Agreement-Based Validation of ISOMETRO for Upper-Limb Isometric Tension Measurements

Area of Science:

• Sports Science
• Biomechanics
• Human Physiology

Background:

• Muscular fitness is crucial for health and athletic performance.
• Isometric strength, a key indicator, is often assessed using specialized devices.
• Validating measurement tools is essential for reliable data in research and training.

Purpose of the Study:

• To validate the Isometric Strength Measurement Device (ISOMETRO) for upper-limb isometric tension measurements.
• To assess the agreement between ISOMETRO and a criterion force plate.
• To evaluate the internal consistency of the ISOMETRO measurement chain.

Main Methods:

• Twenty-one amateur rock climbers performed four upper-limb isometric tensile tests.
• ISOMETRO measurements were compared against a force plate (criterion) and a series-connected load cell (internal consistency).
• Statistical analyses included linear mixed-effects models and Bland-Altman analysis.

Main Results:

• ISOMETRO strongly predicted force plate values (marginal R² > 0.99) with negligible bias and excellent concordance (CCC ≥ 0.996).
• Internal consistency checks also demonstrated near-unity agreement, confirming measurement chain integrity.
• High agreement was observed for vertical axis tensile testing in controlled laboratory conditions.

Conclusions:

• ISOMETRO demonstrates excellent agreement with force plate measurements for upper-limb isometric testing in young amateur rock climbers.
• The device's internal measurement chain integrity is supported by load cell comparisons.
• Further validation is recommended for diverse populations, joint angles, force directions, and non-laboratory environments.