Muscle activation during sit-ups with bent knees and modified sit-ups

Sit-ups are a mainstay of abdominal muscle conditioning.

William Sullivan and colleagues evaluated abdominal and hip muscle activation during traditional sit-ups with bent knees and modified sit-ups using electromyography (EMG) measurements. Traditional sit-ups resulted in the strongest activation of the rectus femoris (thigh muscle that flexes the hip) and the external obliques (lateral abdominal muscles), while modified sit-ups activated the rectus abdominis (six-pack muscle) best.

However, muscle activation is only part of the overall picture. Isometric exercises for the core such as planks and side bridges may be a better way to develop core strength and stiffness as they develop a more functional core and prevent back pain.

(Strength Conditional Research, 29: 3472 - 3479, 2015; Strength Conditional Research, 29: 1515 - 1526, 2015)