# Seated Diagonal Knee Raise On Bench - Canonical: https://fitwill.app/exercise/7805/seated-diagonal-knee-raise-on-bench/ - Media ID: 7805 - Primary muscle: Abs - Body part: Core - Equipment: Flat Bench - Video: https://fitwill.app/videos/7805/seated-diagonal-knee-raise-on-bench.mp4 ## Description The Seated Diagonal Knee Raise On Bench is a bodyweight core exercise performed from the edge of a flat bench. You sit near the end of the bench, lean your torso back to roughly a 45-degree angle, and grip the sides of the bench behind your hips for support. With your legs extended straight out in front of you and your feet off the floor, you draw your knees in toward one shoulder, lower them back to the extended position, and repeat toward the opposite shoulder. That diagonal path is what separates this from a standard seated knee raise and places extra demand on the obliques alongside the lower abdominals. This movement trains the rectus abdominis with strong involvement from the deep hip flexors, which lift the thighs, and the obliques, which control the rotational angle of each knee drive. Because your hands anchor you to the bench and your feet never touch the floor, your trunk has to stay rigid the entire time. That constant bracing is a big part of the value here, especially for anyone whose core tends to collapse the moment a lift gets hard. The setup matters more than it looks. Leaning back too far turns this into a hip flexor exercise with very little abdominal work, while sitting too upright removes the lever length that makes the extended-leg position challenging. Your grip on the bench is also doing real work: it stabilizes your shoulders and lets you tilt the pelvis slightly under at the top of each raise, which is where the abdominal contraction actually happens. To perform it well, keep your chest lifted and shoulders down as you lean back, avoid shrugging into your ears, and move your knees toward the shoulder rather than straight up. Pause briefly when your knees are closest to your chest, then extend the legs back out slowly so your feet do not drop or swing. Alternating sides each rep keeps the workload even and helps you notice if one side rotates better than the other. This exercise suits lifters who have outgrown floor leg raises and want a harder hip-flexion bias without hanging from a bar. It is also a practical option for people whose shoulders or grip struggle with hanging knee raises, since the bench supports your upper body throughout. It fits well at the end of an ab session or as a mid-workout core block, and it can be scaled by bending the knees more on the raise or by limiting how far the legs extend between reps. ## Instructions 1. Sit sideways-centered on a flat bench and scoot forward so only your glutes rest on the edge, with the length of the bench behind you. 2. Place both hands on the sides of the bench just outside your hips, fingers pointing forward or slightly inward, and press down to take weight off your spine. 3. Lean your torso back to about 45 degrees and extend both legs straight out in front of you, lifting your feet off the floor until your hips are fully open and your legs hover above the ground. 4. Pull your shoulders down away from your ears and brace your abdominal wall as if preparing for a light punch to the stomach. 5. Exhale and draw both knees in toward your right shoulder, letting the pelvis tilt under as your thighs approach your chest so your lower back rounds slightly. 6. Pause for a beat at the top, then slowly extend your legs back out to the straight, hovering position without letting your feet touch the floor. 7. Repeat the knee raise toward your left shoulder, and continue alternating sides for the desired number of total repetitions. 8. Keep breathing steadily: exhale on each knee drive, inhale on the controlled extension. 9. Between sets, set your feet down fully and shake out your grip before resetting your lean-back angle for the next set. ## Tips & Tricks - If your feet drop toward the floor between reps, shorten the range: extend the legs only partway out so your core stays loaded instead of your hip joints hanging loose. - Aim your knees at the shoulder, not at your chest. Straight knee raises on the bench train mostly hip flexors; the diagonal angle is what pulls the obliques into the work. - Do not sink into your shoulders. If your traps start creeping up and your neck feels loaded, press harder through your palms and lift your chest before continuing. - Avoid swinging your legs out and snapping them back in. The out-phase is where most of the abdominal control is built, so take two to three seconds to extend. - Keep your glutes planted on the bench edge. If your pelvis slides forward as you tire, you will lose the lean-back angle and the set becomes much easier for the wrong reasons. - Slight rounding of the lower back at the top of each raise is helpful; a full backward slump of the torso is not. Stop the lean at the angle where you can still keep your ribs down. - If your grip gives out before your abs do, chalk your hands or place a folded towel over the bench edge to increase friction. - Start with your knees slightly bent if the straight-leg version causes your thighs to cramp; hip flexor cramping is common in the first few sessions of this position. - Alternate sides every rep rather than doing all reps on one side, so you can catch a left-right imbalance in rotation early. ## Frequently Asked Questions ### What muscles does the Seated Diagonal Knee Raise On Bench work? The lower abdominals and deep hip flexors do most of the lifting, while the obliques work to control the diagonal direction of each knee drive. The shoulders and arms contribute only as stabilizers through your grip on the bench. ### Why do the knees go toward the shoulder instead of straight up in this exercise? The diagonal path adds trunk rotation to the hip flexion, which recruits the obliques far more than a straight seated knee raise. It also lets each side of the abs work through a longer range. ### Can beginners do the Seated Diagonal Knee Raise On Bench? Yes, but beginners should keep the knees bent throughout and extend the legs only partially between reps. Mastering the lean-back angle and braced torso matters more before adding the straight-leg position. ### How far back should I lean on the bench? About 45 degrees is a good starting point. If you lean back much farther, the hip flexors take over and your lower back arches; too upright and the extended-leg position loses its difficulty. ### My feet keep dropping to the floor between reps. What should I change? Shorten the extension phase so your legs only straighten partway, and slow the return down. Feet dropping usually means the legs are moving faster than your core can control, not that you need more effort. ### Is this exercise a good substitute for hanging knee raises? It is one of the best ones, since it trains the same hip-flexion and lower-abdominal pattern without loading the shoulders or requiring grip strength to hang. The bench support also makes it easier to keep the ribcage down. ### Should I do all repetitions on one side first or alternate? Alternate rep by rep. This keeps the obliques evenly loaded and makes any side-to-side difference in rotation obvious so you can address it rather than hide it. ### Why do my hip flexors cramp during the Seated Diagonal Knee Raise On Bench? The fully extended, hovering leg position puts the hip flexors under constant tension, which can cramp when they are unaccustomed to it. Bend the knees slightly, reduce the hold time at the top, and build up gradually. ### How many reps should I aim for? Because the movement is controlled and bodyweight-only, sets of 10 to 20 total alternating reps work well. Stop the set when your feet start dropping or your torso begins to slump forward. ### Is it safe for my lower back? When you keep the lean-back angle moderate and let the pelvis tilt under at the top of each raise, the spine stays supported. If you feel pinching or arching in the lower back, sit up slightly and reduce how far the legs extend.