Loads on spinal tissues during simultaneous lifting and ventilatory challenge

The Effect of a Novel Weight-Supported Kinetic Chain Resistance Training Program on Proximal Core Muscular Endurance, Trunk-to-Arm Muscular Power, and Bat Swing Speed

ABSTRACT

Palmer, TG, and McCabe, M. The effect of a novel weight-supported kinetic chain resistance training program on proximal core muscular endurance, trunk-to-arm muscular power, and bat swing speed. J Strength Cond Res 37(11): 2130-2140, 2023-Muscular stability and muscular power at the proximal core segments of the pelvis, spine, and trunk are essential attributes in maximizing bat swing speed in the sport of softball. Weight-supported kinetic chain resistance training (WsKC) is a novel closed kinetic chain technique that provides synergistic multiplanar stressors to the proximal core segments via the lower and upper extremities while limiting joint compression and sheer forces throughout the kinetic chain. The aim of this study was to assess the effect a 7-week preseason WsKC program would have on an isometric muscular endurance plank, trunk-to-arm peak muscular power (TAPP), trunk-to-arm peak velocity (TAPV), and bat swing speed (BSS) compared with a traditional isotonic weight resistance training program. Twenty-seven female high school softball players (age = 16 years, height = 167.6 cm, body mass = 62.86 kg) were assigned in a blocked randomization to one of 2 groups: a standing weight-supported kinetic chain resistance training (WsT) group (n = 13) or a pseudo-control traditional isotonic training (TT) group (n = 14). The WsT group had significant improvements (p < 0.05) for the isometric endurance plank (p = 0.001), TAPP (p = 0.002), TAPV (p = 0.001), and BSS (p = 0.02) compared with the TT group. The training effect size (ES) was large for the WsT group for all variables (ES = 1.0-7.4) and small to moderate for a majority of the TT variables (ES = 0.06-0.47). The simultaneous improvement in the isometric endurance plank, trunk-to-arm rotations, and BSS indicates that the WsKC contributed to subsequent improvements in BSS in high school softball players.

Interaction of breathing pattern and posture on abdominal muscle activation and intra-abdominal pressure in healthy individuals: a comparative cross-sectional study

We aimed to assess the effects of interaction between several breathing patterns and postures on abdominal muscle activation and intra-abdominal pressure (IAP). This comparative cross-sectional study enrolled fourteen healthy university students majoring in sports science and/or physical education. They performed four active breathing tasks: quiet nasal breathing (Q-Bre), nasal deep breathing (Deep-Bre), completely forced expiration (Forced-Expi), and exertional nasal inhalation with abdominal muscles with isometric contraction (Exertion-Inspi) in the elbow-toe plank and supine postures. Breathing volume; IAP; and transverse abdominis-internal oblique muscle (TrA-IO) and external oblique muscle (EO) activities were recorded. Abdominal muscle activity and IAP significantly interacted with breathing pattern and postures during the expiratory phase (p < 0.05). In the inspiratory phase, TrA-IO activity was significantly affected by breathing pattern and EO activity with posture (p < 0.05). TrA-IO activity significantly increased during Forced-Expi in the supine posture (47.6% of the maximum voluntary contraction) and Exertion-Inspi in the elbow-toe posture (35.7%), whereas no differences were found during Deep-Bre or Q-Bre (< 20%). EO activity increased in the elbow-toe posture (22.5-30.6%) compared with that in the supine posture (< 5%) during all breathing tasks. IAP values were low during all tasks (< 15%) except for Forced-Expi (24.9%). Abdominal muscle activation and IAP interacted with the breathing pattern and posture.

Effects of Diaphragmatic Breathing Patterns on Balance: A Preliminary Clinical Trial

OBJECTIVE

The purpose of this study was to determine the feasibility of performing a larger study to determine if training in diaphragmatic breathing influences static and dynamic balance.

METHODS

A group of 13 healthy persons (8 men, 5 women), who were staff, faculty, or students at the University of Western States participated in an 8-week breathing and balance study using an uncontrolled clinical trial design. Participants were given a series of breathing exercises to perform weekly in the clinic and at home. Balance and breathing were assessed at the weekly clinic sessions. Breathing was evaluated with Liebenson's breathing assessment, static balance with the Modified Balance Error Scoring System, and dynamic balance with OptoGait's March in Place protocol.

RESULTS

Improvement was noted in mean diaphragmatic breathing scores (1.3 to 2.6, P < .001), number of single-leg stance balance errors (7.1 to 3.8, P = .001), and tandem stance balance errors (3.2 to 0.9, P = .039). A decreasing error rate in single-leg stance was associated with improvement in breathing score within participants over the 8 weeks of the study (-1.4 errors/unit breathing score change, P < .001). Tandem stance performance did not reach statistical significance (-0.5 error/unit change, P = .118). Dynamic balance was insensitive to balance change, being error free for all participants throughout the study.

CONCLUSION

This proof-of-concept study indicated that promotion of a costal-diaphragmatic breathing pattern may be associated with improvement in balance and suggests that a study of this phenomenon using an experimental design is feasible.

"Functional" Inspiratory and Core Muscle Training Enhances Running Performance and Economy

Tong, TK, McConnell, AK, Lin, H, Nie, J, Zhang, H, and Wang, J. "Functional" inspiratory and core muscle training enhances running performance and economy. J Strength Cond Res 30(10): 2942-2951, 2016-We compared the effects of two 6-week high-intensity interval training interventions. Under the control condition (CON), only interval training was undertaken, whereas under the intervention condition (ICT), interval training sessions were followed immediately by core training, which was combined with simultaneous inspiratory muscle training (IMT)-"functional" IMT. Sixteen recreational runners were allocated to either ICT or CON groups. Before the intervention phase, both groups undertook a 4-week program of "foundation" IMT to control for the known ergogenic effect of IMT (30 inspiratory efforts at 50% maximal static inspiratory pressure [P0] per set, 2 sets per day, 6 days per week). The subsequent 6-week interval running training phase consisted of 3-4 sessions per week. In addition, the ICT group undertook 4 inspiratory-loaded core exercises (10 repetitions per set, 2 sets per day, inspiratory load set at 50% post-IMT P0) immediately after each interval training session. The CON group received neither core training nor functional IMT. After the intervention phase, global inspiratory and core muscle functions increased in both groups (p ≤ 0.05), as evidenced by P0 and a sport-specific endurance plank test (SEPT) performance, respectively. Compared with CON, the ICT group showed larger improvements in SEPT, running economy at the speed of the onset of blood lactate accumulation, and 1-hour running performance (3.04% vs. 1.57%, p ≤ 0.05). The changes in these variables were interindividually correlated (r ≥ 0.57, n = 16, p ≤ 0.05). Such findings suggest that the addition of inspiratory-loaded core conditioning into a high-intensity interval training program augments the influence of the interval program on endurance running performance and that this may be underpinned by an improvement in running economy.

The Compartment Syndrome of the Abdominal Cavity: A State of the Art Review

Abdominal compartment syndrome gains increasing recognition. It impairs physiology and requires treatment. It occurs more commonly with acute rather than chronic abdominal hypertension. Functional impairments involve the cardiovascular system, respiratory system, hepatic, renal, and gastrointestinal function, and intracranial pressure. Abdominal hypertension decreases venous return, increases systemic vascular resistance and intrathoracic pressure, and therefore reduces cardiac output. It also adversely affects cardiovascular monitoring. In the presence of increased abdominal pressure, atelectasis and pneumonia are likely to develop and impaired ventilation may lead to respiratory failure. Also, blood flow to the liver and kidney may be reduced, resulting in functional impairment of both organs. The adverse effects on gastrointestinal function result from impairing lymphatic, venous, and arterial flow. Anastomotic healing may become a problem under these circumstances. Decreased venous return through the inferior vena cava in obese patients may lead to venous stasis ulcers and hemorrhage. The correlation of increased intracranial pressure and intra-abdominal pressure may be a problem for trauma patients with simultaneous injuries to the head and the abdomen. There are three severity grades of increased intra-abdominal pressure: Acute sustained elevation of intra-abdominal pressure above 10–20 mmHg is called mild abdominal hypertension. Physiologic effects are generally well compensated and usually clinically nonsignificant. Nonoperative therapy may be required. Moderate hypertension is defined as sustained elevation of 21–35 mmHg. Therapy is generally necessary. Surgical abdominal-decompression may be critical. Severe hypertension or abdominal compartment syndrome is defined as sustained elevation above 35 mmHg. Operative decompression is always indicated. The gap between the abdominal wound edges must be temporarily covered to prevent fascia retraction and formation of a huge hernia. All detrimental effects of elevated intra-abdominal pressure and the methods and benefits of its decompression have been well studied, both in the laboratory and in clinical practice. Diagnostic suspicion may be confirmed with objective measurements of intra-abdominal pressure to select patients who may benefit from decompression. Operative decompression is achieved by abdominal fasciotomy and covering the fascial gap with mesh made of Marlex®, Gore-Tex®, silastic, or by a Velcro-like closure mesh (artificial bur). All meshes help to effectively decompress the abdomen. The artificial bur offers further advantages by permitting successive reapproximation of the fascia until final fascial closure, and avoiding the fistula and hernia formation seen with the other meshes.

Balance recovery is compromised and trunk muscle activity is increased in chronic obstructive pulmonary disease

Increased respiration in chronic obstructive pulmonary disease (COPD) requires greater abdominal muscle activation, which may impact on contribution of the trunk to postural control. This study aimed to determine whether recovery of balance from postural perturbations and trunk muscle activity differs in people with and without COPD before and/or after exercise. Electromyography (EMG) of the obliquus internus (OI) and externus (OE) abdominis, rectus abdominis (RA), erector spinae (ES) and deltoid muscles was recorded with surface electrodes during rapid shoulder flexion and extension. Time taken to regain baseline centre of pressure velocity (vCOP) and the number of postural adjustments following arm movement was calculated from force plate data. Time to recover balance in the direction of postural disturbance (anteroposterior vCOP) was longer in COPD, particularly more severe COPD, than controls. Mediolateral vCOP (perpendicular to the perturbation) and the number of postural adjustments did not differ between groups, but people with more severe COPD were less successful at returning their mediolateral vCOP to baseline. Abdominal muscle EMG was similar between groups, but controls had greater ES EMG during arm movements. Individuals with more severe COPD had greater OE and RA EMG both before and during arm movement compared to those with less severe COPD and controls. Following exercise, OE and ES EMG increased in people with less severe COPD. This study shows that severe COPD is associated with impaired ability to recover balance and greater trunk muscle activity during postural challenges. Augmented trunk muscle activity may limit the contribution of trunk movements to balance recovery and could contribute to increased falls risk.

The role of visual feedback in respiratory muscle activation and pulmonary function

[Purpose] It is well known that visual feedback is an important factor contributing to balance and postural control. Nevertheless, there has been little discussion about the effects of visual feedback on pulmonary function. This study was conducted to investigate the role of visual feedback on respiratory muscle activation and pulmonary function. [Subjects and Methods] The subjects were 37 healthy adults who consented to participate in this study. The study measured the muscular activation of the trunk and pulmonary function according to the absence or presence of visual feedback. [Results] The results revealed significant changes in muscular activation and pulmonary function with the use of visual feedback. [Conclusion] These findings suggest that visual feedback may play a role in increasing respiratory muscle activity and pulmonary function.

The effects of core muscle release technique on lumbar spine deformation and low back pain

[Purpose] The purpose of this study was to examine the effects of the core muscle release technique on correction of lumbar deformation and alleviation of low back pain. [Subjects] Ninety patients diagnosed with lumbar deformation and low back pain participated in this study. [Methods] The participants were divided into three groups according to method of treatment. The first group was treated with the core muscle release technique (CRT), the second group was treated with general exercise, and the third group was treated with electrotherapy. The core muscle release technique group received 50-minute of the core muscle release technique 5 times a week for 2 weeks, and the participants in this group were instructed not to receive any other treatments. After the 2 weeks of treatment, the patients were reexamined. The general exercise group performed Williams flexion exercises and McKenzie extension exercises 5 times a week for 2 weeks. The electrotherapy group was treated by application of electrotherapy with an interferential current therapy machine (TM-301. TOPMED. Seongnam, Republic of Korea) to the abdominal muscles and back muscles of the lumbar region. [Results] The data suggest that the core muscle release technique, general exercise, and electrotherapy all helped to decrease the alignment angle and VAS score. Of these treatment methods, however, the core muscle release technique was the most effective for treatment of lumbar spine deformation and low back pain. [Conclusion] The core muscle release technique was most effective for correction of lumbar spine deformation and pain alleviation.

How different modes of child delivery influence abdominal muscle activities in the active straight leg raise

[Purpose] The purpose of this study was to examine the activities of the abdominal muscles of women who had experienced vaginal delivery in comparison with those who had experienced Cesarean childbirth. [Subjects and Methods] A total of 14 subjects (7 vaginal delivery, 7 Cesarean section) performed an active straight leg raise to 20 cm above the ground, and we measured the activities of the internal oblique abdominal muscle, the external oblique abdominal muscle, and the rectus abdominal muscle on both sides using electromyography. The effort required to raise the leg was scored on a Likert scale. Then, the subjects conducted maximum isometric contraction for hip joint flexion with the leg raised at 20 cm, and maximum torque and abdominal muscle activities were measured using electromyography. [Results] During the active straight leg raise, abdominal muscle activities were higher in the Cesarean section subjects. The Likert scale did not show a significant difference. The activities of the abdominal muscles and the maximum torque of the hip joint flexion at maximum isometric contraction were higher in the vaginal delivery subjects. [Conclusion] The abdominal muscles of Cesarean section subjects showed greater recruitment for maintaining pelvic stability during the active straight leg raising, but were relatively weaker when powerful force was required. Therefore, we consider that more abdominal muscle training is necessary for maintaining pelvic stability of Cesarean section subjects.

Balance Deficits are Correlated with Bronchial Obstruction Markers in Subjects with Asthma

[Purpose] Balance deficits are increasingly recognized in chronic obstructive pulmonary disease, but little is known regarding this issue in asthma. Our primary aim was to assess the correlation between postural balance and pulmonary function in adults with asthma. Secondarily, we aimed to correlate balance with functional capacity and body mass index in these subjects. [Methods] A cross-sectional study of 26 adults with asthma was performed in which they were subjected to stabilometry, pulmonary function testing, a 6-minute walking test, and nutritional assessment. [Results] We found significant correlations of forced expiratory volume at one second (ρ=-0.49) and total lung capacity (ρ=0.39) with mediolateral displacement with feet apart/eyes open. Significant correlations were observed between peak expiratory flow and a number of stabilometric parameters. There were several significant correlations between airway-specific conductance and the tasks performed on the force platform, especially one with the feet apart/eyes open. The Berg Balance Scale revealed significant correlations with mediolateral displacement, mediolateral range, and anteroposterior range for feet together/eyes closed (ρ=-0.49). There were no significant correlations between stabilometry, body mass index, and six-minute walking distance. [Conclusion] In adults with asthma, there is an association between balance and the bronchial obstruction markers. This finding may contribute to improvement of rehabilitation programs for these subjects.

'The core': understanding it, and retraining its dysfunction

"Core stability training" is popular in both the therapeutic and fitness industries but what is actually meant and understood by this concept? And does everyone need the same training approach? This paper examines the landscape of 'the core' and its control from both a clinical and research perspective. It attempts a comprehensive review of its healthy functional role and how this is commonly changed in people with spinal and pelvic girdle pain syndromes. The common clinically observable and palpable patterns of functional and structural change associated with 'problems with the core' have been relatively little described. This paper endeavors to do so, introducing a variant paradigm aimed at promoting the understanding and management of these altered patterns of 'core control'. Clinically, two basic subgroups emerge. In light of these, the predictable difficulties that each group finds in establishing the important fundamental elements of spino-pelvic 'core control' and how to best retrain these, are highlighted. The integrated model presented is applicable for practitioners re-educating movement in physiotherapy, rehabilitation, Pilates, Yoga or injury prevention within the fitness industry in general.

Diaphragm postural function analysis using magnetic resonance imaging

We present a postural analysis of diaphragm function using magnetic resonance imaging (MRI). The main aim of the study was to identify changes in diaphragm motion and shape when postural demands on the body were increased (loading applied to a distal part of the extended lower extremities against the flexion of the hips was used). Sixteen healthy subjects were compared with 17 subjects suffering from chronic low back pain and in whom structural spine disorders had been identified. Two sets of features were calculated from MRI recordings: dynamic parameters reflecting diaphragm action, and static parameters reflecting diaphragm anatomic characteristics. A statistical analysis showed that the diaphragm respiratory and postural changes were significantly slower, bigger in size and better balanced in the control group. When a load was applied to the lower limbs, the pathological subjects were mostly not able to maintain the respiratory diaphragm function, which was lowered significantly. Subjects from the control group showed more stable parameters of both respiratory and postural function. Our findings consistently affirmed worse muscle cooperation in the low back pain population subgroup. A clear relation with spinal findings and with low back pain remains undecided, but various findings in the literature were confirmed. The most important finding is the need to further address various mechanisms used by patients to compensate deep muscle insufficiency.

Investigating Individual and Occupational Factors and their Interactions on Low Back Pain Severity in Workers

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Current ergonomic prevention strategies focus on reducing the effect of occupational risk factors. However, other underlying mechanisms may exist since not all workers performing the same task develop an injury. In this study, 36 LBP patients with a previous MRI scan were recruited to investigate the effects of individual and occupational factors and their interactions on LBP severity. Individual and occupational factors information was obtained through questionnaires. LBP severity ratings were obtained through a self-reported Visual Analog Scale (VAS) and the Oswestry Disability Index (ODI) questionnaire and served as the dependent variables. Stepwise linear regression analysis was performed on the variables. For ODI, a model consisting of interaction effects between individual and occupational risk factors with an adjusted R2 value of 0.84 was obtained. These preliminary results may help to develop models to predict and, hence, prevent chronic LBP.

Musculoskeletal myths

This paper discusses a number of common myths in the musculoskeletal pain management and rehabilitation/athletic development fields. The origins or rationale for these beliefs are reviewed. New scientific evidence disputing or refuting the myth is then presented followed by and explanation and evidence for an updated perspective.

Relationships between measures of dysfunctional breathing in a population with concerns about their breathing

BACKGROUND

Dysfunctional breathing (DB) is implicated in physical and psychological health, however evaluation is hampered by lack of rigorous definition and clearly defined measures. Screening tools for DB include biochemical measures such as end-tidal CO(2), biomechanical measures such assessments of breathing pattern, breathing symptom questionnaires and tests of breathing function such as breath holding time.

AIM

This study investigates whether screening tools for dysfunctional breathing measure distinct or associated aspects of breathing functionality.

METHOD

84 self-referred or practitioner-referred individuals with concerns about their breathing were assessed using screening tools proposed to identify DB. Correlations between these measures were determined.

RESULTS

Significant correlations where found within categories of measures however correlations between variables in different categories were generally not significant. No measures were found to correlate with carbon dioxide levels.

CONCLUSION

DB cannot be simply defined. For practical purposes DB is probably best characterised as a multi-dimensional construct with at least 3 dimensions, biochemical, biomechanical and breathing related symptoms. Comprehensive evaluation of breathing dysfunction should include measures of breathing symptoms, breathing pattern, resting CO(2) and also include functional measures such a breath holding time and response of breathing to physical and psychological challenges including stress testing with CO(2) monitoring.

Balance is impaired in people with chronic obstructive pulmonary disease

BACKGROUND

It has recently been suggested that people with chronic obstructive pulmonary disease have an increased risk of falls. Although falls risk is multifactorial, impaired balance may contribute. The primary aim of this study was to compare balance between people with and without chronic obstructive pulmonary disease and the secondary aim was to determine if balance deteriorates when respiratory demand is increased by upper limb exercise.

METHODS

Twelve people with chronic obstructive pulmonary disease and 12 healthy control subjects participated in this study. Participants stood on a force plate to record centre of pressure displacement during a range of conditions that challenge balance. Lumbar spine and hip motion were measured with inclinometers. Balance trials were performed before and after participation in upper limb exercise that increased respiratory demand in those with chronic obstructive pulmonary disease.

FINDINGS

People with chronic obstructive pulmonary disease had increased mediolateral centre of pressure displacement and increased angular motion of the hip compared to healthy controls. Mediolateral centre of pressure displacement was further increased in people with chronic obstructive pulmonary disease following exercise, but unchanged in controls. Anteroposterior centre of pressure displacement did not differ between groups.

INTERPRETATION

People with chronic obstructive pulmonary disease have reduced control of balance in the mediolateral direction. This may contribute to an increased risk of falls in this population.

The effect of resisted inspiration during an active straight leg raise in pain-free subjects

Alterations of respiratory patterns have been observed in pelvic girdle pain subjects during the active straight leg raise (ASLR). This study investigated how pain-free subjects coordinate motor control during an ASLR when this task is complicated by the addition of a respiratory challenge. Trunk muscle activation, intra-abdominal pressure, intra-thoracic pressure, pelvic floor motion, downward pressure of the non-lifted leg and respiratory rate were compared between resting supine, ASLR, breathing with inspiratory resistance (IR) and ASLR+IR. Subjects responded to ASLR+IR with an increase in the motor activation in the abdominal wall and chest wall compared to when ASLR and IR were performed in isolation. Activation of obliquus internus abdominis was greater on the side of the leg lift during the ASLR+IR, in comparison to symmetrical activation observed in the other abdominal wall muscles. The incremental increase of motor activity was associated with greater intra-abdominal pressure baseline shift when lifting the leg during ASLR+IR compared to ASLR. Individual variation was apparent in the form of the motor control patterns, mostly reflected in variable respiratory activation of the abdominal wall. The findings highlight the flexibility of the neuromuscular system in adapting to simultaneous respiratory and stability demands.

Motor control patterns during an active straight leg raise in pain-free subjects

STUDY DESIGN

Repeated measures.

OBJECTIVE

To investigate motor control (MC) patterns of normal subjects during the low level physical load of the active straight leg raise (ASLR).

SUMMARY OF BACKGROUND DATA

Aberrant MC patterns, as observed with the ASLR test, are considered to be a mechanism for ongoing pain and disability in subjects with chronic musculoskeletal pelvic girdle pain. These patterns may not only affect the provision of lumbopelvic stability, but also respiration and the control of continence. Greater understanding of MC patterns in pain-free subjects may improve the management of pelvic girdle pain. METHODS.: Fourteen pain-free nulliparous women were examined during the ASLR. Electromyography of the anterior abdominal wall, right chest wall and the anterior scaleni, intraabdominal pressure (IAP), intrathoracic pressure (ITP), respiratory rate, pelvic floor kinematics, and downward leg pressure of the nonlifted leg were compared between a left and right ASLR.

RESULTS

There was greater activation of obliquus internus abdominis and obliquus externus abdominis on the side of the ASLR. The predominant pattern of activation for the chest wall was tonic activation during an ipsilateral ASLR, and phasic respiratory activation lifting the contralateral leg. Respiratory fluctuation of both IAP and ITP did not differ lifting either leg. The baseline shifts of these pressure variables in response to the physical demand of lifting the leg was also the same either side. There was no difference in respiratory rate, pelvic floor kinematics, or downward leg pressure.

CONCLUSION

Pain-free subjects demonstrate a predominant pattern of greater ipsilateral tonic activation of the abdominal wall and chest wall on the side of the ASLR. This was achieved with minimal apparent disruption to IAP and ITP. The findings of this study demonstrate the plastic nature of the abdominal cylinder and the flexibility of the neuromuscular system in controlling load transference during an ASLR.

When exposed to challenged ventilation, those with a history of LBP increase spine stability relatively more than healthy individuals

OBJECTIVE

To determine if spine stability would be affected by the competing demands of simultaneous challenged ventilation and supporting a hand-held load.

DESIGN

Subjects were their own controls in a repeated measures design where a single task was repeated, once in a different condition, in a random order.

BACKGROUND

Muscle stiffness influences spine stability. The same muscles that contribute to spine stability assist in challenged breathing. We hypothesized that a challenged ventilation task would place low back pain (LBP) sufferers at risk of spine instability.

METHODS

Subjects (14 normal; 14 with low back pain) performed two trials with a 22kg hand-held weight and the trunk angled forward at 30 degrees . One trial was of 60s duration while breathing ambient air, the other of 70s duration, while breathing 10% carbon dioxide. Spine stability and compression were quantified, using an EMG assisted optimization model in both trials.

FINDINGS

Contrary to expectation, spine stability increased during the challenged breathing trials compared to the ambient air condition for subjects with a history of low back pain when abdominal muscle activity was accounted for as a covariate.

INTERPRETATION

Subjects with a history of low back pain had higher stability in challenged breathing trials, indicating that some active mechanism protects the spine for the LBP groups in challenging situations. This may be to provide some margin of safety for damaged passive tissues but could be adversely affected by fatigue in the longer term.

Abdominal muscles dominate contributions to vertebral joint stiffness during the push-up

The goal of this study was to quantify the relative contributions of each muscle group surrounding the spine to vertebral joint rotational stiffness (VJRS) during the push-up exercise. Upper-body kinematics, three-dimensional hand forces and lumbar spine postures, and 14 channels (bilaterally from rectus abdominis, external oblique, internal oblique, latissimus dorsi, thoracic erector spinae, lumbar erector spinae, and multifidus) of trunk electromyographic (EMG) activity were collected from 11 males and used as inputs to a biomechanical model that determined the individual contributions of 10 muscle groups surrounding the lumbar spine to VJRS at five lumbar vertebral joints (L1-L2 to L5-S1). On average, the abdominal muscles contributed 64.32 +/- 8.50%, 86.55 +/- 1.13%, and 83.84 +/- 1.95% to VJRS about the flexion/extension, lateral bend, and axial twist axes, respectively. Rectus abdominis contributed 43.16 +/- 3.44% to VJRS about the flexion/extension axis at each lumbar joint, and external oblique and internal oblique, respectively contributed 52.61 +/- 7.73% and 62.13 +/- 8.71% to VJRS about the lateral bend and axial twist axes, respectively, at all lumbar joints with the exception of L5-S1. Owing to changes in moment arm length, the external oblique and internal oblique, respectively contributed 55.89% and 50.01% to VJRS about the axial twist and lateral bend axes at L5-S1. Transversus abdominis, multifidus, and the spine extensors contributed minimally to VJRS during the push-up exercise. The push-up challenges the abdominal musculature to maintain VJRS. The orientation of the abdominal muscles suggests that each muscle primarily controls the rotational stiffness about a single axis.

The effect of fatigue on trunk muscle activation patterns and spine postures during simulated firefighting tasks

The purpose of this study was to determine the effect of a fatiguing task (3 min intense stair climbing) on the adopted spinal postures and trunk muscular activation patterns during three highly physically demanding simulated firefighting tasks. Following the fatigue protocol, it was observed that individuals adopted significantly greater spinal flexion (16.3 degrees maximum prior to fatigue as compared to 20.1 degrees post fatigue) and displayed reduced abdominal muscle activation as compared to before the fatigue protocol (mean ranging from 16.6% maximum voluntary contraction (MVC) to 30.6% MVC prior to fatigue as compared to ranging from 14.6% MVC to 25.2% MVC post fatigue). The reduced abdominal activation may be due to a reduction in co-contraction during these tasks, which may compromise spinal stability. Reduced co-contraction combined with the increased spinal flexion may increase the risk of sustaining an injury to the low back.

Links between the mechanics of ventilation and spine stability

Spine stability is ensured through isometric coactivation of the torso muscles; however, these same muscles are used cyclically to assist ventilation. Our objective was to investigate this apparent paradoxical role (isometric contraction for stability or rhythmic contraction for ventilation) of some selected torso muscles that are involved in both ventilation and support of the spine. Eight, asymptomatic, male subjects provided data on low back moments, motion, muscle activation, and hand force. These data were input to an anatomically detailed, biologically driven model from which spine load and a lumbar spine stability index was obtained. Results revealed that subjects entrained their torso stabilization muscles to breathe during demanding ventilation tasks. Increases in lung volume and back extensor muscle activation coincided with increases in spine stability, whereas declines in spine stability were observed during periods of low lung inflation volume and simultaneously low levels of torso muscle activation. As a case study, aberrant ventilation motor patterns (poor muscle entrainment), seen in one subject, compromised spine stability. Those interested in rehabilitation of patients with lung compromise and concomitant back troubles would be assisted with knowledge of the mechanical links between ventilation during tasks that impose spine loading.

Natural breath control during lifting tasks: effect of load

Anecdotal evidence suggests that people hold their breath during lifting tasks in order to increase intra-abdominal pressure (IAP) and thereby increase lumbar stability. Studies have shown that voluntary control of the breath influences IAP and that increases in IAP are related to increases in lumbar stability. However, a description of naturally occurring breath control during whole-body lifting tasks in normal healthy subjects is currently not available. Therefore, the specific aims of this study were to: (1) determine the naturally occurring breath patterns during lifting tasks in healthy subjects; (2) determine the effects of different levels of load during lifting tasks on natural breath control patterns in healthy subjects. The present study enrolled 20 healthy subjects to describe inspired volume and categories of airflow direction (inspiration, expiration, or breath hold) during two self-paced lifts of crates loaded at 5, 15, and 25% of body weight. When the breath pattern was examined across all loads there was a significant increase in the magnitude of inspired volume and the frequency of occurrence of inspiration immediately prior to lift-off. When examining the effect of load on breath patterns, there was a significant increase of inspired volume and occurrence of breath holding when lifting the heavy load compared to the medium and light loads. These results suggest that: (1) distinct patterns of natural breath control occur during lifting tasks; and (2) breath control is responsive to the timing and magnitude of load lifted.

Core strengthening

Core strengthening has become a major trend in rehabilitation. The term has been used to connote lumbar stabilization, motor control training, and other regimens. Core strengthening is, in essence, a description of the muscular control required around the lumbar spine to maintain functional stability. Despite its widespread use, core strengthening has had meager research. Core strengthening has been promoted as a preventive regimen, as a form of rehabilitation, and as a performance-enhancing program for various lumbar spine and musculoskeletal injuries. The intent of this review is to describe the available literature on core strengthening using a theoretical framework.

OVERALL ARTICLE OBJECTIVE

To understand the concept of core strengthening.

Spinal stiffness changes throughout the respiratory cycle

Posteroanterior stiffness of the lumbar spine is influenced by factors, including trunk muscle activity and intra-abdominal pressure (IAP). Because these factors vary with breathing, this study investigated whether stiffness is modulated in a cyclical manner with respiration. A further aim was to investigate the relationship between stiffness and IAP or abdominal and paraspinal muscle activity. Stiffness was measured from force-displacement responses of a posteroanterior force applied over the spinous process of L2 and L4. Recordings were made of IAP and electromyographic activity from L4/L2 erector spinae, abdominal muscles, and chest wall. Stiffness was measured with the lung volume held at the extremes of tidal volume and at greater and lesser volumes. Stiffness at L4 and L2 increased above base-level values at functional residual capacity (L2 14.9 N/mm and L4 15.3 N/mm) with both inspiratory and expiratory efforts. The increase was related to the respiratory effort and was greatest during maximum expiration (L2 24.9 N/mm and L4 23.9 N/mm). The results indicate that changes in trunk muscle activity and IAP with respiratory efforts modulate spinal stiffness. In addition, the diaphragm may augment spinal stiffness via attachment of its crural fibers to the lumbar vertebrae.

Coordination of muscle activity to assure stability of the lumbar spine

The intention of this paper is to introduce some of the issues surrounding the role of muscles to ensure spine stability for discussion -- it is not intended to provide an exhaustive review and integration of the relevant literature. The collection of works synthesized here point to the notion that stability results from highly coordinated muscle activation patterns involving many muscles, and that the recruitment patterns must continually change, depending on the task. This has implications on both the prevention of instability and clinical interventions with patients susceptible to sustaining unstable events.

Previous history of LBP with work loss is related to lingering deficits in biomechanical, physiological, personal, psychosocial and motor control characteristics

A cross-sectional retrospective study was made of currently asymptomatic workers who perform physically demanding jobs. To further quantify the association between various biomechanical, physiological, personal psychosocial and motor control parameters that linger due to a history of low back disorders. Seventy-two workers were recruited from heavy industry, 26 of whom had a history of disabling low back disorders (LBDs) sufficient to miss work while the others did not. The strength of the study lies in the many detailed variables measured. Having a history of low back disorders was found to be associated with a larger waist girth, a greater potential for low back pain chronicity as predicted from psychosocial questionnaires, perturbed flexion to extension strength and endurance ratios, and widespread motor control deficits across a variety of tasks, some of which resulted in high back loads. In those workers who had missed work due to back disorders, the length of time since their last disabling episode was 261 weeks on average, suggesting that multiple deficits may remain for a period of time. Having a history of LBD is associated with changes in attitudes, in body composition, and in the way people move, load their backs and respond to a variety of motor and stability challenges.

Spine ergonomics

Occupational low back pain (LBP) is an immense burden for both industry and medicine. Ergonomic and personal risk factors result in LBP, but psychosocial factors can influence LBP disability. Epidemiologic studies clearly indicate the role of mechanical loads on the etiology of occupational LBP. Occupational exposures such as lifting, particularly in awkward postures; heavy lifting; or repetitive lifting are related to LBP. Fixed postures and prolonged seating are also risk factors. LBP is found in both sedentary occupations and in drivers as well as those involved in manual materials handling. Any prolonged posture will lead to static loading of the soft tissues and cause discomfort. Standing and sitting have specific advantages and disadvantages for mobility, exertion of force, energy consumption, circulatory demands, coordination, and motion control. The seated posture leads to inactivity causing an accumulation of metabolites, accelerating disk degeneration and leading to disk herniation. Driver's postures can also lead to musculoskeletal problems. Workers in a driving environment are often subjected to postural stress leading to back, neck, and upper extremity pain. This exacerbates the problems due to the vibration. Prevention is by far the treatment of choice. Improved muscle function can be preventative. Poor coordination and motor control systems are as important as endurance and strength. Fixed postures should be avoided. Seats offering good lumbar support should be used in the office. A suspension seat should be used in vehicles whenever possible. Heavy and awkward lifting should be avoided and lifting aids should be made available. Workers should report LBP as early as possible and seek medical advice if they think occupational exposure is harming them. The combined effects of the medical community, labor, and management are required to cause some impact on this problem.

Factors in breathing maneuvers that affect trunk electromyogram during manual lifting

STUDY DESIGN

A fully randomized experiment was conducted in a laboratory with a breath-by-breath monitor to control accurately the two factors of breathing maneuvers: breathholding duration and air volume within the thoracic cavity.

OBJECTIVES

To resolve the controversy in previous reports about the effect of breathholding on the trunk electromyogram, and to verify the hypothesis that not only the factor of glottis closure, but also that of the air volume inside the thoracic cavity affects the trunk muscular activities during lifting.

SUMMARY OF BACKGROUND DATA

Breathing was shown to affect spinal loading. However, there still is a debate about the effect of breathholding on trunk muscular activation during activities. It is possible that variations in air volume influence this effect.

METHODS

Seven healthy, volunteer men participated in lifting tasks, in which lifting moment was standardized. Three breathing maneuvers were used: sustained breathholding with tidal volume of air, sustained breathholding with functional residual volume, and intended breath-nonholding involving inspiration within tidal capacity. Data on the surface electromyographic activation of the external oblique muscle, rectus abdominis, erector spinae, latissimus dorsi, air volume inside the cavity, and the duration of the one breath held in the last lift were collected and analyzed.

RESULTS

Of the four muscles investigated, the breathing maneuvers affected only the external oblique muscle. The effect of sustained breathhold during lifting was the significantly increased activation of this muscle (P < 0.05). The effect of decreased air volume held was further increased activation. Intention to inspire normally during lifting decreased external oblique activation, but increased compensatory diaphragmatic effort, measured as inspiratory flow acceleration.

CONCLUSIONS

Both the factors of the breathheld state and sustained air volume were verified to affect the external oblique activation during lifting. The current study emphasizes that both factors should be controlled in studies analyzing trunk electromyogram during activities. Otherwise, these breathing variations will be a confounding factor on electromyogram results.

Effect of belt pressure and breath held on trunk electromyography

STUDY DESIGN

This study examined the effect of a belt on ventilation and trunk muscle activities during repetitive lifting tasks with a control of breathing type and belt pressure.

OBJECTIVES

To evaluate the effect of the lifting belt on the trunk muscle electromyography (EMG) and to parse out potential interaction between ventilatory changes and lifting belts.

SUMMARY OF BACKGROUND DATA

Although both tensed thorax and compressed abdomen are considered to assist transferring the force from torso to pelvis in lifting, there has not been any consideration of the interaction between the two chambers in most published analyses.

METHODS

Eleven male study participants participated in the study. They performed five minutes of paced repetitive squat lifts at frequencies of one or three lifts per minute, with loads of 10 or 25 kg. Belt pressure was set at 0 (no belt), 10, and 20 mm Hg. Study participants lifted with inspire-hold and expire-hold for a period of 5 minutes. Lift ventilation data and trunk muscle normalized electromyography (NEMG) (including rectus abdominis, external oblique, latissimus dorsi, and erector spinae) for the final lift were collected for analysis.

RESULTS

The results indicate that the ventilation demand for lifting was not different with or without use of a belt. The prelifting erector spinae NEMG was 8-11% maximum voluntary contraction (MVC) lower and the latissimus dorsi NEMG was 15-21% MVC lower than that without belt. This is also the case in the lifting phase. The rectus abdominis NEMG was increased by 4% MVC and the external oblique NEMG was increased by 3-5% MVC while lifting with a belt.

CONCLUSIONS

These data do not lead to a statistical effect of lifting belt pressure on ventilatory behavior. It appears that the use of a belt in lifting significantly decreased the back muscular activation yet increased the abdominal muscular activation. Thus, claims of benefits derived from the use of a belt in lifting remain controversial. The simultaneous controls of the air volume held and pressure of the belt during the moment-controlled lifting tasks allowed this presentation of belt effects on trunk muscle NEMG unique from that in most of the literature.

Postural activity of the diaphragm is reduced in humans when respiratory demand increases

1. Respiratory activity of the diaphragm and other respiratory muscles is normally co-ordinated with their other functions, such as for postural control of the trunk when the limbs move. The integration may occur by summation of two inputs at the respiratory motoneurons. The present study investigated whether postural activity of the diaphragm changed when respiratory drive increased with hypercapnoea. 2. Electromyographic (EMG) recordings of the diaphragm and other trunk muscles were made with intramuscular electrodes in 13 healthy volunteers. Under control conditions and while breathing through increased dead-space, subjects made rapid repetitive arm movements to disturb the stability of the spine for four periods each lasting 10 s, separated by 50 s. 3. End-tidal CO(2) and ventilation increased for the first 60-120 s of the trial then reached a plateau. During rapid arm movement at the start of dead-space breathing, diaphragm EMG became tonic with superimposed modulation at the frequencies of respiration and arm movement. However, when the arm was moved after 60 s of hypercapnoea, the tonic diaphragm EMG during expiration and the phasic activity with arm movement were reduced or absent. Similar changes occurred for the expiratory muscle transversus abdominis, but not for the erector spinae. The mean amplitude of intra-abdominal pressure and the phasic changes with arm movement were reduced after 60 s of hypercapnoea. 4. The present data suggest that increased central respiratory drive may attenuate the postural commands reaching motoneurons. This attenuation can affect the key inspiratory and expiratory muscles and is likely to be co-ordinated at a pre-motoneuronal site.

The role of the diaphragm during abdominal hollowing exercises

This study investigated the surface electromyographical (EMG) profiles of the diaphragm, anterolateral abdominals and rectus abdominis during abdominal hollowing exercises (AHE) in 20 healthy subjects. Muscle activity was assessed at 1000Hz over two seconds in crook lying at three incremental loads above a baseline of 40mmHg monitored by a pressure biofeedback unit. EMG amplitude increased significantly above resting for all muscles during correct performance of AHE at 5mmHg. At 15mmHg, all subjects were deemed to have performed AHE incorrectly and both the diaphragm and rectus abdominis activity were significantly elevated (p < 0.05). This supports the concept that the diaphragm plays a significant role in motor control strategies used by subjects performing different forms of AHE.