Patients with recurrent low back pain (LBP) exhibit changes in postural control. Stereotypical muscle activations resulting from external perturbations include anticipatory (APAs) and compensatory (CPAs) postural adjustments. This study aimed to determine differences in postural control strategies (APAs and CPAs) between those with and without lumbar disc degeneration (LDD) and LBP. Ninety-seven subjects participated in the study (mean age 50 years (SD 12)). 3T MRI was used to acquire T2 weighted images (L1-S1). LDD was determined using Pfirrmann grading and LBP using the numerical rating scale (NRS). A bespoke perturbation platform was designed to deliver postural perturbations. Electrical activity was analysed from 16 trunk and lower limb muscles during four typical APA and CPA epochs. A Kruskal-Wallis H test with Bonferroni correction for multiple comparisons was conducted.Introduction
Methods
The usefulness of markers of non-specific low back pain (NSLBP), including MRI derived measurements of cross-sectional area (CSA) and functional CSA (FCSA, fat free muscle area) of the lumbar musculature, is in doubt. To our knowledge, such markers remain unexplored in Lumbar Disc Degeneration (LDD), which is significantly associated with NSLBP, Modic change and symptom recurrence. This exploratory 3.0-T MRI study addresses this shortfall by comparing asymmetry and composition in asymptomatic older adults with and without Modic change. A sample of 21 healthy, asymptomatic subjects participated (mean age 56.9 years). T2-weighted axial lumbar images were obtained (L3/L4 to L5/S1), with slices oriented through the centre of each disc. Scans were examined by a Consultant MRI specialist and divided into 2 groups dependent on Modic presence (M) or absence (NM). Bilateral measurements of the CSA and FCSA of the erector spinae, multifidus, psoas major and quadratus lumborum were made using Image-J software. Muscle composition was determined using the equation [(FCSA/CSA)*100] and asymmetry using the equation [(Largest FCSA-smallest FCSA)/largest FCSA*100]. Data were analysed using Mann-Whitney U tests (p value set at). Intrarater reliability was examined using Intraclass Correlations (ICCs).Introduction
Methods
We have recently shown, using transcranial magnetic stimulation (TMS) to assess voluntary activation (VA), that neural drive to back muscles is reduced in subjects with chronic low back pain. There is also evidence that central nervous system drive to abdominal muscles is altered in these subjects, however VA has not yet been assessed for these muscles in healthy subjects; this is the purpose of the present study. Twenty one healthy subjects (10M:11F) participated. Electromyographic activity was recorded from back and abdominal muscles and flexor torque was measured using a dynamometer. Subjects performed a series of isometric voluntary contractions (10%–100% MVC) of rectus abdominis during which TMS was applied to the motor cortex. The resulting superimposed twitches (SIT) were measured and VA was derived.Background:
Methods:
Characteristics of muscle activity, represented by surface electromyography (EMG), have shown differences between patients with low back pain and healthy adults; how they relate to functional/clinical scales remains unclear. The purpose of the current study was to examine the correlation between frequency characteristics of EMG and patients' self-rated score of disability using continuous wavelet transform (CWT) analysis. Fifteen patients with chronic mechanical low back pain (LBP) and 10 healthy adults were recruited. Patients completed the Roland-Morris Disability Questionnaire (RMDQ) and bilateral EMG activity was obtained from erector spinae at vertebral level L4 and T12. Subjects performed 3 brief maximal voluntary contractions (MVCs) of the back extensors and the torque was measured using a dynamometer. CWT was applied to the EMG signals of each muscle in a 200ms window centred around the peak torque obtained during the MVCs. The ratio (low/high frequencies) of the energy, the peak energy, and the frequency of the peak energy were calculated for each muscle and then averaged and correlated with the individual's RMDQ score. Patients had significantly lower peak power than the controls (p=0.04). Additionally, RMDQ positively correlated to the average ratio of energy (rho=0.71; p=0.01), meaning higher disability corresponded to a dominant distribution of energy in the lower-frequencies; but negatively correlated to the average frequency of peak energy (rho=-0.61; p=0.035), meaning lower frequency of peak energy corresponded to higher levels of disability.Purposes of the study and background
Methods and Results
Changes in central nervous system (CNS) pathways controlling trunk and leg muscles in patients with low back pain(LBP) and lumbar radiculopathy have been observed and this study investigated whether surgery impacts upon these changes in the long term. 80 participants were recruited into the following groups: 25 surgery(S), 20 chronic LBP(CH), 14 spinal injection(SI), and 21 controls(C). Parameters of corticospinal control were examined before, at 6, 26 and 52 weeks following lumbar decompression surgery and equivalent intervals. Electromyographic(EMG) activity was recorded from tibialis anterior(TA), soleus(SOL), rectus abdominis(RA), external oblique(EO) and erector spinae(ES) muscles at the T12&L4 levels in response to transcranial magnetic stimulation of the motor cortex. Motor evoked potentials (MEP) and cortical silent periods(cSP) recruitment curves(RC) were analysed.Introduction
Methods
Alterations in the neural drive to trunk muscles have been implicated in low back pain (LBP). This is supported by evidence of reduced corticospinal excitability, delayed muscle activation, reduced endurance and enhanced fatigability of these muscles; whether these changes persist during pain free periods remain unclear. Neural drive (or voluntary activation-VA) can be measured using twitch interpolation and the aim of this study is to investigate if subjects with a history of LBP show reduced VA. Twenty five subjects participated (13 with a history of LBP, 12 controls). Back extensor torque was measured using a dynamometer and bilateral electromyographic (EMG) activity was recorded from erector spinae and rectus abdominis. Transcranial magnetic stimulation of the motor cortex was applied while the subject, lying prone, performed graded voluntary back extensions. VA was calculated from the size of the twitches evoked by the TMS and EMG data were analysed for evidence of altered neural drive.Background
Methods
Changes in the central nervous system (CNS) pathways controlling trunk and leg muscles in patients with low back pain and radiculopathy have been observed and this study investigated whether surgery impacts upon these changes. Parameters of corticospinal control were examined on 3 occasions in 22 patients prior to, at 6 and 26 weeks following lumbar decompression surgery and in 14 control subjects at the same intervals. Electromyographic activity was recorded from tibialis anterior (TA), soleus (SOL), rectus abdominis (RA), external oblique (EO) and erector spinae (ES) muscles at the T12 & L4 levels in response to transcranial magnetic stimulation of the motor cortex.Introduction
Methods
Rowing is associated with a high incidence of low back pain (LBP) often attributed to the associated loading and large trunk rotations. Here we examine electromyographic (EMG) activity in rowers who undertake sweep rowing (asymmetrical) or sculling (symmetrical). 22 right handed elite rowers participated and written informed consent was obtained. Each had a preferred rowing side (bow side [BS, n=6]; stroke side [SS, n=7) or sculling [SC, n=9]). Testing was performed in a Cybex isokinetic dynamometer and bilateral EMG activity recorded from trunk muscles (erector spinae [ES] and rectus abdominis [RA]) synchronously. There were no differences between the groups in peak torque during isokinetic or isometric testing, although extensor torque was higher than flexor torque. Analysis of EMG activity revealed that scullers showed no left/right differences in any of the testing protocols. However, sweep rowers showed significant differences between left and right ES during extension protocols, in the isokinetic testing at 30°s−1 (in the SS rowers [LES 0.11±0.01mV vs RES 0.08±0.01mV] and at 90°s−1 in the BS rowers [LES 0.14±0.02mV vs RES 0.12±0.01mV]. In the isometric tests, the SS rowers showed higher left ES activity than the right [LES 0.11±0.01mV vs RES 0.09±0.01mV]. The flexion protocols did not reveal any left right differences in any groups in any of the protocols used. These results reveal that sweep rowing is associated with asymmetric activity of trunk extensors, but not flexors. This could be a contributing factor to the high incidence of LBP in sweep rowers.
Trunk flexor-extensor asymmetry has been implicated in the development of back pain; however, left-right trunk muscle asymmetry has received little attention. This study examined whether such left-right asymmetries exist and if these are related to differing sporting tasks. Thirty-five subjects were recruited and written informed consent obtained; 12 subjects participated in unilateral (UL) sports e.g. racquet sports (mean age 21.6±0.7 (SEM) years), 13 in bilateral (BL) activities e.g. rugby (mean age 21.7±0.2) and 10 controls (C) not involved in sport (mean age 21.7±0.2) years). Isokinetic and isometric trunk flexions and extensions including a fatiguing isometric hold were performed in a Cybex isokinetic dynamometer synchronised with bilateral electromyographic (EMG) recordings from trunk extensors (erector spinae at L4), and flexors (rectus abdominis at T10). A ratio of left:right EMG activity was calculated for each set of muscles, to examine asymmetry. No differences were seen in left:right extensor EMG ratios across any of the test protocols. However, the UL group had higher (P<
0.05) left:right flexor EMG ratios than the BL group during pre-fatigue (UL:1.32±0.15 vs. BL:0.84±0.07) and post-fatigue (UL:1.30±0.18 vs BL:0.84±0.07) isometric flexion. Torque data suggested that the trunk extensor-flexor ratio was larger (P<
0.05) in the BL group compared to the C in the isokinetic exercises at the 30°s−1 (BL:1.27±0.05; C:1.00±0.06) and at the 90°s−1 speeds (BL:1.28±0.05; C:0.95±0.08), but no differences were seen during isometric testing. This study suggests that training for different sports can generate significant asymmetry in the trunk muscles, particularly in the flexors, the importance of which requires further research.
Poor trunk extensor endurance is implicated in low back pain; less, however, is known about contributions of left and right sides and upper and lower parts to maximum torque production following fatigue. This study examines torque and electromyographic (EMG) activity in different parts of the left and right trunk extensors before and following a maximal voluntary contraction (MVC) hold. 16 student rowers participated and written informed consent was obtained. Testing was performed in a Cybex isokinetic dynamometer with synchronous bilateral EMG recordings (during brief MVCs) from the left and right the erector spinae (ES) muscles at vertebral levels T12 and L4, prior to and immediately after, and 1, 5 and 10 minutes after a 60 second MVC. A small decrease in maximum torque was observed during 60s MVC, followed by a non significant step-wise increase. The torque at 10 minutes post MVC was the highest value recorded. EMG activity rose in the right upper back 5 and 10 mins following the fatigue. Furthermore, the ratios of left:right EMG activity revealed an increase compared to pre-fatigue values in the lower back but a decrease in the upper back, suggesting the task involved differential use of left and right sides in addition to upper and lower back muscles. These results suggest that 60s MVC induces differential activation of left and right sides and upper and lower parts of the trunk extensors. The apparent potentiation in force and asymmetry of activation following the 60s MVC task requires further investigation.
