Do I need a foam roller for short arc quads?

No. A firmly rolled bath towel, a rolled blanket or a small bolster works the same way, as long as it stays firm under the knee and keeps it bent roughly 20 to 30 degrees at the start.

What is the difference between a short arc quad and a long arc quad?

A short arc quad works only the last part of knee straightening with the thigh resting on the floor, while a long arc quad is done sitting on a chair or bench and straightens the knee from about 90 degrees, a much bigger range. Most programs start with short arcs and progress to long arc work such as the Band Seated Leg Extension or the Alternating Seated Leg Extension.

Does the short arc quad target the VMO?

It works the vastus medialis, but not on its own. A small EMG study of healthy adults found no significant difference between vastus medialis oblique and vastus lateralis activity during the short arc quad with the hip in a neutral position, so treat it as an exercise for the whole quadriceps.

How do I make short arc quads harder?

Add a light ankle weight once you can straighten the knee fully and hold it for 5 seconds on every rep, then increase it in small steps. When that is easy, move on to long arc work and standing exercises such as the Bodyweight Box Squat or the Step-Up.

Can I do short arc quads after knee replacement or ACL surgery?

They are a common early exercise after both, but your surgeon or physical therapist decides when to start and when to add weight. After ACL reconstruction, resisted knee straightening is introduced on a schedule because resistance at the ankle increases the pull on the ligament.

How many reps and sets of short arc quads should I do?

A typical starting point is 8 to 12 slow reps per leg with a 5-second hold at the top, for 2 to 3 sets. Add reps or a longer hold before adding weight.

Short Arc Quad

What Is the Short Arc Quad?

Short Arc Quad is an isolation exercise that primarily targets the quads, with the vastus medialis, vastus lateralis and rectus femoris working together to straighten the knee. It is a beginner-level movement done sitting or lying on the floor with a foam roller or a firmly rolled towel under one knee, lifting the heel until the leg is straight while the thigh stays resting on the roll.

The exercise trains the last part of knee straightening, the range that lets the knee lock out when you stand and walk. That range is often the first to go after knee surgery, a knee injury or a long spell of inactivity, which shows up as extensor lag: the knee can be pushed straight but the quads cannot finish the job on their own. Physical therapists use short arc quads early after knee replacement and ligament surgery, and in home programs for knee osteoarthritis. An EMG study of knee rehabilitation exercises found the vastus medialis and vastus lateralis were significantly more active in the last 15 degrees of a short-arc knee extension than earlier in the arc, which is why the pause with the knee fully straight is the part of the rep that counts.

The only load is the weight of the lower leg and foot, and the thigh stays supported throughout, so it is an easy entry point for older clients and for anyone who cannot yet load the knee standing up. The size of the roll sets the arc: a thicker roll bends the knee further and lengthens the lift, while a thinner one shortens it. Once full straightening is easy, a light ankle weight adds resistance, and seated long arc work such as the Band Seated Leg Extension or the Alternating Seated Leg Extension takes the knee through a much larger range.

If the heel will not lift at all, start with the Quad Set to learn to tighten the thigh, and pair it with the Straight Leg Raise as control improves. Focusing on the squeeze at the top, where the kneecap draws up toward the hip, helps clients who struggle to feel the quads switch on. Short arc quads are a stepping stone rather than an end point, and the strength they build is meant to carry over into standing work such as the Bodyweight Box Squat and the Step-Up.

Muscles Worked

MuscleActivation

Vastus Lateralis: Primary
Vastus Medialis: Primary
Rectus Femoris: High
Deltoid: Minimal
Triceps Brachii (Long Head): Minimal

Instructions

Sit on the floor with both legs straight out in front of you.
Lean back slightly and place your hands flat on the floor behind your hips, arms straight, to support your upper body.
Place a foam roller or a firmly rolled towel under the knee of the leg you are working, so the knee rests slightly bent and the heel touches the floor.
Let the other leg rest relaxed on the floor.
Tighten the front of your thigh and straighten the knee to lift your heel off the floor, keeping the back of the knee pressed into the roller.
Straighten the knee all the way until the leg forms a straight line, and hold for about 5 seconds while squeezing the thigh.
Lower the heel slowly back to the floor over about 2 seconds and relax the thigh before the next rep.
Complete 8 to 12 reps, then move the roller under the other knee and repeat.

Common Mistakes

Lifting the thigh off the roll
Raising the whole leg turns the movement into a hip lift, so keep the back of the knee pressed into the roll and let only the lower leg rise.
Stopping short of straight
Leaving the knee slightly bent at the top skips the final degrees of extension, which is the range this exercise exists to train.
Skipping the hold
Flicking the heel up and dropping it straight away gives the quads almost no work, so hold the straight knee for about 5 seconds on every rep.
Dropping the heel
Letting the leg fall back to the floor wastes the lowering half of the rep, so lower it slowly over about 2 seconds.
Using the wrong size roll
A roll that is too thin leaves almost no arc to work through, while one that is too thick bends the knee so far that the lift is hard to finish, so aim for a knee bend of roughly 20 to 30 degrees at the start.
Adding weight too early
Strapping on an ankle weight before the knee can straighten fully without it trades range for load, so earn the full lockout first.

Injuries

Short Arc Quad is a low risk exercise when performed with proper technique. The thigh stays supported on the roll, the knee moves through a small arc and the only load is the weight of the lower leg, so the joint is worked without bearing body weight.

The front of the knee is the usual complaint, and it mostly appears when ankle weights are added faster than the quads can handle them, so increase load in small steps and only once every rep reaches full straightening. Propping the upper body on straight arms for long sets can tire the wrists, shoulders and lower back; lying on your back with your head supported keeps the same leg movement and takes that strain away.

After knee surgery, follow the timeline your surgeon or physical therapist gives you. After ACL reconstruction in particular, the protocol sets when resisted knee straightening and ankle weights are allowed, because resistance at the ankle increases the pull on the ligament as the knee straightens. If the heel cannot lift yet, regress to the Quad Set; when the movement is easy, progress to an ankle weight, then to long arc work such as the Band Seated Leg Extension and standing exercises like the Bodyweight Box Squat.

Mild fatigue in the thigh is expected. Stop and check with a clinician if you feel sharp or catching pain in the knee, if the knee swells more after the session or the next day, or if pain keeps building from one session to the next.

Overview

Primary Focus: Quads
Equipment: Body weight and foam roller
Modality: Strength
Difficulty: Beginner

Alternative Exercises

Frequently Asked Questions

Q: Do I need a foam roller for short arc quads?: No. A firmly rolled bath towel, a rolled blanket or a small bolster works the same way, as long as it stays firm under the knee and keeps it bent roughly 20 to 30 degrees at the start.
Q: What is the difference between a short arc quad and a long arc quad?: A short arc quad works only the last part of knee straightening with the thigh resting on the floor, while a long arc quad is done sitting on a chair or bench and straightens the knee from about 90 degrees, a much bigger range. Most programs start with short arcs and progress to long arc work such as the Band Seated Leg Extension or the Alternating Seated Leg Extension.
Q: Does the short arc quad target the VMO?: It works the vastus medialis, but not on its own. A small EMG study of healthy adults found no significant difference between vastus medialis oblique and vastus lateralis activity during the short arc quad with the hip in a neutral position, so treat it as an exercise for the whole quadriceps.
Q: How do I make short arc quads harder?: Add a light ankle weight once you can straighten the knee fully and hold it for 5 seconds on every rep, then increase it in small steps. When that is easy, move on to long arc work and standing exercises such as the Bodyweight Box Squat or the Step-Up.
Q: Can I do short arc quads after knee replacement or ACL surgery?: They are a common early exercise after both, but your surgeon or physical therapist decides when to start and when to add weight. After ACL reconstruction, resisted knee straightening is introduced on a schedule because resistance at the ankle increases the pull on the ligament.
Q: How many reps and sets of short arc quads should I do?: A typical starting point is 8 to 12 slow reps per leg with a 5-second hold at the top, for 2 to 3 sets. Add reps or a longer hold before adding weight.