N. Pulkovski

Abdominal muscle size and symmetry at rest and during abdominal hollowing exercises in healthy control subjects

The symmetry of, and physical characteristics influencing, the thickness of the lateral abdominal muscles at rest and during abdominal exercises were examined in 57 healthy subjects (20 men, 37 women; aged 22–62 years). M‐mode ultrasound images were recorded from the abdominal muscles at rest and during abdominal hollowing exercises in hook‐lying. The fascial lines bordering the transvs. abdominis, obliquus internus and obliquus externus were digitized and the absolute thickness, relative thickness (% of total lateral thickness) and contraction ratio (thickness during hollowing/thickness at rest), as well as the asymmetry (difference between sides expressed as a percent of the smallest value for the two sides) for each of these parameters were determined for each muscle. Both at rest and during hollowing, obliquus internus was the thickest and transvs. abdominis the thinnest muscle. There were no significant differences between left and right sides for group mean thicknesses of any muscle; however, individual asymmetries were evident, with mean values for the different muscles ranging from 11% to 26%; asymmetry was much less for the contraction ratios (mean % side differences, 5–14% depending on muscle). Body mass was the most significant positive predictor of absolute muscle thickness, for all muscles at rest and during hollowing, accounting for 30–44% variance. Body mass index explained 20–30% variance in transvs. abdominis contraction ratio (negative relationship). The influence of these confounders must be considered in comparative studies of healthy controls and back pain patients, unless groups are very carefully matched. Asymmetries observed in patients should be interpreted with caution, as they are also common in healthy subjects.

TISSUE DOPPLER IMAGING FOR DETECTING ONSET OF MUSCLE ACTIVITY

Tissue Doppler imaging (TDI) is typically used to image and quantify tissue motion. We investigated whether this method would serve as a viable alternative to surface electromyography (EMG) in providing a reliable and valid measure of the onset of muscle activity. Ten healthy subjects performed maximal knee extension exercises at 0°/s (isometric), 60°/s, 120°/s, 180°/s, and 240°/s (5 times each, on each side), using an isokinetic dynamometer. Simultaneous EMG and TDI velocity (superimposed on motion‐mode ultrasound cine‐loops) recordings were made from vastus lateralis. All tests were repeated 1 week later. There was a good correlation between the onset times determined with TDI velocity and EMG: r = 0.78 (day 1), and r = 0.80 (day 2) (each P < 0.001). The mean difference (and SD) in muscle onset time between the two methods (TDI minus EMG) was −20.3 ± 31.0 ms (day 1) and −17.4 ± 27.2 ms (day 2). TDI represents a reliable and valid measure of detecting onset of muscle activity. The mean difference between EMG and TDI onset times (approximately 20 ms) is likely explained by electromechanical delay. TDI represents a viable method for measuring the onset of muscle activity; it may offer a non‐invasive alternative to fine‐wire EMG for use with small or deep muscles. Muscle Nerve, 2008

Goal attainment scaling as a measure of treatment success after physiotherapy for chronic low back pain

OBJECTIVES In some chronic conditions, patient-specific tools with individualized items have proved to be more sensitive outcome instruments than fixed-item tools; their use has not yet been investigated in chronic low back pain (cLBP). METHODS Eleven males and 21 females [mean age 44.0 (12.3) years] with cLBP, undergoing a spine-stabilization physiotherapy programme, completed the Roland Morris (RM) Disability Scale and a 0-10 pain scale pre- and post-therapy. Post-therapy, goal attainment scaling (GAS) scores were calculated regarding achievement of 2-6 priority GAS goals established pre-therapy; global outcome of therapy was assessed on a 5-point Likert scale. RESULTS Approximately one-fifth of the individualized goals were not covered by items of the RM. Of the 121 individualized goals, 41 (34%) were achieved at the expected level, 42 (35%) were exceeded and 38 (31%) were not reached. GAS scores correlated with change scores for pain (r = 0.61, P < 0.0001) and RM (r = 0.49, P = 0.006). Sixty-five per cent of the patients had a successful outcome according to GAS (i.e. a score >or=50); 55%, according to global outcome (therapy helped/helped a lot); 39%, according to the RM score change (score decrease >or=30%); and 44%, according to the pain score change (score decrease >or=30%). CONCLUSIONS GAS demonstrates the achievement of important goals undetected by fixed-item measures and is a valid and sensitive outcome measure for assessing the success of rehabilitation in patients with cLBP.

410 RELIABILITY OF MEASURES OF ABDOMINAL MUSCLE THICKNESS DURING ABDOMINAL HOLLOWING, AS ASSESSED WITH M-MODE ULTRASOUND

psychosocial distress measured with the Symptom Checklist-90-Revised (SCL-90-R) and self reported disability measured with the Roland Morris Disability Questionnaire (RMDQ) has not been investigated. Aim of this study is to analyze the relationship between psychosocial distress measured with the SCL-90-R and disability measured with the RMDQ in patients with CLBP. Methods: The study was performed in an outpatient pain rehabilitation setting. The study sample consisted of 152 patients with CLBP admitted for multidisciplinary treatment. All patients completed the SCL-90-R and RMDQ. Results: Pearson’s correlation coefficients between SCL-90-R (Global Severity Index and subscales) and RMDQ ranged from 0.18 to 0.31 (p< 0.05). Conclusion: The relationship between psychosocial distress measured with the SCL-90-R and self reported disability measured with the RMDQ in CLBP patients is weak.

411 TISSUE DOPPLER IMAGING: AN ALTERNATIVE TO FINE-WIRE EMG FOR RECORDING FEED-FORWARD ACTIVITY OF THE ABDOMINAL MUSCLES DURING SUDDEN ARM MOVEMENTS?

Background: During rapid movements of the arm the transversus abdominis muscle (TA) is typically activated before the prime mover (deltoid), to stabilise the spine before the impending postural disturbance. This feedforward activity is compromised in patients with low back pain (LBP), although the phenomenon has not been investigated widely, because of the invasiveness of the assessment technique [fine-wire intramuscular electromyography (iEMG)]; we examined whether ultrasound tissue Doppler imaging (TDI) could represent a non-invasive alternative. Methods: 14 subjects (8M, 6F;23.0±2.0 yrs) performed 10 repetitions each of rapid shoulder flexion, extension and abduction, whilst surface EMG recordings from medial deltoid, and iEMG and M-mode TDI tissuevelocity recordings from the contralateral TA, internal (IO) and external (EO) oblique muscles were made. Muscle onsets were determined by visual inspection of blinded EMG and TDI signals using custom-built software (MATLAB) and expressed relative to the deltoid onset (values −150ms to + 50ms = feed-forward). Results: The TDI-determined onsets were later than those of iEMG by 32.5 (SD 32.8) ms for TA, 17.9 (SD 23.3) ms for IO, and 15.8 (SD 25.3) ms for EO. The methods showed moderately high, significant correlations: r = 0.55 (TA); r = 0.61 (IO); r = 0.56 (EO) (each p< 0.0002). Conclusion: The mean differences between the methods were likely due to electromechanical delay. The SDs of the differences were comparable to those for repeated measurements with either technique. TDI appears to be a valid means of assessing abdominal muscle feed-forward activity, and should allow this phenomenon to be investigated in larger numbers of LBP patients. Support: NFP53–405340–104787/1.