To investigate low back posture and trunk muscle activation while exercising on an unstable chair (Flexchair ®) in a healthy population.

Background: Low back pain (LBP) is one of the most common and costly musculoskeletal pain syndromes of modern society (Dankaerts et al 2009). The Flexchair® is a novel dynamic sitting device that is equipped with a sensor measuring movement of the chair. It has been hypothesised that it may be helpful in providing feedback and eliciting the contraction/relaxation phenomenon. This may be achieved while performing trunk muscle exercises on it which may aid in improving trunk stability. Objectives: To assess if there is a difference in trunk muscle activation between different exercises and conclude if the Flexchair ® could possible provide adequate feedback and production of a contraction/ relaxation phenomenon. Methods: 10 healthy subjects (6M, 4F mean age 23± 3 years) performed 6 specific exercises on a Flexchair ®. Data was recorded using EMG and SPMD software. Analysis was performed using a repeated-measures analysis of variance (ANOVA) with post-hoc least significant difference (LSD) applied (Ekstrom, Donatelli and Soderberg 2003). Results: The activation of IO (p= 0.037) and LM (p=0.036) were significantly greater in exercise 6 (21% of MVIC) and exercise 5 (19% of MVIC). The contraction/relaxation of TES (p=0.030), ICLT (p=0.080) and LM (p=0.019.) were significantly greater in exercise 2 (9% of MVIC) and in exercise 6 for both ICLT (12% of MVIC) and LM (13% of MVIC). Conclusions: The findings in this study may be useful in selecting specific exercises to enhance a motor control/endurance training programme for individuals who may be appropriate for biofeedback and encouragement of contraction/ relaxation of their back muscles.