The curl-up test measures abdominal muscular endurance, not strength. It assesses how long your abdominal muscles can perform repeated contractions before fatiguing. This makes it different from exercises that test how much force your abs can produce in a single effort. The test is widely used in school fitness programs, military assessments, and personal training to gauge core stamina.
What the Test Actually Measures
The curl-up test targets the endurance of your trunk flexor muscles, primarily the rectus abdominis (the “six-pack” muscle) and the deeper stabilizing muscles of your core. You perform slow, controlled partial sit-ups at a set pace, and your score is the number of repetitions you complete before you can no longer keep up or lose proper form.
An important distinction: the test does not measure abdominal strength. Research published in the Journal of Strength and Conditioning Research found no significant correlation between curl-up scores and isometric trunk flexor strength when tested on a laboratory machine. The correlations ranged from weak to essentially zero. What the test captures is your muscles’ ability to keep working over time, which is a separate fitness quality from raw force production.
How the Test Works
There are several versions of the curl-up test, but most follow the same basic structure. You lie on your back with your knees bent, feet flat on the floor, and arms at your sides. Two strips of tape (or a measuring strip) are placed on the mat beneath you. Your fingertips start on the near edge of tape, and each repetition requires you to slide your fingers forward to the far edge, then return. The distance between the strips is typically 12 cm for people under 45 and 8 cm for those 45 and older, which keeps the movement in a controlled, partial range of motion (roughly 30 degrees of spinal flexion).
A metronome is set to 40 beats per minute, and you perform one curl-up every three seconds: up on one beat, down on the next. The test continues until you either can’t maintain the pace, lose proper form, or reach the maximum number of repetitions (which varies by protocol). Some versions use a timed format, such as 60 or 90 seconds, where you count total reps instead.
Equipment is minimal: a mat, a metronome or timer, and something to mark the sliding distance (tape, Velcro strips, or a cardboard measuring strip). This simplicity is one reason the test is so common in schools and gyms.
Why Endurance Matters More Than Strength
The curl-up test was designed around the idea that abdominal endurance is more relevant to everyday health than peak abdominal strength. Your core muscles spend most of the day performing low-level, sustained contractions to keep your torso stable while you sit, stand, walk, and lift. That’s an endurance task, not a strength task. Programs like FitnessGram (used in U.S. schools) and the Canadian Physical Activity, Fitness & Lifestyle Approach chose curl-ups specifically because they reflect this type of functional demand.
The slow, controlled pace of the test also keeps hip flexor involvement low. Traditional full sit-ups tend to shift the work toward the hip flexors as you fatigue, which makes the test less accurate as a measure of abdominal fitness. The partial range of motion in the curl-up keeps the focus on the abs.
How Accurate Is the Test?
The curl-up test is a reasonable field test, but it has real limitations. In a study of college-aged men and women, the timed bench trunk-curl version correlated moderately with lab-measured abdominal endurance, with correlation values around 0.50 for men and 0.46 for women. That means the test and the lab measurement shared only about 25% of their variance. In plain terms, the test captures some of what’s happening with your abdominal endurance, but a lot of your score is influenced by other factors like technique, motivation, and body proportions.
The standard modified curl-up (the version most commonly used in schools) showed even weaker correlations with lab-measured endurance. Researchers attributed this to a ceiling effect: the test is easy enough that many people max it out, which makes it hard to distinguish between someone with good endurance and someone with excellent endurance. If you’re reasonably fit, you may hit the maximum and never learn where your actual limit is.
This doesn’t mean the test is useless. It’s a practical, no-equipment way to get a general snapshot of core endurance. But fitness standards and “healthy zones” based on curl-up scores should be taken as rough guidelines, not precise measurements.
Spinal Load During the Test
One common concern with any abdominal exercise is the force placed on the lower back. Biomechanical modeling has quantified the lumbar compressive and shear forces during different curl-up variations. The standard flat-back (longlaying) position produces the highest spinal loads. Bending your knees (hooklaying position) reduces shear forces on the spine by 39 to 46% but barely changes compressive forces, cutting them by only 4 to 5%.
The bench curl-up, where your calves rest on a bench with hips and knees at roughly 90 degrees, is the gentlest option. It reduces compressive forces by 17 to 18% and shear forces by 87 to 97% compared to the flat-back version. If you have a history of lower back issues, this variation places significantly less stress on the lumbar spine.
For most people with healthy backs, the standard knees-bent curl-up is safe. The partial range of motion and slow pace keep forces well below what a full sit-up generates. But the test isn’t ideal for anyone currently dealing with disc injuries, acute back pain, or conditions that make repeated spinal flexion problematic.
Common Versions of the Test
- FitnessGram curl-up: Used in U.S. schools for children and adolescents. Performed at a set cadence (one rep every three seconds) with a measuring strip to control range of motion. The test ends at 75 repetitions or when the student falls behind the pace twice.
- Canadian trunk curl (modified): Similar setup with a slow cadence and 30-degree range of motion. Commonly used in adult fitness appraisals.
- Timed bench trunk-curl: Performed for 60 or 90 seconds with calves on a bench. This version showed the strongest correlation with lab-measured endurance in research and places the least stress on the spine.
- Military-style timed sit-ups: Some military fitness tests still use full sit-ups rather than partial curl-ups, which is a different test measuring a different combination of abdominal and hip flexor endurance.
How to Interpret Your Score
Scoring depends entirely on which version of the test you take and which norms you’re comparing against. FitnessGram uses “Healthy Fitness Zones” that vary by age and sex. For example, a 15-year-old male typically needs to complete 24 to 75 curl-ups to fall within the healthy zone, while a 15-year-old female needs 18 to 75. These cutoffs are meant to represent a level of abdominal endurance associated with general health, not athletic performance.
For adults, norms are less standardized. Many personal trainers use tables that break scores into categories (below average, average, above average, excellent) by age decade and sex. A 30-year-old completing 30 to 40 curl-ups in one minute is generally rated as average, though the exact number depends on the protocol. Because of the ceiling effect mentioned earlier, scores at the high end don’t differentiate well between fit and very fit individuals.
The most useful way to use your score is as a personal baseline. Test yourself, train your core for several weeks, then retest under the same conditions. Improvement over time is a more meaningful indicator than comparing yourself to a norm table, especially given the test’s moderate accuracy.