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If you are building out abs training, the Crunch (straight Leg Up) is a beginner-level option that uses bodyweight. Mechanically, the target muscles flex the spine and brace the trunk — the reason this exercise carries over to trunk stability and force transfer. It sits in the calisthenics category, so the emphasis falls on movement quality and repeatable output. Note the 'Crunch straight Leg' component of the name: it specifies how this variation differs from otherwise similar abs movements. Support comes from the hip flexors and obliques; the hip flexors in particular help draw the thigh toward the torso, which is why fatigue there often shows up before the abs is fully worked. Training this with bodyweight needs no equipment at all and can be done virtually anywhere, though it is harder to load progressively once you outgrow it. Programme it alongside your other abs work rather than as a standalone. The pattern is accessible enough to learn in a single session, which makes it a sound entry point before progressing to heavier or more complex variations.
The Crunch (straight Leg Up) is primarily a abdominals exercise, but it is never only the abdominals doing the work.
The general rule for the Crunch (straight Leg Up) is simple: establish a steady breathing rhythm matched to your cadence. Keep the breath flowing continuously — there is no need to hold pressure in this pattern. If your breathing falls apart, it is usually the first sign the set has gone past useful.
Shorten the range of motion to the portion you can control, then extend it as confidence builds. Stay at this level until every Crunch (straight Leg Up) rep looks the same as the first.
Add load in small increments while holding the same tempo and range you established. Track your Crunch (straight Leg Up) numbers so you can see whether the abs is actually progressing.
Add a drop set on the last working set to extend the stimulus beyond your normal stopping point. Use the Crunch (straight Leg Up) as your accessory once your main abs lift is done for the day.
The Crunch (straight Leg Up) suits most healthy trainees, but it is not appropriate for everyone.
This is general educational information, not medical advice. If you are managing an injury or medical condition, check with a qualified professional before adding this exercise to your programme.
It primarily trains the abdominals, with the hip flexors and obliques assisting. The pattern is classified as cardio, so the the working muscles plus your cardiovascular system share the workload.
Yes. It is rated beginner-level, and the pattern can usually be learned in a single session with light resistance.
A practical starting point is 3 sets of 6-8, resting 2-3 min between sets, roughly 2x per week. Adjust from there based on how you recover.
You need bodyweight. This needs no equipment at all and can be done virtually anywhere, though it is harder to load progressively once you outgrow it.
As a general rule, establish a steady breathing rhythm matched to your cadence. Avoid holding your breath for the entire set.
Starting far too hard and losing form as fatigue accumulates. The simplest correction is to settle into a repeatable rhythm you can hold for the full interval.
Good substitutes that train the same abs pattern include Hold The World Med Ball, Air Swing Side To Side Swing, and Ball Sit-up. Pick whichever matches the equipment you have available.
About 2x per week suits most people. Recovery, not frequency, is what limits progress.
The Crunch (straight Leg Up) fits into that picture as a beginner option using bodyweight, leaning on the hip flexors and obliques alongside the abs.
The core is far more than a visible six-pack. It is a coordinated group of muscles that includes the rectus abdominis — the long muscle that creates the six-pack appearance and flexes the spine — the internal and external obliques on the sides that rotate and bend the torso, and the deep transverse abdominis that wraps around the midsection like a belt to stabilise the spine and protect the lower back.
Effective core training works all of these functions rather than relying on endless crunches. Flexion exercises such as crunches, sit-ups, and hanging leg raises target the rectus abdominis and are excellent for building visible abdominal muscle. Rotational and anti-rotation work such as Russian twists and cable woodchops develops the obliques and the ability to resist twisting forces. Bracing and isometric holds like the plank and its variations train the deep stabilisers that give you a strong, protected midsection during heavy lifts and everyday movement.
Because the core is involved in stabilising almost every compound lift, it already gets significant indirect work from squats, deadlifts, and overhead presses. Direct ab training a few times per week, with a mix of weighted flexion work in the 8 to 15 range and longer isometric holds, is enough for most people to build a strong, defined midsection. Adding resistance to ab exercises over time is just as important as it is for any other muscle.
The most important thing to understand about abs is that visibility is primarily a function of body-fat level, not the number of crunches you do. You can build thick, strong abdominal muscles, but they will only show when body fat is low enough, which is achieved through nutrition and overall training rather than spot reduction. There is no exercise that burns fat from the stomach specifically. Focus ab training on building and strengthening the muscles, and rely on a sensible diet and full-body activity to reveal them.
A strong core improves posture, protects the lower back, transfers force between the upper and lower body, and underpins performance in virtually every sport and lift. Train it deliberately using the popular core exercises below.