The test methodologies described in this study were developed with healthy control subjects and patients with vestibular disorders. Healthy control subjects had no known history of neurologic, otologic, or musculoskeletal disorders. Patients with vestibular disorders had abnormal responses on a battery of objective tests of the vestibular system, including tests of the vestibulo-ocular reflex in darkness, positional tests, and cervical vestibular-evoked myogenic potentials. These studies were approved by the Institutional Review Board for Human Subjects Research at Baylor College of Medicine, Houston, Texas, USA.

NOTE: In a study of 1869, healthy subjects aged 4 to 85 years who were tested at Space Center Houston, a community science education center, subjects were tested with the methodology described in this paper. Participants first removed their shoes but wore socks. Science educators then tested participants on Tandem Walking with eyes closed and on CTSIB on compliant foam with three conditions, each with eyes closed, standing still with the head still, standing still with slow head nodding in pitch (up/down), and standing still with slow head shaking in yaw (right/ left).

1. Patients/research subjects

1. Ensure that individuals can stand erect, unsupported, for at least 30 s. They must be able to follow the instructions.

2. Environment and equipment

1. Perform the tests in a well-lighted room with a firm surface, e.g., vinyl tile or industrial carpeting. Do not perform these tests on plush carpeting.
2. Use a stopwatch, clock with a second hand, or digital timer for CTSIB. No timing device is needed for TW.
3. To perform CTSIB, use medium-density, compliant foam which meets the following compliance criterion: PSI = 0.85-0.95. This type of foam is commonly known as temper foam or memory foam. The norms were developed with foam of the following size: 40.64 cm X 45.72 cm X 10 cm. A larger slab of foam may be used if desired, but it is not necessary.
   ​NOTE: More than one manufacturer makes this foam. Using the foam with the correct compliance characteristics is essential. If another type of foam is used, the published norms will not apply.

3. Methodology for CTSIB

1. Place the foam near a corner of the room or a wall for safety. Have the individual first practice the test on the floor with eyes open to learn the basic movements involved.
   1. Instruct the individual being tested to stand erect, not touching anything against the legs or back, with feet together, side by side. Ensure that the individual's arms are crossed at the waist, with each hand holding the contralateral elbow or comfortably crossed at the waist.
   2. Instruct the individual to look straight ahead. Perform 1-3 test trials for 5-10 s, on the foam, with arms crossed at the waist, feet adjacent, standing erect and looking straight ahead, with nothing touching the legs or back.
   3. To steady the individual, place a hand on the person's shoulder while the person looks straight ahead.
   4. To start the test trial say, "Close your eyes". Remove the hand from the person's shoulder, say "Go", and begin timing the trial for up to 30 s. Perform this trial only once. If the individual appeared frightened, distracted by a noise, or did not understand the instructions, perform a second trial and consider the first trial a training trial.
      NOTE: The individual will have increased postural sway with eyes closed, which may be a source of concern to the person being tested. Gently advise the individual not to worry about it.
   5. Dependent measure: Measure the time the individual can maintain the erect posture before making an error, up to 30 s, for each CTSIB condition.
      ​NOTE: Errors are opening the eyes, moving the arms, taking a step, or leaning against the wall.
2. Perform Trial 1 with the head stationary. If the person has difficulty on Trial 1 the first time, consider that trial a training trial, and give it a second time. Use the score from the second trial.
3. Perform Trial 2 with head nodding (up/down) slowly at 0.3 Hz in time to a real metronome or digital metronome application.
   1. Prior to starting Trial 2, have the individual stand on the floor with eyes open and practice nodding the head in time to the sound until the maximum upper and lower head movements occur in time to the maximum and minimum sounds on the application so that the individual can move at 0.3 Hz.
   2. To perform Trial 2, instruct the individual to stand on the foam, with feet adjacent and arms crossed, as in Trial 1.
   3. Start the sound on the metronome or metronome app before the individual closes his/ her eyes. Then instruct the individual to close his/ her eyes while the hand of the investigator is on the person's shoulder to steady him/her.
   4. To begin Trial 2, instruct the individual to nod his/her head (head moves up/ down) in time to the sound when "Go" is heard.
   5. Remove the hand from the individual's shoulder, say "Go" and simultaneously start the timer.
   6. After this trial, allow the individual to rest for a few seconds by stepping off the foam and sitting down if desired.
4. Perform Trial 3 with the head shaking (left/right) at 0.3 Hz, in time to the sound. Otherwise, use the same procedure for Trial 2.

4. Methodology for Tandem Walking

1. Make sure the room has no obstructions where the individual will walk over a distance of approximately 4.5 m forward and approximately 1 m on either side of the individual. More space can be used but is not required.
2. Demonstrate the test for the individual for 3 to 5 steps: Put one foot heel-to-toe in front of the other foot. Repeat for 4 more steps so the individual will know the task.
3. Practice trial:
   1. Instruct the individual to perform a practice trial with eyes open, arms crossed at the waist as for the CTSIB, without wearing shoes but wearing socks for good hygiene.
   2. Have the individual place one foot directly in front of the other, with no more than 2.4 cm (1 inch) between the front and rear feet. Ensure that the individual performs the practice trial for up to 5 steps. If needed, use more than one practice trial for the individual to understand the motor task.
4. Test trial: Have the individual stand with arms crossed, feet at a comfortable distance apart, without wearing shoes but wearing socks for good hygiene. Instruct the individual to close his/her eyes and perform 10 heel-to-toe steps, as described in step 4.3, when the investigator says, "Go."
5. Do not time the test.
6. Dependent measure: Measure the total number of correct tandem steps performed out of 10 steps, even if the steps are not consecutive. To count incorrect steps, count with the fingers of one hand, the way children use fingers to count. Count the total number of steps aloud, but do not say the number of incorrect steps aloud during the test.
   ​NOTE: Errors are: opening the eyes, moving the arms, stepping out of line, or stepping too far ahead of the rear foot.

5. Scoring for CTSIB and TW

1. To score the trials, two sources provide data. Use the norms for children and young adults on CTSIB and TW from the paper with those published data⁹. Also, CTSIB and TW norms for adults aged 21 to 90 are available in the paper with those published data⁸.
2. Compare the individual's scores to the published data to determine if the scores are normal or abnormal for the individual's age group and, for CTSIB, for each condition.