Trunk rotates toward the working arm
Body twists to assist the single-arm fly; pec loses its load.
Overactive muscles
ObliquesAnterior deltoid
Corrective work
Foam RollPectorals↗StretchQL side-bend stretch↗Push · Upper Body
Unilateral Pec Deck
Coaching cues
- Pec deck machine; use only one arm at a time
- Non-working arm rests at the side or holds the machine
- Resist trunk rotation — core braced throughout
- Exposes bilateral pec strength differences
Common faults 2
Shoulder shrugs on the working side
Upper trap assists the machine fly under the unilateral demand.
Overactive muscles
Upper trapeziusPec minor
Corrective work
Foam RollUpper traps↗StretchLevator scapulae stretch↗