The new research paper by Laird et al (2018) is a useful guide to help the interpretation of the EMG data.
It is difficult to provide EMG normative values, because the placement of the sensor, soft tissue and other factors can influence the data readings, so direct comparison is invalid, unless comparing different reading from the same sensor in one session. For this reason, we provide normative values for a Flexion / Relaxation Ratio which is calculated through measurement of the Flexion Relaxation Response.
Flexion Relaxation Response: a response where the lumbar extensor muscles show full relaxation in the fully flexed position in healthy individuals (Area 1 below)
Flexion Relaxation Ratio: the summed EMG activity demonstrated in the fully flexed position, divided by the sum of EMG activity during eccentric (standing to full flexion) and concentric (return from full flexion) phases.
The dotted green vertical lines mark the beginning of flexion, reaching endo of range, initiating return to standing & return to standing.
Individuals who are unable to relax their lumbar erector muscles in full flexion will have a higher FRRatio. On average, individuals with low back pain demonstrate a higher FRR than individuals without low back pain (Laird et al, 2018).
Values greater than 0.2 will appear as an alert in when performing a Low Back Live Assessment in dorsaVi Movement Suite.
Laird RA, Keating JL, Kent P. Subgroups of lumbo-pelvic flexion kinematics are present in people with and without persistent low back pain. BMC Musculoskeletal
McGorry RW, Lin J-H. Flexion relaxation and its relation to pain and function over the duration of a back pain episode. PLoS ONE, 2012; 7(6): e39207.