# Lying Side Straight Legs Reverse Crunch - Canonical: https://fitwill.app/exercise/10450/lying-side-straight-legs-reverse-crunch/ - Media ID: 10450 - Primary muscle: Abs - Body part: Core - Equipment: Body Weight - Video: https://fitwill.app/videos/10450/lying-side-straight-legs-reverse-crunch.mp4 ## Description The Lying Side Straight Legs Reverse Crunch is a floor-based core exercise that combines a lower-abdominal reverse crunch with a lateral bias, so the pelvis curls up and slightly toward one side instead of straight up. You lie on your back with your arms spread wide for stability, hold your legs straight and stacked, raise them to vertical, then lift your hips off the floor while steering your feet slightly sideways. The result is a movement that hits the lower fibers of the rectus abdominis while the obliques work to control and direct the angled path. This exercise suits anyone who has outgrown basic leg raises and wants to challenge the lower abs and waist without equipment. Because the legs stay straight, the lever is long, which makes the movement demanding on both the abdominals and the hip flexors. It is a common choice in bodyweight ab circuits, calisthenics warm-ups, and programs aimed at building control through the trunk rather than just chasing reps. The setup matters more than it looks. Lying flat on a mat with arms out at roughly shoulder height creates a wide base that stops you from rolling as the hips lift. Keeping the knees locked and the legs pressed together keeps the lever consistent from rep to rep, and starting from legs-vertical means the abs, not momentum from a big leg swing, drive the crunch. If the legs drift or the arms claw at the floor, the work shifts away from where you want it. To execute it well, think about peeling the hips off the floor rather than pushing the feet toward the ceiling. Exhale as the pelvis curls up and angles a few degrees to one side, pause briefly at the top when the lower back has clearly left the ground, then lower the hips back down with control before the legs come down. The range is short; a few honest inches of hip flexion off the floor beats a violent heave that uses swing instead of muscle. In practice, this movement works well as a mid-to-late set exercise when the abs are pre-fatigued, or in low-rep strength sets for people with a solid bracing foundation. Beginners should earn it first with bent-knee reverse crunches and standard straight-leg raises. Because the spine stays supported by the floor throughout, the main safety concerns are jerky reps, cranking the neck or shoulders, and letting the lower back slam down on the return, all of which are easy to fix by slowing the tempo. ## Instructions 1. Lie flat on your back on an exercise mat with your legs fully extended and pressed together, and your arms spread out to the sides at about shoulder height with palms down. 2. Raise your straight legs until they point at or near the ceiling, so your hips are bent to roughly 90 degrees; this is your starting position. 3. Brace your abdominals gently and press your upper back and arms into the floor to create a stable base before each rep. 4. Exhale and curl your hips up off the floor by pulling your pelvis toward your ribs, letting your straight legs travel a few degrees toward one side as you lift. 5. Continue the curl until your lower back has clearly lifted and your feet are stacked above or slightly past your lower ribs, keeping the knees locked the whole time. 6. Pause for a beat at the top and squeeze the lower abs and the oblique on the side you angled toward. 7. Inhale as you lower your hips back to the floor under control, keeping the legs vertical and together rather than dropping them toward your head. 8. Complete all reps on one side if you are targeting a specific oblique, or alternate sides rep by rep for balanced work. 9. When the set is finished, bend your knees, lower the legs slowly to the mat, and rest before standing up. ## Tips & Tricks - If your shoulders lift and your hands start clawing the floor, your base is too narrow or the rep is too fast; widen the arms slightly and slow the tempo so the upper body stays glued down. - A common mistake is swinging the legs from the hip to generate momentum. Fix it by pausing one second with legs vertical before every crunch, so the only way up is through the abs. - If your hamstrings pull and the knees bend, shorten the range slightly or regress to bent-knee reverse crunches for a few weeks; a straight-leg lever you cannot control is just teaching bad reps. - The angle toward the side should be a small tilt of the pelvis, not a big sideways sweep of the feet. If your legs travel far to the side, you are rolling the spine instead of crunching it. - Keep the neck relaxed and your gaze straight up. Craning the chin to watch your feet is a sign the rep is too hard or too fast. - Avoid letting the lower back drop and bounce off the mat on the return; the eccentric half of this exercise is where most of the control is built. - If the floor hurts your tailbone or spine, use a thicker mat, but not so thick that you wobble; a stable surface is part of the setup. - Breathe out sharply as the hips lift. Holding your breath through the whole crunch is a common habit that makes the obliques brace instead of move. - Progress by adding reps first, then by pausing two to three seconds at the top, before ever considering ankle weights. ## Frequently Asked Questions ### Which muscles does the Lying Side Straight Legs Reverse Crunch work? The primary movers are the lower fibers of the rectus abdominis, with the obliques on the side you angle toward working hard to steer and control the path. The hip flexors assist by holding the straight legs, and the deep core stabilizes the trunk throughout. ### Why do the legs need to stay straight instead of bent? Straight legs create a longer lever, which increases the demand on the lower abs and hip flexors. If you cannot keep the knees locked without swinging, the bent-knee version is the better starting point. ### Is the Lying Side Straight Legs Reverse Crunch suitable for beginners? It is better treated as an intermediate progression. Beginners should build up through bent-knee reverse crunches and standard lying leg raises first, since the straight-leg lever makes momentum and lower-back strain easy to slip into. ### How high should my hips come off the floor? Enough that your lower back clearly leaves the mat and your feet sit above or slightly past your lower ribs. The range is short by design; a few controlled inches of hip curl is a complete rep. ### Should I alternate sides or do all reps on one side? Alternating rep by rep works well for general core training, while completing all reps on one side before switching gives a stronger oblique-focused stimulus. Either approach is fine as long as both sides get equal volume. ### What is the most common mistake with this exercise? Swinging the legs or pushing the feet toward the ceiling instead of curling the pelvis. Both turn the movement into a hip-flexor swing. Pause with legs vertical before each rep and think about pulling the hips toward the ribs. ### Can I do the Lying Side Straight Legs Reverse Crunch without a mat? Yes, on carpet or any firm but padded surface. A mat is recommended because your spine and tailbone bear the repeated contact, especially on the lowering phase. ### What can I use as a substitution if this is too hard? Bent-knee reverse crunches with the same arm position are the closest easier substitute, followed by lying straight-leg raises with no hip curl. Both train the same lower-abdominal pattern with a shorter lever. ### Is it safe for my lower back? For most people, yes, because the floor supports the spine and the range is controlled. Keep the return slow, avoid bouncing the hips off the mat, and stop if you feel pinching or sharp discomfort rather than muscular effort. ### How many reps and sets should I do? Two to four sets of 8 to 15 controlled reps is a solid range, adjusting for how fatigued your abs already are. Quality of the hip curl matters far more than reaching a rep number.