Stroke phase differences in the linear relationship between swimming velocity and vertical body position during front...

Area of Science:

• Biomechanics
• Sports Science
• Fluid Dynamics

Background:

• Understanding the relationship between swimming velocity and body position is crucial for optimizing front crawl technique.
• Previous research has explored body roll and pitch, but the specific influence of velocity on vertical center of mass (CoM) position across stroke phases requires further investigation.

Purpose of the Study:

• To determine if a linear relationship exists between swimming velocity and vertical body position in front crawl.
• To analyze differences in velocity effects on vertical body position across distinct stroke phases (entry, pull, push, release, recovery).

Main Methods:

• Eleven male swimmers performed front crawl at varying speeds over 15m.
• Whole-body center of mass (CoM) was calculated using inverse kinematics and digital human models.
• Vertical CoM position and horizontal CoM velocity were analyzed across five stroke phases per cycle.

Main Results:

• A significant positive linear trend was observed between mean swimming velocity and mean vertical CoM position across all stroke phases (p < 0.001).
• The interaction between stroke phase and swimming velocity was significant (p < 0.001).
• Slopes for propulsive phases (pull, push) were significantly steeper than for non-propulsive phases (entry, release, recovery) (p < 0.001).

Conclusions:

• Vertical body position in front crawl is velocity-dependent and can be assessed independently of stroke phase when accounting for velocity effects.
• Focusing on propulsive phases (pull and push) offers a more sensitive approach to detecting changes in vertical body position related to swimming velocity.