Phone Goniometer: Reliability Between Testers

In groups of three, two testers separately measure the same joint ranges on a classmate with a phone inclinometer and compare results. After seeing how far apart they are, they write a standard protocol and check whether the error shrinks.

How to play

1. Each group opens the phone's level or inclinometer feature, calibrates it on the floor and practices placing it on a body segment (4 min).
2. Without seeing each other's results, the two testers measure three ranges on the student being tested: shoulder flexion lying face up, hip flexion with the knee bent, and knee flexion lying face down (10 min).
3. Compare the data: a difference over 5 degrees counts as a disagreement; look at the causes (where the phone sat, starting position, compensations) (5 min).
4. Write a measurement protocol for each range: position, landmark marked with tape, phone placement and when to read the number (5 min).
5. Repeat the measurements using the protocol, switching who gets tested, and check whether the gap between testers has narrowed (6 min).

Rules

• The student being tested moves actively to their limit; testers don't push the limb.
• Phones are placed carefully and set on the floor in a fixed spot when not in use.
• Only angles are recorded, never photos or video without the student's permission.
• Anyone may decline to be measured and take part as a tester.

Variations

Adaptations

• Limited mobility: serves as a tester or measures upper-body ranges while seated.
• Visual impairment: uses an inclinometer app with voice output, or acts as the tested student and protocol writer with a screen reader.
• Attention difficulties: has a worksheet with a checkbox for each step of the measurement.

Learning goals

• Use digital tools to measure range of motion.
• Understand why reliability matters in fitness assessment.
• Design a standard measurement protocol as a team.

Equipment for a class of 25

• tablets or phones: 14
• exercise mats: 10
• worksheets: 28
• tape: 3

Teacher tip

Many phones include a level in the measure app; check before class that at least one device per group works. It's a good way in to discussing why tests must always be done the same way.

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