Investigation of Trunk Neuromuscular Control in Patients With Non-specific Low Back Pain

This study will use a sample of convenience between the ages of 21 - 65. Patients with non-specific low back pain (NSLBP) will be recruited by advertisement in 2 Mahidol university physical therapy clinics and participating clinics and hospitals. Asymptomatic participants will be also recruited by flyers posted in 2 Mahidol university physical therapy clinics.

Based upon power analysis for change in kinematic pattern in patients with NSLBP after an 8-week core stabilization exercise program, a total required sample size is 29 patients with NSLBP to detect a medium effect size (Cohen's d) of .48 at level (α) of .05 and power (1-β) of .80. Fifteen percent drop-out rate is used as a conservative sample size calculation. Therefore, 34 patients with NSLBP (29 X 15% drop-out) and 34 age-, sex-, and BMI-matched asymptomatic participants will be included for each independent intervention study (core stabilization exercise approach, movement system impairment approach, neuromuscular activation using suspension, and kinematic linkage imbalance approach). Each intervention will be separately collected and analyzed. The total of 272 participants will be recruited to fulfill this study project (4 independent intervention studies). However, sample size for asymptomatic participants can be decreased if participant from one intervention study is matched with patients with NSLBP in other intervention studies.

Patients with NSLBP who are interested in participation will undergo a screening process using inclusion-exclusion criteria checklist and receive brief information regarding the study. If they meet all inclusion criteria, the consent process and biomechanical testing will be scheduled. On date of consent and biomechanical testing, both asymptomatic participants and participants with NSLBP will be provided a consent form. To ensure they understand the study, they will be simply asked regarding the study (i.e. objectives, benefits, etc.) before signing the consent form. After the participants provide a written informed consent, they will undergo a standardized physical therapy examination performed by an experienced physical therapist (PT-A). For patients with NSLBP, they will also complete 3 clinical outcome measures including 1) numeric pain rating scale (Thai version), 2) Oswestry disability index (Thai version), and 3) general health status questionnaire (Thai version). This pre-biomechanical data collection process will last approximately 60 minutes.

For biomechanical testing, body landmarks will be identified and marked with a skin pen for 4 motion sensors and 16 pairs of surface electromyography (EMG) electrodes in lower back and abdominal areas. Any hair in the area around the sensors and electrodes will be shaved. Before placing surface EMG electrodes, the skin will be lightly abraded using abrasive paper and cleaned using cotton with alcohol to lower the skin impedance. Electrodes will be aligned parallel to the muscle fibers. This process will take approximately 30 minutes. Then, participants will proceed to the biomechanical testing which includes 1) trunk muscle strength test, 2) functional trunk and pelvic movement tests, and 3) core control tasks.

Trunk muscle strength test Strength test Participants will wear a climbing harness connecting with a tension load cell and sit in a testing apparatus in a neutral trunk position with pelvic securely locked. This apparatus intends to reduce compensation from lower extremities during sub-maximal (15% of body weight) and maximal voluntary isometric contractions. Participants will be instructed to use their trunk gradually pulling the load cell (isometric contraction in neutral trunk position) for 10 seconds in forward, backward, and 2 side bending directions. Participants will be given 2 practice trials in each direction to adjust the force and reduce a learning effect. Visual feedback of force to sub-maximal target will be provided. Two trials of sub-maximal voluntary isometric contractions will be collected in each direction. Only 1 trial of maximal voluntary isometric contraction will be collected to avoid muscle fatigue (in both asymptomatic participants and patients with NSLBP) and pain exacerbation (in patients with NSLBP). The intention of collecting maximal contraction data is to use for EMG standardization. Participants will rest in between each trial to minimize fatigue. Pain and rating perceived exertion (RPE) will be monitored and recorded at the end of trunk strength test. This protocol will take approximately 15 minutes.