What is a sit-and-reach test?

A sit-and-reach test measures hamstring and lower-back flexibility. You sit on the floor with legs straight and reach forward as far as possible. The distance reached (in cm) is your score.

Why can my score be negative?

If you can't reach your feet, your score is negative — measured in cm short of the baseline at foot position. Negative scores are common for people with tight hamstrings.

How accurate is this flexibility assessment?

The norms are based on standardised fitness testing tables and are reasonable estimates. Individual variation means professional assessment gives more precise results.

How long does it take to improve flexibility?

Most people see measurable flexibility gains within 4–8 weeks of consistent daily stretching. Dynamic warm-up and static cool-down stretching work best together.

Is this tool free and private?

Yes. AI Fit Hub tools are free, browser-based, and no-signup. Your inputs stay in your browser.

Does this replace medical or fitness assessment?

No. This is a general estimate based on population norms — not a medical assessment. Consult a physiotherapist for a full flexibility evaluation.

Methodology: Flexibility Score Calculator

Scope

Estimates a flexibility percentile and rating from a sit-and-reach test, adjusted for age and sex.

Formula

percentile = lookup(score_cm, age_band, sex) against ACSM sit-and-reach norms.

Coefficients

Parameter	Value	Note
Test	`Standard sit-and-reach (box at 26 cm feet line)`

Data sources

American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th ed. Wolters Kluwer, 2021. — Source of the sit-and-reach percentile tables used in the tool.
Canadian Society for Exercise Physiology. Canadian Physical Activity, Fitness & Lifestyle Approach (CPAFLA) Reference Manual, 3rd ed. 2003. — Secondary set of sit-and-reach norms used as a cross-check.
Ayala F, Sainz de Baranda P, De Ste Croix M, Santonja F. Reproducibility and criterion-related validity of the sit and reach test and toe touch test for estimating hamstring flexibility in recreationally active young adults. Phys Ther Sport. 2012;13(4):219-226. — PMID 23068896. Validation paper for the sit-and-reach protocol.

Assumptions

Test administered after a 5–10 minute warmup; knees flat.

Approximation range

Sit-and-reach reflects posterior-chain flexibility (hamstrings, lumbar) and does not generalize to shoulder or ankle mobility.

Limitations

Many mobility limitations are not detected by sit-and-reach; use sport-specific screens as well.

Reproducibility

Male, 30, score 30 cm: lookup returns ~60th percentile, rating 'Above Average'.

Change log

2026-04-24: methodology page first published.

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Worked example

Computed by the same engine bundle served at /engines/flexibility-score-calculator.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: flexibility_score
reach_cm: 25
age: 30
sex: male

Output

rating: Good
percentile: 60
targetCm: 28
improvementCm: 3
ratingMessage: Above average flexibility. Keep up your routine and explore yoga or dynamic stretching to push higher.
ageGroupLabel: 26–35

FAQ

What is a sit-and-reach test?: A sit-and-reach test measures hamstring and lower-back flexibility. You sit on the floor with legs straight and reach forward as far as possible. The distance reached (in cm) is your score.
Why can my score be negative?: If you can't reach your feet, your score is negative — measured in cm short of the baseline at foot position. Negative scores are common for people with tight hamstrings.
How accurate is this flexibility assessment?: The norms are based on standardised fitness testing tables and are reasonable estimates. Individual variation means professional assessment gives more precise results.
How long does it take to improve flexibility?: Most people see measurable flexibility gains within 4–8 weeks of consistent daily stretching. Dynamic warm-up and static cool-down stretching work best together.
Is this tool free and private?: Yes. AI Fit Hub tools are free, browser-based, and no-signup. Your inputs stay in your browser.
Does this replace medical or fitness assessment?: No. This is a general estimate based on population norms — not a medical assessment. Consult a physiotherapist for a full flexibility evaluation.