The facilitation of trunk muscles by abdominal bracing during walking in chronic low back pain patients

Walking is known to be beneficial for chronic low back pain (LBP) patients and fast walking recruits more trunk muscles. Abdominal bracing has also been shown to improve LBP and facilitate several trunk muscles. We aimed to investigate the effects of walking velocity and abdominal bracing on the activation of trunk muscles in chronic LBP patients during walking. Forty-six volunteers with chronic LBP underwent walking exercise on the treadmill without ("non-braced walking") and with abdominal bracing ("braced walking") at speeds of 4, 5, and 6 km/h, with the surface electrodes placed on their trunk muscles to measure muscle activity. The root mean square values of the surface electromyography amplitude data were obtained at the multifidus of lower (ML) and upper lumbar (MU), erector spinae of lower lumbar (EL) and thoracic (ET), rectus abdominis (RA), and external oblique (EO). All muscles activated significantly more at faster walking. The "braced walking" facilitated the ET and RA significantly more than the "non-braced walking". The interaction between the walking speed and abdominal bracing was significant at ML, MU, and RA. The increase in muscle activation observed at lower speed diminished as speed increased. Since "braced walking" seems to additionally facilitate the trunk muscles especially at slower gait speeds, patients who cannot walk fast may still be able to train their muscles by "braced walking."