Inhibition of Pain and Pain-Related Brain Activity by Heterotopic Noxious Counter-Stimulation and Selective Attention in Chronic Non-Specific Low Back Pain.

The aim of the present study was to assess inhibition of pain and somatosensory-evoked potentials (SEPs) by heterotopic noxious counter-stimulation (HNCS) and by selective attention in patients with chronic non-specific LBP. Seventeen patients and age/sex-matched controls were recruited (10 men, 7 women; mean age ±â€¯SD: 43.3 ±â€¯10.4 and 42.7 ±â€¯11.1, respectively). On average, patients with LBP reported pain duration of 7.6 ±â€¯6.5 years, light to moderate disability (19.3 ±â€¯5.7/100) and low clinical pain intensity (21.8 ±â€¯1.5/100), while pain catastrophizing, state and trait anxiety and depressive symptoms were not significantly different between groups (all p's >0.05). HNCS and selective attention had differential inhibitory effects on pain and SEP, but no difference was observed between groups. Across both groups, HNCS decreased pain (p = 0.06) as well as the N100 and the N150 components of SEP (p's <0.001), while selective attention only decreased pain (p < 0.01) and the N100 (p<0.001). In contrast, the P260 was decreased by HNCS only when attention was directed toward the HNCS stimulus (p<0.01). This indicates that patients with the characteristics described above do not show altered pain inhibitory mechanisms involved in HNCS and selective attention. Importantly, this experiment was carefully designed to control for non-specific effects associated with the repetition of the test stimulus and the effect of an innocuous counter-stimulation. It remains to be determined if these results hold for patients with severe LBP and psychological symptoms or whether symptom severity may be associated with pain inhibition deficits.

Trunk neuromuscular responses to a single whole-body vibration session in patients with chronic low back pain: a cross-sectional study.

OBJECTIVE: Whole-body vibration (WBV) exercise is progressively adopted as an alternative therapeutic modality for enhancing muscle force and muscle activity via neurogenic potentiation. So far, possible changes in the recruitment patterns of the trunk musculature after WBV remain undetermined. The main objective of this study was to evaluate the short-term effects of a single WBV session on trunk neuromuscular responses in patients with chronic low back pain (cLBP) and healthy participants. METHODS: Twenty patients with cLBP and 21 healthy participants performed 10 trunk flexion-extensions before and after a single WBV session consisting of five 1-minute vibration sets. Surface electromyography (EMG) of erector spinae at L2-L3 and L4-L5 and lumbopelvic kinematic variables were collected during the trials. Data were analyzed using 2-way mixed analysis of variance models. RESULTS: The WBV session led to increased lumbar EMG activity during the flexion and extension phases but yielded no change in the quiet standing and fully flexed phases. Kinematic data showed a decreased contribution to the movement of the lumbar region in the second extension quartile. These effects were not different between patients with cLBP and healthy participants. CONCLUSIONS: Increased lumbar EMG activity after a single WBV session most probably results from potentiation effects of WBV on lumbar muscles reflex responses. Decreased EMG activity in full trunk flexion, usually observed in healthy individuals, was still present after WBV, suggesting that the ability of the spine stabilizing mechanisms to transfer the extension torque from muscles to passive structures was not affected.

Modulation of pain-induced neuromuscular trunk responses by pain expectations: a single group study.

PURPOSE: The purpose of this study was to investigate the alteration of pain-induced neuromuscular trunk responses by expectations in healthy volunteers. METHODS: Twenty-three asymptomatic participants performed series of flexion-extension movements in 3 different experimental conditions: innocuous heat stimulation (control) and noxious heat stimulation associated with expectations of low or high pain intensity. These stimuli were administered by a contact thermode placed over the lumbar region (L4 and L5) to assess the modulation of neuromuscular responses and kinematics during the flexion-extension task. Surface electromyography (EMG) of lumbar erector spinae at L2 and L3 and L4 and L5 as well as lumbopelvic kinematic variables were compared across conditions. RESULTS: Noxious stimulation significantly altered EMG responses but only in full trunk flexion. Interestingly, this alteration was significant only for muscles where noxious stimulation was applied (L4 and L5) and not for the other segment (L2 and L3). Conversely, expectations significantly altered EMG activity at L2 and L3 but not at the segment where noxious stimulation was applied. CONCLUSION: These results confirm previous findings and indicate that experimental pain can alter neuromuscular responses during a trunk flexion-extension task. Furthermore, this study suggests that expectations can alter some of these alterations. Future studies should determine whether neuromuscular changes induced by expectations may contribute to the transition from acute to chronic low-back pain.

Physical and psychosocial predictors of functional trunk capacity in older adults with and without low back pain.

OBJECTIVE: The purpose of this study was to determine the physical and psychosocial predictors of functional trunk capacity in a group of healthy elderly individuals and a group of elderly patients with chronic low back pain (LBP). METHODS: The study was done in Canada and included 61 community-dwelling elderly individuals (29 patients with nonspecific chronic LBP and 32 healthy participants) who performed maximal trunk endurance and force tasks. Participants completed various psychologic and functional questionnaires. Sequential linear regression analyses were performed with functional capacity results (endurance and force) as dependent variables and questionnaire scores as independent variables. RESULTS: Endurance time and peak force were significantly lower in patients compared with healthy elderly individuals (all P values < .001), whereas pain-related fear of movement, pain catastrophizing, and depression levels were higher in patients than their healthy counterpart (all P values < .001). After adjusting for physical activity and disability levels (R(2) = 33.7%-50.5% in patients; R(2) = 0.1%-5.7% in healthy individuals), none of the psychologic questionnaire could explain variations observed in functional capacity in patients (R(2) changes, 4.8%-6.7%) and in healthy participants (R(2) changes, 5.2%-10.6%). CONCLUSION: Patients showed diminished functional capacity compared with healthy participants. Moreover, physical activity levels represent the most important predictors of functional capacity in elderly patients with LBP.

A comparison of 2 assessment protocols to specifically target abdominal muscle endurance.

OBJECTIVE: The purpose of this study was to compare 2 variations of a test designed to evaluate abdominal muscle endurance. METHODS: This study included 21 healthy adults (10 men and 11 women) aged 23.2 ± 3.3 years. Participants recruited from a chiropractic institution performed 2 fatiguing protocols (with a lordotic posture or free of instructions), each immediately preceded and followed by a maximum voluntary contraction. Force data and surface electromyography of 6 muscles were recorded. The influence of posture on endurance time as well as the effect of posture on MedF/time slopes for each individual muscle throughout the first 4 30-seconds time segments was assessed. RESULTS: Mean time until exhaustion was 261.3 ± 149.8 seconds for the lordotic condition and 358.8 ± 206.4 seconds for the free condition. The lordotic condition induced significantly more fatigue than the free condition in 3 muscles during the first 30 seconds. However, both conditions induced similar levels of fatigue for the following 30 seconds. After the first 60 seconds, no significant differences in fatigability were noted between the 2 experimental conditions. CONCLUSION: For the subjects studied, lumbar lordosis had a significant influence on trunk muscle fatigue during abdominal muscle endurance assessment. Specifically targeting the abdominal muscles during an endurance task remains a challenge.

A randomised controlled trial of preventive spinal manipulation with and without a home exercise program for patients with chronic neck pain.

BACKGROUND: Evidence indicates that supervised home exercises, combined or not with manual therapy, can be beneficial for patients with non-specific chronic neck pain (NCNP). The objective of the study is to investigate the efficacy of preventive spinal manipulative therapy (SMT) compared to a no treatment group in NCNP patients. Another objective is to assess the efficacy of SMT with and without a home exercise program. METHODS: Ninety-eight patients underwent a short symptomatic phase of treatment before being randomly allocated to either an attention-group (n = 29), a SMT group (n = 36) or a SMT + exercise group (n = 33). The preventive phase of treatment, which lasted for 10 months, consisted of meeting with a chiropractor every two months to evaluate and discuss symptoms (attention-control group), 1 monthly SMT session (SMT group) or 1 monthly SMT session combined with a home exercise program (SMT + exercise group). The primary and secondary outcome measures were represented by scores on a 10-cm visual analog scale (VAS), active cervical ranges of motion (cROM), the neck disability index (NDI) and the Bournemouth questionnaire (BQ). Exploratory outcome measures were scored on the Fear-avoidance Behaviour Questionnaire (FABQ) and the SF-12 Questionnaire. RESULTS: Our results show that, in the preventive phase of the trial, all 3 groups showed primary and secondary outcomes scores similar to those obtain following the non-randomised, symptomatic phase. No group difference was observed for the primary, secondary and exploratory variables. Significant improvements in FABQ scores were noted in all groups during the preventive phase of the trial. However, no significant change in health related quality of life (HRQL) was associated with the preventive phase. CONCLUSIONS: This study hypothesised that participants in the combined intervention group would have less pain and disability and better function than participants from the 2 other groups during the preventive phase of the trial. This hypothesis was not supported by the study results. Lack of a treatment specific effect is discussed in relation to the placebo and patient provider interactions in manual therapies. Further research is needed to delineate the specific and non-specific effects of treatment modalities to prevent unnecessary disability and to minimise morbidity related to NCNP. Additional investigation is also required to identify the best strategies for secondary and tertiary prevention of NCNP. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00566930.