Leg Extension
Muscles worked
Instructions
- 1For this exercise you will need to use a leg extension machine. First choose your weight and sit on the machine with your legs under the pad (feet pointed forward) and the hands holding the side bars. This will be your starting position. Tip: You will need to adjust the pad so that it falls on top of your lower leg (just above your feet). Also, make sure that your legs form a 90-degree angle between the lower and upper leg. If the angle is less than 90-degrees then that means the knee is over the toes which in turn creates undue stress at the knee joint. If the machine is designed that way, either look for another machine or just make sure that when you start executing the exercise you stop going down once you hit the 90-degree angle.
- 2Using your quadriceps, extend your legs to the maximum as you exhale. Ensure that the rest of the body remains stationary on the seat. Pause a second on the contracted position.
- 3Slowly lower the weight back to the original position as you inhale, ensuring that you do not go past the 90-degree angle limit.
- 4Repeat for the recommended amount of times.
About Leg Extension
The leg extension is performed seated on a machine, straightening the legs to lift a pad against resistance, to full knee extension. It is the reference isolation exercise for the quadriceps, with no involvement of other muscle groups, which is rare for a leg movement. Ideal at the end of a session to burn out the quads after the big exercises, or for beginners learning to contract the thigh. Extend until the legs are straight while squeezing the quad, hold briefly, then lower under control without letting the weight drop. Set the backrest so the machine's axis of rotation aligns with your knee.
check_circleBenefits
- check_circleFully isolates the quadriceps with no other muscles involved
- check_circleLets you finish a session by pre-exhausting the quads
- check_circleA guided movement that is simple to control for beginners
lightbulbExecution tips
- lightbulbAdjust the backrest so the pivot lines up with your knees
- lightbulbFully extend the legs and pause briefly at the top
- lightbulbLower slowly to maximize time under tension
- lightbulbKeep the hips pressed into the seat
warningCommon mistakes
- warningSwinging the weight with momentum instead of controlling it
- warningLifting the hips off the seat to cheat
- warningLoading too heavy and shortening the range
- warningLetting the weight drop in free fall
helpFrequently asked questions
Is the leg extension bad for the knees?expand_more
Done well with reasonable load it is safe; pain usually comes from excessive weight or a poor machine setup.
Can it replace the squat?expand_more
No, it is a complementary isolation exercise; the squat remains superior for overall leg strength and mass.
Is the leg extension bad for the knees?expand_more
For a healthy knee, it is not dangerous at a reasonable load and controlled range. It creates strong tension on the knee at full extension: if you have pain or a knee issue, reduce the load, the range, or seek a professional's advice.
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