Abstract

Purpose Muscle activation can reflect the stability of the lumbar spine based on the electrical features and kinematics during a dynamic test. However, there is a lack of knowledge of the activation of paravertebral muscles i.e., during the flexion-relaxation test. Hence, we determine the band frequency differences between eccentric (ECC) and concentric (CON) contraction during the flexion-relaxation test in healthy untrained participants without lumbar pain, both multifidus lumborum and longissimus muscles. Methods 40 healthy participants (aged 30.6 +/- 6.9 years) were recruited. Kinematic and surface electromyography were collected to compare the ECC and CON spectral characteristics of both multifidus lumborum and longissimus. The bursts were transformed using a discrete wavelet transform (Daubechies). The band frequencies were compared through mean comparison test with alpha set to 5%. Results Both multifidus lumborum and longissimus muscles had higher intensity in ECC contraction than CON for frequency bands lower than 32 Hz (P < 0.05); meanwhile, there was a higher intensity in CON contraction than ECC for frequency bands higher than 32 or 64 Hz until 256 Hz (P < 0.05). Conclusion For both paravertebral muscles analyzed, discrete wavelet decomposition suggests that during the flexion-relaxation test there is an ECC contraction characterized by low-frequency bands compared with the CON phase characterized by medium- and higher-frequency bands both paravertebral muscles analyzed. The spectral characteristics might be a useful physiological neuromuscular reference to the pathophysiology adaptations of the paravertebral muscle contraction.