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Abstract
Low back pain (LBP) is one of the most common medical problems, afflicting around 80% of the world’s population at one time or other in their lifetime. The LBP episodes usually resolve quickly but a high number of individuals often relapse and suffer repeated episodes of LBP. This leads to a loss in work productivity and a decrease in their quality of life. Hence, it becomes imperative to understand and possibly correct the underlying factors responsible for recurrent LBP. Alterations in trunk muscle response patterns such as delays in muscle onset times, increased agonist/antagonist co-activation levels, and loss of anticipatory control have been observed in subjects with LBP. Altered muscle responses contribute to impaired postural control and instability which may be a contributing factor to the recurrence of LBP. Stabilization exercise programs have been shown to decrease the risk of LBP recurrence in a select group of patients with acute, first episode LBP. However, there is little evidence to demonstrate if the stabilization exercise program influences the underlying neuromuscular control of the spine and postural stability. Hence, the purpose of this study was to determine whether a 10-week stabilization exercise program improved postural stability or altered the neuromuscular control in subjects with LBP. Two experiments were designed for that purpose: (1) A sudden perturbation test to assess the trunk muscle reflex responses, and (2) A seated postural control task to assess postural stability and trunk equilibrium control. 30 subjects (15 subjects with sub acute recurrent LBP, 15 healthy) aged between 18–55 years participated in the study. The LBP group was tested before (PRE) and after (POST) the 10-week physical therapy intervention program. The healthy control (CNTL) group was tested on one occasion.
In the sudden perturbation test it was observed that the subjects with LBP at PRE therapy had delayed and dampened trunk muscle reflexes compared to the CNTL group subjects. Postural stability assessed using a fractional Brownian motion analysis of the force plate data from the wobble chair revealed that the subjects with LBP at PRE therapy had increased postural sway and large trunk displacements. In addition, the subjects with LBP displayed compensatory flexor activation during the seated postural task compared to the CNTL group subjects. At POST therapy in the subjects with LBP, the reflex responses remained delayed but there was a significant increase in the reflex amplitudes. In the seated postural task, there was a decrease in the postural sway and a reduction in the compensatory trunk flexor activity. In addition compared to the CNTL group, the LBP group at POST therapy demonstrated increased extensor activity. In conclusion, a 10-week stabilization program improved the neuromuscular control of the spine and postural stability in subjects with LBP.
