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Hydrodynamic Flow Characteristics of a Recirculating Pool: Examining the Ecological Validity for Training and Testing
Kellen T Krajewski1, Anne Z Beethe2, Dennis E Dever1
1Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, Pennsylvania.
Journal of Strength and Conditioning Research
|September 20, 2023
Summary
Recirculating swimming flumes (RSFs) exhibit variable and turbulent flow, diminishing mean flow velocity with distance. This instability may alter swim mechanics, making them dissimilar to traditional swimming environments.
Area of Science:
- Biomechanics
- Exercise Physiology
- Aquatic Training Technologies
Background:
- Recirculating swimming flumes (RSFs) are increasingly popular for rehabilitation and training due to their compact design and versatility.
- Despite their adoption in laboratory settings for studying swimming and underwater treadmill running, the hydrodynamic characteristics of RSFs are not well understood.
- This lack of understanding raises questions about the ecological validity of research conducted in these environments.
Purpose of the Study:
- To investigate the hydrodynamic flow characteristics of a recirculating swimming flume (RSF).
- To assess flow velocity profiles at various distances and manufacturer-set speeds within the RSF.
- To determine how these characteristics might influence training and testing outcomes in aquatic environments.
Main Methods:
- Hydrodynamic velocity profiles were measured using a 3D profiling velocimeter (200 Hz sampling rate) in an RSF.
- Data were collected at 0.5 and 1.5 meters from the projection channel across flume speeds from 30 to 95 (+99) in 5-unit increments.
- Mean flow velocity (MFV) was calculated for cross-sectional areas (CSAs) of 10, 20, 30, and 40 cm², analyzed using two-way ANOVA.
Main Results:
- Significant differences in MFV were found across different CSAs, with larger areas exhibiting lower MFV at the same speed, indicating variable and turbulent flow.
- MFV decreased significantly with increased distance from the flow channel, exposing individuals to varying flow velocities simultaneously.
- The flow velocity centroid demonstrated limited stability.
Conclusions:
- The variable and turbulent flow characteristics within RSFs, particularly the diminished velocity with distance, challenge their ecological validity for replicating traditional swimming.
- The instability of the flow velocity centroid may alter natural swim mechanics.
- Findings suggest that swimming in an RSF may be more akin to swimming in a turbulent river than in a standard pool or open water.
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