Sources of variation in back and leg dynamometry

Area of Science:

• Biomechanics
• Kinesiology
• Sports Science

Background:

• Assessing maximal voluntary contraction strength is crucial in clinical and sports settings.
• Portable dynamometers offer a convenient alternative to laboratory-based equipment.
• Evaluating the validity and reliability of new measurement tools is essential.

Purpose of the Study:

• To determine the concurrent validity of the Takei portable dynamometer against a criterion measure (Lido Active).
• To assess the test-retest reliability of the Takei dynamometer for back and leg strength.
• To investigate the influence of time of day on strength measurements using the Takei dynamometer.

Main Methods:

• Concurrent validity was assessed by comparing Takei dynamometer measurements with Lido Active measurements for leg extension and back strength.
• Test-retest reliability was evaluated by measuring back and leg strength twice on the Takei dynamometer with a six-day interval.
• The effect of time of day was examined by measuring strength at six different times over a single day.

Main Results:

• The Takei dynamometer showed significant correlations with the Lido Active for both leg strength (r=0.90) and back strength (r=0.79).
• High test-retest reliability was found for leg strength (r=0.80) and back strength (r=0.91), with no significant difference in leg strength means.
• A significant, though small, difference was observed in back strength means between test and retest, and a time of day effect was noted for both measures.

Conclusions:

• The Takei portable dynamometer demonstrates good concurrent validity and reliability for assessing back and leg strength.
• Measurement protocols should consider the potential influence of time of day on strength outcomes.
• This device is a viable tool for field-based strength assessments.