Concurrent Validity of a Portable Force Plate Using Vertical Jump Force-Time Characteristics.

Area of Science:

• Biomechanics
• Sports Science
• Human Movement

Background:

• Assessing jumping performance requires accurate force measurement.
• Portable force plates offer convenience but require validation against laboratory systems.
• Reactive strength index modified and force-time characteristics are key performance indicators.

Purpose of the Study:

• To determine the concurrent validity of a portable force plate system.
• To compare measurements of reactive strength index modified and force-time characteristics against a laboratory system.
• To assess the interchangeability of portable and laboratory force plates for countermovement vertical jumps.

Main Methods:

• Twenty-eight male participants performed bilateral countermovement vertical jumps.
• Jumps were performed simultaneously on portable and in-ground laboratory force plates.
• Vertical ground reaction force was recorded at 1000 Hz to calculate key variables.

Main Results:

• High correlations (r ≥ .99) were found between portable and laboratory systems for all variables.
• Small, significant differences were noted in impulse and mean net force variables.
• Excellent agreement (mean difference 1.7%) was observed across all measured variables.

Conclusions:

• The portable force plate system demonstrates concurrent validity for assessing countermovement vertical jumps.
• It accurately measures reactive strength index modified and underlying force-time variables.
• Practitioners can confidently use portable and laboratory force plates interchangeably.