REF-1633 · Oliva-Lozano & Muyor, 2020 · International Journal of Environmental Research and Public Health, · Paper · PubMed

No single type of core exercise works every trunk muscle hardest: in a systematic review of EMG studies in healthy adults (2012 to March 2020), free-weight exercises drew the most rectus abdominis, external oblique and erector spinae activity, core stability exercises the most internal oblique, and traditional exercises the most multifidus; the transversus abdominis was barely studied and EMG methods varied between studies

Main caveat: Acute EMG amplitude only; no training outcome.
limited, mixed evidenceMeasured on non-athletes to trained athletesRead from the abstract only

Oliva-Lozano and Muyor reviewed studies that recorded electrical activity (EMG) of six core muscles (rectus abdominis, internal and external oblique, transversus abdominis, lumbar multifidus and erector spinae) while healthy adults did core exercises.

Following PRISMA, they searched Cochrane, EBSCO, PubMed, Scopus and Web of Science for studies from January 2012 to March 2020 that reported EMG as a percentage of maximal voluntary contraction or in millivolts or microvolts.

Across the included studies, free-weight exercises produced the highest rectus abdominis, external oblique and erector spinae activity, core stability exercises the highest internal oblique activity, and traditional exercises the highest multifidus activity. The authors found little research on the transversus abdominis and inconsistent EMG methods between studies.

Participants

Healthy adults, by the inclusion criteria. The number of studies and participants, sex and training status are not in the abstract.

Methods

Search: Cochrane, EBSCO, PubMed, Scopus and Web of Science, January 2012 to March 2020; PRISMA guidelines.
Inclusion: full text in English; cross-sectional or longitudinal (experimental or cohort) design; EMG reported as % maximal voluntary isometric contraction, millivolts or microvolts; at least one of the six named trunk muscles; physical fitness exercises for core training; healthy adults.
Synthesis: results reported by exercise category; the abstract gives no pooled estimate and does not name the synthesis method.
Not in the abstract: number of included studies, a risk-of-bias or quality appraisal, the exercises in each category, and any activation values.

Key Results

MuscleExercise category with the highest activity
Rectus abdominisFree-weight exercises
External obliqueFree-weight exercises
Erector spinaeFree-weight exercises
Internal obliqueCore stability exercises
Lumbar multifidusTraditional exercises
Transversus abdominisToo little research to say
EMG methods were inconsistent across studies, which limits comparison.

Practical Application

There is no one best core exercise; different types of exercise work different trunk muscles. Loaded free-weight exercises drew the most activity from the rectus abdominis, external oblique and erector spinae, stability exercises from the internal oblique, and traditional exercises from the multifidus.
Inference, not tested here: a core routine that mixes loaded free-weight work with a stability exercise covers more of the trunk than one move repeated; if the free-weight category is mostly squat- and hinge-type lifts (the abstract does not name them), an athlete who already lifts heavy is already loading the rectus abdominis, external oblique and erector spinae.
Activation is a marker, not a result. Higher EMG in one session does not show more strength, endurance or fewer injuries after weeks of training; for what core training does over weeks in athletes see REF-1632.
Not settled by this design: rankings of named exercises (plank, side plank, anti-rotation presses and others), the transversus abdominis, and whether any core exercise choice changes running or cycling performance.

Limitations

Acute EMG amplitude only; no training outcome.
Number of studies, participants, exercises per category and quality appraisal are not in the abstract.
EMG methods and normalisation differed between studies, so cross-study rankings are approximate.
Healthy adults; training status and sex unknown from the abstract.
Written from the abstract and the PubMed record; full text not read.
How this entry was checked and changed
Why this level

a review of EMG measurement studies is B by design (descriptive, within-session comparisons), and the abstract gives no study count and no quality appraisal; the claim rests on a marker (EMG amplitude), not on strength, performance or injury, one step down (rule 3)

Content correction 2026-11-07
2026-11-07: added from the abstract and the PubMed record; level B- (review of EMG measurement studies, B by design, one step down for a marker outcome).