[Research Review] Hydrodynamics of the Flip Turn and the Effect of the Underwater Dolphin Kick: A Study of Elite Swimmers’ Physical Characteristics (No. 777)

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

This article examines the hydrodynamic characteristics of underwater glide length and the dolphin kick effect 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 force output at the moment of wall push-off, and the underwater glide with dolphin kick transition after push-off. Among these, the explosive force at push-off and the glide 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 underwater glide depth after push-off: too shallow (near the surface) is affected by wave-making resistance at the surface, while too deep requires additional distance and time costs to ascend. 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 the kick is initiated while the glide speed is still faster than the cruise pace, the resistance generated by the kicking motion itself will actually slow down the overall speed; the high-frequency, low-amplitude dolphin kick should only be initiated when the glide speed drops to near the normal pace 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
• Streamline posture practice: Body posture during the underwater glide phase (arms pressed against ears, body extended) directly affects glide resistance and deserves dedicated technical training sessions
• Individualized glide distance: A longer glide distance is not necessarily better; the optimal transition point must be found based on individual push-off strength and dolphin kick ability—excessively prolonging the glide will cause excessive speed decay
• Integrating turn rhythm into pace training: Long-distance training sessions 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 for too long will actually lower the average speed. The key is to find the critical point where “the glide is still faster than pace” and transition into the dolphin kick.

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 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 Flip Turn and the Effect of the Underwater Dolphin Kick: A Study of Elite Swimmers’ Physical Characteristics (No. 942)
• Research Review: Hydrodynamics of the Flip Turn and the Effect of the Underwater Dolphin Kick: A Study of Elite Swimmers’ Physical Characteristics (No. 24)
• Research Review: Hydrodynamics of the Flip Turn and the Effect of the Underwater Dolphin Kick: A Study of Elite Swimmers’ Physical Characteristics (No. 396)
• Research Review: Hydrodynamics of the Flip Turn and the Effect of the Underwater Dolphin Kick: A Study of Elite Swimmers’ Physical Characteristics (No. 891)