The effect of experimental low back pain on lumbar muscle activity in people with a history of clinical low back pain: a muscle functional MRI study.

In people with a history of low back pain (LBP), structural and functional alterations have been observed at several peripheral and central levels of the sensorimotor pathway. These existing alterations might interact with the way the sensorimotor system responds to pain. We examined this assumption by evaluating the lumbar motor responses to experimental nociceptive input of 15 participants during remission of unilateral recurrent LBP. Quantitative T2 images (muscle functional MRI) were taken bilaterally of multifidus, erector spinae, and psoas at several segmental levels (L3 upper and L4 upper and lower endplate) and during several conditions: 1) at rest, 2) upon trunk-extension exercise without pain, and 3) upon trunk-extension exercise with experimental induced pain at the clinical pain-side (1.5-ml intramuscular hypertonic saline injections in erector spinae). Following experimental pain induction, muscle activity levels similarly reduced for all three muscles, on both painful and nonpainful sides, and at multiple segmental levels (P = 0.038). Pain intensity and localization from experimental LBP were similar as during recalled clinical LBP episodes. In conclusion, unilateral and unisegmental experimental LBP exerts a generalized and widespread decrease in lumbar muscle activity during remission of recurrent LBP. This muscle response is consistent with previous observed patterns in healthy people subjected to the same experimental pain paradigm. It is striking that similar inhibitory patterns in response to pain could be observed, despite the presence of preexisting alterations in the lumbar musculature during remission of recurrent LBP. These results suggest that motor output can modify along the course of recurrent LBP.

Influence of combined aerobic and resistance training on metabolic control, cardiovascular fitness and quality of life in adolescents with type 1 diabetes: a randomized controlled trial.

OBJECTIVE: To evaluate the effect of combined exercise training on metabolic control, physical fitness and quality of life in adolescents with type 1 diabetes. DESIGN: A double-blind randomized controlled trial with patients receiving combined aerobic and strength or no training. SETTING: University Hospital Ghent (Belgium). SUBJECTS: Sixteen children with type 1 diabetes were randomized into a control group (n = 8) and an intervention group (n = 8). INTERVENTIONS: Patients participated twice a week for 20 weeks in the combined aerobic and strength group. The control group continued their normal daily activities. MAIN MEASURES: Before and after the intervention anthropometric variables (weight, length, BMI, body composition), metabolic control (glycaemia, HbA1c, daily insulin injected), aerobic capacity (peak Vo(2), peak power, peak heart rate, 6-minute walk distance), strength (1 repetition maximum of upper and lower limb, hand grip strength, muscle fatigue resistance, sit-to-stand) and quality of life (SF-36) were assessed. RESULTS: At baseline, none of the measured parameters differed significantly between the two groups. There was no significant evolution in the groups concerning anthropometric indices, glycaemia and HbA1c. However, the daily doses of insulin injected were significantly lowered in the training group (0.96 IU/kg.day pre versus 0.90 IU/kg.day post; P < 0,05), while it was increased in the control group. Physical fitness increased significantly in the training group. General health, vitality and role emotional had a tendency to improve. CONCLUSION: Combined exercise training seemed to lower daily insulin requirement and improve physical fitness, together with better well-being.

A magnetic resonance imaging investigation into the function of the deep cervical flexors during the performance of craniocervical flexion.

OBJECTIVE: Evidence suggests that the deep cervical flexors (DCFs) are important for the control of the cervical spine. The craniocervical flexion (CCF) test is a clinical test developed for patients with neck pain disorders based on the action of the DCFs. Because these muscles are deeply situated, it is difficult to reach the DCFs with surface electromyography. Magnetic resonance imaging (MRI) can be used to measure these muscles in cross section. The objective of this study was (1) to determine the reliability of MRI for measuring cross-sectional area (CSA) of the longus colli (Lco) and longus capitis (Lca) and (2) to evaluate the changes in CSA during contraction. METHODS: Thirty healthy subjects aged 29 +/- 9.3 years were imaged using MRI. The CSA of the Lco and Lca was evaluated at 4 different levels (C0-C1, C2-C3, C4-C5, and C6-C7) at rest and during CCF. RESULTS: The intraclass correlation coefficients for the CSA of the Lco and Lca showed good to excellent reliability (0.73-0.92), except at the C4-C5 level. There was a significant increase in CSA of both Lco (F = 6.79, P = .015) and Lca (F = 19.20, P

Altered trunk muscle coordination during rapid trunk flexion in people in remission of recurrent low back pain.

People with a history of low back pain (LBP) are at high risk to encounter additional LBP episodes. During LBP remission, altered trunk muscle control has been suggested to negatively impact spinal health. As sudden LBP onset is commonly reported during trunk flexion, the aim of the current study is to investigate whether dynamic trunk muscle recruitment is altered in LBP remission. Eleven people in remission of recurrent LBP and 14 pain free controls performed cued trunk flexion during a loaded and unloaded condition. Electromyographic activity was recorded from paraspinal (lumbar and thoracic erector spinae, latissimus dorsi, deep and superficial multifidus) and abdominal muscles (obliquus internus, externus and rectus abdominis) with surface and fine-wire electrodes. LBP participants exhibited higher levels of co-contraction of flexor/extensor muscles, lower agonistic abdominal and higher antagonistic paraspinal muscle activity than controls, both when data were analyzed in grouped and individual muscle behavior. A sub-analysis in people with unilateral LBP (n = 6) pointed to opposing changes in deep and superficial multifidus in relation to the pain side. These results suggest that dynamic trunk muscle control is modified during LBP remission, and might possibly increase spinal load and result in earlier muscle fatigue due to intensified muscle usage. These negative consequences for spinal health could possibly contribute to recurrence of LBP.

Lumbar muscle dysfunction during remission of unilateral recurrent nonspecific low-back pain: evaluation with muscle functional MRI.

OBJECTIVES: After cessation of a low-back pain (LBP) episode, alterations in trunk muscle behavior, despite recovery from pain, have been hypothesized to play a pathogenic role in the recurrence of LBP. This study aimed to identify the presence of lumbar muscle dysfunction during the remission of recurrent LBP, while performing a low-load trunk-extension movement. METHODS: Thirteen participants with unilateral recurrent LBP were tested at least 1 month after cessation of the previous LBP episode and were compared with a healthy control group without any history of LBP (n=13). Also, differences between previously painful and nonpainful sides were examined. Muscle functional magnetic resonance imaging, based on quantitative T2-imaging, was used to examine muscle tissue characteristics (T2 rest) and muscle recruitment (T2 shift) during prone trunk extension. The lumbar multifidus, erector spinae, quadratus lumborum, and psoas were bilaterally visualized on 2 lumbar levels using a T2-weighted (spin-echo multicontrast) magnetic resonance imaging sequence. RESULTS: Linear mixed model analysis revealed a significantly lower T2 rest (P=0.044) and a significantly higher T2 shift (P=0.034) solely for the multifidus in the LBP group compared with the control group. No significant differences between pain sides were found. DISCUSSION: Lower T2-rest values have been suggested to correlate with a conversion of the multifidus' fiber typing toward the glycolytic muscle spectrum. Elevated T2 shifts correspond with increased levels of metabolic activity in the multifidus in the LBP group, for which several hypotheses can be put forward. Taken together, these findings provide evidence of concurrent alterations in the multifidus structure and activity in individuals with unilateral recurrent LBP, despite being pain free and functionally recovered.

Increased intramuscular fatty infiltration without differences in lumbar muscle cross-sectional area during remission of unilateral recurrent low back pain.

Lumbar muscle degeneration is a common feature in non-specific low back pain (LBP). It is hypothesized that degenerated muscles might compromise spinal stability and lead to further injury/pain. However, little is known about lumbar muscle morphometry after resolution of LBP. Therefore, this study investigated the extent of lumbar muscle atrophy and fatty infiltration in individuals who are at risk for a recurrence of LBP. Thirteen participants in remission of unilateral recurrent LBP were compared to 13 healthy controls, comparable for age, weight, length and level of physical activity. Total, lean muscle and fat cross-sectional area (CSA) of lumbar multifidus (MF), erector spinae (ES) and psoas (PS) were investigated on T1-weighted Magnetic Resonance Imaging (MRI), bilaterally and at 3 lumbar levels (L3 upper, L4 upper and L4 lower endplate). In addition, a muscle-fat-index (MFI) was calculated reflecting the amount of fatty infiltration in lean muscle tissue. No significant differences for total, lean muscle and fat CSA were found between people in remission of recurrent LBP and the control group. Conversely, MFI was increased bilaterally at the 2 lowest lumbar levels. There were no differences between the previously painful and non-painful side of the LBP group for any of the parameters. These results show a generalized increase in intramuscular fatty infiltration in lean muscle tissue in the absence of macroscopical signs of muscle degeneration after resolution of LBP. These findings reflect a decreased muscle quality, but not quantity, and might indicate a pathophysiological mechanism contributing to recurrence of LBP.

Muscle functional MRI as an imaging tool to evaluate muscle activity.

Muscle functional magnetic resonance imaging (mfMRI) is an innovative technique that offers a noninvasive method to quantify changes in muscle physiology following the performance of exercise. The mfMRI technique is based on signal intensity changes due to increases in the relaxation time of tissue water. In contemporary practice, mfMRI has proven to be an excellent tool for assessing the extent of muscle activation following the performance of a task and for the evaluation of neuromuscular adaptations as a result of therapeutic interventions. This article focuses on the underlying mechanisms and methods of mfMRI, discusses the validity and advantages of the method, and provides an overview of studies in which mfMRI is used to evaluate the effect of exercise and exercise training on muscle activity in both experimental and clinical studies.

Magnetic resonance imaging and electromyography to measure lumbar back muscle activity.

STUDY DESIGN: Mixed model analysis of muscle functional magnetic resonance imaging (MRI) and electromyography (EMG) changes in lumbar muscles during trunk extension exercise at varying intensities. OBJECTIVE: To gain insight within the relationship between muscle functional MRI and activity of the lumbar back muscles, which is related to exercise intensity. SUMMARY OF BACKGROUND DATA: It is known that muscle activity during exercise induces a force-sensitive T2 increase; however, it is not known how sensitive this T2 change is. In addition, the association between MRI and EMG measurement was investigated. METHODS: Multifidus and erector spinae muscle activity was investigated during a trunk extension exercise at 5 increasing loads (from 40% to 80% of 1 repetition maximum), with both MRI and EMG. Data were analyzed using mixed model analysis. RESULTS: Our results indicate a linear relationship between MRI and exercise intensity; for both muscles an increase of 10% exercise intensity corresponds with an increase of the T2 value with 1.18 (0.89, 1.47) ms. Also for EMG there is a linear relationship with exercise intensity; an increase of 10% exercise intensity corresponds with an increase of 6.98 (5.33, 8.62) microV. Furthermore, a linear association between MRI and EMG is acceptable. For the multifidus, an increase of 1 muV (EMG) corresponds with an increase of 0.168 (0.117, 0.219) ms (MRI). For the erector spinae, an increase of 1 microV corresponds with an increase of 0.078 (0.042, 0.114) ms. CONCLUSION: Both muscle functional MRI and EMG have specific (dis-) advantages and therefore have to be seen as complementary techniques. Nevertheless, our results support the validity of each method and indicate that MRI and EMG can be used independently to quantify lumbar muscle activity.