Finding one side more flexible than the other is the most common result in any per-side test, and the least well explained anywhere. Almost everyone is asymmetric. What is worth asking is how much asymmetry is normal, how much of your measured gap is the measurement rather than you, and whether closing it does anything.
This page answers all three, including the part where our own threshold is easier to trip than it looks.
The short answer
- Side differences are the norm, not the exception.
- Measurement error is large on home tests, and on some of them it is larger than the threshold that flags an imbalance.
- A gap is worth re-measuring before it is worth training.
- The evidence that correcting asymmetry prevents injury is weak. The evidence that a low absolute reading matters is better.
- Some asymmetries are adaptations to what you do, and closing them is not obviously the goal.
One side more flexible than the other
Start with the boring explanation, because it is usually the right one.
You are not symmetrical. Handedness and footedness shape decades of loading. Your organs are not arranged symmetrically. Small differences in leg length, pelvic geometry and rib position are common in people with no complaints at all. Sports with a dominant side — throwing, kicking, racquets, single-sided lifting — produce large, predictable, permanent asymmetries.
So the base rate of "one side reads lower" is close to everyone, and a difference is not itself a finding. What makes it a finding is size, repeatability and direction over time.
Which tests can even see it
Only per-side tests. A forward fold gives you one number for both legs and hides everything.
In Limber's battery, three of the five tests are taken and recorded per side:
| Test | Reported as | Smallest gap it can show |
|---|---|---|
| Knee to wall | Centimetres, 0–20 | 5 points |
| Shoulder reach | 5 bands | 20 points |
| Hip flexor | 3 bands | 30 points |
The toe touch and the deep squat are single readings, not because sides do not matter there but because there is no honest way to separate them in those positions.
You can take all three per-side tests here for nothing: the knee to wall test, the shoulder mobility test and the hip flexor test. Each records left and right separately, and the Range Score restates every gap it finds rather than averaging the two sides into one flattering number.
The twelve-point threshold
Limber calls a difference of 12 points or more an imbalance, on the app's 0–100 scale. Under that, the app says the two sides read level enough that neither gets extra work. At or over it, the day's session adds one extra move on the weaker side until the gap closes.
Twelve is a judgement, not a finding. It was chosen to sit above the ordinary noise in these tests and below a difference worth acting on. No study establishes 12 as the right number, and this page is not going to pretend otherwise.
What can be said for it is that it is a fixed, published, checkable rule rather than a per-session opinion, and that the app tells you the number rather than quietly biasing your routine.
The arithmetic problem with bands
Here is the awkward part, and it belongs on our own page rather than in someone else's review.
On a banded test, the smallest difference you can record is one band. Work out what one band is worth on each of the per-side tests:
- Shoulder reach scores 10, 30, 55, 75, 95. One band is worth 20 or 25 points.
- Hip flexor scores 25, 60, 90. One band is worth 30 or 35 points.
Both are above the twelve-point threshold. So on those two tests, any difference at all between your sides is flagged as an imbalance. There is no such thing as a small gap on a three-band test — the instrument cannot express one.
The knee-to-wall is different because it is measured in centimetres and interpolated. There, one centimetre is worth between 5 and 10 points depending on where you sit on the scale, so it can show a gap under the threshold — and equally, a centimetre of sloppiness in where you placed your toe can manufacture ten points of imbalance out of nothing.
Two rules follow, and they are the practical heart of this page:
- On a banded test, treat a one-band gap as "re-measure", not as a finding. Take it again on another day before you believe it.
- On the knee-to-wall, be fanatical about foot placement, because the scale is fine enough to punish carelessness.
The general version of this is in how to measure flexibility at home: the noise on home tests is larger than it looks, and a change smaller than the noise is not a change.
Is asymmetry a problem?
The honest answer is that the evidence is much weaker than the confidence with which asymmetry is discussed.
Screening does not predict injury well. Moran and colleagues' 2017 systematic review in the British Journal of Sports Medicine found Functional Movement Screen composite scores predict injury poorly, and Bahr argued in the same journal in 2016 that this is a general property of screening tests: to identify individuals who will get hurt, a test needs a discriminative power that essentially no movement screen has demonstrated.
Symmetry indices can mislead in the other direction too. Wellsandt, Failla and Snyder-Mackler showed in the Journal of Orthopaedic & Sports Physical Therapy in 2017 that limb symmetry indices overestimate knee function after anterior cruciate ligament injury, because the uninjured side also declines — so the ratio looks fine while both legs are worse. Symmetry is a ratio, and a ratio conceals its own terms.
Where the evidence is better, it is about the absolute value, not the gap. Backman and Danielson followed junior elite basketball players prospectively for a year in the American Journal of Sports Medicine in 2011 and found low ankle dorsiflexion associated with developing patellar tendinopathy. That is a finding about a low reading, not about a difference between sides.
Grade: weak for asymmetry as a predictor, moderate for low absolute readings at specific joints.
When a gap is an adaptation
Some asymmetries are the correct answer to what you do, and removing them is not obviously desirable.
The clearest documented case is the throwing shoulder. Baseball pitchers reliably lose internal rotation on the throwing side and gain external rotation, and Wilk and colleagues, in the American Journal of Sports Medicine in 2011, found that total rotational motion — the sum of the two — was more informative than the internal-rotation deficit taken alone. A pitcher whose two sides match may simply not have thrown much.
The same logic applies more loosely to any single-sided sport, and to work: a plasterer, a violinist and a right-handed golfer have all trained an asymmetry on purpose without meaning to.
What this argues for is not ignoring gaps. It is knowing which of your gaps has an obvious cause in what you do, and treating those with more curiosity and less alarm.
What to do about a real gap
A gap survives two measurements on separate days and is bigger than one band on the test that showed it. Now what?
- Do not chase it with volume alone. Adding four times the work on the weak side is a good way to make the weak side sore.
- Add one thing. Limber's rule is one extra move on the weak side per session, held until the gap closes. One extra position, on the low side, in an otherwise unchanged plan.
- Work the low side first, when you are fresh, rather than last.
- Re-measure on a slow clock. Three weeks, same conditions, same order.
- Check whether the low side is low, or the high side is high. A gap does not say which. If both sides read well and one reads slightly better, the "weak" side may need nothing.
- If one side hurts, stop measuring it and get it looked at. A gap that appeared with pain is a different problem from a gap that has always been there. Pain that radiates into a limb, numbness, weakness, pain that followed a fall or an injury, or back pain with fever, unexplained weight loss or a change in bladder or bowel control needs a clinician who can examine you. Nothing on this page diagnoses or treats anything.
Where the evidence is weak
The 12-point threshold. Ours, published, and not derived from a study. Defensible as a rule, not as a fact.
Asymmetry as a risk factor. Weak. Screening tests built on it do not predict injury well, and the reviews saying so are recent and clear.
That closing a gap changes anything. Essentially unstudied. There is no trial showing that reducing a left–right range difference reduces injuries or improves performance, and this site will not imply there is.
Self-rated bands per side. Two coarse readings on a body you cannot see are not a precision instrument. That is why the shoulder test names the arm going over the top and the hip flexor test names the hanging thigh — so that at least the sides cannot be mixed up between sessions.
The rest of the cluster sits under mobility, measured, and what any of these numbers mean is in what is a good flexibility score.
Questions
Is it normal to be more flexible on one side?
Yes — it is the usual result. Handedness, single-sided sports, occupation and ordinary anatomical variation all produce side differences in people with no complaints at all. A difference is only worth attention if it repeats across separate measuring sessions and is larger than the test's own error.
How big does a left–right difference have to be to matter?
Limber flags 12 points or more on its 0–100 scale, which is a published rule rather than a research finding. Practically, on a banded test the smallest gap you can record is already 20 to 35 points, so a one-band difference should be treated as a prompt to measure again rather than as a result.
Why is one hip tighter than the other?
Most often because of what you do — a dominant side in sport, a habitual sitting or standing posture, a job that loads one side. Joint shape also varies between your own two hips, and bone differences do not respond to stretching. If the difference appeared suddenly or came with pain, see a clinician who can examine you rather than stretching it harder.
Should I stretch the tight side more?
A little more, not a lot more. Adding one extra position on the low side in an otherwise unchanged plan is a reasonable dose — that is the rule Limber applies, one extra move per session until the gap closes. Large asymmetric volume tends to produce soreness rather than symmetry.
Does fixing an imbalance prevent injury?
There is no good evidence that it does. Movement screens built on asymmetry predict injury poorly, and no trial has shown that reducing a left–right range difference reduces injuries. The better-supported finding is that low absolute range at specific joints — ankle dorsiflexion, for instance — is associated with some problems.
Which tests show a left–right difference?
Only tests taken separately on each side. In this battery that is the knee-to-wall, the shoulder reach and the hip flexor test. A forward fold or a squat produces one number for both sides and cannot show asymmetry at all, which is a limitation of those tests rather than evidence that you are symmetrical.