Reproducibility of the 6-minute walk test in lung transplant recipients.

PURPOSE: There is reason to believe that the favorable measurement properties of the 6­minute walk test (6MWT) reported for retest reliability and its capability to detect a true change in healthy individuals or persons with chronic respiratory disease may not apply to lung transplant recipients (LuTXr). We therefore investigated retest reliability of the 6MWT and, in addition, made an attempt to explore whether the 6MWT was sensitive enough to detect important changes that occur with postacute rehabilitation in LuTXr after first time LuTX. METHODS: Immediately before postacute rehabilitation, 50 LuTXr completed 6MWT testing twice, separated by 1-2 workdays (retest reliability), and were reassessed after completion of rehabilitation 2 months later (sensitivity to changes). Body function measures and health-related quality of life (HRQoL) assessments were collected at baseline. RESULTS: Baseline retest 6­minute walk distance (6MWD) and the age-related predicted walking distance (6MWD%pred) scores significantly increased before postacute rehabilitation. The intraclass coefficient of correlation ICC of the 6MWD was 0.93 (95% confidence interval, CI: 0.88-0.96) and its smallest real difference (SRD) 79 m (95% CI: 52;107). Receiver operating curve analyses revealed the rehabilitation associated changes in 6MWD/6MWD%pred to exceed the SRD/SRD% values in a highly accurate way. CONCLUSION: The 6MWT overall represents a reliable functional performance tool in LuTXr that is sensitive to detect changes in physical performance as a result of medical postacute rehabilitation.

Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises.

Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG) data. Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's), an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG) and the instantaneous median frequency (IMDF-SEMG) estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise. Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise. Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior.

Degeneration and Instability and the Relation to Patients' Function Late After Lumbar Disc Surgery: Data from a 12-Year Follow-Up.

OBJECTIVE: To investigate the excess risk of degeneration and segmental instability in operated segments late after lumbar disc surgery in patients with presurgically stable segments, and whether local pathological findings relate to patients' back health. DESIGN: This retrospective analysis reports on 69 patients 12 years after first-time, uncomplicated lumbar disc surgery. Two independent radiologists evaluated the patients' lumbar functional x-rays; the Back Pain Rating Score (LBP-RS) assessed back-specific function. RESULTS: At 12 years after lumbar disc surgery, degenerative changes as well as segmental instability occurred significantly more frequently in the operated than nonoperated lumbar segments, but there was no association between increased degeneration and segmental instability rates. The risk for acquiring segmental instability was significantly associated with surgery (odds ratio, 6.5; 95% confidence interval, 1.5-28.8). Prevalence of segmental instabilities was associated with better LBP-RS scores. Analyses of LBP-RS subscores revealed a clear association of segmental instability with physical function, but not with pain or activities of daily living. CONCLUSIONS: Lumbar disc surgery seems to be associated with an increased risk of degeneration and segmental instability in the long term. This structural impairment, however, seems functionally well compensated and does not seem to be a relevant causal factor for a chronic back pain syndrome. TO CLAIM CME CREDITS: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES:: Upon completion of this article, the reader should be able to: (1) Describe the impact of lumbar disc surgery on segmental instability and degenerative changes; (2) Recognize the lack of association between degenerative changes and segmental instability after lumbar disc surgery; and (3) State the value of lumbar spinal functional tests in the evaluation of patients after lumbar disc surgery. LEVEL: Advanced ACCREDITATION:: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The Association of Academic Physiatrists designates this activity for a maximum of 1.5 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Twelve-year follow-up of a randomized controlled trial of comprehensive physiotherapy following disc herniation operation.

OBJECTIVE: To evaluate the long-term effects of postoperative comprehensive physiotherapy starting one week after lumbar disc surgery. DESIGN: Twelve-year follow-up of a three-armed, randomized, controlled, single-blinded clinical trial. SETTING: Department of Physical Medicine & Rehabilitation. PARTICIPANTS: Of 111 patients following first-time, uncomplicated lumbar disc surgery who participated in the original study and completed the treatment originally allocated, 74 ((67%; 29 (73%) physiotherapy, 22 (58%) sham therapy, 23 (68%) no therapy) completed a 12-year follow-up examination. INTERVENTIONS: In the original study, patients had been randomly assigned to comprehensive physiotherapy, sham intervention (neck massage), or no therapy. MEASURES: Low Back Pain Rating Scale; best score 0, worst score 130 points). RESULTS: At 12 years after surgery, the group participating in comprehensive physiotherapy had significantly better functional outcomes, as rated on the Low Back Pain Rating Score, than the untreated group (mean difference: -13.2 (95% CI: (-25.4; -1.0)). Equally, there was a clinically relevant, non-significant difference between the sham therapy and no therapy (mean difference: -12.5 (95%CI: -26.1; 1.1)). Consequently, the Low Back Pain Rating Score outcome did not differ between physiotherapy and sham therapy (mean difference: -0.7 (95%CI: -14.2; 12.8)). CONCLUSIONS: Participating in a comprehensive physiotherapy program following lumbar disc surgery may be associated with better long-term health benefits over no intervention, but may not be superior to sham therapy.

Physiotherapy-based rehabilitation following disc herniation operation: results of a randomized clinical trial.

STUDY DESIGN: Three-group, randomized, single blinded, controlled trial. OBJECTIVE: To test the effectiveness of physiotherapy-based rehabilitation starting 1 week after lumbar disc surgery. In addition, we tried to estimate the contribution of specific effects to the observed outcome (efficacy). SUMMARY OF BACKGROUND DATA: Physiotherapy-based rehabilitation is usually recommended for patients following lumbar disc surgery. Few and conflicting data exist for the relative effectiveness of this intervention. METHODS: A total of 120 patients following first-time, uncomplicated lumbar disc surgery were randomly assigned to "comprehensive" physiotherapy, "sham" neck massage, or no therapy. Before enrollment, all subjects completed a minimal physiotherapeutic intervention. Physiotherapy was administered by experienced physiotherapists and consisted of 20 sessions per patient over 12 weeks. Masseurs administered "sham massage" to the neck. The amount of treatment time was equal to that of physiotherapy. The main outcome measure was the Low Back Pain Rating Score (LBPRS) at 6 and 12 weeks, and 1.5 years after randomization. Secondary parameters were patients' overall satisfaction with treatment outcome and socioeconomic and psychologic measures. RESULTS: At the end of therapy (12 weeks), the LBPRS revealed a significantly better improvement in the physiotherapy group than in the untreated group. LBPRS outcome, however, did not significantly differ between physiotherapy and "sham" therapy. There was a tendency toward significance between the sham therapy and no therapy. Within the 1.5-year follow-up, LBP rating scales remained significantly improved compared with baseline, but there were no significant outcome differences. No statistically significant between-group differences were found for the secondary outcome parameters. CONCLUSION: As compared with no therapy, physiotherapy following first-time disc herniation operation is effective in the short-term. Because of the limited benefits of physiotherapy relative to "sham" therapy, it is open to question whether this treatment acts primarily physiologically in patients following first-time lumbar disc surgery, but psychological factors may contribute substantially to the benefits observed.

Muscle fatigue and fatigue-related biomechanical changes during a cyclic lifting task.

STUDY DESIGN: Electromyographic and biomechanical methods were utilized to investigate correlations between indexes of localized muscle fatigue and changes in the kinematics and kinetics of motion during a cyclic lifting task. SUMMARY OF BACKGROUND DATA: Recent advances in time-frequency analysis procedures for electromyographicic signal processing provide a new way of studying localized muscle fatigue during dynamic contractions. These methods provide a means to investigate fatigue-related functional impairments in patients with low back pain. OBJECTIVES: To study the relationship between localized muscle fatigue and the biomechanics of lifting and lowering a weighted box. Fatigue-related changes in the electromyographicic signal of trunk and limb muscles were evaluated and compared to kinematic and kinetic measures in order to determine whether lifting strategy is modified with fatigue. METHODS: A total of 14 healthy male subjects (26 +/- 5 years) cyclically lifted and lowered a 13 kg box (12 lifts/min) for 4.5 minutes. A 5-second static maximum lifting task was included immediately before and after the cyclic lifting task to measure changes in lifting strength and static electromyographicic fatigue indexes. Electromyographic signals from 14 muscle sites (including paravertebral and limb muscles) were measured. Changes in the electromyographicic Instantaneous Median Frequency, a fatigue index, were computed using time-frequency analysis methods. This index was compared with more standardized measures of fatigue, such as those based on electromyographicic median frequency acquired during a static trunk extension test, subjective fatigue measures, and maximal static lifting strength. Biomechanical measures were gathered using a motion analysis system to study kinematic and kinetic changes during the lifting task. RESULTS: During the cyclic lifting task, the electromyographic Instantaneous Median Frequency significantly decreased over time in the paravertebral muscles, but not in the limb muscles. Paravertebral electromyographicic Instantaneous Median Frequency changes were consistent with self-reports of fatigue as well as decreases in trunk extension strength. The magnitude of muscle-specific changes in electromyographicic Instantaneous Median Frequency was not significantly correlated with electromyographicic median frequency changes from the static trunk extension task. The load of the box relative to the maximal static lifting strength significantly affected the electromyographicic Instantaneous Median Frequency changes of paravertebral back muscles. Significant changes with fatigue during the task were found in the angular displacements at the knee, hip, trunk, and elbow. These biomechanical changes were associated with increased peak torque and forces at the L4-L5 vertebral segment. CONCLUSIONS: Our results demonstrate correlation between localized muscle fatigue and biomechanical adaptations that occur during a cyclic lifting task. This new technique may provide researchers and clinicians with a means to investigate fatigue-related effects of repetitive work tasks or assessment procedures that might be useful in improving education, lifting ergonomy, and back school programs. Although both the dynamic and static tasks resulted in spectral shifts in the electromyographicic data, the fact that these methods led to different muscle-specific findings indicates that they should not be considered as equivalent assessment procedures.

Reliability of EMG time-frequency measures of fatigue during repetitive lifting.

PURPOSE: To test the short-term and long-term reliability of time-frequency electromyographic (EMG) measures of fatigue during repetitive dynamic lifting and compare it with the reliability of median frequency (MF) EMG measures of fatigue during static lifting. METHODS: Fourteen' healthy male subjects (26 +/- 5 years) repetitively (12 lifts/min) lifted and lowered a box (29 x 25 x 23 cm, 13 kg) for 4.5 min during 3 different tests on 2 different days. EMG data and the biomechanics of motion were recorded. Before and after dynamic lifting, static maximum lifting tests were performed. At the end of each of the two sessions, subjects performed a static lift at 80% of their maximum lifting force for 30 s. RESULTS: Significant fatigue-related changes were observed during the lifting exercise via EMG time-frequency analysis at the paravertebral L5, L2, T10, and vastus lateralis (VL) electrode sites. Two parameters for assessing fatigue during dynamic contractions [i.e., the Instantaneous Median Frequency (IMDF) and its time dependent change] were shown to be reproducible both in the short-term (2 h) and long-term (2 wk). The corresponding ICCs reflecting the reproducibility of values between sessions were 96.9% (L5), 98.1% (L2), 90.1% (T10), 96.4% (UT), 98.0% (GM), 89.5% (VL), and 99.0% (BF), respectively. For most EMG recording sites, the reliability of the IMDF measures was not dependent upon the postural strategy that the subject used to accomplish the lifting task or on the subject's strength as measured via the static maximum lifting test. A comparison between the ICC values of the IMDF measures and those of the parameters utilized to assess fatigue during static sustained lifts [i.e., the Median Frequency (MDF) and its change during the test] revealed equally good reproducibility for most EMG recording sites. The respective ICC values that took into account time dependent trends for the IMDF parameter were 87.1% (L5), 62.4% (L2), 90.1% (T10), 0% (UT), 72.7% (GM), 45.4% (VL), and 100% (BF), and for the MDF parameter 94.9% (L5), 73.0% (L2), 80.9% (T10), 100% (UT), 89% (GM), 91.7% (VL), and 90.9% (BF), respectively. CONCLUSIONS: The time-frequency approach allows one to derive EMG spectral parameters that can be used to monitor muscle fatigue during dynamic real-world tasks such as lifting.