Endurance of trunk muscles in persons with chronic low back pain: assessment, performance, training.

Trunk muscles are designed to fulfill their role of continuous activity throughout the day, but pain and inactivity alter muscles so that they fatigue in normal situations. Lack of endurance of the trunk muscles is an important factor in low back pain (LBP). This paper examines some methods to objectively test endurance of trunk flexor and extensor muscles in static and dynamic situations, and presents results of endurance testing in persons with chronic LBP compared to nonimpaired cohorts.

Some endurance measures in persons with chronic low back pain.

Muscle fatigue and lack of endurance are complaints of persons with chronic low back pain, but there are no standard ways to assess endurance in this population. The purposes of this study were to examine three measures of endurance; to determine relationships of these measures to each other; and to describe effects of gender, obesity, smoking, and self-reported fitness on the clinical measures. The measures of endurance selected were not dependent on maximal voluntary muscular contractions.

Distinguishable groups of musculoskeletal low back pain patients and asymptomatic control subjects based on physical measures of the NIOSH Low Back Atlas.

Study Design: The authors performed an empirical prospective study of 115 patients referred to physical therapy for low back pain and 112 control subjects of similar age and gender.

Objectives: The authors defined and compared subgroups based on physical tests and described demographic and psychosocial characteristics by group.

Summary Of Background Data: Prospective studies of intervention for persons with low back pain are limited by inability to randomize subjects into distinguishable groups.

Endurance training of trunk extensor muscles.

Background And Purpose: The purpose of this study was to assess the effects of an endurance exercise protocol on the isometric holding time of the trunk extensor muscles (mechanical fatigue measure) and on the recorded median frequency (MF) measurements from the surface electromyogram (physiological fatigue measure).

Subjects: Twenty-eight healthy female volunteers were selected to participate in the study.

Methods: The subjects were stratified by activity level and then assigned to an exercise or a control group and tested at weeks 0, 3, and 6.

A technique for needle localization in paraspinal muscles with cadaveric confirmation.

Invasive electromyography (EMG) of the paraspinal muscles is useful in clinical and research settings. No technique for localization of the needle in specific fascicles has been validated. Recent descriptions of the segmented innervation of the multifidus imply that such a technique would add greatly to the EMG determination of root level of a radiculopathy.

EMG to torque relationship in rectus abdominis muscle. Results with repeated testing.

Rectus abdominis muscles of young healthy female volunteers were studied to determine both the maximum strength in isometric flexion and the relation between the surface electromyogram (RMS EMG) and torque. Both the upper and lower portions of the abdominal muscle were studied during graded increase and decrease of torque. Repeated testing was performed over 6 weeks.

Comparison of acoustic and electrical signals from erectores spinae muscles.

Comparison was made between simultaneous recordings of the electromyogram (EMG) and acoustic myogram (AMG) signals and the torque produced by the lumbar erectores spinae muscles of three healthy subjects while they performed isometric contractions. Repeatability of each signal was studied. The AMG had a relationship to the torque which was more quadratic than linear, whereas that of the EMG was more linear.

Trunk extensor EMG-torque relationship.

The integrated surface electromyogram (IEMG) of the lumbar erectores spinae and the torque generated were simultaneously recorded from 27 healthy subjects in the standing posture while they pulled isometrically against resistance provided by a harness around the shoulders. The IEMG-torque ratio (efficiency of electrical activity, or EEA) was used to characterize each subject. Individual recordings showed evidence of nonlinearity of the IEMG-torque relationship in that a statistically better fit to experimental recordings was obtained by using two straight lines with a breakpoint between them.

The power struggle: definition and evaluation of power of muscular performance.

The authors define five different measurements of power of muscular performance. Using an isokinetic dynamometer, the velocity of motion is constant and thus can be controlled. Power, therefore, can be readily assessed.