【Research Review】Hydrodynamics of the Pool Flip Turn and the Effect of the Underwater Dolphin Kick: A Review of Recent Academic Literature and Training Practice (Article 879)

Source Journal Reference: Sports Biomechanics • International Research Findings Review Series

This article examines the hydrodynamic characteristics of the underwater glide length and dolphin kick effect in the pool flip turn.

Breakdown of the Mechanical Phases of the Flip Turn

The flip turn can be broken down into four mechanical phases: the final stroke approaching the wall, the somersaulting motion, the explosive power output at the moment of wall push-off, and the underwater glide and dolphin kick transition after push-off. Among these, the explosive power at push-off and the gliding posture are key to maintaining speed after the turn—the faster the initial push-off velocity and the better the body’s streamline, the longer the high-speed distance that can be maintained during the underwater glide.

Underwater Glide Depth and Dolphin Kick Initiation Timing

There is an optimal range for the underwater glide depth after push-off: too shallow (near the surface) is affected by wave drag at the surface, while too deep incurs additional distance and time costs for ascending. Most studies recommend an optimal glide depth in the range of 0.5–0.9 meters underwater. The timing of dolphin kick initiation is equally critical—if you start kicking while the glide speed is still faster than your cruise pace, the drag from the kicking motion itself will actually slow down your overall speed; you should wait until the glide speed drops to near your normal pace before initiating high-frequency, low-amplitude dolphin kicks to sustain underwater momentum.

Time Allocation Across Turn Phases (Schematic)

Core Research Conclusions and Practical Recommendations

• Wall push-off strength training: Dry-land training targeting lower-body explosive power (e.g., jump training) helps improve the initial velocity at the moment of push-off
• Streamline posture practice: Body position during the underwater glide phase (arms pressed against ears, body extended) directly affects gliding drag and deserves dedicated technical training sets
• Individualized glide distance: A longer glide is not always better; the optimal transition point depends on individual push-off strength and dolphin kick ability—overextending the glide causes excessive speed decay
• Integrating turn rhythm into pace training: Long-distance training sets should incorporate actual turn practice rather than only straight-line swimming, as the cumulative effect of turn quality is considerable in long-distance races

Common Research Q&A (FAQ)

Q: Is a longer underwater glide always better?

A: No. Glide speed continuously decays with distance, and gliding too long actually lowers the average speed. The key is to find the critical point where “the glide is still faster than race pace” and transition into the dolphin kick.

Q: Do amateur swimmers also need to practice flip turn technique?

A: Yes. Even for amateur-level long-distance swimmers, the cumulative time benefit of optimized turn technique across an entire race or training session is quite significant and warrants dedicated practice time.

References and Academic Citations

1. Sports Biomechanics — Research related to the mechanical phase analysis of swimming turn movements.
2. Journal of Sports Sciences — Literature related to quantitative research on underwater glide depth and dolphin kick efficiency.

Related Reading

• 【Research Review】Hydrodynamics of the Pool Flip Turn and the Effect of the Underwater Dolphin Kick: A Review of Recent Academic Literature and Training Practice (Article 714)
• 【Research Review】Hydrodynamics of the Pool Flip Turn and the Effect of the Underwater Dolphin Kick: A Review of Recent Academic Literature and Training Practice (Article 627)
• 【Research Review】Hydrodynamics of the Pool Flip Turn and the Effect of the Underwater Dolphin Kick: A Review of Recent Academic Literature and Training Practice (Article 516)
• 【Research Review】Hydrodynamics of the Pool Flip Turn and the Effect of the Underwater Dolphin Kick: A Review of Recent Academic Literature and Training Practice (Article 639)