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Although core stiffness enhances athletic performance traits, controversy exists regarding the effectiveness of isometric vs. dynamic core training methods. This study aimed to determine whether long-term changes in stiffness can be trained, and if so, what is the most effective method. Twenty-four healthy male subjects (23 ± 3 years; 1.8 ± 0.06 m; 77.5 ± 10.8 kg) were recruited for passive and active stiffness measurements before and after a 6-week core training intervention. Twelve subjects (22 ± 2 years; 1.8 ± 0.08 m; 78.3 ± 12.3 kg) were considered naive to physical and core exercise. The other 12 subjects (24 ± 3 years; 1.8 ± 0.05 m; 76.8 ± 9.7 kg) were Muay Thai athletes (savvy). A repeated-measures design compared core training methods (isometric vs. dynamic, with a control group) and subject training experience (naive vs. savvy) before and after a 6-week training period. Passive stiffness was assessed on a "frictionless" bending apparatus and active stiffness assessed through a quick release mechanism. Passive stiffness increased after the isometric training protocol. Dynamic training produced a smaller effect, and as expected, there was no change in the control group. Active stiffness did not change in any group. Comparisons between subject and training groups did not reveal any interactions. Thus, an isometric training approach was superior in terms of enhancing core stiffness. This is important since increased core stiffness enhances load bearing ability, arrests painful vertebral micromovements, and enhances ballistic distal limb movement. This may explain the efficacy reported for back and knee injury reduction.

Novel ideas for core endurance training are continually being created. However, studies of their mechanism of action assist in evaluation of their potential as a training tool, for a variety of people and purposes. The specific purpose of this study was to evaluate a weighted hula hooping training program for its efficacy on improving core muscular endurance and influence on measures of body composition. Eighteen women participated in a weighted hula hooping trial lasting 6 weeks, although only 13 returned for posttrial re-assessment. Hip and waist circumferences, 5 torso muscle endurance tests, and 5 skinfold measurements ("sum of 5") were measured before and after the exercise program. Paired samples t-tests were performed to examine pre/post changes. On average, participants experienced a significant decrease in waist and hip circumference -3.4 cm (p < 0.01) and -1.4 cm (p ≤ 0.05), respectively and waist-to-hip ratio from 89.3 cm down to 87.3 cm (t = 3.312, p < 0.01). There were no significant changes in torso muscular endurance after the 6 weeks of hooping; however, the average "sum of 5" skinfold measurements increased by 10.5 cm (p ≤ 0.05). This study of weighted hula hooping suggested that regular hooping was associated with reduced waist and hip girth together with a redistribution of body mass; however, there were no improvements in torso muscular endurance as measured by isometric testing.

The back squat is a well-researched and widely used exercise to enhance fundamental movement competency that creates a foundation for optimal mechanical strategies during a broad range of activities. The primary commentary introduced the Back Squat Assessment (BSA): a criterion based assessment of the back squat that delineates 30 potentially observable functional deficits. This follow-up commentary provides a targeted system of training cues and exercises to supplement the BSA to guide corrective intervention. We propose a criterion driven approach to corrective exercise that can support practitioners in their goal to help individuals achieve movement competency in the back squat.

Purpose: To describe female lumbar spine motion and posture characteristics during coitus and compare these characteristics across five common coital positions. Exacerbation of low back pain during coital movements and positions is a prevalent issue reported by female low back pain (LBP) patients. To address this problem, the first study to examine lumbar spine biomechanics during coitus was conducted., Methods: Ten healthy males and females performed coitus in the following pre-selected positions and variations: QUADRUPED (fQUAD1 and fQUAD2 where the female is supporting her upper body with her elbows and hands, respectively), MISSIONARY (fMISS1 and fMISS2 where the female is minimally and more flexed at the hips and knees, respectively), and SIDELYING. An electromagnetic motion capture system was used to measure three-dimensional lumbar spine angles that were normalized to maximum active range of motion-a transmitter and receiver were affixed to the skin overlying the lateral aspect of the pelvis and the spinous process of the twelfth thoracic vertebra, respectively. To determine if each coital position had distinct spine kinematic profiles (i.e., amplitude probability distribution function and total range of lumbar spine motion), separate univariate general linear models followed by Tukey's honestly significant difference post hoc analysis were used. The presentation of coital positions was randomized., Results: Female lumbar spine movement varied depending on the coital position; both variations of QUADRUPED, fQUAD1 and fQUAD2, were found to use a significantly greater range of spine motion than fMISS2 (p = 0.017 and p = 0.042, respectively). With the exception of both variations of MISSIONARY, fMISS1 and fMISS2, the majority of the range of motion used was in extension. These findings are most pertinent to patients with LBP that is exacerbated by motions or postures. Based on the spine kinematic profiles of each position, the least-to-most recommended positions for a female flexion-intolerant patient are: fMISS2, fMISS1, fQUAD1, fSIDE, and fQUAD2. These recommendations would be contraindicated for the extension-intolerant patient., Conclusions: The findings provided here may guide the clinician's specific recommendations, including alternative coital positions and/or movement patterns or suggesting a lumbar support, depending on the female LBP patient's specific motion and posture intolerances.

Background: Within the context of evaluating individuals' movement behavior it is generally assumed that the tasks chosen will predict their competency to perform activities relevant to their occupation., Objective: This study sought to examine whether a battery of general tasks could be used to predict the movement patterns employed by firefighters to perform select job-specific skills., Methods: Fifty-two firefighters performed a battery of general and occupation-specific tasks that simulated the demands of firefighting. Participants' peak lumbar spine and frontal plane knee motion were compared across tasks., Results: During 85% of all comparisons, the magnitude of spine and knee motion was greater during the general movement tasks than observed during the firefighting skills. Certain features of a worker's movement behavior may be exhibited across a range of tasks. Therefore, provided that a movement screen's tasks expose the motions of relevance for the population being tested, general evaluations could offer valuable insight into workers' movement competency or facilitate an opportunity to establish an evidence-informed intervention.

This study examined pulling exercises performed on stable surfaces and unstable suspension straps. Specific questions included: which exercises challenged particular muscles, what was the magnitude of resulting spine load, and did technique coaching influence results. Fourteen males performed pulling tasks while muscle activity, external force, and 3D body segment motion were recorded. These data were processed and input to a sophisticated and anatomically detailed 3D model that used muscle activity and body segment kinematics to estimate muscle force, in this way the model was sensitive to each individual's choice of motor control for each task. Muscle forces and linked segment joint loads were used to calculate spine loads. There were gradations of muscle activity and spine load characteristics to every task. It appears that suspension straps alter muscle activity less in pulling exercises, compared to studies reporting on pushing exercises. The chin-up and pull-up exercises created the highest spine load as they required the highest muscle activation, despite the body "hanging" under tractioning gravitational load. Coaching shoulder centration through retraction increased spine loading but undoubtedly adds proximal stiffness. An exercise atlas of spine compression was constructed to help with the decision making process of exercise choice for an individual., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Study Design: Repeated measures design., Objective: To describe male spine movement and posture characteristics during coitus and compare these characteristics across 5 common coital positions., Summary of Background Data: Exacerbation of pain during coitus due to coital movements and positions is a prevalent issue reported by low back pain patients. A biomechanical analysis of spine movements and postures during coitus has never been conducted., Methods: Ten healthy males and females engaged in coitus in the following preselected positions and variations: QUADRUPED, MISSIONARY, and SIDELYING. An optoelectronic motion capture system was used to measure 3-dimensional lumbar spine angles that were normalized to upright standing. To determine whether each coital position had distinct spine kinematic profiles, separate univariate general linear models, followed by Tukey's honestly significant difference post hoc analysis were used. The presentation of coital positions was randomized., Results: Both variations of QUADRUPED, mQUAD1 and mQUAD2, were found to have a significantly higher cycle speed than mSIDE (P = 0.043 and P = 0.034, respectively), mMISS1 (P = 0.003 and P = 0.002, respectively), and mMISS2 (P = 0.001 and P < 0.001, respectively). Male lumbar spine movement varied depending on the coital position; however, across all positions, the majority of the range of motion used was in flexion. Based on range of motion, the least-to-most recommended positions for a male flexion-intolerant patient are mSIDE, mMISS2, mQUAD2, mMISS1, and mQUAD1., Conclusion: Initial recommendations-which include specific coital positions to avoid, movement strategies, and role of the partner-were developed for male patients whose low back pain is exacerbated by specific motions and postures., Level of Evidence: N/A.

Objective: To establish torso muscle endurance values in children aged 7 to 14 years, as well as ratios between torso extensors, flexors, and lateral torso flexors, with applications in clinical assessment, rehabilitation, physical education targets, and athletic training program designs. It was hypothesized that boys and girls mature differently in terms of torso muscle endurance., Design: Measurements of torso muscle endurance were performed by using 4 tests in healthy children., Setting: Elementary school in Novi Sad, Province of Vojvodina, Republic of Serbia., Participants: Children from 1 elementary school (N=753, n=394 boys and n=359 girls) were grouped into 8 age strata., Interventions: Not applicable., Main Outcome Measures: Four tests established isometric physical endurance: Biering-Sørensen test for extensor endurance, flexor endurance test, and right- and left-side bridge tests. The mean, ratio, standard deviation, and 25th, 50th, and 75th percentile scores were determined for each sex/age stratum., Results: A 2-way analysis of variance indicated that girls had higher mean endurance times for torso extension and torso flexion than did boys. For example, times measured by using Biering-Sørensen and right-side bridge tests were significantly greater for girls than for boys across all age groups (P<.023). Boys can sustain the side torso test longer than can girls. Furthermore, 3-dimensional torso muscle endurance is under significant impact of age. Tukey Honestly Significant Difference post hoc tests confirmed that within and between sex exist significant differences in mean endurance times in all age strata at the significance level P=.05., Conclusion: Both age and sex influence differences in torso endurance in children aged 7 to 14 years. These data of endurance times, their ratios, and percentiles in healthy subjects form a database that may be useful for providing training and rehabilitation targets., (Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.)

Background: The elliptical trainer is a popular exercise modality, yet its effect on the lumbar spine is poorly understood. The purpose of this study was to analyze the effect of different hand positions, speed and stride lengths on spine kinematics and corresponding muscle activity while using the elliptical trainer, and compare with those demonstrated in normal walking., Methods: Electromyographic data was collected over 16 trunk and gluteal muscle sites on 40 healthy males (mean age (SD)=23(3)) while on the elliptical trainer. Two stride lengths (46, 66cm), 2 speeds (self-selected, 30% faster), and 3 hand positions (freehand, central bar, handles) were analyzed. Lumbar spine kinematics was calculated from data collected using a motion capture system. Results were compared to those found in walking using repeated measures ANOVA for each dependent variable with Bonferroni adjustments (P<0.004. Correlations were made between lumbar motion and various anthropometric measures., Findings: All significance levels comparing walking to elliptical varied according to stride length, speed and hand position. Average lumbar flexion angles and lumbar rotation were generally greater on the elliptical trainer, whereas walking produced more frontal motion. Total lumbar flexion/extension was similar between the two activities. Muscle activation patterns of the gluteal muscles were consistently higher on the elliptical, whereas the back extensors, latissimi and internal obliques were greater in only selected conditions., Interpretation: The various hand positions, speeds and stride lengths affect lumbar motion and muscle activity on the elliptical trainer, thus must be considered when incorporated into an exercise protocol., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Hip mobility is known to affect lumbar spine motion, yet the literature is unclear as to what constitutes normal, limited or excessive motion, given differences in methods, postures, age, etc. The purpose of this study was to establish normative and percentile data for hip rotation and extension, in a young adult male population, using varying methods of quantification., Methods: 77 males (age 18-35) were recruited. Position data was captured using the Vicon Motion capture system, as participants were passively positioned in hip extension (using the Modified Thomas test) and prone hip rotation. 22 of these participants also had measurements obtained with a goniometer. 3D hip extension angles were calculated using Euler angles, and compared to those calculated in 2D. Goniometric results were compared to 2D measurements., Findings: Normal distribution of hip extension and rotation range of motion was established, as were average values for the 5th through 95th percentiles. No significant differences existed between hip extension angles measured with the 2D and 3D approaches. Goniometric measurements of hip extension averaged 3.9° less than 2D, less than 1° different for external rotation, and not different for internal rotation., Interpretation: The normative and percentile data documented here for hip rotation and extension appear to be validly quantified with goniometric techniques when compared to more objective techniques. Further, hip restriction in one plane may not predict restrictions in other planes., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Ultrasound imaging is a valuable tool which, when applied appropriately, has the potential to provide information regarding the mechanics of abdominal muscle contraction. Typically, changes in muscle thickness are obtained and interpreted. However, the link between ultrasound measures of muscle thickening and EMG measures of activation is not clear., Methods: Five healthy males performed a series of abdominal muscle contractions while surface EMG and trunk posture were monitored and ultrasound images of the internal oblique and external oblique were captured both at relaxation and upon contraction. Ramped isometric flexor and extensor moment contractions were also assessed and compared between EMG and ultrasound., Findings: No definitive relationship between increases in muscle activation and corresponding measures of thickening was observed. Correlations between the two measures, across all contraction types, were 0.14 for internal oblique and -0.22 for external oblique., Interpretation: The lack of clear association between abdominal muscle activation and thickening may be due to the composite laminate-like structure of the abdominal wall, with force being transmitted between obliquely oriented muscle layers. Thus, ultrasound alone may not be a valid measure of muscle activation or force in the unique architecture of the abdominal wall., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

The main issue addressed here is the paradox of muscle contraction to optimize speed and strike force. When muscle contracts, it increases in both force and stiffness. Force creates faster movement, but the corresponding stiffness slows the change of muscle shape and joint velocity. The purpose of this study was to investigate how this speed strength is accomplished. Five elite mixed martial arts athletes were recruited given that they must create high strike force very quickly. Muscle activation using electromyography and 3-dimensional spine motion was measured. A variety of strikes were performed. Many of the strikes intend to create fast motion and finish with a very large striking force, demonstrating a "double peak" of muscle activity. An initial peak was timed with the initiation of motion presumably to enhance stiffness and stability through the body before motion. This appeared to create an inertial mass in the large "core" for limb muscles to "pry" against to initiate limb motion. Then, some muscles underwent a relaxation phase as speed of limb motion increased. A second peak was observed upon contact with the opponent (heavy bag). It was postulated that this would increase stiffness through the body linkage, resulting in a higher effective mass behind the strike and likely a higher strike force. Observation of the contract-relax-contract pulsing cycle during forceful and quick strikes suggests that it may be fruitful to consider pulse training that involves not only the rate of muscle contraction but also the rate of muscle relaxation.

Background: Epidemiological studies have found associations between lifting, lifting and twisting and twisting alone with increased incidence of disc herniation. This study investigated the role of repeated dynamic axial torque/twist combined with repeated flexion on the disc herniation mechanism., Methods: Porcine cervical spines were tested in one of the following four testing protocols: flexion-extension only; axial torque/twist only; flexion-extension followed by axial torque/twist; or axial torque/twist followed by flexion-extension. Plane film radiographs and computed tomography with contrast in the nucleus were obtained at regular intervals during and following the mechanical testing process together with final dissection to determine the disc injury patterns., Findings: Axial torque/twist in combination with repetitive flexion extension motion, regardless of order, encouraged radial delamination within the annulus (67.5% of specimens). Alternatively, repetitive flexion motion alone encouraged posterior or posterolateral nucleus tracking through the annulus. Axial torque/twist alone was unable to initiate a disc herniation. Both X-ray images with contrast and computed tomography were not good at detecting radial delamination observed during dissection., Interpretation: The clinical relevance is that twisting may cause more radial delamination while repeated flexion causes more posterior tracking of the nucleus giving guidance for both prevention and rehabilitation decisions. In addition, X-ray images with contrast are not effective at detecting the radial delamination which was exacerbated by combined loading in flexion extension and axial torque/twist.

Prolonged sitting with spine flexion has been linked to low back disorders. A variety of mechanisms account for this based on biomechanical and neurological variables. Airline seats typically cause pronounced lumbar flexion due to their hollowed seat back design. A pneumatic support, placed between the seat back and the lumbar spine, was tested to see if lumbar flexion was reduced. Results showed that when the seats were positioned in the upright position, 15 of 20 participants experienced reduced lumbar flexion (by 15 degrees on average) with the support. The study was repeated on the five non-responders with the seatback set in the reclined position. This resulted in another four experiencing less lumbar flexion. Since seated flexion is associated with disc stress, reducing flexion with the support reduced lumbar stress. Spine flexion that results from prolonged sitting is associated with disc stress and pain. The pneumatic support tested here reduced spine flexion. While it is not known why airline seats are designed with no lumbar support, which causes excessive lumbar flexion while seated, the pneumatic support corrected this deficit. Reclining the seatback enhanced this effect.

Strongman events are attracting more interest as training exercises because of their unique demands. Further, strongman competitors sustain specific injuries, particularly to the back. Muscle electromyographic data from various torso and hip muscles, together with kinematic measures, were input to an anatomically detailed model of the torso to estimate back load, low-back stiffness, and hip torque. Events included the farmer's walk, super yoke, Atlas stone lift, suitcase carry, keg walk, tire flip, and log lift. The results document the unique demands of these whole-body events and, in particular, the demands on the back and torso. For example, the very large moments required at the hip for abduction when performing a yoke walk exceed the strength capability of the hip. Here, muscles such as quadratus lumborum made up for the strength deficit by generating frontal plane torque to support the torso/pelvis. In this way, the stiffened torso acts as a source of strength to allow joints with insufficient strength to be buttressed, resulting in successful performance. Timing of muscle activation patterns in events such as the Atlas stone lift demonstrated the need to integrate the hip extensors before the back extensors. Even so, because of the awkward shape of the stone, the protective neutral spine posture was impossible to achieve, resulting in substantial loading on the back that is placed in a weakened posture. Unexpectedly, the super yoke carry resulted in the highest loads on the spine. This was attributed to the weight of the yoke coupled with the massive torso muscle cocontraction, which produced torso stiffness to ensure spine stability together with buttressing the abduction strength insufficiency of the hips. Strongman events clearly challenge the strength of the body linkage, together with the stabilizing system, in a different way than traditional approaches. The carrying events challenged different abilities than the lifting events, suggesting that loaded carrying would enhance traditional lifting-based strength programs. This analysis also documented the technique components of successful, joint-sparing, strongman event strategies.

Objective: To compare trunk muscle activation patterns and trunk kinematics when using an oscillating blade in standing and unsupported sitting postures, and with different orientations of the blade., Design: A cross-sectional survey of trunk muscle activities and lumbar motion., Setting: Biomechanics research laboratory., Participants: Healthy men (N=13)., Interventions: An oscillating blade was held with 2 hands and oscillated with vertical and horizontal orientations of blade. These exercises were performed both in an erect standing position and in an erect sitting position., Main Outcome Measures: Surface electromyography from 14 trunk and 2 shoulder muscles, together with lumbar angular displacement in the 3 planes of motion, were measured while subjects used an oscillating blade at different performance variations. Electromyographic signals were normalized to isometric maximal voluntary contraction (MVC) amplitudes., Results: With the exception of internal oblique and anterior deltoid for the horizontal condition, and erector spinae at L5 level for the vertical condition, the subject's posture had no effect on trunk muscular recruitment when using the oscillating blade. The vertical blade orientation resulted in higher amplitudes of spine rotation on the horizontal plane and produced the greatest activation levels of the internal oblique (47% MVC), pectoralis major (33% MVC), and external oblique (23% MVC). On the other hand, the horizontal orientation resulted in the greatest activation levels of erector spinae at T9 level (28% MVC), latissimus dorsi (26% MVC), and rectus abdominis (17% MVC)., Conclusions: Muscle activation and spine motion from using an oscillating blade were not affected by the standing or sitting posture of the subject. The choice of blade orientation was more important, because it defined the main group of muscles recruited during the exercise.

Objective: To determine the utility of the active straight leg raise (ASLR) test as a screen of lumbar spine stability and abdominal bracing (AB) ability., Design: A biomechanical study of the ASLR test as a clinical evaluation of lumbar spine stability and AB., Setting: Clinical research laboratory., Participants: Fourteen participants who were currently asymptomatic for back pain and leg pain were evaluated., Methods: Spine posture, muscle activation, and pressure distributions underneath the supine subject were determined., Main Outcome Measurements: An estimation of lumbar spine stiffness, a direct correlate with spine stability, was obtained using an anatomically detailed spine model., Results: AB during the ASLR reduced the center of pressure (CoP) movement on a strain-based pressure mat in lumbar rotation (P < .0125) as well as reducing directly measured lumbar rotation (P = .02). Active AB increased lumbar spine stiffness (P < .002). Regression analysis between stiffness and CoP movement suggested that different participants used different strategies to control torso motion., Conclusions: This study demonstrates that the ASLR has utility as a screen of lumbar spine stability and AB ability. The ASLR maneuver can assess control of lumbar rotational movements in the transverse plane. Finally, this study demonstrated that AB can measurably improve the rotational (transverse plane) stiffness of the lumbar spine.

The purpose of this study was to document the muscle activity and spine motion during several tasks requiring rapid abdominal contraction. Eight healthy men from a university population were instrumented to obtain surface electromyography of selected trunk and hip muscles, together with video analysis to calculate joint moments and electromagnetic lumbar spine position sensor to track spine posture. Exercises included a punch, throw, and a ballistic torso-stiffening maneuver. This study found that no muscle turned on significantly before any other muscle during both the 1-in. punch and ballistic torso-stiffening maneuver. Conversely, there was a significant order or muscle onset during the baseball throw. Muscles reached peak activation significantly before any other muscle during the baseball throw and 1-in. punch, but there were no significant differences for the torso-stiffening maneuver. The exercises quantified in this study demonstrated how muscle contraction dynamics change to meet differing demands for stiffening, for force/moment production, and for rapid movements. Specifically, it seems that there is an order of contraction when movement is the goal but not when just spine stability is required. Thus, a different intensity of abdominal bracing is required to achieve the different objectives of sports tasks and exercises.

The purpose of this study was to document the muscle activity, spine motion, spine load, and stiffness during several movement-based or "functional" exercises and to assess the effect of technique change. Eight subjects, all healthy men from a university population, were instrumented to obtain surface electromyography of selected trunk and hip muscles, together with video analysis and electromagnetic lumbar spine position sensor to track spine posture. Exercises included a walkout in the sagittal plane that compared an upright form against a wall with those performed on the floor, overhead cable pushes, lateral cable walkouts, the good morning exercise, and the bowler's squat. Generally, muscle activation levels were quite modest even though the tasks were quite strenuous in many cases. Even though similar joint moments were required in different exercises, the pattern of activity between muscles was different. Abdominal bracing increased spine stiffness at the expense of more spine load. Thus, muscle activity seems to be constrained in "functional" exercises. There are several possible reasons for this. Single muscles cannot be activated to 100% of the maximum voluntary contraction in functional exercises because this would upset the balance of moments about the 3 orthopedic axes of the spine, or it would upset the balance of stiffening muscles around the spine required to ensure stability of the spinal column. The one exception was the floor walkout, which resulted in full activation of the rectus abdominis; however, this was a sagittal plane task without the joint moment constraints of multiplanar exercise. Therefore, maximal muscle activity is observed during single-plane tasks, but muscle activation levels were constrained during functional tasks. Thus, strength training muscles may not help in "functional multiplanar" tasks. These data can be used to assist decisions regarding the selection of exercises, specifically choices regarding the starting challenge, progression, exercise form, and possibly corrective technique for those who have spine concerns, or those simply looking for performance enhancement.

The ProFitter 3-D Cross Trainer is a labile surface device used in the clinic and claimed to train spine stability. The purpose of this study was to quantify the spine mechanics (compression and shear forces and stability), together with muscle activation mechanics (surface electromyography) of the torso and hip, during three ProFitter exercises. Trunk muscle activity was relatively low while exercising on the device (<25%MVC). Gluteus medius activity was phasic with the horizontal sliding position, especially for an experienced participant. Sufficient spinal stability was achieved in all three exercise conditions. Peak spinal compression values were below 3400 N (maximum 3188 N) and peak shear values were correspondingly low (under 500 N). The exercises challenge whole-body dynamic balance while producing very conservative spine loads. The motion simultaneously integrates hip and torso muscles in a way that appears to ensure stabilizing motor patterns in the spine. This information will assist with clinical decision making about the utility of the device and exercise technique in rehabilitation and training programs.

Objective: To quantify several forms of the curl-up, side-bridge, and birddog exercises (muscle activity and 3-dimensional [3D] spine position) including some corrective techniques to assist clinical decision-making., Design: A basic science study of a convenience sample with a retest of expert intervention., Setting: Spine Biomechanics Laboratory/Research Clinic., Participants: Healthy men (N=8) performed the exercises, and 5 subjects repeated the exercises as an expert applied corrective techniques., Interventions: Not applicable., Main Outcome Measures: Surface electromyography of selected trunk and hip muscles together with video analysis and 3D spine posture were collected., Results: Comparison of muscle activation levels showed there were justifiable progressions in each exercise form. In general, bracing of the abdominal wall enhanced activation of the obliques, but different techniques caused migration of muscle activity to other muscles. Examples of specific findings include the following. Movement during these traditionally isometric exercises such as drawing squares with the hand/foot while in the birddog posture enhances activation of many muscle groups. Breathing while holding the isometric exercises had differing effects on muscle activation which was exercise dependent. Some corrective exercise techniques, such as fascial raking, substantially changed relative activation between muscles in the abdominal wall., Conclusions: The data presented in this study may be used to guide the clinical decision process when choosing a specific exercise form together with selecting the correct starting level, a logical progression, suitable dosage, and possible corrective technique to enhance tolerance of a patient.

This study assessed several mechanical issues related to low back loading during pushing and/or pulling tasks. Nine male participants performed two-handed pushing and pulling tasks at two handle heights with three loads, using a cable pulley system. Four of these men were professional firefighters trained in performing pushing and pulling tasks while the other five were graduate students who lacked manual work experience. The more experienced firefighters produced less spinal compression and shearing forces when compared to the less experienced students under the same conditions. The firefighters were able to create less muscle activation as compared to the students, which indicated a more efficient technique. The main contributing factors to the forces produced on the low back were the quantity of the load being pushed or pulled, handle height, experience level and the technique of the participant. Thus, attempts to set load limits for pushing and pulling tasks are difficult, since technique has such a large influence on back loading. In order to create safer working environments, education on proper pushing and pulling techniques is very important--more important than the physical variables in many cases.

Study Design: A repeated measures biomechanical analysis of the effects of abdominal bracing in preparation for a quick release of the loaded trunk., Objectives: To quantify the ability of individuals to abdominally brace the externally loaded trunk, and assess their success in achieving and enhancing appropriate spine stability., Summary of Background Data: Spine stability requires trunk muscle coactivation, which demands motor control skill that differs across people and situations. The quick release protocol may offer insight into the motor control scheme and subsequent effect on spine stability., Methods: There were 10 individuals who sat, torso upright, in an apparatus designed to foster a neutral spine position. They were instructed to support a posteriorly directed load to the trunk in either their naturally chosen manner, or by activating the abdominal muscles to 10%, 20%, or 30% of maximum ability. The externally applied load was then quickly released, thereby unloading the participant. Muscle pre-activation patterns, spine stability, and kinematic measures of trunk stiffness were quantified., Results: Participants were able to stabilize their spine effectively by supporting the load in a naturally selected manner. Conscious, voluntary overdriving of this natural pattern often resulted in unbalanced muscular activation schemes and corresponding decreases in stability levels., Conclusions: Individuals in an externally loaded state appear to select a natural muscular activation pattern appropriate to maintain spine stability sufficiently. Conscious adjustments in individual muscles around this natural level may actually decrease the stability margin of safety.