Concurrent Validity and Reliability of a Handheld Dynamometer in Measuring Isometric Shoulder Rotational Strength

Area of Science:

• Biomechanics and Sports Medicine
• Musculoskeletal Rehabilitation

Background:

• Accurate measurement of isometric shoulder rotational strength is crucial for assessing motor function in athletes with shoulder injuries.
• Handheld dynamometry offers a portable and cost-effective alternative for clinical strength assessments.

Purpose of the Study:

• To evaluate the concurrent validity of handheld dynamometry against isokinetic dynamometry.
• To determine the intrarater and interrater reliability of handheld dynamometry for measuring isometric shoulder rotational strength.

Main Methods:

• A cross-sectional study was conducted in a biomechanics laboratory with 39 healthy participants.
• Peak isometric strength of internal and external rotators was measured using handheld and isokinetic dynamometry.
• Interrater and intrarater reliability were assessed by two physiotherapists across three sessions.

Main Results:

• Interrater reliability for external and internal rotation strength was excellent (ICC=.914) and good (ICC=.842), respectively.
• Intrarater reliability was good to excellent for both external (ICC=.865) and internal rotation (ICC=.901).
• Concurrent validity showed moderate to good correlations (r=.792 for external, r=.664 for internal rotation).

Conclusions:

• Handheld dynamometry exhibits good to excellent reliability and moderate to good validity for assessing isometric shoulder rotational strength.
• This portable device is a viable option for sports professionals and clinicians in field-based assessments of shoulder strength.