[Research Review] Fluid Dynamics of the Flip Turn and the Effect of Underwater Dolphin Kicking in the Pool: A Study of Elite Swimmers’ Physiological Characteristics (Article 24)

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

This article examines the fluid dynamic characteristics of underwater glide distance and dolphin kick effectiveness in the pool flip turn.

Mechanical Phase Breakdown of the Flip Turn

The flip turn can be broken down into four mechanical phases: the final stroke approaching the wall, the somersault motion, the explosive power output at the moment of wall push-off, and the underwater glide with 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 streamlining, 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 underwater glide depth after push-off: too shallow (near the surface) is affected by wave-making drag at the water surface, while too deep incurs additional distance and time costs for ascending. Most studies recommend an optimal glide depth in the 0.5–0.9 m range below the surface. The timing of dolphin kick initiation is equally critical—if kicking begins while the glide speed is still faster than cruise pace, the drag from the kicking motion itself will slow overall speed; instead, wait until the glide speed drops close to 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

• Push-off strength training: Dry-land training targeting lower-body explosive power (e.g., jump training) helps increase initial velocity at the moment of push-off
• Streamlined posture practice: Body posture during the underwater glide phase (arms pressed against ears, body extended) directly affects glide drag and warrants dedicated technical training sessions
• Individualized glide distance: Longer glide distance 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; the cumulative effect of turn quality is substantial 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 average speed. The key is finding the critical point where “gliding is still faster than pace” to transition into dolphin kicks.

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

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

References and Academic Citations

1. Sports Biomechanics — Research directions related to 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.

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