The purpose of this study is to determine if trunk neuromuscular control strategies are changed by therapeutic exercises emphasizing core stabilization.

Hypothesis: subjects with low back pain who demonstrate clinically meaningful improvements in function and pain will have significantly improved trunk motor control strategies.

Hypothesis: measures of trunk control will demonstrate 'construct-validity'. This will be tested using a known group method demonstrating:

• no significant change in motor control measures within the untreated, healthy control group.
• significant changes within the low back subjects who demonstrate clinically meaningful improvements.

A growing body of evidence suggests that poor neuromuscular control of the lumbopelvic region is an important finding in a large number of patients with recurrent and chronic low back pain and may play a role in recurrence of symptoms. Despite findings of altered trunk motor control in individuals with low back pain, the neuromuscular strategies underlying these alterations have not been satisfactorily characterized. The aims of this study are to(1) identify which neural control strategies are altered following a rehabilitation program that emphasizes trunk control and stability using a motor learning approach and (2) provide preliminary evidence of a link between hypothesized mechanism and effectiveness for programs designed to improve trunk control.

Inclusion criteria for healthy controls:

No history of low back is defined as:

1. no pain limiting performance of daily activities for greater than 3 days,
2. no pain for which they sought medical or allied health intervention.

Inclusion Criteria for individuals with a history of low back pain:

1. duration of the current episode of low back pain less than 3 months,
2. average pain intensity over past 2 weeks at least 3 on an 11 point (0 = no pain, 10 = worst pain ever) numeric pain rating scale,
3. no medical intervention for low back pain in last 6 months,
4. Oswestry disability score greater than 20%
5. a physical therapy diagnosis of clinical lumbar instability based upon specific examination findings.

Exclusion Criteria for both groups:

1. permanent structural spinal deformity (e.g., scoliosis)
2. history of spinal fracture or diagnosis of osteoporosis
3. diagnosis of inflammatory joint disease
4. signs of systemic illness or suspected non-mechanical LBP (i.e. spinal tumor or infection)
5. previous spinal surgery
6. frank neurological loss, i.e., weakness and sensory loss
7. history of neurologic disease that required hospitalization,
8. active treatment of another medical illness that would preclude participation in any aspect of the study or any lower extremity injury that would potentially alter trunk movement in standing
9. leg length discrepancy of greater than 2.5 cm.
10. pregnancy
11. vestibular dysfunction

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