Intersession Variability of Knee Extension Kinetics Using a Strain Gauge Device With Differing Clinically Practical...

Area of Science:

• Biomechanics
• Kinesiology
• Sports Science

Background:

• Intrasession reliability of isometric knee extension kinetics using portable strain gauges is established.
• Intersession variability, crucial for longitudinal studies, remains under-quantified.
• Portable strain gauges offer an accessible method for assessing knee extension strength.

Purpose of the Study:

• To quantify the intersession variability of knee extension kinetics.
• To evaluate the reliability of a portable strain gauge for assessing isometric knee extension strength over three sessions.
• To compare variability between constrained and unconstrained testing conditions.

Main Methods:

• Eleven healthy adults performed maximal voluntary isometric knee extensions over three separate sessions.
• Measurements included peak force (PF), peak rate of force development, rate of force development (RFD), and impulse (IMP).
• Testing was conducted under both constrained (isokinetic setup) and unconstrained (plinth) conditions.

Main Results:

• Peak force demonstrated the lowest intersession variability (CV 5.5%-13.8%).
• Rate of force development and impulse exhibited moderate to high variability (CV up to 35.4%).
• Constrained conditions and practice sessions significantly reduced variability for RFD and IMP.

Conclusions:

• Peak force measurements are reliable for assessing knee extension strength with portable strain gauges.
• Rate of force development and impulse require careful interpretation due to intersession variability.
• Utilizing backrests, thigh straps, and at least one familiarization session improves the reliability of kinetic measurements.