Plank (Straight-Arm)
The Straight-Arm Plank is a foundational isometric core exercise performed at the top of a push-up position to build total-body stability. It targets the deep abdominal muscles while simultaneously strengthening the shoulders, chest, and wrists.
Iridium accounts for the significant shoulder stability required here by analyzing recent anterior deltoid volume to ensure arm fatigue doesn't limit your core work. For progression, the system tracks your RPE and historical hold times to incrementally increase duration rather than external load.
Form Cues
- Place hands directly under shoulders
- Push the floor away to spread shoulder blades
- Squeeze glutes and quads tightly
- Tuck your tailbone slightly under
- Gaze at the floor to keep neck neutral
- Don't let your hips sag toward the floor
- Don't pike your hips up toward the ceiling
- Don't look forward or crane your neck
- Don't let your shoulder blades collapse together
- Don't hold your breath
Common Mistakes
- Sagging hips (hyperextension)
- Piking hips too high
- Winged scapula
- Placing hands too far forward
- Holding breath
Muscles Worked
This exercise is an anti-extension movement that primarily targets the transverse abdominis and rectus abdominis to stabilize the spine. Unlike the forearm variation, the straight-arm position places significant demand on the anterior deltoids and serratus anterior for upper body support, while the glutes and quadriceps engage isometrically to maintain rigid alignment.
Primary
Secondary
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