Exercise guide
Leg Extensions
Leg Extensions isolate knee extension on a seated machine. The quadriceps straighten the knees while the seat, backrest, and thigh position stabilize the body.
Training context
Who May Find Leg Extensions Useful?
The exercise can provide direct quadriceps work without requiring balance or loading the spine. It may be useful in bodybuilding, general strength training, or appropriately supervised rehabilitation.
The source's universal 90-degree restriction and knees-behind-toes explanation are inaccurate. Comfortable range depends on the machine, individual knee tolerance, and training goal.
Technique overview
Align the knee with the machine pivot
Adjust the seat so the machine's pivot lines up closely with the knee joint and position the lower pad above the ankles. Extend the knees smoothly without lifting the hips from the seat. Pause briefly, then lower through a comfortable range without letting the weight stack slam.
Treat this as an overview and use a range, pace, and setup you can control.