 3 months, and one or two a week for the following 3 months. Primary outcome measures are average lumbar spine intervertebral disc T2 relaxation time and changes in thickness of the transversus abdominis muscle on a leg lift using magnetic resonance imaging (MRI). Secondary outcomes include muscle size and fat content, vertebral body fat content, intervertebral disc morphology and water diffusion measured by MRI, body composition using dual energy X-ray absorptiometry, physical function through functional tests, changes in corticospinal excitability and cortical motor representation of the spinal muscles using transcranial magnetic stimulation and self-reported measure of pain symptoms, health and disability. Outcome measures will be conducted at baseline, at the 3-month follow-up and at 6 months at the end of intervention. Pain, depressive symptomology and emotions will be captured fortnightly by questionnaires.

Discussion

Chronic low back pain is ranked the highest disabling disorder in Australia. The findings of this study will inform clinical practice guidelines to assist with decision-making approaches where outcomes beyond pain are sought for adults with chronic low back pain.

Trial registration

Australian New Zealand Clinical Trials Registry, ACTRN12615001270505. Registered on 20 November 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1913-8) contains supplementary material, which is available to authorized users.

Improvements in Vertebral-Column Angles and Psychological Metrics After Abdominoplasty With Rectus Plication

BACKGROUND

Substantial fluctuations in body weight can result in diastasis recti and weakening of the connections between the lateral abdominal muscles and the rectus sheath.

OBJECTIVES

The authors sought to determine the postural and psychological effects of abdominoplasty with vertical rectus plication.

METHODS

Forty women with substantial back and lumbar pain owing to abdominal lipodystrophy were evaluated in a prospective study. Preoperatively and 6 months postoperatively, patients underwent bidirectional radiography of the thoracic and lumbar regions. A visual analog scale (VAS), the Beck Depression Inventory (BDI), and the Nottingham Health Profile (NHP) were applied to assess physical, psychological, and quality-of-life changes following surgery.

RESULTS

Significant improvements in posture, assessed in terms of lumbar lordosis, thoracic kyphosis, and the lumbosacral angle, were observed 6 months after abdominoplasty with rectus plication. Results of the VAS and BDI indicated significant improvements in pain and quality of life, respectively. Results of the NHP indicated significant postoperative improvements in fatigue, pain, and sleep.

CONCLUSIONS

Abdominoplasty with rectus plication improves posture by tightening the thoracolumbar fascia. In selected patients, abdominoplasty can reduce back and lumbar pain, thereby improving quality of life.

The acute effects of targeted abdominal muscle activation training on spine stability and neuromuscular control

Background

Targeted activation of the transversus abdominis (TrA) muscle through the abdominal drawing-in maneuver (ADIM) is a frequently prescribed exercise for the prevention and rehabilitation of low back pain. However, there is still debate over the role the ADIM plays in maintaining a stable spine during movement. Thus, a single cohort pre/post-intervention protocol was used to examine whether 5 min of ADIM training prior to a dynamic movement task alters dynamic spine stability and control.

Methods

Thirteen healthy participants performed a repetitive spine flexion task twice, once before and once after they received biofeedback training on how to correctly perform the ADIM in standing. Abdominal and back muscle activation (indwelling and surface electromyography, EMG) and 3D kinematic data were recorded during all trials. EMG activation (percent maximum) and local dynamic stability of spine movement [maximum finite-time Lyapunov exponent (λ_max)] were compared before and after the training using Friedman’s rank test and repeated-measures ANOVA, respectively. To assess the moderating effects of absolute changes in EMG (∆EMG) of each muscle after training on changes in stability, the ∆EMG (peak and mean) were added to the ANOVA as separate covariates (ANCOVA).

Results

Following ADIM training, there were greater peak and mean levels of activation in all tested abdominal muscles, including TrA, (p < 0.05), but not in the back muscles. The ANOVA showed no significant change in λ_max following training (p = 0.633). However, after considering the moderating effects of the ∆EMG seen in each muscle with training, it was found that only changes in TrA EMG significantly influenced stability. The ANCOVA revealed a significant main effect of training on stability as well as a significant interaction effect between training and ∆EMG recorded from TrA (p < 0.05); those with larger increases in TrA activation demonstrated larger improvements in stability.

Conclusion

As a group, 5 min of ADIM training did not change spine stability during dynamic movement. However, those who were most successful in improving TrA activation with a 5-min ADIM training session showed the greatest improvements in local dynamic spine stability after training. As such, dynamic spine stability in some individuals may benefit from ADIM training.

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-016-0126-9) contains supplementary material, which is available to authorized users.

Trunk Muscle Activation at the Initiation and Braking of Bilateral Shoulder Flexion Movements of Different Amplitudes

The aim of this study was to investigate if trunk muscle activation patterns during rapid bilateral shoulder flexions are affected by movement amplitude. Eleven healthy males performed shoulder flexion movements starting from a position with arms along sides (0°) to either 45°, 90° or 180°. EMG was measured bilaterally from transversus abdominis (TrA), obliquus internus (OI) with intra-muscular electrodes, and from rectus abdominis (RA), erector spinae (ES) and deltoideus with surface electrodes. 3D kinematics was recorded and inverse dynamics was used to calculate the reactive linear forces and torque about the shoulders and the linear and angular impulses. The sequencing of trunk muscle onsets at the initiation of arm movements was the same across movement amplitudes with ES as the first muscle activated, followed by TrA, RA and OI. All arm movements induced a flexion angular impulse about the shoulders during acceleration that was reversed during deceleration. Increased movement amplitude led to shortened onset latencies of the abdominal muscles and increased level of activation in TrA and ES. The activation magnitude of TrA was similar in acceleration and deceleration where the other muscles were specific to acceleration or deceleration. The findings show that arm movements need to be standardized when used as a method to evaluate trunk muscle activation patterns and that inclusion of the deceleration of the arms in the analysis allow the study of the relationship between trunk muscle activation and direction of perturbing torque during one and the same arm movement.

Mechanical Contribution of the Rib Cage in the Human Cadaveric Thoracic Spine

STUDY DESIGN

An in vitro biomechanical human cadaveric study of T1-T12 thoracic specimens was performed with 4 conditions (with and without rib cage, instrumented and uninstrumented) in flexion-extension, lateral bending, and axial rotation.

OBJECTIVE

The objective was to understand the influence of the rib cage on motion and stiffness parameters of the human cadaveric thoracic spine. Hypotheses tested for overall motion in all modes of bending for both uninstrumented and instrumented specimens were (i) in-plane range of motion and neutral and elastic zones will be greater without the rib cage, (ii) neutral and elastic zone stiffness values will be different for specimens without the rib cage, and (iii) out-of-plane rotations will be different for specimens without the rib cage.

SUMMARY OF BACKGROUND DATA

The rib cage is presumed to provide significant stability to the thoracic spine, but no studies have been conducted to determine the influence of the rib cage in both uninstrumented and instrumented conditions in the full thoracic human cadaveric specimens.

METHODS

Seven human cadaveric spine specimens (T1-T12) with 4 conditions (with and without rib cage, instrumented and uninstrumented) were subjected to 5 N·m pure moments in flexion-extension, lateral bending, and axial rotation. Range of motion, neutral and elastic zones, neutral and elastic zone stiffness values, and out-of-plane rotations were calculated for the overall specimen.

RESULTS

In-plane range of motion was significantly higher without a rib cage for most modes of bending. Out-of-plane motions were also influenced by the rib cage. Neutral zone stiffness was significantly higher with a rib cage present.

CONCLUSION

Testing without a rib cage yields different motion and stiffness measures, directly impacting the translation of research results to clinical interpretation. Researchers should consider these differences when evaluating the mechanical impact of surgical procedures or instrumentation in cadaveric or computational models.

LEVEL OF EVIDENCE

5.