Abdominal muscle activation: An EMG study of the Sahrmann five-level core stability test.
Ebby Waqqash Mohamad Chan, Mohamad Shariff A Hamid, Ali Md Nadzalan and 1 others
PMID 33005073WHAT IT FOUND
In healthy young men, Sahrmann levels 3 and 5 produced significantly higher abdominal muscle activity than levels 1, 2, and 4.
Level 5 elicited the greatest activation across all three muscle groups. No significant difference was found between levels 3 and 5, or between the three muscles within any level.
Key findings
01Level 5 elicited significantly greater EMG signals from all three abdominal muscles compared to levels 1, 2, and 4.
02No significant difference in abdominal muscle EMG signals was noted between Sahrmann levels 3 and 5.
03No significant difference was found between RA, EO, and TrA/IO EMG activities during each level of the test.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only healthy young men, so findings may not apply to women or individuals with musculoskeletal conditions like low back pain. Surface EMG of the TrA/IO site is susceptible to cross-talk from superficial muscles and largely reflects internal oblique activity rather than transverse abdominis. The sample size was small (22 participants), though an a priori power calculation justified it for the specific effect size used. The study examined asymptomatic individuals, limiting generalizability to clinical populations with core stability deficits.
Declared interests
The authors declared no conflicts of interest. The research did not receive any grants from funding agencies.
The easy way to misread this
Do not interpret the lack of difference between levels 3 and 5 as evidence that unilateral and bilateral leg lowering are interchangeable for all core functions. The study only measured abdominal muscle activity in healthy young men and did not assess lumbar spine stability, back pain outcomes, or other muscle groups, so clinical equivalence for patient care is not established.