Are Leg Extension Alternatives Viable?
Research substitutes for the leg extension, and you’ll find endless recommendations for compound free weight options like squats, lunges, and step-ups.
These exercises do work numerous muscles. The leg extension is certainly not a natural movement, and it can stress the knees. Nonetheless, from a bodybuilding perspective, this completely ignores its unique quad-building value.
Traditional front thigh exercises focus on the single-joint vasti, which includes the vastus medialis, vastus lateralis, and vastus intermedius. They overload these muscles at a strong position for overall active tension at the midrange, and therefore are rightfully known as mass builders. Other muscles like the glutes, hamstrings, and lower back get involved too.
Nonetheless, when hip extension occurs simultaneously with knee extension, the biarticulate rectus femoris muscle, attached to both the knee and the hip, will activate minimally. It facilitates smooth movement since it barely changes length instead.
A pure knee extension or done with countercurrent hip flexion is required to activate the rectus femoris. This impressive two-headed, V-shaped muscle etches fine detail into the upper front thigh.
Due to the flexed hip position while seated on a leg extension machine, even despite a seat adjustment, the rectus femoris lacks strength. Along with minimal range of motion for nearly all models at the knee, it lacks the tension possible through these leg extension alternatives…
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Good Leg Extension Alternatives
Bodybuilders can’t rely solely on squats to build the legs. True, the squat involves some hamstring action, some calf involvement, some sartorius, etc., but legs need more variety to pull them into real shape.
– Bob Paris
Many try to do an old-school barbell hack squat with heels elevated on a block in open space, with the weight behind you, but I find this limits the range of motion while not necessarily preventing hip extension.
You can use a hack squat machine at a gym, but even at home you can have your own hack squat setup by performing it next to a wall with limited friction.
Done properly, the wall prevents most hip extension, keeping you upright. By placing the shoulder blades against the wall and your feet as close to it as possible, while keeping the hips slightly forward, you ensure a purer knee extension.
A 2-inch wooden block may be helpful to elevate your heels, though you should allow them to lift up naturally as you descend.
Place the barbell or dumbbells across the cruces of your hips in front or even rest them on the upper quads. Though not ideal, this compression won’t affect the contraction, and this setup relies on far less weight than a machine hack squat. Smaller diameter plates like 25s may be needed to prevent them from hitting the wall.
The hack squat works fairly well since at the bottom of the movement, even with limited range of motion if needed, since it feels hardest with the knees furthest out. This is where the rectus femoris reaches an ideal medium length.
Unfortunately, even minimal hip extension can suppress rectus femoris involvement, which does occur on the hack squat.
This maximal knee bend allows the vasti to stretch. Any stretch can lead to more distal muscle growth near the knee since sarcomeres in-series are added. Growth near the knee draws the eye distally for an aesthetic physique.
This leg extension alternative has you extend the hips utmost as you descend, with the knees going beyond the toes, which really stretches the rectus femoris.
The more you drive the hips forward to extend the hips at the bottom, the greater stretch for the rectus femoris. As explained, this leads to more distal growth via overstretch. Active tension eventually shifts to this new longer length.
Due to this extreme position, you’ll require hip flexion to ascend. This involves unique motor units for the proximal or upper fibers of the rectus femoris.
This hip flexion combined with knee extension likely makes the sissy squat the best overall exercise for the rectus femoris.
Vince Gironda added a special movement called a burlesque bump to achieve a full range of motion. I’m unsure this is needed as his variation invites hip extension for a specific phase of the movement. This will reduce rectus femoris involvement.
Flexing During Exercises?
In his excellent bodybuilding guide Beyond Built, Bob Paris suggests flexing throughout the range of motion on all exercises. He argues, for example, that even raising the toes off the platform for a leg press to facilitate this will bring out separation of the front thigh, especially for the teardrop vastus medialis.
The leg extension does have unique value by overloading the lockout of the knee’s range of motion. This shortened state combines with constant tension for a cell swelling muscle-building stimulus. This may lead to more proximal growth for the quads region near the hip by maximizing intramuscular pressure.
Also, even though the muscle is often too short at the hip on the leg extension, the lack of any hip extension still ensures a high contribution from the rectus femoris.
Many bodybuilders feel the leg extension helps develops the teardrop-shaped vastus medialis, especially with the toes pointing out for a valgus position. This quad muscle may activate more near both the stretched and shortened endpoints for knee extension due to longer sarcomere lengths. The upper region of the vastus medialis could be better worked due to cell swelling as well.
A partial solution is to flex in the shortened position for any quadriceps exercise, and perhaps even throughout the whole range of motion. This is a bodybuilding trick of the trade that leads to greater development, focused on stressing the muscle, while using manual contractions for the range of motion less overloaded by external weight.
Bodybuilding Alternatives for Leg Extensions
The ideal quad exercise would involve a leg extension machine that didn’t limit the range of motion at the knee, yet allows you to lean back enough so that all muscles were hit optimally around 90°.
It’s important though not to equate best with perfect. Every exercise variation overloads a different portion of the range of motion, and regional hypertrophy studies and the experience of bodybuilders supports that each exercise is unique.
Returning to Bob Paris, he espoused the concept of equipping an armory, or forming a set of great exercises to rotate in and out for variety, also suggested modernly through Dante Trudel’s Doggcrapp (DC) training philosophy.
As hopefully clear now, the leg extension is a good exercise since it overloads the muscle uniquely. It may not be the most effective one, since it has a lower peak tension due to the flexed hip position while seated.
Steve Reeves possessed a well-developed rectus femoris yet rarely did leg extensions. He focused on hack squats, often using a special belt apparatus while elevating the heels. He included front squats and parallel-depth back squats on a block, with lunges occasionally, to develop his vasti.
As a warning, hack and sissy squats are far tougher on the knees than common exercises. The pure knee bend increases shear over compression force. It’s likely even worse than leg extensions, so make sure to warm up with light-weight reps and a limited range of motion.
Nonetheless, more conventional squats alone cannot be the answer to fuller quad development. Consider the hack squat, the sissy squat, and flexing throughout the range of motion, especially at the top, as leg extension alternatives. Realize that as a bodybuilder, no exercise is perfect; the leg extension is still valuable despite the alternatives.