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Exercises

Trunk Twists (Rotary Torso)

Evidence-grounded — sourced from Fysiqal's fitness knowledge graph· 1 min read
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In one line

Seated machine torso rotation (rotary torso) working the obliques and erector spinae; rotates the torso ~40 degrees with hips fixed.

Detail

Trunk twists / rotary-torso work train torso rotation. Torso rotation is produced by the erector spinae and the external and internal obliques; contraction of an external oblique and the opposite internal oblique causes trunk rotation. The torso rotates approximately 40 degrees with the hips in a fixed position (spinal rotation is very limited in the lumbar region). Performed on Cybex/Paramount rotary-torso machines — the source explicitly states free bars are NOT allowed for this movement. The standing torso twist with a barbell is a contraindicated ("X-rated") version.

Key facts

  • Works external oblique, internal oblique, and erector spinae (rotation).
  • Torso rotation ROM ~40 degrees with fixed hips.
  • Machine only — no free bars allowed.

Connections

  • external-oblique / internal-oblique — produce rotation.
  • erector-spinae — assists in torso rotation.
  • standing-torso-twist — the dangerous standing barbell version.
SourceReference manual
p.280p.596p.624p.632
Cited authorities in source: Thompson (1989).
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Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.

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Atlas Connections

Erector Spinae (Sacrospinalis)
Three muscle-group columns (iliocostalis, longissimus, spinalis) running skull-to-sacrum that extend, laterally flex, and rotate the vertebral column.
External Oblique
The largest, most superficial flat abdominal; flexes the trunk and rotates it toward the opposite side.
Internal Oblique
A flat abdominal sandwiched between the external obliques and transversus; its fibers run at right angles to the external oblique and it twists the trunk to the same side.
Intensity
The amount of weight (resistance) lifted — also shaped by speed, reps, sets, rest interval, and workout duration.
The Standing Torso Twist — Contraindicated Stretch
The standing torso twist (with or without weights) strains the knee ligaments and relies on momentum that can exceed the tissues' absorbing capacity — marked "X".