6 Best Quad Isolation Exercises (Target 4 Quadricep Muscles)

After incorporating sissy squats into my workouts, I found them to be a fantastic variation of the traditional squat and a quad-dominant exercise.

Its goal is to change the angle of your ankle and knees, activating your quadriceps muscles more due to bigger leverage.

Sissy squats were historically classified as a dangerous lower body exercise.

Many people implement this exercise to experience healthier knee joints and less pain in the joints above and below.

How to Perform a Sissy Squat:

1. Assume a standing position with your feet closer than shoulder-width apart and your back flat.
2. Stand near the squat rack and hold the barbell or the rack's side with both hands.
3. Start the exercise by lowering yourself to a squat position, but plantar flex your ankles, push your knees forward, and lean your body backward to enter the sissy squat position.
4. Return to the starting position when you reach the end range of motion and can’t go deeper into the sissy squat position.
5. Repeat for as many reps as possible without compromising the form and for up to 3 sets.

3. Step-Ups

Step-ups are excellent lower body exercises for developing your posterior and anterior chain leg muscles.

They will activate hamstrings, glutes, hip flexors, and all four quadriceps muscles.

Depending on your personal goals, you may perform step-ups with your back straight up or bent forward.

Bending forward will activate more posterior chain muscles and vice versa.

How to Perform Step-Ups:

1. Assume a standing position shoulder-width apart before the elevated surface, a box, and hold dumbbells in each hand.
2. Select the dumbbell weight to perform up to 6 repetitions with each leg.
3. Start the exercise by stepping on the box with your right foot while maintaining a straight back.
4. Push through with your right foot and propel yourself up into the standing position on the box.
5. When you reach the top position, reverse the movement to return to the starting position, encapsulating one repetition.
6. Finish with one leg first before working out the other one, and repeat for up to 3 sets.

Single-leg extension isometric holds are a variation of traditional bilateral extension isometric holds.

The unilateral version makes this exercise more functional than its original version.

This exercise isolates all the necessary quad muscles while keeping your other muscle relaxed due to the unique position and angles of the machine.

How to Perform a Single-Leg Extension Isometric Holds:

1. Load the leg extension machine with the appropriate weight to perform up to 6 reps/holds with each leg.
2. Sit on the leg extension machine, then place your right foot under the leg machine attachment while keeping your left leg on the floor.
3. Start the exercise by extending your knee and keeping your body balanced by holding the handles near the machine.
4. When you extend your knees fully, hold the position for 6 seconds.
5. Reverse the motion by flexing your knee to return to the starting position.
6. Repeat for up to 6 reps/holds with each leg and three sets.

5. Resistance Band Single-Leg Extension

Resistance band single-leg extension is similar to the cable machine single-leg extension exercise, but the band will add progressive resistance.

Banded single-leg extensions are functional exercises that build strength in all quadriceps muscles.

How to Perform Resistance Band Single-Leg Extensions:

1. Wrap the band around the squat rack and place your right foot in the loop of the band.
2. Face away from the rack and step outside to keep the band's tension active (feet shoulder-width apart).
3. Start the exercise by extending your knee joint while keeping your hips parallel to the ground.
4. When you fully extend the knee, hold that position for a second, and reverse the whole motion to return to the starting position.
5. Repeat for up to 8 reps with each leg and 3-4 sets.

Leg machine extension is a quad dominant exercise that will isolate all your quadriceps muscles due to the unique nature of the machine.

It is frequently used for rehabilitation purposes where individuals aren’t allowed to exercise with their feet on the ground.

It can also serve as an excellent quad isolation exercise and should be implemented into a weekly workout regime, preferably at the end of the workout.

How to Perform Leg Machine Extensions

1. Assume a sitting position on the leg machine and set the appropriate weight to perform up to 12 repetitions.
2. Hold the bars near the leg extension machine to ensure maximal stability.
3. Start the exercise by extending your knees and keeping your ankles slightly dorsiflexion.
4. Hold that position for a second or two when your knees are fully extended.
5. Reverse the motion of the exercise by slowly bending your knees to return to the starting position.
6. Repeat for up to 12 repetitions and 3-4 sets.

Related: Best Leg Extension Alternatives

The Vastus medialis is another quad muscle located on the femur's inner side.

Vastus medialis originates from the upper part of the femur bone and inserts into the quadriceps femoris tendon, which then inserts into the patella, the small sesamoid bone.

Together with other muscles of the quadriceps complex, the vastus medialis has the primary function of helping extend the knee.

However, it also contributes to the accurate tracking of the patella bone.

Weakness of this muscle is often associated with patellofemoral pain and patellar maltracking.

3. Vastus Intermedius

The Vastus intermedius is the shortest of all four quadriceps muscles and is located centrally, below the rectus femoris.

Furthermore, it is located in the anterior compartment of the thigh muscles.

The vastus intermedius originates from the upper portion of the lateral and anterior surfaces of the femur bone and the intermuscular septum.

Together with the rest of the quadriceps muscles, the vastus intermedius inserts into the patella.

The primary function of the vastus intermedius is knee extension.

Vastus lateralis is the outer quadriceps muscle on the femur bone's outer side.

In addition, the vastus lateralis is the largest muscle of the entire quadriceps complex.

It has the same function as the vastus medialis, intermedius, and rectus femoris, knee extension.

Lastly, it inserts into the patellar bone with the other three quadriceps muscles.

Isolation exercises are all movements that include the work of a single joint and a specific muscle or muscle group.

According to a study published by the National Institutes of Health (NIH), compound exercises are all movements that simultaneously work multiple joints and activate large muscle groups [1].

The main difference between isolation and compound exercises is the number of joints and muscle groups involved and the complexity of the movement.

Always perform compound exercises at the beginning of the workout since they require much more energy than isolation exercises.

Compound exercises are more demanding on your central nervous system and require you to be fresh to perform the exercise safely.

On the contrary, isolation exercises are much less demanding energy-wise and you can include them as supplementary lifts at the end of the workout.

Both types of quad exercises should be incorporated into the single workout program, but with the proper sequence and workload.

"To zero in on the quads without having to balance yourself standing, the leg extension (misnamed because the action is technically knee extension) is often done as a final movement in your leg assault."

- Parker Hyde, M.S. in Exercise Science & The Lead Graduate Student in the Human Performance Lab

Based on a study published by the National Institutes of Health (NIH), some quad isolation or quad-centric exercises put a lot of stress on knee joints [3].

The sissy squat or knees-over-toes lunges are the perfect example.

If you feel discomfort from doing quad exercises from the list, it doesn't mean you should stop doing them but adjust the workload.

Lower the sets and repetitions or increase the rest periods between the sets.

Related: Best Resistance Band Exercises to Relieve Knee Pain

3. Tight Quads

Intense resistance training often leads to tight and short muscles, especially if you forget to stretch during the week.

You shouldn't stretch after the lifting session, but do a separate workout just for stretching.

You must take care of tight quads because they can negatively affect your ankle or hip joints.

According to a study published by the National Institutes of Health (NIH), tight quads can lead to several issues, such as patellar alta and patellar tilt, which may cause weakness and muscle imbalance [4].

Implement stretching workouts like the half kneeling quad stretch at least twice weekly to avoid adverse effects in subsequent joints.