Figure 1. A. The orientation of efforts and neutral position (N). extension (E), right posterior oblique (RPO), right lateral flexion (RLF), right anterior oblique (RAO), left posterior oblique (LPO), left lateral flexion (LLF), left anterior oblique (LAO) and flexion (F). B. Experimental setup showing the subject performing an isometric contraction resisting the adjustable mass in the left posterior oblique direction (LPO). The subject is standing on a force platform covered by a bi-layer foam pad. The effort is produced against a cable placed over a pulley to an adjustable mass. The surface electrodes can be seen over the left shoulder and neck