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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.)

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 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.

Objective: To determine whether the abdominal hollowing technique is more effective for lumbar spine stabilization than a full abdominal muscle cocontraction., Design: Within-subject, repeated-measures analysis of variance was used to examine the effect of combining each of 4 loading conditions with either the hollow or brace condition on the dependent variables of stability and compression. A simulation was also conducted to assess the outcome of a person activating just the transversus abdominis during the hollow., Setting: Laboratory., Participants: Eight healthy men (age range, 20-33y)., Interventions: Electromyography and spine kinematics were recorded during an abdominal brace and a hollow while supporting either a bilateral or asymmetric weight in the hands., Main Outcome Measures: Spine stability index and lumbar compression were calculated., Results: In the simulation "ideal case," the brace technique improved stability by 32%, with a 15% increase in lumbar compression. The transversus abdominis contributed .14% of stability to the brace pattern with a less than 0.1% decrease in compression., Conclusions: Whatever the benefit underlying low-load transversus abdominis activation training, it is unlikely to be mechanical. There seems to be no mechanical rationale for using an abdominal hollow, or the transversus abdominis, to enhance stability. Bracing creates patterns that better enhance stability.

Objective: To evaluate the neuromuscular strategy adopted during sitting balance on an unstable surface in the frontal plane., Design: Electromyographic evaluation of trunk muscles., Setting: University spine biomechanics laboratory., Participants: Seventy asymptomatic men (mean age, 34.5 y)., Interventions: Not applicable., Main Outcome Measures: "Balancers" and "nonbalancers" were identified by principal component analysis of their lumbar spine side flexion angle during sitting balance. Average electromyographic levels were used as a measure of muscle activation. Pearson correlations were used to identify coactivation versus asymmetrical muscle activation of opposite muscle groups., Results: External oblique, internal oblique, and thoracic erector spinae (TES) were most active, and most likely to be used asymmetrically, with other muscles showing low levels of coactivation. Between groups, the average electromyographic levels in the balancers was lower than in the nonbalancers (P<.05), with further differences in the symmetry of external oblique, internal oblique, and TES activation between groups., Conclusions: Sitting balance in the frontal plane appears to involve a combined feedforward-feedback strategy of muscle activation. Successful balance was characterized by low levels of muscle coactivity, along with higher levels of asymmetric activation in the global trunk muscles, specifically external oblique, internal oblique, and TES.

Objective: To develop a clinical prediction rule to predict treatment response to a stabilization exercise program for patients with low back pain (LBP)., Design: A prospective, cohort study of patients with nonradicular LBP referred to physical therapy (PT)., Setting: Outpatient PT clinics., Participants: Fifty-four patients with nonradicular LBP., Intervention: A standardized stabilization exercise program., Main Outcome Measure: Treatment response (success or failure) was categorized based on changes in the Oswestry Disability Questionnaire scores after 8 weeks., Results: Eighteen subjects were categorized as treatment successes, 15 as treatment failures, and 21 as somewhat improved. After using regression analyses to determine the association between standardized examination variables and treatment response status, preliminary clinical prediction rules were developed for predicting success (positive likelihood ratio [LR], 4.0) and failure (negative LR, .18). The most important variables were age, straight-leg raise, prone instability test, aberrant motions, lumbar hypermobility, and fear-avoidance beliefs., Conclusions: It appears that the response to a stabilization exercise program in patients with LBP can be predicted from variables collected from the clinical examination. The prediction rules could be used to determine whether patients with LBP are likely to benefit from stabilization exercises.

Objective: To establish isometric endurance holding times, as well as ratios between torso extensors, flexors, and lateral flexors (stabilizers), for clinical assessment and rehabilitation targets., Design: Simple measurement of endurance times in four tests performed in random order by a healthy cohort. To measure reliability, a subsample also performed the tests again 8 weeks later., Setting: University laboratory., Participants: Seventy-five young healthy subjects (31 men, 44 women)., Results: Women had longer endurance times than men for torso extension, but not for torso flexion or for the "side bridge" exercise, which challenges the lateral flexors (stabilizers). Men could sustain the "side bridge" for 65% of their extensor time and 99% of their flexion time, whereas women could sustain the "side bridge" for only 39% of their extensor time and 79% of their flexion time. The tests proved reliable, with reliability coefficients of >.97 for the repeated tests on 5 consecutive days and again 8 weeks later., Conclusion: Healthy young men and women possess different endurance profiles for the spine stabilizing musculature. Given the growing support for quantification of endurance, these data of endurance times and their ratios between extensor, flexor, and lateral flexor groups in healthy normal subjects are useful for patient evaluation and for providing clinical training targets.

Objective: To document the three-dimensional (3D) kinematics of the lumbar spine and the myoelectric activity of trunk muscles throughout the range of motion in selected tasks performed by healthy subjects., Design: A survey of a single population., Setting: A research laboratory in a university setting., Participants: Twenty-four men and women, university-age, with no history of chronic lower back pain volunteered for this study., Interventions: The selected tasks consisted of lateral bend and axial twists to the right and left plus four different flexion-extension tasks that varied a hand-held weight (10kg and 0kg), and flexion-extension velocity (free-paced and 20 degrees/sec)., Main Outcome Measure: 3D lumbar spine kinematics and normalized, linear enveloped electromyogram (EMG) of trunk muscles., Results: The motion time histories were illustrated graphically. Consistent spinal kinematics and EMG activation patterns during each task across subjects were seen. Peak displacement values between tasks, using one-way analysis of variance, showed no significant difference., Conclusion: A database of healthy spine kinematics and normalized linear enveloped trunk muscle activation patterns were developed for future comparison of elderly and pathological subjects.

Objective: To examine the changes in length of the spine during prolonged bedrest., Design: The height of subjects was recorded over two control days and subsequently during the course of 32 hours of bedrest., Setting: Data were collected in a student dormitory., Participants: Eight male volunteers from an undergraduate student population., Results: Subjects lost approximately 10mm in spine height over the course of each of two control days. When they remained in bed after a usual night's rest, their spine height did not increase further. Even after 32 hours of continuous bedrest, the spine did not increase its length beyond the normal morning height., Conclusions: Bedrest does not allow normal expulsion of fluids from the disc leading to higher stresses associated with fully imbibed discs.

The kinetics and kinematics of swing-through crutch gait in children were investigated assisted by the development of a computer package to aid in data analysis. Eight volunteer subjects ambulated with crutches of various lengths as cinefilm, axial crutch, and foot contact forces were recorded. Instantaneous segment energies and powers were calculated from digitized, filtered, cinefilm data. Values of internal mechanical work expenditure were also calculated using 9-segment and 10-segment models of the body. Mechanical inefficiencies in individual gait patterns were identified by abnormalities in the instantaneous energy and power traces augmented by force information. Although crutch length was found to be a critical determinant of efficient gait, the formula to find correct length varied among individuals. Normalized work output values for children, corrected for body weight and distance covered per stride, were found to be much greater than those found in adults.