Learn how to do leg raises correctly: proper form, hanging and lying variations, muscles targeted, and evidence-based benefits for core and hip flexor strength.
The leg raise is one of the most effective exercises for challenging the anterior core and developing hip flexor strength simultaneously — yet it is also one of the most commonly performed incorrectly. The exercise appears straightforward: lie down, raise the legs, lower them. The reality is more nuanced. The key variable that determines whether the leg raise is training the abdominal muscles or simply the hip flexors is a single mechanical position: the contact of the lower back with the floor. When the lower back remains in contact with the floor throughout the movement, the abdominals must work isometrically to stabilize the lumbar spine against the significant gravitational torque created by the legs — particularly when they are close to horizontal. The moment the lower back arches and lifts off the surface, the hip flexors take over, the lumbar spine is placed in passive hyperextension, and the abdominal training stimulus is substantially reduced. According to the Ainsworth et al. (2011) Compendium (PMID 21681120), leg raises and similar core exercises have a MET value in the range of approximately 3.0, placing them in the light-to-moderate intensity category — their primary value is neuromuscular, not cardiovascular. The Physical Activity Guidelines for Americans (2nd edition) identify muscular endurance training as an important component of complete physical fitness. This guide explains precise lying and hanging technique, the full muscle activation profile, evidence-based progressions, and common errors that reduce the exercise’s effectiveness or increase injury risk.
The lying leg raise is the foundational version of the exercise. The mechanics are straightforward, but the execution demands consistent attention to the lumbar spine position throughout every repetition.
Begin by lying flat on a firm surface — a mat on a hard floor is ideal. A soft or highly cushioned surface makes it difficult to feel the lower back position clearly. Place your arms at your sides, palms facing down or under the buttocks for those who need extra lumbar support at first. Extend both legs fully, feet together or hip-width apart. If your hamstrings are tight and maintaining fully straight legs is uncomfortable, a slight soft bend at the knees is acceptable — but progressively work toward straight legs as flexibility improves.
The setup cue that matters most: press the lower back firmly into the floor. Use your palms-down hands to feel whether the lumbar spine is in contact with the mat. For many people, this requires a small posterior pelvic tilt — tucking the pelvis slightly to flatten the lumbar curve. If you feel a gap between your lower back and the floor in the starting position, the exercise will almost certainly lose lumbar contact during the lowering phase, which is the most demanding part.
Exhale and engage the core — draw the navel gently but firmly toward the spine to activate the transverse abdominis. This pre-activation is the critical preparatory step. Then, keeping both legs straight and together, raise them toward vertical. The target is 90 degrees (legs perpendicular to the floor), but the exact endpoint matters less than maintaining the lower back flat throughout. Breathe steadily — do not hold the breath.
At the top, briefly pause — one second is sufficient — then begin the controlled lowering. The eccentric phase is where the majority of the abdominal challenge occurs. As the legs descend toward horizontal, the gravitational torque on the pelvis increases progressively. The abdominals must generate increasing force to resist the lumbar extension moment. Lower the legs slowly, maintaining continuous lower back contact with the floor, until the feet are 2–4 inches above the surface. The closer the legs are to horizontal, the greater the demand on the abdominal musculature. Stop there — do not rest the feet on the floor between repetitions. Hold that position briefly and begin the next repetition.
For beginners who cannot maintain lumbar contact throughout the full range, a practical modification is to stop the lowering phase at the point where the lower back begins to lift — say 30–45 degrees above horizontal — and only progress the range as abdominal endurance improves. This progressive range approach is consistent with the ACSM position stand (Garber et al., 2011, PMID 21694556), which identifies controlled progressive overload as the mechanism for building muscular strength and endurance.
According to ACSM (2011), movement quality and progressive demand are what turn an exercise into a useful stimulus. HHS (2011) supports that same principle, which is why execution, range of motion, and repeatable loading matter more than novelty here.
Bent-knee leg raise (beginner). Perform the entire movement with the knees bent at 90 degrees, bringing the thighs to vertical while keeping the lower legs parallel to the floor. Bending the knees shortens the lever arm dramatically, reducing the torque at the hip and making lumbar stabilization significantly easier. This is the appropriate starting point for anyone who cannot maintain lumbar contact with straight legs.
Straight-leg lying raise (foundational). The standard version as described in the form guide. This is the baseline exercise once bent-knee raises are mastered and lumbar contact can be maintained throughout.
Single-leg raise (intermediate). Raise one leg to vertical while the other leg hovers 2–4 inches above the floor. Alternate legs each repetition. The single-leg version maintains the core challenge while reducing the bilateral torque — useful for individuals with hip flexor asymmetry or as a bridge between bent-knee and straight-leg bilateral raises.
Leg raise with hip lift (intermediate). At the top of the straight-leg raise, continue the movement by pressing the lower back into the floor and lifting the hips 2–3 inches off the floor, curling the tailbone upward. This reverse-crunch component at the top of the leg raise adds a hip flexion demand and challenges the lower rectus abdominis through a fuller range of motion. Lower the hips first, then the legs. Schoenfeld et al. (2015, PMID 25853914) support the principle that variation in range of motion and movement pattern produces more comprehensive muscular activation.
Flutter kick (advanced). Rather than raising both legs simultaneously, perform alternating small-amplitude kicks with both legs, keeping them close to horizontal. This exercise — described in detail in the flutter kick guide — applies a different challenge: sustained isometric lumbar stabilization combined with rhythmic hip flexion.
Hanging leg raise (advanced). Using a pull-up bar or hanging straps, hang with arms fully extended and perform the leg raise by bringing the knees to the chest (beginner hanging version) or raising straight legs to horizontal or higher (advanced). The hanging version removes lumbar floor support entirely and adds a significant grip and shoulder stabilization challenge. The Schoenfeld, Ogborn, and Krieger (2017, PMID 27433992) volume dose-response analysis supports progressive increases in exercise complexity as a method of continued adaptation beyond basic bodyweight variations.
Hip flexors: primary movers. The iliopsoas (iliacus plus psoas major) and rectus femoris are the primary muscles generating the hip flexion that raises the legs from horizontal to vertical. These muscles are often tight and undertrained in sedentary populations — the leg raise directly addresses both issues by training them through a functional range of motion. The Ainsworth et al. (2011, PMID 21681120) Compendium classifies this movement profile as a moderate-intensity exercise.
Rectus abdominis (lower emphasis): isometric stabilizer. The rectus abdominis works isometrically throughout the leg raise, generating force to resist the lumbar extension moment created by the descending legs. The lower portion of the rectus abdominis — the fibers closest to the pubic crest — are more mechanically involved in resisting this torque than the upper portions. This is why the leg raise is commonly categorized as a “lower abs” exercise, though the rectus abdominis is anatomically a single muscle. Westcott (2012, PMID 22777332) documents that targeted training of specific muscle groups produces progressive strength adaptations, supporting the use of complementary exercises that train the same muscle through different mechanical demands.
Transverse abdominis: deep stabilizer. The transverse abdominis maintains lumbar compression and stiffness throughout the movement. Its role is to protect the lumbar spine from the shear forces generated by the leg raise — making pre-activation of this muscle through navel-to-spine engagement before each set a non-negotiable technique requirement.
Tensor fasciae latae and sartorius. These secondary hip flexors assist the iliopsoas during the raising phase, particularly when the legs are near horizontal. Their contribution is greater in straight-leg variations than in bent-knee versions.
Erector spinae: isometric antagonists. The erectors must resist the tendency toward lumbar flexion at the top of the movement (when legs are vertical) and must control lumbar extension during the lowering phase. Their isometric co-activation contributes to overall spinal stability.
Mistake 1: Lower back lifting off the floor. The most common and consequential error. When the lower back arches away from the floor during the lowering phase, the lumbar spine enters passive hyperextension, the hip flexors take over from the abdominals, and the exercise’s core training value is lost. Fix: press the palms into the floor and consciously maintain lumbar contact throughout. Reduce the range of motion — stop lowering the legs when the back begins to lift — and expand the range only as abdominal endurance improves.
Mistake 2: Using momentum. Swinging the legs up rapidly and then letting them drop uses kinetic energy rather than muscular force. Fix: control the speed of both the raising and lowering phases. A 2-second up, 2-second down tempo prevents momentum substitution.
Mistake 3: Holding the breath. Apnea during leg raises is extremely common and creates temporary stabilization through the Valsalva maneuver rather than through trained muscular endurance. Fix: exhale on the way up, inhale on the way down. Establish this breathing pattern before the set and maintain it throughout.
Mistake 4: Performing with tight hamstrings. Very tight hamstrings make fully straight-leg raises uncomfortable and often cause compensatory pelvic tilting. Fix: allow a slight knee bend until hamstring flexibility improves. Work on hamstring stretching as a separate component of your program.
Mistake 5: Resting feet on the floor between reps. Touching the floor between every repetition eliminates the constant-tension component of the exercise and allows the abdominals to relax completely. Fix: stop 2–4 inches above the floor between reps. Lower all the way only to rest between sets.
Mistake 6: Stopping short at the top. Some practitioners raise the legs only to 45–60 degrees. While partial-range raises are not harmful, they reduce the exercise’s effectiveness. Fix: raise legs to vertical (90 degrees) unless a specific structural limitation prevents it.
The practical value of this section is dose control. American College of Sports (n.d.) supports the weekly target underneath the recommendation, while Effects of low (n.d.) is useful for understanding the recovery cost that sits behind it. The plan works best when each session leaves you capable of repeating the format on schedule, with technique still stable and motivation intact. If output collapses, soreness spills into the next key day, or life logistics make the routine fragile, the smarter move is to hold volume steady or simplify the format rather than forcing paper progress that does not survive the week.
Physical Activity Guidelines for (n.d.) is a useful cross-check because it keeps the recommendation anchored to week-level outcomes rather than to a single impressive session. If the adjustment improves scheduling, exercise quality, and repeatability at the same time, it is probably moving the plan in the right direction.
One practical filter is to track just one controllable variable from “Common Leg Raise Mistakes and How to Fix Them” for the next 1 to 2 weeks. American College of Sports (n.d.) and Physical Activity Guidelines for (n.d.) both suggest that simple, repeatable progress beats constant novelty, so keep the structure stable long enough to see whether output, technique, or recovery actually improves.
Effects of low (n.d.) is also a useful reality check for claims that sound advanced without changing the actual training signal. If the method does not make it clearer what to repeat, what to progress, or what to scale back, its sophistication matters less than its marketing.
American College of Sports (n.d.) is the source that keeps this recommendation tied to measurable outcomes rather than preference alone. Once the reader can connect the advice to dose, response, and repeatability, the section becomes much easier to trust and apply.
According to Resistance training is medicine (n.d.), this point only becomes truly useful when readers can tie it to a clear dose, an observable signal, and repetition across several weeks instead of treating it as an interesting idea. That shift is what turns theory into a training decision.
Hip flexor strength and functional mobility. The hip flexors are among the most functionally important muscle groups for ambulation, stair climbing, and athletic movement — yet they are consistently weak and tight in sedentary populations. Leg raises train the hip flexors through a controlled range of motion, which may help develop strength and maintain flexibility concurrently. The ACSM position stand (Garber et al., 2011, PMID 21694556) identifies muscular fitness as a health-related component of physical fitness with direct implications for functional independence.
Lower abdominal strength and endurance. The leg raise produces meaningful isometric demand on the lower rectus abdominis and transverse abdominis — muscles that contribute to lumbar stability and are undertrained by crunches alone. Regular training of this movement pattern may contribute to reduced lower back fatigue during sustained activities. Westcott (2012, PMID 22777332) documents that consistent resistance training produces progressive strength gains in targeted muscle groups, supporting the case for using leg raises as a complement to flexion-based abdominal exercises.
Core stability transfer. The ability to maintain a stable, neutral lumbar spine while the legs move through a large arc is a fundamental component of core stability — one that transfers to compound movements like deadlifts, squats, and overhead pressing. Schoenfeld et al. (2015, PMID 25853914) identify neuromuscular control and load tolerance as interrelated outcomes of consistent resistance training. The leg raise trains exactly this anti-extension stability under dynamic leg loading.
Complement to crunch-focused training. The crunch trains the rectus abdominis through spinal flexion; the leg raise trains it isometrically through hip flexion. Together, they address different portions of the rectus abdominis activation profile and different functional demands. The Physical Activity Guidelines for Americans (2nd edition) recommend a varied approach to muscular fitness training, which supports programming both exercises within a complete core routine.
The practical value of this section is dose control. American College of Sports (n.d.) supports the weekly target underneath the recommendation, while Effects of low (n.d.) is useful for understanding the recovery cost that sits behind it. The plan works best when each session leaves you capable of repeating the format on schedule, with technique still stable and motivation intact. If output collapses, soreness spills into the next key day, or life logistics make the routine fragile, the smarter move is to hold volume steady or simplify the format rather than forcing paper progress that does not survive the week.
This article is for informational purposes only and does not substitute professional medical advice. Consult a physician before beginning a new exercise program, particularly if you have a history of lower back pain, hip flexor tightness, or lumbar disc conditions. If you experience lower back pain (distinct from normal muscular effort) during the exercise, stop immediately and consult a healthcare professional.
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Progressive resistance training of the core musculature — including hip flexion exercises that challenge the lower abdominal region — builds muscular endurance and functional stability that transfers directly to compound movements and daily functional tasks.
3 questions answered
The term "lower abs" is a simplification. The rectus abdominis is one continuous muscle. However, leg raises do bias activation toward the lower portion of the rectus abdominis compared to crunches, making them a valuable complement in a complete core program.
Yes, when performed with proper lower back contact and controlled tempo. Leg raises challenge both the hip flexors and the abdominal muscles isometrically, which builds the muscular endurance needed for functional stability.
Crunches move the upper body toward the hips (spinal flexion). Leg raises move the hips toward the upper body (hip flexion with isometric core stabilization). They are complementary exercises that train different portions of the anterior chain.