Agreement between Different Methods to Measure the Active Drag Coefficient in Front-Crawl Swimming

Area of Science:

• Sports Science
• Biomechanics
• Fluid Dynamics

Background:

• Accurate measurement of hydrodynamic forces is crucial for optimizing swimming performance.
• The active drag coefficient is a key parameter in assessing a swimmer's efficiency.
• Previous studies have primarily used drag-based methods for measurement.

Purpose of the Study:

• To analyze the agreement between active drag coefficient measurements obtained via drag and propulsion methods.
• To determine if propulsion-based systems offer a viable alternative for hydrodynamics assessment.
• To provide insights for coaches and researchers on selecting appropriate measurement techniques.

Main Methods:

• Employed the velocity perturbation method for drag measurement and the Aquanex system for propulsion measurement.
• Included 18 elite swimmers (9 male, 9 female) from a national team.
• Utilized mean value comparison, simple linear regression, and Bland Altman plots to assess agreement.

Main Results:

• No significant differences (p > 0.05) were found between drag and propulsion methods when comparing mean values.
• Linear regression (R² = 0.82, p < 0.001) and Bland Altman plots indicated a very high agreement between the two methods.
• Active drag coefficient demonstrated less sensitivity to swimming velocity compared to other metrics.

Conclusions:

• The active drag coefficient is a reliable indicator of a swimmer's hydrodynamic profile, irrespective of the measurement method (drag or propulsion).
• Propulsion-based systems provide a valid alternative for calculating the active drag coefficient, expanding measurement options for the swimming community.
• Coaches and researchers can confidently use either drag or propulsion methods for hydrodynamics analysis, enhancing accessibility and flexibility in performance assessment.