Clinical Guidance

Standard Use Procedures

Step-by-step measurement protocols for occupational and physical therapists using the Splayometer for finger extension and abduction force assessment.

Overview

Before You Begin

These procedures apply to the Digital Splayometer. Following a consistent protocol is essential for obtaining reliable, comparable measurements across sessions and examiners.

Indications for Use

The Splayometer is indicated for quantitative assessment of voluntary finger and hand extension and abduction force in adults. Intended use contexts include:

  • Baseline hand strength assessment at the start of a course of care
  • Serial measurement to monitor progress over time
  • Bilateral comparison of affected versus unaffected hand
  • Outcome documentation for clinical, insurance, or medico-legal purposes
  • Research and data collection in hand function studies

Contraindications and Precautions

  • Open wounds or active infection — do not apply attachments over broken skin or infected tissue
  • Acute fracture or surgical repair — defer until cleared by the referring physician or surgeon
  • Severe edema — use clinical judgment; finger rings may be contraindicated if digital circumference prevents safe fit
  • Significant pain on motion — record pain level; do not override voluntary effort limits
  • Cognitive impairment — ensure the patient can understand and follow instructions before proceeding

Note: The Splayometer measures voluntary maximal force. Results reflect patient effort and cooperation as well as true strength. Document any factors that may have limited maximal effort.

Equipment Required

  • Splayometer digital unit (load cell and display module)
  • Appropriate finger rings for the digit(s) being tested
  • Hand loop (for whole-hand assessment)
  • Surface for patient to rest arm (table or treatment plinth)
  • Recording form or electronic documentation system
  • Disinfectant wipe compatible with plastic and silicone materials

Clinical Framework

Within the Occupational Therapy Practice Framework: Domain and Process (4th ed.; AOTA, 2020), hand strength assessment addresses client factors — specifically neuromusculoskeletal and movement-related body functions, including muscle power functions. These client factors underlie a client's ability to perform occupations such as activities of daily living (ADLs), instrumental activities of daily living (IADLs), work, and leisure.

Splayometer measurement is conducted as part of the occupational therapy evaluation process to analyze how finger extension and abduction strength contribute to or limit occupational performance. Results directly inform goal setting, intervention planning, and outcome measurement — all core elements of the OTPF-4 process. Because the OTPF-4 frames assessment holistically, clinicians should interpret Splayometer findings in context: alongside the client's occupational profile, environmental factors, and performance patterns (AOTA, 2020).

Device Setup

Preparing the Splayometer

Complete device setup before positioning the patient to minimize wait time and distraction during the measurement.

1

Power On and Allow Warm-Up

Turn on the display module. Allow at least 30 seconds before recording measurements to allow the load cell to stabilize at ambient temperature.

2

Select and Attach the Appropriate Accessory

Choose finger rings sized to fit the target digit(s) snugly without restricting circulation. For whole-hand assessment, select the hand loop. Connect the attachment to the load cell using the twist-lock mechanism — insert and rotate 90° clockwise until it clicks.

3

Tare (Zero) the Device

With the attachment connected but no load applied, press the tare button to zero the display. Tare should be performed at the start of each session and any time the attachment is changed.

4

Select Units

Set the display to your preferred unit of measurement (kilograms or pounds). Record which unit was used and use the same unit consistently across all sessions for a given patient to allow valid comparison.

5

Enable Peak Hold (Recommended)

If using peak hold mode, enable it now. Peak hold captures the maximum force achieved during the trial, which is the value used for recording. Confirm the mode indicator is visible on the display before proceeding.

Patient Positioning

Standard Positioning Principles

Consistent positioning reduces examiner variability and ensures measurements are comparable across sessions. Follow these principles for all measurement types.

Seated Position

The patient should be seated with the tested arm resting on a flat surface (table or treatment plinth) at approximately elbow height. The shoulder should be adducted and in neutral rotation, with the elbow flexed to approximately 90°. The forearm may be pronated, supinated, or in neutral depending on patient comfort and clinical judgment — record the position used and replicate it across sessions.

Consistency is key. Because normative data for the Splayometer is still being developed, within-patient comparisons are currently more meaningful than reference to population norms. Replicating position exactly across sessions is therefore essential.

Wrist Position

For finger extension and abduction measurements, position the wrist in neutral (0° extension/flexion, 0° ulnar/radial deviation) unless the clinical question requires otherwise. Avoid extremes of wrist flexion, which inhibit finger extensor force. Record any deviation from neutral.

Bilateral Comparison

When measuring both hands for comparison, test the unaffected (or dominant) hand first to establish the patient's understanding of the task. Mirror the position as closely as possible for the contralateral hand.

Measurement Procedures

Protocol by Measurement Type

The Splayometer supports three distinct measurement configurations. Follow the appropriate procedure for each.

Single-Digit Extension

Finger-to-Thumb Extension

  1. Select finger rings sized for the target finger and for the thumb.
  2. Place one ring on the distal or middle phalanx of the target digit; place the second ring on the thumb. Ensure rings are seated comfortably and do not cause discomfort or restrict blood flow.
  3. Instruct the patient to extend the target finger away from the thumb — spreading the two rings apart — with maximum voluntary effort.
  4. Demonstrate the motion once if needed. Ensure the patient understands: they are extending, not flexing, and that motion should be smooth rather than jerky.
  5. Perform three trials. Allow 15–30 seconds of rest between trials.
  6. Record the peak force displayed for each trial. Compute and record the average of three trials as the summary value.

Test each digit of interest individually. Document which digit was tested (D1–D5) and which digit served as the anchor (typically thumb / D1).

Inter-Finger Abduction

Adjacent-Digit Spreading

  1. Select finger rings sized for the two adjacent digits to be tested.
  2. Place one ring on each of the two adjacent digits (e.g., index and middle, middle and ring, ring and little).
  3. Instruct the patient to spread the two fingers apart — abducting one or both fingers — with maximum voluntary effort.
  4. Perform three trials with 15–30 seconds rest between trials.
  5. Record peak force for each trial and compute the three-trial average.
  6. Document which digit pair was tested (e.g., D2–D3).

Inter-finger abduction primarily tests the dorsal interosseous muscles. This measure may be particularly relevant in conditions affecting intrinsic hand function (e.g., ulnar nerve palsy, rheumatoid arthritis).

Whole-Hand Assessment

Hand Extension & Abduction

  1. Attach the hand loop to the load cell using the twist-lock connector.
  2. Position the loop over the dorsum of the four fingers (index through little). The loop should rest at approximately the level of the proximal phalanges. The thumb may be included or excluded — document which configuration is used and replicate it across sessions.
  3. Instruct the patient to open the hand — extending and spreading the fingers against the loop — with maximum voluntary effort.
  4. Perform three trials with 15–30 seconds rest between trials.
  5. Record peak force for each trial and compute the three-trial average.

Whole-hand measurement provides a composite of total hand opening force. It is a useful global indicator but does not isolate individual digit contributions. Use single-digit protocols where digit-specific data is required.

Thumb Extension

Thumb-to-Finger Extension

  1. Select finger rings sized for the thumb and for the index or middle finger (whichever serves as the stable anchor).
  2. Place one ring on the thumb and one on the anchor digit.
  3. Instruct the patient to extend the thumb away from the anchor finger with maximum voluntary effort.
  4. Perform three trials with 15–30 seconds rest between trials.
  5. Record peak force for each trial and compute the three-trial average.
  6. Document which digit served as the anchor.

Thumb extension and abduction may be clinically relevant in conditions such as de Quervain's tenosynovitis, CMC joint arthritis, or post-operative thumb reconstruction.

Trial Protocol

The Three-Trial Standard

A three-trial protocol is consistent with established dynamometry practice for grip and pinch and is recommended for all Splayometer measurements.

Instructions to the Patient

Before the first trial, instruct the patient clearly:

  • "Push as hard as you can."
  • "Keep pushing until I tell you to stop." (approximately 3 seconds)
  • "Rest between each attempt."

Standardize verbal encouragement or eliminate it entirely — and be consistent across sessions.

Scoring

Record the peak force value for each of the three trials. Compute the mean (average) of all three trials as the primary summary value. The mean of three trials is more reliable than any single trial and is the standard reported value for grip dynamometry.

Some clinicians also record the maximum trial value; if your documentation protocol requires this, record both. Label clearly which value is the mean and which is the maximum.

Between Trials

Rest Interval: 15–30 Seconds

Allow at least 15 seconds of rest between trials to minimize fatigue effects. Extend to 30 seconds for patients with limited endurance or significant weakness.

Outlier Trials

Effort Consistency

If one trial differs from the other two by more than 20%, note it in the record and consider whether a fourth trial is warranted. Do not automatically discard outliers — they may reflect true variability or inconsistent effort.

Bilateral Testing

Order of Testing

Complete all trials for one hand before switching to the other. Test the unaffected or dominant hand first when possible to establish patient understanding of the task.

Documentation

Recording Results

Complete documentation supports accurate longitudinal comparison and defensible clinical records.

Minimum Data to Record

  • Date and time of measurement
  • Examiner name
  • Device: Splayometer Digital
  • Measurement type: e.g., "Right D2 extension, D2 to D1"
  • Units: kg or lbs
  • Trial values: Trial 1, Trial 2, Trial 3 (peak force each)
  • Mean value: average of three trials
  • Patient position: forearm position, wrist position
  • Effort quality: any limitations to maximal effort (pain, fatigue, comprehension)

Comparing Across Sessions

To make valid serial comparisons, replicate the following exactly at each visit:

  • Same measurement type and digit pair
  • Same forearm and wrist position
  • Same units
  • Same time of day where possible (strength can vary diurnally)
  • Note any medications, activity level, or pain status that may affect performance
Infection Control

Cleaning Between Patients

Standard infection control procedures apply to all reusable hand therapy equipment, including the Splayometer.

Finger Rings & Hand Loop

Wipe all contact surfaces with a hospital-grade disinfectant wipe compatible with silicone and hard plastic. Allow to air-dry completely before next use. Do not autoclave or immerse in liquid disinfectant unless verified as compatible.

Load Cell Housing

Wipe the exterior of the load cell housing with a disinfectant wipe. Avoid moisture entering the connector port. Do not spray disinfectant directly onto the device.

Display Module

Wipe the display and cable with a lightly dampened disinfectant wipe. Avoid excess moisture near the display screen and buttons. The display module is not waterproof.

If the patient has a known or suspected infectious condition, consider using a disposable glove as a barrier between the skin and the finger ring. The force measurement is not affected by thin barrier materials.

References

Bibliography

Sources supporting the protocols, clinical context, and recommendations described on this page.

  1. American Occupational Therapy Association. (2020). Occupational therapy practice framework: Domain and process (4th ed.). American Journal of Occupational Therapy, 74(Suppl. 2), 7412410010. https://doi.org/10.5014/ajot.2020.74S2001
  2. Coldham, F., Lewis, J., & Lee, H. (2006). The reliability of one vs. three grip trials in symptomatic and asymptomatic subjects. Journal of Hand Therapy, 19(3), 318–327. https://doi.org/10.1197/j.jht.2006.04.002
  3. Fess, E. E. (1992). Grip strength. In J. S. Casanova (Ed.), Clinical Assessment Recommendations (2nd ed., pp. 41–45). American Society of Hand Therapists.
  4. Mathiowetz, V., Kashman, N., Volland, G., Weber, K., Dowe, M., & Rogers, S. (1985). Grip and pinch strength: Normative data for adults. Archives of Physical Medicine and Rehabilitation, 66(2), 69–74.
  5. Mathiowetz, V., Weber, K., Volland, G., & Kashman, N. (1984). Reliability and validity of grip and pinch strength evaluations. Journal of Hand Surgery, 9(2), 222–226. https://doi.org/10.1016/S0363-5023(84)80146-X
Reference Data

Looking for Normative Reference Values?

See our compiled reference norms for grip, pinch, and published finger extension and abduction force data.

View Norms Clinical Overview