Active Straight Leg Raise Test (ASLR): Flexibility and Core Control

The Active Straight Leg Raise (ASLR) is one of those tests that look simple but hide a lot of information: at first glance it measures how high a straight leg goes, but it's actually evaluating posterior chain flexibility and, at the same time, the ability to keep the pelvis and trunk stable during that movement. That's why it's part of the Functional Movement Screen and is widely used in assessing lumbopelvic pain.

If you only look at how many degrees the leg rises, you're missing half the test.

What does this test measure?

The ASLR measures two things at once:

• Hamstring and posterior chain flexibility, similar to the AKE, but with the leg straight instead of the hip and knee at 90°
• Motor control and lumbopelvic stability: the ability to raise one leg without the pelvis rotating, without the opposite leg moving, and without compensating through the lower back

In other words, a "low" result in degrees could be due to a lack of flexibility, but it could also mean the person can't stabilize the pelvis and "brakes" the movement for safety.

Equipment needed

• A flat surface where the subject can lie supine
• Goniometer or inclinometer
• Optional: a board or rod to place under the opposite leg to detect compensations

Execution protocol

1. The subject lies supine, both legs extended and relaxed, head resting on the surface
2. Ask them to actively raise one leg, keeping the knee extended, as high as possible
3. The opposite leg and the pelvis must remain still and in contact with the table
4. During the movement, observe:

- Whether the pelvis rotates or one side lifts - Whether the opposite leg flexes or lifts off the table - Whether lumbar compensation appears (hyperextension or flexion)

1. Measure the angle between the raised leg and the table at the point where the first compensation appears (not the maximum range "at any cost")
2. Repeat with the other leg and compare

Common mistakes

• Measuring the maximum angle even when pelvic or lumbar compensation occurs (this overestimates real flexibility)
• Not visually fixing the opposite leg and pelvis
• Confusing this test with the AKE: here the hip isn't pre-set at 90°, the movement is free
• Not recording the motor control component, only the degree of elevation

How to interpret the result

Result	Interpretation
Elevation ≥ 70-80° without pelvic/lumbar compensation	Good flexibility and control
Elevation 50-70° without compensation	Acceptable flexibility/control, functional range
Elevation < 50° or pelvic compensation appearing before 50°	Significant limitation — determine whether it's due to flexibility (hamstrings) or lack of motor control
Marked asymmetry between legs	Also review in the context of lumbopelvic pain

The ASLR is also used as a screening test in the FMS and as an assessment tool in patients with pregnancy-related lumbopelvic pain (where an unstable pelvis tends to produce low results on both legs).

Relationship with other tests

• Active Knee Extension test (AKE) — if you want to isolate hamstring flexibility without the motor control component, the AKE is the best comparative reference
• Functional Movement Screen test — the ASLR is one of the seven patterns assessed in the FMS

Track both components

Since the ASLR mixes flexibility and motor control, it's worth recording both the degree achieved and whether compensation occurred. In Movalytics you can log both values at each assessment and see whether, with training, control improves first (less compensation at the same range) or flexibility (more degrees), helping you adjust the program's focus.

Frequently asked questions

Is the ASLR the same as the AKE? No. The AKE isolates hamstring flexibility by fixing the hip at 90°, while the ASLR evaluates a free leg-raise movement, combining flexibility and core/pelvis motor control. Does a low result always mean tight hamstrings? Not necessarily. It can be due to a lack of lumbopelvic control. That's why it's worth comparing with the AKE: if the AKE is normal but the ASLR is low, the issue is likely motor control, not flexibility. Is it used for anything besides sports assessment? Yes, it's a common test in physical therapy for assessing lumbopelvic pain, including pregnancy-related posterior pelvic pain.