The muscle activation of the erector spinae during hyperextension with and without the pelvis restrained

The purpose of this study was to determine if pelvic restraint during hyperextension on a variable angle Roman chair (VARC) changes the muscle activation of the erector spinae musculature. Seventy volunteers (18-35 years) performed hyperextension exercises on the VARC with and without the pelvis restrained. Surface electromyography (EMG) was used to measure the muscle activation of the erector spinae at the third lumbar vertebra (L3). Total root mean square (RMS) for eccentric and concentric phases were amplitude normalized to a maximal voluntary isometric contraction (MVIC). A post test questionnaire was used to determine the subjective feeling of localized fatigue. The EMG data were analyzed with a Multivariate Hotelling's T-2 test and univariate t-tests. The questionnaire data were analyzed using McNemar's test. Alpha was set at 0.05. A statistically significant (p < 0.01) but small (approximately 3%) increase in the RMS of the erector spinae was demonstrated in the unrestrained condition for both independent variables: concentric and eccentric motion. Conversely, a greater proportion of participants subjectively reported greater effort in the lumbar extensors with the pelvis restrained. It is unclear if these observed changes in muscle activation and subjective perceptions can direct changes in the clinical practice. (C) 2002 Elsevier Science Ltd. All rights reserved.