90 degrees Single Knee Crunch

Instructions

1
Lie flat on your back on a mat or floor with legs extended. Keep your head and upper back relaxed against the surface, arms at your sides with palms down for stability.
2
Engage your core by drawing your navel toward your spine. One leg remains extended on the floor while the other leg is prepared to lift. Maintain neutral spine alignment throughout.
3
Slowly lower the working leg toward the floor in a controlled manner, maintaining slight tension. Do not allow the lower back to arch excessively. Keep the non-working leg planted for stability.
4
Drive the leg back up to the starting position by contracting the quadriceps, lifting the foot toward the ceiling. Return to the initial position with control and repeat for desired repetitions before switching legs.
PRIMARY MUSCLESRectus Femoris
SECONDARY MUSCLESVastus Lateralis, Vastus Medialis, Iliopsoas, Tensor Fasciae Latae
EQUIPMENTBody weight
DIFFICULTYBeginner

Overview

Athletic trainers and bodybuilding coaches frequently recommend the 90 degrees Single Knee Crunch because it challenges the Rectus Femoris through a dynamic range of motion. By relying on Body weight, it reinforces proper movement patterns and builds robust strength in the Waist region.

Benefits

  • Reduces the likelihood of Waist injuries by reinforcing connective tissue strength.
  • Utilizes Body weight to create sustained mechanical tension, forcing deep muscle adaptation.
  • Improves overall Waist stability and proprioception during heavy loads.
  • Significantly enhances the structural integrity and power of the Rectus Femoris.

Pro Tips

Control the eccentric (lowering) phase of the 90 degrees Single Knee Crunch for 3-4 seconds to drastically increase time under tension.

Exercise Variations

  • Dumbbell 90 degrees Single Knee Crunch
  • Cable 90 degrees Single Knee Crunch
  • Banded 90 degrees Single Knee Crunch

Beginner Tips

If you are new to the 90 degrees Single Knee Crunch , focus on mastering the movement pattern with zero weight before adding Body weight.

Frequently Asked Questions