[show abstract][hide abstract] ABSTRACT: To understand the effects of a resistive vibration exercise (RVE) countermeasure on changes in lumbo-pelvic muscle motor control during prolonged bed-rest, 20 male subjects took part in the Berlin Bed-Rest Study (in 2003-2005) and were randomised to a RVE group or an inactive control group. Surface electromyographic signals recorded from five superficial lumbo-pelvic muscles during a repetitive knee movement task. The task, which required stabilisation of the lumbo-pelvic region, was performed at multiple movement speeds and at multiple time points during and after bed-rest. After excluding effects that could be attributed to increases in subcutaneous fat changes and improvements in movement skill, we found that the RVE intervention ameliorated the generalised increases in activity ratios between movement speeds (p⩽0.012), reductions in lumbo-pelvic extensor and flexor co-contraction (p=0.058) and increases in root-mean-square electromyographic amplitude (p=0.001) of the lumbar erector spinae muscles. Effects of RVE on preventing increases in amplitude-modulation (p=0.23) of the lumbar erector spinae muscles were not significant. Few significant changes in activation-timing were seen. The RVE intervention during bed-rest, with indirect loading of the spine during exercise, was capable of reducing some, but not all, motor control changes in the lumbo-pelvic musculature during and after bed-rest.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 02/2012; 22(1):21-30. · 2.00 Impact Factor
[show abstract][hide abstract] ABSTRACT: Microgravity and inactivity due to prolonged bed rest have been shown to result in atrophy of spinal extensor muscles such as the multifidus, and either no atrophy or hypertrophy of flexor muscles such as the abdominal group and psoas muscle. These effects are long-lasting after bed rest and the potential effects of rehabilitation are unknown. This two-group intervention study aimed to investigate the effects of two rehabilitation programs on the recovery of lumbo-pelvic musculature following prolonged bed rest. 24 subjects underwent 60 days of head down tilt bed rest as part of the 2nd Berlin BedRest Study (BBR2-2). After bed rest, they underwent one of two exercise programs, trunk flexor and general strength (TFS) training or specific motor control (SMC) training. Magnetic resonance imaging of the lumbo-pelvic region was conducted at the start and end of bed rest and during the recovery period (14 and 90 days after re-ambulation). Cross-sectional areas (CSAs) of the multifidus, psoas, lumbar erector spinae and quadratus lumborum muscles were measured from L1 to L5. Morphological changes including disc volume, spinal length, lordosis angle and disc height were also measured. Both exercise programs restored the multifidus muscle to pre-bed-rest size, but further increases in psoas muscle size were seen in the TFS group up to 14 days after bed rest. There was no significant difference in the number of low back pain reports for the two rehabilitation groups (p=.59). The TFS program resulted in greater decreases in disc volume and anterior disc height. The SMC training program may be preferable to TFS training after bed rest as it restored the CSA of the multifidus muscle without generating potentially harmful compressive forces through the spine.
European Spine Journal 05/2011; 20(5):808-18. · 2.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: prospective longitudinal study.
to evaluate the effect of bed-rest on the lumbar musculature and soft-tissues.
earlier work has suggested that the risk of low back injury is higher after overnight bed-rest or spaceflight. Changes in spinal morphology and atrophy in musculature important in stabilizing the spine could be responsible for this, but there are limited data on how the lumbar musculature and vertebral structures are affected during bed-rest.
nine male subjects underwent 60-days head-down tilt bed-rest as part of the second Berlin Bed-Rest Study. Disc volume, intervertebral spinal length, intervertebral lordosis angle, and disc height were measured on sagittal plane magnetic resonance images. Axial magnetic resonance images were used to measure cross-sectional areas (CSAs) of the multifidus (MF), erector spinae, quadratus lumborum, and psoas from L1 to L5. Subjects completed low back pain (LBP) questionnaires for the first 7-days after bed-rest.
increases in disc volume, spinal length (greatest at lower lumbar spine), loss of the lower lumbar lordosis, and move to a more lordotic position at the upper lumbar spine (P < 0.0097) were seen. The CSAs of all muscles changed (P < 0.002), with the rate of atrophy greatest at L4 and L5 in MF (P < 0.002) and at L1 and L2 in the erector spinae (P = 0.0006). Atrophy of the quadratus lumborum was consistent throughout the muscle (P = 0.15), but CSA of psoas muscle increased (P < 0.0001). Subjects who reported LBP after bed-rest showed, before reambulation, greater increases in posterior disc height, and greater losses of MF CSA at L4 and L5 than subjects who did not report pain (all P < 0.085).
these results provide evidence that changes in the lumbar discs during bed-rest and selective atrophy of the MF muscle may be important factors in the occurrence of LBP after prolonged bed-rest.
[show abstract][hide abstract] ABSTRACT: To evaluate the effect of short-duration, high-load resistive exercise, with and without whole body vibration on lumbar muscle size, intervertebral disk and spinal morphology changes, and low back pain (LBP) incidence during prolonged bed rest, 24 subjects underwent 60 days of head-down tilt bed rest and performed either resistive vibration exercise (n = 7), resistive exercise only (n = 8), or no exercise (n = 9; 2nd Berlin Bed-Rest Study). Discal and spinal shape was measured from sagittal plane magnetic resonance images. Cross-sectional areas (CSAs) of the multifidus, erector spinae, quadratus lumborum, and psoas were measured on para-axial magnetic resonance images. LBP incidence was assessed with questionnaires at regular intervals. The countermeasures reduced CSA loss in the multifidus, lumbar erector spinae and quadratus lumborum muscles, with greater increases in psoas muscle CSA seen in the countermeasure groups (P ≤ 0.004). There was little statistical evidence for an additional effect of whole body vibration above resistive exercise alone on these muscle changes. Exercise subjects reported LBP more frequently in the first week of bed rest, but this was only significant in resistive exercise only (P = 0.011 vs. control, resistive vibration exercise vs. control: P = 0.56). No effect of the countermeasures on changes in spinal morphology was seen (P ≥ 0.22). The results suggest that high-load resistive exercise, with or without whole body vibration, performed 3 days/wk can reduce lumbar muscle atrophy, but further countermeasure optimization is required.
Journal of Applied Physiology 12/2010; 109(6):1801-11. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: To determine whether resting activity of the pelvic floor muscles (PFMs) and abdominal muscles varied in different sitting postures in parous women with and without stress urinary incontinence (SUI).
PFM and abdominal muscle activity was recorded in 3 sitting postures: slump supported, upright unsupported, and very tall unsupported. Spinal curves were measured in slump supported and upright unsupported.
A research laboratory.
Women (N=17) with a history of vaginal delivery, 8 who were symptomatic of SUI and 9 who were asymptomatic.
Electromyographic activity of (1) the resting PFM recorded per vaginam with surface electrodes and (2) superficial abdominal muscles using surface electrodes. Changes in spinal curves were measured with a flexible ruler.
Electromyographic activity of the PFM increased significantly from slump supported to upright unsupported postures in both groups (P<.001) but with lower levels of activity in women with SUI (P<.05). PFM activity increased further in very tall unsupported sitting in comparison with slump supported sitting (P<.001). Obliquus internus abdominis electromyographic activity was greater in upright unsupported than in slump supported sitting (P<.05), and electromyographic activity of other abdominal muscles was greater in very tall unsupported than slump supported. Women with SUI had a trend for greater activity in the abdominal muscles in upright unsupported than asymptomatic women. Asymptomatic women had a greater depth of lumbar lordosis in upright unsupported sitting than women with SUI (P=.04).
More upright sitting postures recruit greater PFM resting activity irrespective of continence status. Further investigation should consider the effect of sitting posture in rehabilitation.
Archives of physical medicine and rehabilitation 10/2008; 89(9):1741-7. · 2.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: A single-blinded, pretreatment-posttreatment assessment.
To investigate, using ultrasound imaging, the cross-sectional area (CSA) of the lumbar multifidus muscle at 4 vertebral levels (L2, L3, L4, L5) in elite cricketers with and without low back pain (LBP) and (2) to document the effect of a staged stabilization training program on multifidus muscle CSA.
Despite high fitness levels and often intensive strength training programs, athletes still suffer LBP. The incidence of LBP among Australian cricketers is 8% and as high as 14% among fast bowlers. Previous researchers have found that the multifidus muscle contributes to segmental stability of the lumbopelvic region; however, the CSA of this muscle has not been previously assessed in elite cricketers.
CSAs of the multifidus muscles were assessed at rest on the left and right sides for 4 vertebral levels at the start and completion of a 13-week cricket training camp. Participants who reported current or previous LBP were placed in a rehabilitation group. The stabilization program involved voluntary contraction of the multifidus, transversus abdominis, and pelvic floor muscles, with real-time feedback from rehabilitative ultrasound imaging (RUSI), progressed from non-weight-bearing to weight-bearing positions and movement training. Pain scores (using a visual analogue scale) were also collected from those with LBP.
The CSAs of the multifidus muscles at the L5 vertebral level increased for the 7 cricketers with LBP who received the stabilization training, compared with the 14 cricketers without LBP who did not receive rehabilitation (P = .004). In addition, the amount of muscle asymmetry among those with LBP significantly decreased (P = .029) and became comparable to cricketers without LBP. These effects were not evident for the L2, L3, and L4 vertebral levels. There was also a 50% decrease in the mean reported pain level among the cricketers with LBP.
Multifidus muscle atrophy can exist in highly active, elite athletes with LBP. Specific retraining resulted in an improvement in multifidus muscle CSA and this was concomitant with a decrease in pain.
Therapy, level 2b.
Journal of Orthopaedic and Sports Physical Therapy 04/2008; 38(3):101-8. · 2.95 Impact Factor
[show abstract][hide abstract] ABSTRACT: To determine if asymmetry of trunk muscles and deficits of motor control exist among elite cricketers with and without low back pain (LBP).
Single-blinded observational quasi-experimental design study
Assessments were conducted in a hospital setting.
Among a total eligible sample of 26 male elite cricketers (mean age 21.2 (SD 2.0) years), selected to attend a national training camp, 21 participated in the study. Risk factors: The independent variables were 'group' (LBP or asymptomatic) and 'cricket position' (fast bowler versus the rest of the squad). Main outcome measurements: The dependent variables were the cross-sectional areas (CSA) of the quadratus lumborum (QL), lumbar erector spinae plus multifidus (LES + M) and psoas muscles, the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles, and the amount of lateral slide of the anterior abdominal fascia.
The QL and LES + M muscles were larger ipsilateral to the dominant arm. In the subgroup of fast bowlers with LBP, the asymmetry in the QL muscle was the greatest. The IO muscle was larger on the side contralateral to the dominant arm. No difference between sides was found for the psoas and TrA muscles. Cricketers with LBP showed a reduced ability to draw in the abdominal wall and contract the TrA muscle independently of the other abdominal muscles.
This study provides new insights into trunk muscle size and function in elite cricketers, and evidence of impaired motor control in elite cricketers with LBP. Rehabilitation using a motor control approach has been shown to be effective for subjects with LBP, and this may also benefit elite cricketers.
British journal of sports medicine 01/2008; 42(10):809-13. · 3.67 Impact Factor
[show abstract][hide abstract] ABSTRACT: Test-retest intrarater reliability study.
To examine reliability of abdominal musculature measurements across a broad range of conditions for a physical therapist newly trained in assessment using rehabilitative ultrasound imaging (RUSI).
RUSI has previously been used to assess abdominal muscle function during a drawing-in maneuver of the anterior abdominal wall, and measurements conducted by an experienced assessor have been validated by comparison with magnetic resonance imaging. Few studies have examined the reliability of less experienced operators, and only in isolated measurement conditions.
Nineteen subjects (11 female, 8 male) without a history of low back pain performed the abdominal drawing-in maneuver in a supine hook-lying position. RUSI was used bilaterally to assess the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles at rest and on contraction, as well as changes in the length of the TrA muscle (indicated by slide of the anterior abdominal fascia). The reliability of a novice rater who received 8 hours of training was examined (a) across 3 measurements of the same ultrasound image, (b) across 3 separate ultrasound images (averaged for days and sides of abdomen), and (c) across 2 days (averaged for images and sides).
Reliability of assessing muscle thickness was very high across 3 measurements of the sale image (intrarater correlation coefficients [ICC3.1] were all greater than 0.97), fair to high across 3 images (ICC(3,4) = 0.62-0.82), and fair to high across 2 days (ICC(3,6) = 0.63-0.85). Reliability of measuring the slide of the anterior abdominal fascia was very high across measurements from the same image (ICC(3,1) = 0.98) but very low across images (ICC(3,4) = 0.44) and across 2 days (ICC(3,6) = 0.36).
High reliability of a novice rater was demonstrated for some measurement conditions. Measures of reliability for recapturing the image and repetition across days ranged from low to high. Inconsistencies in the pattern of results suggest that for a novice assessor using RUSI, training should be performed and reliability assessed for each abdominal muscle and measurement condition intended to be used for research and clinical practice.
Journal of Orthopaedic and Sports Physical Therapy 09/2007; 37(8):480-6. · 2.95 Impact Factor
[show abstract][hide abstract] ABSTRACT: The pattern of tonic and phasic components in an EMG signal reflects the underlying behaviour of the central nervous system (CNS) in controlling the musculature. One avenue for gaining a better understanding of this behaviour is to seek a quantitative characterisation of these phasic and tonic components. We propose that these signal characteristics can range between unvarying, tonic and intermittent, phasic activation through a continuum of EMG amplitude modulation. In this paper, we present two new algorithms for quantifying amplitude modulation: a linear-envelope approach, and a mathematical morphology approach. In addition we present an algorithm for synthesising EMG signals with known amplitude modulation. The efficacy of the synthesis algorithm is demonstrated using real EMG data. We present an evaluation and comparison of the two algorithms for quantifying amplitude modulation based on synthetic data generated by the proposed synthesis algorithm. The results demonstrate that the EMG synthesis parameters represent 91.9% and 96.2% of the variance of linear-envelopes extracted from lumbo-pelvic muscle EMG signals collected from subjects performing a repetitive-movement task. This depended, however, on the muscle and movement-speed considered (F=4.02, p<0.001). Coefficients of determination between input and output amplitude modulation variables were used to quantify the accuracy of the linear-envelope and morphological signal processing algorithms. The linear-envelope algorithm exhibited higher coefficients of determination than the most accurate morphological approach (and hence greater accuracy, T=8.16, p<0.001). Similarly, the standard deviation of the coefficients of determination was 1.691 times smaller (p<0.001). This signal processing algorithm represents a novel tool for the quantification of amplitude modulation in continuous EMG signals and can be used in the study of CNS motor control of the musculature in repetitive-movement tasks.
Journal of Electromyography and Kinesiology 08/2007; 19(1):10-21. · 1.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: Prospective longitudinal study. OBJECTIVE.: To investigate, using magnetic resonance imaging (MRI), the influence of bed rest on the lumbopelvic musculature.
Reduced gravitational loading and inactivity (bed rest) are known to result in significant change in musculoskeletal function, although little is known about its effects on specific muscles of the lumbopelvic region.
Ten healthy male subjects underwent 8 weeks of bed rest with 6 months of follow-up. MRI of the lumbopelvic region was conducted at regular time-points during and after bed rest. Using uniplanar images at L4, cross-sectional areas (CSAs) of the multifidus, lumbar erector spinae, quadratus lumborum, psoas, anterolateral abdominal, and rectus abdominis muscles were measured.
Multifidus CSA decreased by day 14 of bed rest (F = 7.4, P = 0.04). The lumbar erector spinae and quadratus lumborum CSA showed no statistically significant difference to baseline across the time of bed rest (P > 0.05). The anterolateral abdominal, rectus abdominis, and psoas CSA all increased over this time. Psoas CSA increased by day 14 (F = 6.9, P = 0.047) and remained so until day 56, whereas the anterolateral abdominal CSA (F = 29.4, P = 0.003) and rectus abdominis CSA (F = 8.9, P = 0.03) were not statistically larger than baseline until day 56. On reambulation after completion of the bed rest phase, multifidus, anterolateral abdominal, and rectus abdominis CSA returned to baseline levels (P > 0.05) by day 4 of follow-up, whereas psoas CSA returned to baseline level after day 28 of the follow-up period.
Bed rest resulted in selective atrophy of the multifidus muscle. An increased CSA of the trunk flexor musculature (increases in psoas, anterolateral abdominal, and rectus abdominis muscles) may reflect muscle shortening or possible overactivity during bed rest. Some of the changes resemble those seen in low back pain and may in part explain the negative effects of bed rest seen in low back pain sufferers.
[show abstract][hide abstract] ABSTRACT: Cross-sectional study.
To investigate the function of the transversus abdominis (TrA) and internal oblique (10) muscles bilaterally during a simulated weight-bearing task using ultrasound imaging.
An important aspect of neuromuscular control at the lumbopelvic region is stabilization. Biomechanical models have predicted that activation of transversely oriented muscles, such as the TrA and 10 muscles, can stiffen the sacroiliac joints and actively stabilize the pelvis for weight bearing.
Nineteen healthy subjects were positioned in supine lying with their right heel against a footplate linked to a force transducer. Each subject performed a static simulated weight-bearing task of the right lower extremity. Ultrasound imaging was used to assess resultant changes in thickness of the 10 and TrA muscles, as well as the lateral slide of the anterior abdominal fascia on each side of the abdomen alternately. Muscle thickness and slide of the fascia were assessed at standardized force levels (0% and 25% of body weight).
Substantial increases (P < .0001) in mean (+/- SD) thickness of the 10 (18.5% +/- 9.7%) and TrA (24.7% +/- 175%) muscles during the weight-bearing task were measured. Lateral movement (slide) of the anterior abdominal fascia of the TrA muscle also occurred (mean +/- SD, 1.3 +/- 2.0 mm; P = .014) with weight bearing. Changes in muscle thickness and amount of slide were similar for the left and right side of the abdomen (P > or = .11).
The findings are consistent with biomechanical models that predicted symmetrical activation of the deep transversely oriented lumbopelvic muscles in healthy subjects in response to a unilateral functional weight-bearing task. Ultrasound imaging as a measurement tool represents a noninvasive method for measuring abdominal muscle function in functional axial loading.
Journal of Orthopaedic and Sports Physical Therapy 08/2007; 37(8):467-71. · 2.95 Impact Factor
[show abstract][hide abstract] ABSTRACT: Prior motor control studies in unloading have shown a tonic-to-phasic shift in muscle activation, particularly in the short extensors. Tonic muscle activity is considered critical for normal musculoskeletal function. The shift from tonic-to-phasic muscle activity has not been systematically studied in humans in unloading nor at the lumbo-pelvic (LP) region. Ten healthy young male subjects underwent 8 wk of bed rest with 6-mo follow up as part of the "Berlin Bed-Rest Study." A repetitive knee movement model performed in the prone position is used to stimulate tonic holding LP muscle activity, as measured by superficial EMG. Tonic and phasic activation patterns were quantified by relative height of burst vs. baseline electromyographic linear-envelope signal components. Statistical analysis shows a shift toward greater phasic activity during bed rest and follow up (P < 0.001) with a significant interaction across muscles (P < 0.001) specifically affecting the short lumbar extensors. These changes appear unrelated to skill acquisition over time (P all > or = 0.196). This change of a shift from tonic LP muscle activation to phasic is in line with prior research on the effects of reduced weight bearing on motor control.
Journal of Applied Physiology 07/2007; 103(1):48-54. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: Longitudinal study.
To gain insight into the effects of inactivity on lumbopelvic stabilization.
Some authors have suggested a link between inactivity and lumbopelvic (LP) pain. Studies examining the superficial musculature in LP pain have shown overactivity and increased cocontraction. Studies in inactivity (bed rest, microgravity) have shown similar effects on the musculature of the legs. Here we examine the effect of bed rest on superficial LP activity and cocontraction.
Ten male subjects participated in the "Berlin Bed Rest Study" and underwent 8 weeks of bed rest with a 1-year follow-up. A repetitive knee movement model at four movement speeds in non-weightbearing was used to assess, via electromyography, activity (amplitude-ratios) in five superficial LP muscles and abdominal flexor-lumbar extensor cocontraction for LP stabilization. Testing was conducted at regular intervals during and after bed rest.
Analysis of the amplitude-ratio data showed a significant effect of testing date (F = 2.38, P = 0.005). This effect was generalized across all muscles, however (F = 0.59, P = 0.989). During bed rest, subjects exhibited higher levels of activity but lower levels of cocontraction (F = 8.84, P < 0.001), and the changes were still present up to 1 year after bed rest.
The bed rest protocol resulted in the development of superficial muscle overactivity but decreased cocontraction. These changes could reflect dysfunction of central nervous system control of LP stabilization. These changes were still apparent 1 year after bed rest, suggesting a stable change in motor control.
[show abstract][hide abstract] ABSTRACT: Randomized controlled trial.
To determine if the provision of visual biofeedback using real-time ultrasound imaging enhances the ability to activate the multifidus muscle.
Increasingly clinicians are using real-time ultrasound as a form of biofeedback when re-educating muscle activation. The effectiveness of this form of biofeedback for the multifidus muscle has not been reported.
Healthy subjects were randomly divided into groups that received different forms of biofeedback. All subjects received clinical instruction on how to activate the multifidus muscle isometrically prior to testing and verbal feedback regarding the amount of multifidus contraction, which occurred during 10 repetitions (acquisition phase). In addition, 1 group received visual biofeedback (watched the multifidus muscle contract) using real-time ultrasound imaging. All subjects were reassessed a week later (retention phase).
Subjects from both groups improved their voluntary contraction of the multifidus muscle in the acquisition phase (P<.001) and the ability to recruit the multifidus muscle differed between groups (P<.05), with subjects in the group that received visual ultrasound biofeedback achieving greater improvements. In addition, the group that received visual ultrasound biofeedback retained their improvement in performance from week 1 to week 2 (P>.90), whereas the performance of the other group decreased (P<.05).
Real-time ultrasound imaging can be used to provide visual biofeedback and improve performance and retention in the ability to activate the multifidus muscle in healthy subjects.
Journal of Orthopaedic and Sports Physical Therapy 12/2006; 36(12):920-5. · 2.95 Impact Factor
[show abstract][hide abstract] ABSTRACT: Do different sitting postures require different levels of pelvic floor and abdominal muscle activity in healthy women?
Eight parous women with no pelvic floor dysfunction. Outcome measures: Bilateral activity of pelvic floor muscles (assessed vaginally) and two abdominal muscles, obliquus internus abdominis and obliquus externus abdominis, during three sitting postures.
There was a significant increase in pelvic floor muscle activity from slump supported sitting (mean 7.2% maximal voluntary contraction, SD 4.8) to both upright unsupported sitting (mean 12.6% maximal voluntary contraction, SD 7.8) (p = 0.01) and very tall unsupported sitting (mean 24.3% maximal voluntary contraction, SD 14.2) (p = 0.004). Activity in both abdominal muscles also increased but did not reach statistical significance.
Both unsupported sitting postures require greater pelvic floor muscle activity than the supported sitting posture.
The Australian journal of physiotherapy 02/2006; 52(3):219-22. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: Patients with low back pain (LBP) often present with impaired proprioception of the lumbopelvic region. For this reason, proprioception training usually forms part of the rehabilitation protocols. New exercise equipment that produces whole body, low frequency vibration (WBV) has been developed to improve muscle function, and reportedly improves proprioception. The aim of this pilot study was to investigate whether weightbearing exercise given in conjunction with WBV would affect lumbosacral position sense in healthy individuals. For this purpose, twenty-five young individuals with no LBP were assigned randomly to an experimental or control group. The experimental group received WBV for five minutes while holding a static, semi-squat position. The control group adopted the same weightbearing position for equal time but received no vibration. A two-dimensional motion analysis system measured the repositioning accuracy of pelvic tilting in standing. The experimental (WBV) group demonstrated a significant improvement in repositioning accuracy over time (mean 0.78 degrees) representing 39% improvement. It was concluded that WBV may induce improvements in lumbosacral repositioning accuracy when combined with a weightbearing exercise. Future studies with WBV should focus on evaluating its effects with different types of exercise, the exercise time needed for optimal outcomes, and the effects on proprioception deficits in LBP patients.
The Australian journal of physiotherapy 02/2005; 51(4):259-63. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of the present study was to investigate the between-days reliability of electromyographic (EMG) measurement of 6 bilateral trunk muscles and also the torque output in 3 planes during isometric right and left axial rotation at different exertion levels.
Ten healthy subjects performed isometric right and left axial rotation at 100, 70, 50 and 30% maximum voluntary contractions in two testing sessions at least 7 days apart. EMG amplitude and frequency analyses of the recorded surface EMG signals were performed for rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured.
For both EMG amplitude and frequency values, good (intraclass correlation coefficient, ICC=0.75-0.89) to excellent (ICC>/=0.90) reliability was found in the 6 trunk muscles at different exertion levels during axial rotation. The reliability of both maximal isometric axial rotation torque and coupling torques in sagittal and coronal planes were found to be excellent (ICC>/=0.93).
Good to excellent reliability of EMG measures of trunk muscles and torque measurements during isometric axial rotation was demonstrated. This provides further confidence of using EMG and triaxial torque assessment as outcome measures in rehabilitation and in the evaluation of the human performance in the work place.
[show abstract][hide abstract] ABSTRACT: To examine the changes in torque output resulting from fatigue, as well as changes in electromyographic measures of trunk muscles during isometric axial rotation and to compare these changes between directions of axial rotation.
Subjects performed fatiguing right and left isometric axial rotation of the trunk at 80% of maximum voluntary contraction while standing upright.
A rehabilitation center.
Twenty-three men with no history of back pain.
Surface electromyographic signals were recorded from 6 trunk muscles bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured.
During the fatiguing axial rotation contraction, coupling torques of both sagittal and coronal planes were slightly decreased and no difference was found between directions of axial rotation. Decreasing median frequency and an increase in electromyographic amplitude were also found in trunk muscles with different degrees of changes in individual muscles. There were significant differences (P<.05) between right and left axial rotation exertions in median frequency slope of external oblique, internal oblique, latissimus dorsi, and iliocostalis lumborum muscles, but no such difference was found in median frequency slope of rectus abdominis and multifidus muscles. This could be attributed to different functional roles among the muscles. Similar differences (P<.05) between right and left axial rotation in median frequency slope were also detected in the electromyographic amplitude slope of the trunk muscles. Coefficient of variation of the torque output and electromyographic activation in most of the trunk muscles increased during the fatigue process.
The changing coupling torque, different fatigue rate, and activation changes of trunk muscles, as well as the increase in variability during fatiguing axial rotation exertion, could affect the internal loading and stability of the spine; this needs to be further quantified in future studies.
Archives of Physical Medicine and Rehabilitation 03/2003; 84(3):374-81. · 2.36 Impact Factor