Quadriceps handheld dynamometry during the post-ICU trajectory: using strictly the same body position is mandatory...

Area of Science:

• Rehabilitation Medicine
• Clinical Biomechanics
• Physical Therapy

Background:

• Quadriceps strength (QS) measurement varies significantly between supine and seated positions.
• Consistent QS assessment is vital for tracking recovery post-intensive care unit (ICU) stay.
• Existing methods lack reliable conversion equations for position-dependent QS data.

Purpose of the Study:

• To develop and validate novel equations for estimating QS in one position based on measurements from another.
• To enable comparable QS follow-up across different measurement setups.

Main Methods:

• Isometric QS was measured using a handheld dynamometer in both supine and seated positions.
• Two conversion equations were derived using a multivariate model (age, sex, BMI, baseline QS) in a cohort of 77 healthy adults.
• External validation was performed in a second cohort of 62 healthy adults and a third cohort of 50 ICU survivors using ICC and Bland-Altman analysis.

Main Results:

• One developed equation showed good agreement in healthy adults (ICC=0.87), but this did not translate to ICU survivors (ICC=0.60).
• The equation failed to demonstrate consistent predictive accuracy across different populations.
• Significant bias and wide limits of agreement were observed in the ICU survivor cohort.

Conclusions:

• No validated equation currently exists for converting QS measurements between supine and seated positions.
• Repeated QS measurements must be conducted in the exact same standardized position for accurate patient monitoring.
• Standardized documentation of the measurement position is essential for reliable clinical interpretation.