The effect of muscle fatigue and low back pain on lumbar movement variability and complexity

• Published in: Journal of electromyography and kinesiology 2017-04, Vol.33, p.94-102
• Main Authors: Bauer, C.M, Rast, F.M, Ernst, M.J, Meichtry, A, Kool, J, Rissanen, S.M, Suni, J.H, Kankaanpää, M
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Biomechanical Phenomena; Fatigue; Female; Humans; Low back pain; Low Back Pain - physiopathology; Lumbosacral Region - physiology; Lumbosacral Region - physiopathology; Male; Middle Aged; Movement; Movement disorders; Muscle Fatigue; Muscle, Skeletal - physiology; Muscle, Skeletal - physiopathology; Physical Medicine and Rehabilitation
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2017.02.003

Abstract Introduction Changes in movement variability and complexity may reflect an adaptation strategy to fatigue. One unresolved question is whether this adaptation is hampered by the presence of low back pain (LBP). This study investigated if changes in movement variability and complexity after fatigue are influenced by the presence of LBP. It is hypothesised that pain free people and people suffering from LBP differ in their response to fatigue. Methods The effect of an isometric endurance test on lumbar movement was tested in 27 pain free participants and 59 participants suffering from LBP. Movement variability and complexity were quantified with %determinism and sample entropy of lumbar angular displacement and velocity. Generalized linear models were fitted for each outcome. Bayesian estimation of the group-fatigue effect with 95% highest posterior density intervals (95%HPDI) was performed. Results After fatiguing %determinism decreased and sample entropy increased in the pain free group, compared to the LBP group. The corresponding group- fatigue effects were 3.7 (95%HPDI: 2.3 to 7.1) and -1.4 (95%HPDI: -2.7 to -0.1). These effects manifested in angular velocity, but not in angular displacement. Discussion The effects indicate that pain free participants showed more complex and less predictable lumbar movement with a lower degree of structure in its variability following fatigue while participants suffering from LBP did not. This may be physiological responses to avoid overload of fatigued tissue, increase endurance, or a consequence of reduced movement control caused by fatigue.