Which muscle activity prevents forward trunk jackknifing during gait?

Which muscle activity prevents forward trunk jackknifing during gait?

• A. Erector spinae
• B. Rectus abdominis
• C. Gluteus maximus
• D. Hip abductors

Answer: (A)

Maintaining an upright trunk during gait relies on back extensor muscles to counteract forward bending forces. The erector spinae run along the spine and provide extension and stabilization of the trunk as you step, especially when the body’s weight shifts forward. Without their activity, gravity and momentum would push the torso into forward flexion, creating a jackknife posture. The other muscles wouldn’t serve this primary role. The rectus abdominis flexes the spine, which would promote forward bending rather than prevent it. The gluteus maximus mainly controls hip extension and helps stabilize the pelvis and thigh, but it isn’t the main force preventing forward trunk collapse. The hip abductors stabilize the pelvis laterally, not the sagittal position of the trunk.

Maintaining an upright trunk during gait relies on back extensor muscles to counteract forward bending forces. The erector spinae run along the spine and provide extension and stabilization of the trunk as you step, especially when the body’s weight shifts forward. Without their activity, gravity and momentum would push the torso into forward flexion, creating a jackknife posture.

The other muscles wouldn’t serve this primary role. The rectus abdominis flexes the spine, which would promote forward bending rather than prevent it. The gluteus maximus mainly controls hip extension and helps stabilize the pelvis and thigh, but it isn’t the main force preventing forward trunk collapse. The hip abductors stabilize the pelvis laterally, not the sagittal position of the trunk.