Elite swimmers spend up to 40% of a race underwater. Training starts, turns, and dolphin kick means programming the most time-efficient gains on the clock.
In a 100 metres freestyle, a world-class swimmer spends roughly 30 to 40% of total race time underwater: the dive start, two flip turns, and the associated dolphin kick phases. For a club swimmer, that proportion is often half of that, not because of talent, but because these phases are systematically undertrained.
The gap shows up in splits. A swimmer who loses 0.3 seconds on each of three turns in a 200 m freestyle drops 0.9 seconds to an opponent who does not. Optimising starts and turns is not a detail. It is the single most time-efficient investment a coach can make in a swimmer's clock.
A flip turn has four measurable phases: approach, rotation, push-off, and underwater dolphin phase. Most coaches focus on the rotation, the acrobatic part. Research points to the approach and the push-off as the largest sources of time loss.
Approach too slow into the wall and you lose the momentum the push-off depends on. Push off at the wrong depth and you increase drag. Research by Lyttle et al. (2000) established that optimal push-off depth is approximately 0.35 to 0.55 m below the surface. Too shallow creates turbulence and surface drag. Too deep requires extra energy to climb back to optimal swimming depth.
The push-off trajectory matters too. Aiming for an angle of 10 to 15 degrees above horizontal from the wall produces the optimal balance of depth maintenance and forward momentum. A flat push-off keeps the swimmer deep too long. A steep angle causes early surfacing and wasted vertical energy.
The underwater dolphin kick after starts and turns is now recognised in practice as a fifth stroke discipline. World Aquatics race analysis confirms that world-class backstroke and butterfly swimmers dolphin kick up to 15 m off every wall. In freestyle, the rule cap is 15 m and elite swimmers exploit it fully.
Research suggests that for most trained competitive swimmers, dolphin kick velocity exceeds surface swimming velocity for approximately 10 to 12 metres from the wall. Beyond that point, surfacing and beginning the stroke cycle is faster. For less trained swimmers, this threshold is closer to 7 to 9 metres. Knowing each swimmer's breakout point is one of the most actionable metrics a coach can track.
"The underwater dolphin kick has become the determining factor in backstroke and butterfly. Swimmers who cannot maintain their velocity from the push-off through the breakout point are giving away a metre or more on every wall."
— Bob Bowman, Head Coach, Arizona State University (formerly Michael Phelps' coach)
Frequency versus amplitude is the key training decision in dolphin kick:
Reaction time has a physiological floor. Elite swimmers average around 0.65 seconds from the start signal to leaving the block. For a trained club swimmer, 0.70 to 0.80 seconds is realistic. Coaches cannot dramatically change reaction time. What they can train: block technique, entry angle, streamline position, and the breakout.
Entry angle is decisive. An angle of approximately 30 to 35 degrees from horizontal produces the optimal depth for transitioning into dolphin kick without losing horizontal velocity. Too steep puts the swimmer deep and far from the surface. Too shallow and the swimmer skips across the surface, burning the momentum of the start.
| Criteria | Grab start | Track start |
|---|---|---|
| Foot position | Both feet at front of block | One foot at rear (hip-width) |
| Take-off power | Moderate | Higher (typically) |
| Consistency | More consistent | More variable |
| Best for | Beginners, junior swimmers | Trained competitive swimmers |
| Block lean angle | More horizontal | More forward-leaning |
| Reaction time advantage | — | Slight (~0.02–0.04 s) |
For junior swimmers, coach consistency first. A well-executed grab start beats a poorly executed track start every time. Introduce the track start only once the grab start is automatic and reproducible under competition conditions.
The rule is simple: you get better at turns by doing turns. Ten minutes at the start of every session, before fatigue accumulates, is more effective than one dedicated session per month. Target 400 to 600 m of structured turn work per session during competition preparation. Practical sets by objective:
Signs of adaptation after 4 to 6 weeks: breakout distance increases by 0.5 to 1 m; turn splits drop 0.1 to 0.2 seconds per turn; swimmers hold their breathing pattern better after turns. These gains compound across a 200 m event: 3 turns × 0.15 s = 0.45 s gained purely from turn efficiency.
For the broader context of integrating this technical work into a competition preparation block, the article on taper and peaking for competition describes how to structure technical sessions in the final 4 to 6 weeks before racing.
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