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Start turn optimization is the subfield of competitive swimming that studies how swimmers execute the two major non-swimming phases of a race—the start from the block and the turn at the wall—and seeks to minimize the time and energy lost in these transitions. Though starts and turns occupy only a small fraction of a race's total duration, they are disproportionately decisive: in sprint events, a poor start or turn can erase the advantage gained by superior swimming speed, while in longer races, repeated turns accumulate into seconds of difference. The subfield therefore treats the start and the turn not as mere interruptions of swimming but as discrete, trainable skills with their own biomechanics, physics, and race strategy.
A start comprises everything from the swimmer's position on the block to the first few strokes of swimming. A turn comprises the approach to the wall, the rotation or somersault, the push-off, and the underwater glide and kick that follow. Despite their surface differences, both share a common structure: they convert a stationary or decelerating state into forward motion, and both reward the ability to generate high speed while managing the body's orientation in the water.
The central physical principle governing both is that water is roughly 800 times denser than air. This means that drag—resistance to forward motion—is enormous compared with land-based movement, and that any increase in frontal surface area or turbulence exacts a severe cost. Conversely, it means that a swimmer who can maintain a streamlined position while moving underwater can travel at speeds that exceed their surface swimming speed, because the underwater glide avoids the wave-making drag created at the water's surface. This insight underlies the modern emphasis on underwater work after both starts and turns.
A second shared principle is that the swimmer's body is a system of linked segments. The force generated by the legs on the block or the wall must be transmitted through the torso and arms without leaking into unwanted rotation or wobble. Any misalignment—a head lifted too early, a hip dropped, a kick initiated before the body is fully extended—dissipates energy and increases drag. Start turn optimization is therefore as much about body control and timing as about raw power.
The start begins on the block, where the swimmer's goal is to convert muscular force into horizontal velocity as quickly as possible. The modern competitive start has several recognized phases: the reaction to the starting signal, the generation of force against the block, the flight through the air, the entry into the water, and the transition into underwater kicking and the first surface stroke.
Two broad families of starting technique have dominated competitive swimming. The grab start, in which the swimmer grips the front edge of the block with both hands and pulls themselves forward at the signal, was the standard for decades. It is relatively simple, reliable, and well-suited to swimmers who prefer a quick, low-trajectory entry. The track start, in which one foot is placed forward and the other back, like a sprinter's stance, allows the swimmer to generate force sequentially from the rear leg and then the front leg. The track start generally produces greater horizontal velocity off the block, at the cost of slightly slower reaction times and greater technical complexity. Most elite swimmers now use some variant of the track start, though the grab start remains viable and is still taught to developing swimmers.
A further refinement is the distinction between flat starts and circular starts. In a flat start, the swimmer's body remains relatively straight during the flight, entering the water at a shallow angle. In a circular start, the swimmer rotates the body forward during flight, so that the feet rise above the head and the entry is steeper. Circular starts can produce a deeper, faster underwater entry, but they require precise timing; if the rotation is mistimed, the swimmer may enter at an angle that increases drag or lose speed in the air.
The underwater phase after entry is now considered the most important part of the start. Swimmers are permitted to remain submerged for up to 15 meters in most events, and elite swimmers use this distance to perform a rapid dolphin kick—an undulating, full-body movement that generates propulsion without breaking the surface. The optimal depth, kick rate, and duration of the underwater phase depend on the swimmer's body type, flexibility, and kick efficiency, and on the event distance. A sprinter may stay underwater for the full 15 meters; a distance swimmer may surface earlier to conserve energy.
The turn is more complex than the start because it occurs mid-race, when the swimmer is already moving at speed. The challenge is to reverse direction with minimal loss of that speed, which requires a carefully timed approach, a compact rotation, and a powerful push-off.
The dominant technique in freestyle and backstroke is the flip turn (also called the tumble turn), in which the swimmer performs a forward somersault near the wall, plants both feet on the wall, and pushes off. The approach matters as much as the rotation itself: a swimmer who glides into the wall loses speed before the turn even begins, while a swimmer who arrives too fast and must brake loses momentum in a different way. The ideal is to arrive at the wall at full speed, initiate the somersault at the correct distance, and plant the feet so that the push-off direction is exactly opposite the incoming direction.
The open turn, in which the swimmer touches the wall with one hand, brings the feet to the wall, and pushes off, is used in breaststroke and butterfly, where the rules require a two-handed touch. It is slower than the flip turn but allows the swimmer to take a breath and to set up the required stroke pattern. In individual medley events, swimmers must execute a different turn for each stroke and must also manage the transition between strokes, which adds a layer of strategic complexity.
The push-off from the wall is governed by the same principles as the start's block push-off: the swimmer must extend the body fully, keep the head aligned with the spine, and enter a streamlined glide before beginning the underwater kick. The depth of the push-off is a key variable. Pushing off too shallowly creates wave drag; pushing off too deeply requires the swimmer to spend time rising to the surface before swimming can begin. The optimal depth is typically around 0.5 to 0.8 meters, but it varies with the swimmer's size and the stroke.
The single most important development in start turn optimization over recent decades has been the recognition that the underwater dolphin kick is a powerful propulsive tool in its own right, not merely a way to return to the surface. Swimmers who can generate substantial speed with the dolphin kick can extend their underwater phase, effectively swimming a portion of each lap in a more efficient position than surface swimming allows.
The dolphin kick is performed with the body in a streamlined position, arms extended overhead, and the propulsion comes from a wave-like undulation that begins in the chest and travels through the hips and legs. The kick can be performed on the front (after a start or freestyle/backstroke turn), on the back (after a backstroke turn), or on the side (during the transition in individual medley). The mechanics are demanding: the kick requires flexibility in the ankles and core strength to maintain the undulation without breaking the streamlined position.
Research and coaching practice have identified several variables that affect underwater kick performance: the amplitude (size) of the kick, the frequency (rate), the depth of the body, and the timing of the kick relative to the glide. There is no universally optimal combination; swimmers vary widely in their kick efficiency, and coaches use video analysis and timing to individualize the prescription. What is uncontested is that a strong underwater kick can produce speeds that exceed the swimmer's surface swimming speed, making the underwater phase a genuine opportunity to gain time rather than merely a transition to be endured.
Start turn optimization is not a single method but a convergence of several ways of understanding the same problem. The most prominent approaches are biomechanical analysis, hydrodynamic testing, and race modeling.
Biomechanical analysis uses video, force plates, and motion capture to break the start and turn into measurable components: reaction time, force output on the block or wall, flight trajectory, entry angle, push-off velocity, and underwater kinematics. This approach identifies which components are slow or inefficient for a given swimmer and allows coaches to target specific corrections. Its limitation is that it measures the swimmer in isolation, often in a laboratory or with instrumentation that may alter the movement.
Hydrodynamic testing examines the swimmer's interaction with the water itself, typically through drag measurements, pressure sensors, or computational fluid dynamics (CFD) models. This approach has clarified the importance of streamlining and the costs of poor body position, and it has informed the design of racing suits and training equipment. Its limitation is that it often simplifies the complex, unsteady movements of actual swimming into steady-state conditions, and CFD models must be validated against real-world measurements.
Race modeling treats the start and turn as components of a whole race, using timing data to calculate how much time is spent in each phase and how changes in one phase affect overall performance. This approach is useful for strategy—for example, deciding whether a swimmer should surface earlier to preserve energy for the final lap—but it depends on the accuracy of the underlying phase measurements and cannot by itself tell a swimmer how to improve a specific movement.
These approaches are complementary rather than rival. A coach might use race modeling to identify that a swimmer loses time on the third turn of a 200-meter race, biomechanical analysis to see that the swimmer's push-off angle is too steep, and hydrodynamic testing to confirm that the resulting depth increases drag. The integration of these methods, rather than any single one, defines the modern practice of start turn optimization.
The current state of start turn optimization reflects several settled findings and one ongoing tension. The settled findings are that underwater work is essential, that streamlining is non-negotiable, and that individualization is required—there is no single best start or turn that suits all swimmers. The ongoing tension is between the pursuit of maximum speed in the underwater phase and the energy cost of that pursuit. A swimmer who performs a maximal-effort underwater kick after every turn may gain time in the short term but fatigue before the race's end. The optimal strategy therefore depends on the event distance, the swimmer's fitness, and the race situation, and it is a matter of ongoing debate and individualized coaching rather than a settled formula.
Another durable feature is the role of rules. Swimming's governing body sets limits on underwater distance (15 meters in most events), requires specific touches for breaststroke and butterfly, and regulates the start signal and starting positions. These rules define the boundaries within which optimization occurs, and changes to the rules—such as the historical shift from allowing any start position to requiring a stationary start—have reshaped the subfield. Start turn optimization is thus not a purely scientific enterprise; it is a practical craft that operates within a regulatory framework.
For the educated newcomer, the essential map is this: starts and turns are high-stakes transitions governed by the physics of drag and the mechanics of the human body. The start converts stillness into speed; the turn converts incoming speed into outgoing speed. Both are dominated by the underwater phase, where a streamlined body with a powerful dolphin kick can travel faster than surface swimming. The field's methods—biomechanics, hydrodynamics, and race modeling—are tools for understanding and improving these movements, and they are used together, not in competition. The field's enduring questions are about individual optimization: how deep, how fast, how long, and at what cost.